Does a Rear Mount Turbo have a Lot of Lag? Remote Mount Turbo Benefits and Drawbacks Explained

[@d4a]

Become a Tuning Pro: hpcdmy.co/dr4a Support the channel by shopping through this link: amzn.to/3RIqU0u Patreon: www.patreon.com/d4a Note: Cylinder surface formula is not the right one for the example as it places to much importance on cylinder bases which are not important in the case of a long pipe. However, the statement is still correct and a larger diameter exponentially increases heat loss since it lowers gas velocity. More time in the pipe is more time to pass heat. Become a member: kzbin.info/door/wosUnVH6AINmxtqkNJ3Fbgjoin

[@leocurious9919]

Heat loss does not scale exponentially here. Why should it? Also, why could have mentioned how a lower temperature makes the turbo less effective: Lower temperature = higher density = lower flow velocity. Same reason cooling the fresh air after the turbo helps, just the other way around.

[@GriderTornado]

This is true for the same length of tube - my question is but isn't for the same volume of hot air in the tube, the acutal length of the tube shorter? Let's say 1dm³ of hot air takes in a 2" tube (Ø5,08cm) take a total length of 49,3cm while a 3" tube (Ø7,62cm) takes a total length of 21,9cm. So the surface area of a 2" tube for 1l is 31cm² while for the 3" tube for 1l is 13,8cm²? [EDIT] Nevermind, with the increased surface the heatloss increases, so even if in the tube there is more total heat stored, there are still 1 effect working against it: with the expansion of the volume the heat goes down (presure dropes) and even if between the turbo and exhaust valves we would maintain the same pressure the increased surface area and therefore higher cooling might(?) outweigh the total amount of heat stored between an 2" and 3" tube

[@kabalder]

@@GriderTornado It's probably possible to set up a pipe system that has higher diameter, more area in the material - and that doesn't expand or draw heat off it (type graphite, or some composite with very low heat-capacity). So it would be theoretically speaking better than a very thin steel pipe system. But you'd run into a lot of issues with it that you wouldn't have in, say.. a water-cooled PC or something like that XD Shocks, pressure peaks not being easily aligned, things like that. Or, I know parts of the physics of it makes sense, but I'd hesitate a great deal to replace steel pipes in a car. So what the legend up there is pointing out is that if you have higher volume of a pipe, you do need to compress more air (volume, ^3) to get the pressure, and you get much higher surface area and also higher volume of piping. So there will be a lowered pressure effect as the compression builds and cools the air - long before any cooling stage happens (which is outside of the turbine step). And it will scale with larger tubing (just not exactly at that formula).

[@UPR91]

Every crazy piston head after seeing that video: "I'm gonna locate my turbo behind, insulate the exhaust line and return back the intake air through a full trunk of heat exchanger and air tank. With enought tank i can also get rid of the dump valve and benefit from the release phase to fill those tank" Nice job

[@leocurious9919]

@@Sir_Cactus The loss would be linear, probably even less than that given how radiation is a mayor contributor at higher temperatures, which scales to the power of 4. So since the temperature of the larger tube is lower, the loss will be less than what the surface increase would indicate.

[@JJFX-]

Very well said! What's most impressive about your videos is I don't think you're even referencing a script for most sections. You do a brilliant job outlining the subject matter clearly and concisely but unlike so many creators, you obviously know your stuff inside and out. It's that undeniable passion that makes you such a great educator. I always learn something I didn't expect from your content. Creators like yourself are becoming more and more of a rare breed and I genuinely respect your efforts. Keep killing it man.

[@d4a]

Thank you so much for the kind words! I did mess up the cylinder surface area thing though 😞

[@adrianzmajla4844]

​@@d4aYes but you admitted to that, and corrected later. You are a brilliant mind! And someone that can take constructive criticism and build on that. Very rare these days.

[@Zenvo-uu9tm]

That's because he knows well his stuff , hence the smooth delivery of an explanation

[@boywonderrr71]

@@d4a All good brother. You are not perfect and we dont expect it. You did pin it so ....

[@lovesrc4296]

Well said 👍 totally agree.

[@davidblalock9945]

Decades ago I had a C4 Corvette ZR1 that was modified with a remote mount turbo. Yes it had noticeable boost lag, as you will undoubtedly have with an 83mm turbo, but the remote mount I think contributed to a more subtitle boost ramp. Also, the added air volume meant that the turbo was far less interrupted by momentary throttle cuts as the transmission shifted. All in all, it was a 9 second car every day of the week, and breaking 200 on a one mile was easy.

[@snowcow1173]

Beautiful

[@yeetmeme6027]

would you recommend the c4 as a first car or are they hard to work on?

[@davidblalock9945]

@@yeetmeme6027 No not particularly difficult, they’re a Chevy. They’re a parts bin special. The ZR1 is the only one to avoid, unless you have deep pockets, as the engine is a special, 1 vehicle only engine. But all the others had a tuned up truck motor. The manual transmission in early C4’s is a bit funky. GM was trying to do a thing, and that thing didn’t really make much sense. But later models had a BorgWarner T5, which was plenty stout enough for the power it produced. If you’re planning to swap to a modern engine, like a 5.3, then you’ll definitely need to upgrade to a TKO or T56 transmission because a bone stock 5.3 straight out of the wrecking yard will break T5 on the first rip.

[@fuckyachickenstrips]

@@yeetmeme6027 I second @davidblalock9945 on this bit. Not difficult, just quirky and some quirks can be expensive. My first car I still have to this day is my 1996 Chevy Impala SS. Pain in the ass to find suspension parts for, but easy enough to work on.

[@THESLlCK]

@@davidblalock9945 isn't an 83MM a pretty huge turbo for that engine size? I would be more inclined to blame turbo lag on the fact that you say this was decades ago before the incredible boost management we have now paired with a fairly large turbo for the motor it's feeding.

[@davidbrayshaw3529]

Fun fact. The WW2 era P47 Thunderbolt had a turbocharger located in the rear of the fuselage, well back from the 2,800 ci. (45 litre!!!) twin row 18 cylinder radial.

[@mrb.5610]

Don't forget that aeroplane engines run pretty much at a constant speed - they don't have to worry about spool up speed.

[@alanmartinez45]

Also don't forget that the turbos in plane engines are always by themselves in separated chambers so the heat doesn't fuck anything...

[@rafaelrp07]

​@@mrb.5610 Dude....this is a WW2 warbird! Ofc it was designed to handle extreme use of the engine ...

[@ronnysundt3249]

True and the same goes for most ww2 turbocharged planes

[@TheDustyShredder]

​@@ronnysundt3249The turbos for the b25j20 engines were located at the back of the engine nacelles for the same reasons, but also for the fact that if shot at from the rear, the turbo would be the first thing hit. Yes, the engine would lose a fair bit of power, but at least it would still run until the oil leaked out, long enough at least to get to a FOB for repairs if the bomber survived the encounter. The B25 was a frontline bomber, so it was designed for increased survival rates against flak and small arms fire. It was kinda between an attacker and a bomber. It had 6 .50cal Browning M2s on the nose, 2 gunner turrets with 2 M2s each, and two side gunner positions with 1 m2 each. It had a payload capacity of 12 250lb bombs, 8 500lb bombs, or 3 1000lb bombs. Dammit, now you got me wanting to play war thunder again. Bastard.

[@kyle0003]

Mechanical Engineer here - what he says @13mins into the video is crucial. Thermal energy is the source energy. The ''hot side'' of the turbo is just a gas turbine and the simplest form in thermodynamics to relate the work done (Wout) by a gas turbine is Qin = Qout + Wout.... Qin - thermal energy IN, Qout - thermal energy OUT, Wout - Work produced. This is the basic thermodynamic law of any heat engine and this will make it easier to understand the basics on how a gas turbine or engine work from a scientific perspective. So when you relocate a turbo to the rear, there is heat loss in the exhuast gas, therefore your Qin becomes less, resulting in your work produced by the turbine being less which is not good. The turbine side of a turbo is designed as a adiabatic system meaning they try to make it as insulated as possible because any heat loss is just a loss in potential energy - therefore turbos are manufactured very robust. Obviosuly there are China turbos too which dont comply to this but every big turbo manufacturer designs there turbos to run at very high temps so a drop in turbine temp is again not really a win w.r.t turbo life span. (This is why modern car engine designers put the turbo as close as possible to the exhuast manifold). Now this issue of charge air being too hot can very easily be solved by selecting the correct intercooler, but I also know space is usually a problem - a short fat intercooler is not as effecienct as a large thin one. If you want to learn the in depth science of intercoolers, go look at Gale Bank's videos on intercooling, he explains it very simple and easy. Remember folks, chase efficiency, not power. Power is a by-product of eficiency. If you build an efficient, well designed engine, it will produce more power at less stress levels.

[@DadGamingLtd]

My initial thoughts where more along the lines of conservation of mass (flow). As the air cools, it gets denser, which means it will travel slower to keep the same flow of air in weights per time unit. Basically bernoulis principle, except with gas density instead of flow diameter.

[@Alice.1219]

That's why you wrap the exhaust system.

[@spyder2383]

Too high of temperatures is the Achilles heel of internal combustion engines. The materials we use have a much lower heat durability limit to fully use the potential heat energy in the fuels.

[@blackmarkettrucking5821]

I'm with that notion and believe if I'm wrong but could reduce nox right? It came to me but my brain just turned on so forgive me

[@volkris]

Physicist here. About 3 minutes into the video that thermodynamic principle was blinking like a giant red light in my mind, and by about 5 minutes I was looking at the comment section to see if anyone had mentioned this, but I wasn't going to actually make my own comment until I had finished the video :-) Glad to see you bring it up! And glad to hear that he addresses it later in the video! Thermo has been my professional focus, so I just couldn't help myself, I just couldn't wait! :-)

[@peteraustin4295]

So glad to see the steady growth in viewership of this channel over the last year or so. This video is pretty damn niche, even among auto engineering videos, and yet it has almost 200k views in just two days. Love to see that because it's very well deserved. It also shows me that there's still a few knowledge-seekers left in our increasingly vain, self-obsessed world

[@d4a]

I feel like the vain are just louder and more prominent, not necessarily more numerous. At least I hope...

[@thomasjefferson6334]

​@@d4aone thing id like to know is- looking at the differences in the dyno graph.... just how much improvement in building boost would you see by wrapping the exhaust and headers to the turbo??

[@nikki5399]

669k after 2 months. Crazy good numbers for the topic.

[@windhelmguard5295]

one extra thing to consider: all the infrastructure (piping for oil, air and exhaust gas) is going to add more weight to the vehicle, which does effect performance, but you are also lowering the cars centre of mass since you're installing it all way down low so it might also have benefits.

[@mrb.5610]

If it's hanging off behind the rear axle, I'd say definitelynot good for handling but probably good for straight line traction.

[@skylancer-zer0205]

If you have a front heavy car it could also improve weight distribution as well, very slightly but every little bit counts.

[@piccalillipit9211]

And you are moving the mass to the rear, which is nearly always good

[@mrb.5610]

@@piccalillipit9211 'Simplify then add lightness'. Colin Chapman.

[@christopherfowler1549]

Not that much weight, the turbo is going to be the heaviest part that you are adding. You will have to run a scavenge pump for the oil drain to get the oil back to the engine. Still not very much weight

[@JJHurst]

There are no solutions, only compromises...

[@Valverde713]

With modern setups Lag doesn't exist anymore

[@kenkendal3143]

all solutions gave comprises...dont kid ya self

[@rayshadow6796]

There are no solutions, only compressors...

[@noideawhat2]

Is that John Lennon?

[@RailsofForney]

@@rayshadow6796GET REKT

[@subynut]

Nicely explained! I appreciate the distinction between Turbo Lag and Boost Threshold. So many car enthusiasts equate the two terms, but as you said, they are not the same!

[@dj_laundry_list]

I agree with you, especially when the enthusiasts are journalists and should distinguish the two, but I wish he didn't explain the implications here incorrectly. Boost threshold is concerned with steady state operation, in which the volume of the tubing makes little difference other than thermal losses. Lag is concerned with the total energy in the system at a given time, so if you have a large pipe that needs to change in pressure by one atmosphere or more, that's going to take a noticeable amount of time.

[@Kz-lq2nv]

My biggest problem was the position of my exhaust manifold, now that turbo lag is not a big problem in my case, I will be using the rear mounted setup I am so gratefull

[@glengaff3361]

Very well done mate. What a fantastic video. So much information crammed into it (which was all relevent to the subject) but more to the point, this was for the first time in a long time where i havent found myself getting easily distracted or catching myself bailing out after 10-15 minutes because of the lack of interesting content or poor delivery of it. In fact I think this is the first time ive bothered to comment on any video in all the years of watching youtube, so thats speaking volumes right there. This is how you're meant to get people to like and subscribe, not by begging them to. I've not seen any of your other videos but you've already got my sub mate. Plus on top of all that, Im gonna bet that English most likely isnt your native language, and you still delivered it clearly and I never missed a trick. Honestly you killed it guys. Bloody good on ya. Very good form.

[@d4a]

Thank you so much for the kind words of support! But it's not guys, all of it is just 1 guy 😁

[@colinelrick]

Perfect video. It is frustrating how many people look individually at pressure and flow but it is prevalent throughout the engineering world! A pressure washer with 2,000 psi is not more powerful than a get engine with 700psi discharge pressure (50:1 EPR) You describe things so clearly, please keep it up. Another fantastic video. Clear and concise with common sense easily relatable concepts. 👌

[@piccalillipit9211]

CORRECT - I have had so many arguments with people, in an ironic way high PSI is BAD. High PSI is a result of NOT being able to get the air into the cylinders. What you would REALLY like is STP [edit: standard temperature and pressure] and huge air VELOCITY EDIT: his is why a jet engine is so powerful - you can have the massive air velocities cos its not a fixed volume of combustion. You have to have high PSI cos you cant get the air VOLUME into the cylinder without compressing it.

[@asianboyyy117]

@@piccalillipit9211what is stp and where can I go to become smart like you

[@piccalillipit9211]

@@asianboyyy117 - OH sorry - STP is standard temperature and pressure and the answer to your second question is a book called " Turbocharging and Supercharging" by Alan Allard

[@adrianzmajla4844]

Yes i can recommend this book. ​@piccalillipit9211

[@gameonyolo1]

Ok, I understand that high flow restrictions or any restrictions can reduce effective boost. But can you explain how a big turbo with 14 psi and a small turbo with 14psi make different power. Only thing I can assume is that he's measuring boost at the turbo outlet. But if you measure at the intake valve or intake manifold, and two different turbos produce the same boost what's the difference? Assuming you have a good intercooler and the temps fall to more or less the same temp what's the difference. It's my understanding that boost is usually measured after the intake valve, after the turbo, and therefore any flow restrictions in the turbo are irrelevant.

[@383mazda]

Great explanation. I worked at STS back in the day and i dont know how many times ive explained the remote turbo lag myth to people. The best argument was just giving them a ride - the average car guy could not tell the difference from a remote mount vs under hood mount system (other than the exhaust note of course).

[@brettdavies-young7102]

Guess I don’t have to share this link with you….

[@jeeplivion]

its fun hearing dodo heads say the sts turbo kit was stupid because " it only made 7 psi" *eyeroll*

[@nocturnalspecialties642]

I had a STS kit on my silverado back in 2003 or 2004. Fun times! Confused everyone cause nothing noticeable was under the hood and stock exhaust manifolds...

[@nickdeluca7742]

Did you live in Utah?

[@383mazda]

@@nickdeluca7742 I used to, went to college in Provo

[@sinamohseni2799]

16:40 Small correction: the 2pi*r^2 term of the surface area formula represents the two circles at the ends of a cylinder. In the case of an tube like an exhaust pipe these are absent, therefore A=2pi*rh (hence a 10% increase in r will increase surface area by 10%, etc)

[@noer0205]

Shouldn't the correction be that it is the volume of the cylinder that is important. Where we again find an r^2 term. Since the area ahead of the turbo spool needs to be pressurized (filled with exhaust gas from the engine) before the spool starts to spin up.

[@zakpodo]

​​@@noer0205 Not in this case, he's talking about heat loss- which is related to surface area. The increased area (The R^2 term) would be a factor in the lag/delay that is attributable to the time time it takes to flow the amass of air in the pipe as you said. This seemed to be pretty negligible relative to the rate of flow of a turbo even if it increases by area instead of radius- at least according to his calculations.

[@shadowartifact9426]

Came here to say the same thing

[@cleartape229]

The dyno graph label is also wrong. He labeled "front/rear mount torque" on the power curve, not the torque curve. Torque tends to fall off, but power will still increase due to RPM. 12:49

[@petrsindler1525]

Indeed

[@Alice.1219]

I designed and built a rear mount twin turbo set up for my 2010 Camaro 3.6 V6 back in 2011. I am a retired engineer and this gentleman is absolutely 100% correct in everything he says. My build consists of twin Borg Warner 6258 EFR turbos, heat wrapped exhaust, 3800 stall converter, front mounted air to air cooler and many other features too numerous to mention. It is my daily driver and I have never had an issue with it, so far. The car turns 11.55 sec. in the quarter mile. Amazing power. No noticeable turbo lag and is a blast to drive. No heat issues either. Love the concept and would never do it any other way. Rear mount turbo systems, if designed as this gentleman suggests, perform as well as front mounts. I have done many in my career. This is the first video I have seen on this subject that is pure fact!

[@mischaburns5593]

Did you have any issues with rain/snow splashing up in there? I get a lot of slush in winter and puddles in summer, curious if that caused noticable damage or problems.

[@Alice.1219]

None. I designed a rear guard to prevent that.

[@byronlove4759]

I'm kinda mad at myself for putting off watching this video for so long... This was an incredibly well planned, scientific and detailed explanation! I think i found a new favorite car science channel! You are awesome man, thanks for the content!

[@captainobvious9188]

I've played with remote mount turbos through the years. They are surprisingly effective, the thing I found mostly different was that it has similar gains to a log manifold even with tuned header(s). This makes sense because you are using a much higher amount of built up static pressure for the turbine as opposed to the individual exhaust pulses of pressure - so even tuned headers are working against a much higher base pressure. It is sort of the extreme opposite of cleanly delivering the pulses and eliminating the base pressure buildup like you get when dividing an exhaust between multiple turbo scrolls.

[@adampatterson707]

I've had experience with two vehicles with rear mounted turbos. One was an early 2000 model Z28 and the other was a Nissan Hardbody pickup truck. Both vehicles ran extremely well and were daily drivers.

[@azi9_ity]

That hardbody sounds glorious

[@ddzn80]

Thinking about this setup on my 80 datsun 720 with a l20b, would be pretty crazy with side draft carbs too

[@brendanbenoit]

@@ddzn80My dad was the original owner of a 1980 Datsun 4X4 king cab truck.His truck was modified, Custom red&gold metallic boat flake paint, 33” Michelin, off-road tires,custom rims,Rancho suspension,5” body lift, aftermarket stereo system, Weber carburetor, aluminum, aftermarket intake & filter,hand crafted fiberglass camper,Aftermarket glass quad headlamps, PIAA Jap made bulbs,Aftermarket taillights…RIP Dad

[@98f5]

I ran a rear mount turbo well midmount, on a 2000 camaro ss. I miss that car she was amazing.

[@firstNamelastName-ho6lv]

Woah that's awesome. I'm looking into a rear mounted setup for my 95 z28. There is so much room back there, with zero room in the engine bay.

[@michaelblacktree]

I've been considering a rear-mount turbo in my project car, for two main reasons: 1) Weight distribution -- My car is already front heavy. A traditional turbo setup would exacerbate that. 2) Exhaust sound -- I have long tube headers, and love the sound. A turbo manifold will make my BMW sound like a pickup truck.

[@cannaroe1213]

Weight distribution is something not discussed, and it can really help balance things out, particularly on a mid-engine car with a front mount (remote!) intercooler. The other unmentioned benefit is cops will rarely find a remote turbo, because, well obviously, when they make you pop the hood it isn't there :P There can also be a reduction in drag (passive up-pipe cooling vs FMIC) which can be non-insignificant.

[@RogerFrigola]

Excellent video, as always. Just a comment about the small vs large turbo both giving 1 bar of boost (timestamp 5:50): from the engine head perspective if 1 bar of pressure gets there it does not matter if the turbo that generated the boost was big or small. For a given engine, if the turbo can provide 1 bar of boost then that determines the amount of extra fuel that can be burnt in the cylinders.

[@gummostump4217]

True. If the same turbo flow was applied to two different cylinder heads, one high flow and one low flow, the boost would be higher on the low flow head. With more turbo flow, the higher flow head could read the same boost as the lower, as the whole system flows more air.

[@shadwills8594]

I was wondering if I was missing something, but I tend to agree with you. 1psi for a given intake volume (engine volume, efficiency) will make the same power no matter the turbo size. The blowoff valve might be working harder with the larger turbo, but still... And you could have a turbo small enough that it couldn't produce 1psi for a given setup , or a turbo too large for that setup. Otherwise I generally agree with the video.

[@scootypuffjr.]

​@shadwills8594 No. The restriction in the small exhaust turbine side restricts airflow. Airflow makes power by having more air available to burn fuel. Put a less restricted hot side on the turbo and the compressor side of the turbo won't move enough air to make boost. It's a balance.

[@anthonylove6639]

Well it does work in situations where there isn’t much room under the hood but it’s not the most practical or efficient way to turbocharge your vehicle. Because if that was so OEM manufacturers would be doing that all the time. Right? The shortest path from the exhaust side of the engine and to the turbine of the turbo is the most optimal. The sonic waves, heat and exhaust velocity is at its highest next to the engine. Your turbo response at spool up is so much better. I have experienced that kind of engineering on my engine and it’s amazing!

[@jeffreychang6165]

A video on the pros and cons of a hot-v configuration would be a nice counterpoint to this.

[@andrewt9204]

If you're measuring 1 bar at the intake manifold that's all that matters. Doesn't really matter if it's from a 30mm turbo or an 80mm turbo. The airflow is the same. (unless the temperature is significantly different as you mentioned) It's basic fan laws and fluid dynamics. If you change something downstream of the pressure sensor however, then that 1 bar could mean something totally different. Also, flow and pressure are related by a function of square. So yes, doubling the pressure doesn't double the flow rate. The calc for determining new flow rate based on static pressure change is CFM2 = CFM1 x Sq.Rt(SP2/SP1). So for example: 7 psi making 1000 CFM would mean 14 psi is only making 1414 CFM.

[@williamebrahim2612]

finally someone that called this out also eqn mdot=(P/RT)*(pi*r^2)*V. unless the velocity (V) or temperature (T) is different then mass flow rate would be the same but i wouldnt expect it to change significantly

[@CyroTheSpider]

I e-mailed the video creator about this. The thing is, he's not wrong. Nothing he says is wrong. I would call this the "you're not wrong, you're misleading" category. Here's my comment (that got buried in the comments) Regarding the turbo size - I just want to warn people to carefully listen to the video to not come to the wrong conclusion (like I did initially and embarrassingly e-mailed the author about it). You can't just put a bigger turbo on the same engine and magically make more power at lower intake pressures. The video states "which one makes more power?" And the conclusion is the bigger one can make the same power at lower pressures. The question asks nothing and also assumes nothing about the engine being matched to the turbo. Later, the video also states "match your turbo to the engine". So, if anyone is still confused about this: In a car engine, turbos are regulated - through intake pressures. Turbos don't just simply work at 100% of their air flow capacity during the engine operation, in fact, that is rarely even a thing, except maybe in some diesel engines with small turbos. Air flow doesn't magically stay the same at the same engine RPM and the same engine capacity but lower intake pressure. In his example, we are flowing the same amount of air into the engine with a bigger turbo (and lower intake pressure). But how? More engine RPM? More engine capacity? The question doesn't bother itself with that and doesn't assume anything. So the answer is right. Same airflow, same power. It doesn't care about the package. Just the turbo. But if we are talking about the real world, where you usually modify the same engine, the intake pressure IS ACTUALLY an indicator of airflow at certain engine RPM. There is no way around that. Bigger turbos DO make more power, but only if the engine parameters change. That's the only way you get more air into the engine at lower intake pressures (more RPM or more capacity). Boost controllers work by regulating the intake pressure. And if BOTH the turbos can maintain the same air pressure, what actually happens is we have the same air flow. The boost controller is simply regulating the bigger turbo to run at a lower speed, providing the same air flow as the smaller turbo and maintaining the same air pressure. Example: You set your boost controller at 14.5PSI. Your smaller turbo worked at 80% capacity at 4600RPM (for example). Keeping the same boost controller setting at 14.5PSI, this means your bigger turbo is now working at 20% capacity, keeping the same air flow (again, just an example). Engines are not magic. They can't magically take more air flow at lower intake pressures. This is why a bigger turbo might not make more power. It can only do that if you go into higher RPM, make the engine bigger or make more boost - all parameters where the smaller turbo can't keep up the air flow and ergo... The intake air pressure. If both the turbos can keep a certain intake pressure throughout the whole RPM range, this means they can both provide all the required air flow for its operation. It'll be more or less the same amount of air flow. Again, turbos don't always (in fact, almost never) work at 100% air flow capacity. Their air flow is actually regulated through engine intake air pressure. The questions and statements themselves don't assume keeping the same engine parameters. They only ask how much power the turbos themselves can make. The author later even says you also need to match your turbo to your engine. This is a warning to anyone watching this, - be careful not to misunderstand this. Your 1.6 turbo gasoline engine will not make more power if you give it a bigger turbo with a lower pressure on the boost controller setting (unless you're going significantly into higher RPM). The question doesn't assume you're keeping the engine parameters the same.

[@marceloxxx]

Big turbo makes more Power with same intake pressure because have less backpressure in exhaust.

[@Sbinott0]

Finally found this comment, higher flow rate means nothing, the only meaningful thing is pressure at the intake, very misleading video in this part.

[@802Garage]

Congratulations on 1M subscribers man. Absolutely colossal achievement. I've always believed you would be huge, but this is wild! So well deserved.

[@StephenWhite55]

An excellent presentation - thanks! I can almost hear Gail Banks applauding, somewhere in the distance... 😎 Keep up the great work!

[@williamzk9083]

The remote mounting of turbos was the norm in aviation such as P-38, B17, P-47 etc. the long exhaust duct actually cooled the exhaust enough to avoid damaging the turbine.

[@mrb.5610]

Only because the first generation of heat resistant steels weren't that good ...

[@arthurfoyt6727]

@@mrb.5610 It was all size and packaging; no one cared about "longevity" of replaceable parts. Remember that in wartime the average life of the aircraft itself was maybe just a few missions.

[@mrb.5610]

@@arthurfoyt6727 Not sure 'longevity' comes into it - the turbine blades either melt or they don't - they don't exactly wear out !

[@NalinKhurb]

Perhaps bearings could be affected by temperature? @@mrb.5610

[@arthurfoyt6727]

@@mrb.5610 The Germans were happy with 10 hours service life on their jet engines. Replacing just a turbo in 10 ours is child's play. In wartime you only cared about winning.

[@SpeedofCheeseRacing]

Great video. I was directly involved in the STS turbo thing. I got tired of trying to explain just what you discussed in the video. Especially the lag.

[@goatsplitter]

Your videos are always so informative. I learned a lot with this one. While I've never really thought about this kind of setup, I definitely went straight to "oh man that's gotta increase the lag" and now I know how that is wrong frameset, and the "heat energy" vs. kinetic explanation was great. Thank you again all around. Great work!

[@thatcheapguy525]

before watching this video I thought the whole rear mounted turbo story was mad. now it makes complete sense. to avoid all the muck and damage of the air filter one simple solution that comes to mind is to plumb it away from the underside

[@suddendilemma5137]

The biggest benefit BY FAR that was briefly touched on….. with no muffler and rear mount you literally sound like the Batman going by. It’s glorious

[@Waccoon]

Holy cow... I had no idea this was a thing. My first thought was when Subaru said they couldn't stuff a turbo into the BRZ because there was no room, and some crazy people were shoehorning turbos into the bay by chopping holes everywhere. Now I'm fascinated with the idea of a rear-turbo BRZ. Not like I'd be ditching my WRX, of course.

[@gamersplaygroundliquidm3th526]

I akso just thought about so many cars I owned or want to now to run this lol. Like how the fuck I never heard or think of this since I bought my first Turbo car 20 years ago and fell in love but always wished I could move it away from the engine and get the heat down, 2 decades and now it seems so simple 😆 😆

[@kadmow]

- and many dragracers - merely mount the turbo outside the hood... Everyone loves a set of horns on their V8. :) )

[@Kim_Miller]

My son has front mount turbo in his Toyota 86, which is the BRZ rebadged. No fancy hole boring, it can fit when it's done well.

[@luislongoria6621]

If you believed every KZbin mechanic, there'd be no Subarus except for salvage yard enthusiasts who enjoy destroying engines on purpose

[@Sir_Cactus]

It is absolutly true that it is important to reduce the cooling of the exhaust infront of the turbo, yes, and that can be achieved by a smaller diametre exhaust, as in increase exhaust gas velocity and has a smaller surface area. However, the formula required to calculate this surface area does NOT include the radius squared. The 2×Pi×r^2 are just the two circles on either end a cylinder, which we do not have, as the exhaust pipe is a pipe and not a cylinder.

[@gregm8262]

I would like to hear more about the heat energy recovery in the turbine… from my Navy days it was my understanding that the majority of the energy exchange was from expansion through the turbine, less about our typical view of kinetic energy from impingement and more about expansion from hot high pressure to cooler low pressure. Maybe too fine a point, but I can see why close coupled turbines would harvest much more power during the blowdown phase particularly when paired with an early exhaust valve opening event… I’m also wondering if a remote setup would benefit from cam timing changes that would increase exhaust gas temperatures down the length of the pipe. Also seems that you could better manage front to rear weight ratios with remote installations.

[@trev0rbr]

Flow is always from higher pressure zone to lower pressure zone so you're definitely right.

[@donventura3844]

Hence pressure differential

[@dennisrobinson8008]

Richard Holdener did front vs rear mount turbo tests adding like 10ft of piping in between the exhaust and turbo. The max power level was exactly the same. What the increase in piping did was delay when the turbo would spooling. The difference in spool was not very large perhaps 500 rpm. If the spool was important you could change the AR of the housing or use a smaller turbo that spools earlier. Also he did not use heat wrapping on the turbine side piping.

[@lucaslutzerler5429]

The house of cards in my head with the name "Turbo" has just crumbled. I have learnt something again and D4A has corrected my half-knowledge. Greetings Lucas

[@mxaxcbpg6500]

I watch loads of car KZbin but you are by far the most easy to watch an understandable keep it up mate

[@MrFordy90]

I prefer the term “transient throttle response” over turbo lag, just more logical to my brain 😂

[@SeekYHWHsface]

That response is laggy

[@merlosso]

Another great video, thank you. I’ve always been curious about this and had assumed lag would be bad due to the distance from the engine. I was wrong! Great explanation and presentation. You make complex topics so easy to understand.

[@arlowelee]

Bro really said "jokes on you heat energy and kinetic energy are the same thing" and I had a revelation and went holy shit hes so right lmao

[@musicauthority674]

Ford motor company figured out a way to overcome turbo lag. several years ago on their rally cars. by putting a reservoir tank near the rear bumper of the car. and basically with waste gate valves this reservoir tank stores boost pressure. and then releasing it when needed to overcome turbo lag. it worked pretty good but when the sanctioning body discovered this trick. they were disqualified from using it.

[@johnnymcnubs4527]

I have a 5.7L LS. Cammed it, rear turbo'd it, widened the wheels, tuned it. I did it because that TINY bit of delay is beneficial for the car to hook up and take off. These things work great!

[@arthur_za]

Bro always speaks like he's recordings at 1am and doesn't want to wake up his roommates.

[@DEATHWISHVQ]

Just shut up and enjoy go make a meme account if u wanna be so funny

[@schawn4925]

It’s peaceful

[@lookaaaa]

@arthur_za, I've just watched this at 1am and I didn't wake up my wife or my 5-y.o. son 😂

[@anarchyr32]

lol lol lol bro I thought the same thing and then saw this comment lol lol fffffuck lol

[@fireraid]

Wouldn't have it any other way

[@TurboHappyCar]

Well this is timely. I have a "Stealth" remote mount turbo kit on order for my 2006 Miata. The lag and boost threshold have been debated to death on the forums, so I'm going to see what it's all about. Great video as always man! 👍

[@jiijijjijiijiij]

It would be really cool if you could record a video about it and put it on your channel! There are basically no videos online discussing installs for smaller displacement engines and I'm sure lots of people would be curious about it.

[@TurboHappyCar]

@@jiijijjijiijiij Sure. I'll definitely do some videos about the boost response and work it into my track videos. TBD if we do installation videos. It's a pain to do work and film at the same time in a driveway with cars driving by.

[@cannaroe1213]

@@TurboHappyCarRemote-mount your house.

[@luislongoria6621]

Fantastic! I was only looking at Daigo Saito's MX-5 with spare tires on the rears drifting in 1st gear from an exterior perspective without mentioning the build

[@carty_a_fool1838]

If ever went rear mounted I would definitely go anti lag just for the critics lbs

[@flameburstgt6503]

Another benefit of rear mounted turbos: you can make your engine bay look like normal so people think your car is not fast without knowing you have a sneaky turbo 😂. Great for trolling Also turns out that I have been mixing up turbo lag and boost threshold. Thanks for clearing it up

[@d4a]

Definitely! You can be very stealthy with it

[@Wagonman5900]

Join the club. I mixed those up too.

[@charlesmayberry2825]

Love that you explain the Turbo lag problem and Turbo size, I have a car with a very small engine, and a very small turbo, with a large boost. 1.3 liter engine with a 14mm turbo, it's pushing a 21PSI boost. Having such a little engine, there is a small amount of lag even with that little turbo, a bigger turbo will have more lag due to the small engine size. As you mention Lag is mechanical lag as the turbo spools up. An example my car the actual lag is a moment of lag, but under 3K rpm, you're below the boost threshold of the turbo so it acts like an N/A, and I mean that in that the power is similar to the naturally aspirated version of the same engine. Something that you don't really touch on in this, an additional advantage of a remote mount turbo is that in a tight engine bay the biggest enemy of the turbo is the associated plumbing needing to have a lot more tight bends and turns which can severely effect flow rate, and in turn cost you a lot of power. Remote you can often get a more direct flow, this can be a huge net benefit.

[@allareasindex7984]

Commenting to boost your numbers for the algorithm. Love your videos!

[@QPC_LLC]

I've been running a rear mount turbo setup for over 8 years now on my Audi 4.2L. I've gone through six different turbos. I've gone through three piping changes. I've gone through non-intercooled and two different intercooler setups. I'm very well versed in how to make a rear mount setup as efficient as possible within the confines of my vehicle. with that said every vehicle is going to be a little different but the rules will still apply. conservation of energy is the biggest hurdle to overcome if you're trying to maintain response similar to that of a front mount turbo car. My first setup was a 60 mm turbo with dual 2.25 in piping all the way back to the twin scroll turbine housing. This was fun but the 60 mm compressor really wasn't enough for the V8 so I sold it and upgraded to a 64 mm. after I got used to that I sold that one and transferred to a 69 mm. The difference in lag to reach peak boost from the 60 to the 69mm was almost a thousand RPM later. Boost threshold remained relatively the same but the buildup to peak boost pressure which in my case at that time was 1 bar was pretty slow. I decided I'm going to taper the exhaust all the way back so now I went from 2.25in down to 2 down to 1.75in to feed each scroll of the turbo. This gave me favorable response. I reduced time to peak boost 2 to 300 RPM earlier. With both of these setups I always ran fiberglass insulated exhaust but on this new one I wrapped it twice. Cruising down the highway my EGT at the turbo was roughly 400C, at WOT, my temperatures reached upwards of 700c I got a good deal on a 72 mm testing vs the 69 and later on I got a 76 mm. My greed for more power and a reduction in exhaust back pressure led me to the largest turbo being a 7675. The downside to having a rear mount setup is just that, the exhaust back pressure. The primary reason for this is the turbine side of the turbo. you either go to a larger housing or a larger wheel or both to reduce the back pressure. Back pressure increases the more bends you have and friction placed on air flow from the walls of the piping. What also increases back pressure is the compressor having to spin faster to meet your target boost level. The harder your compressor has to work the more your turbine has to spin and the higher your drive pressure goes up. after all this, I did not like the 7675 despite it having back pressure upwards of 2.5:1 It was laggy. My new setup aim to address all the shortcomings while still remaining rear mount. I changed my piping to a single 2.25 pipe (so both Banks merged into 1). I dropped my turbo to a modern xona 10569 with a smaller turbine wheel but it utilizes their new wheel design which has staggered blade heights. I insulated the exhaust with ceramic wool and wrapped it in titanium sheet. I changed my intercooler piping and got rid of five 90° bends before the intercooler. I changed the intercooler to a bigger core with a bigger opening and a bigger exit. All of this resulted in a 1200 RPM reduction to reach peak boost and an average increase of 100 to 150c for my EGTs. Furthermore, spool is ONLY 100-200rpm later than that of my friend's 4.0T with the same turbo. I'll take those numbers! My boost controller required 20% less duty cycle to reach the same boost. My exhaust back pressure ratio dropped from 2.5 to 1.9. I MAKE MUCH MORE POWER AT LESS BOOST. These are the things folks have to consider and do if they want a rear mount turbo setup to truly perform. I invite any of y'all who want details to take a look at the videos on my channel look at the things I've gone through look at how my car performed the past years versus recently.

[@locky2562]

Yawn.

[@QPC_LLC]

@@locky2562 drink more coffee

[@Sir_Cactus]

Boost pressure is actually quite important. Mass air flow is indeed the important metric, but you have to put all the air into the cylinders. The volume of the cylinders is limited, meaning the only way to put in more air is to increase the air density. As you can not cool down the intake air infinitly, you need to increase it's pressure, meaning you want high boost pressure. That being said, mass air flow is still important, as building boost pressure requires lots of air and the larger and higher revving the engine is, the more air leaves the system through the exhaust.

[@willemstark4733]

Exactly. The CFM (airflow) going into the engine is directly linked to the boost pressure. You can not simply say a turbo "has" 15 psi. He also didnt take into account that the exhaust pipe can be relatively cold wich initially draws extra heat from the exhaust gas. I doubt if the exhaust gas speed is correct, did he take into account that it is also pressurized until it has been trough the turbine?

[@Sir_Cactus]

@@willemstark4733 The exhaust gas cools down in the long exhaust. This means it reduces in volume and slowing down. Same pricipal a jet engine uses, but in reverse.

[@willemstark4733]

I did not deny that. The only thing what makes this effect worse was not mentioned.

[@samthing4thetrack806]

Very good! The overall effect is a "lag" but we can slice that up with your definitions. I think this is a very good method for cars that were never envisioned as turbo. There should be some weight loss benefit. As exhaust are very heavy usually.

[@tyquanwashington.8510]

Would love to see datalogs comparing identical cars. One car with remote mounted and the other traditional orientation.

[@techienate]

This guy is an absolutely brilliant communicator

[@ltmcolen]

To calculate the spooling up time you should use the cfm of the engine not the turbo. It will be depend on the volume of displacement, the RPM, the volumetric efficiency of the engine (and exhaust flow, which reduces when lengthening the exhaust) and the inertia of the turbo compressor itself. The last thing is to regard the back pressure on the Turbo. If in any case all the inlet valves are closed, the turbo pressure will increase rapidly but the volume displaced will be 0.

[@Greatdudeguy]

Yeah, he was acting as if the cold side of the turbo is routed back into the exhaust or something. Leaving out that variable makes the whole message of the video relatively incorrect. It is like a game of Telephone because this guy seems to have to heard most of this stuff on youtube and is just relaying it back in the video.

[@meyo1860]

Holy smokes dude! As a child growing up in the 80s turbo era, I initially assumed turbos were rear mounted and I felt like a moron when I discovered they were “hiding” deep in the engine bay! Thanks so much for this video! ❤

[@piccalillipit9211]

Some were rear-mounted, I think the 6R4 had rear mounted turbo's

[@simonroth7126]

Right when I thought I knew how turbos worked and that “duh obviously having the turbos farther from the engine causes lag” you make a new video and I realize just how much I don’t understand! Awesome video!

[@martinfalls1023]

Thank you for killing the myth with straight forward facts. This opens up location and design placement of a new system. Wonderful!!!!

[@Lofi.z34]

Some points to consider: - The long pipes add unnecessary weight to the car. - The amount of pipe connections make a significantly greater risk of getting Boost Leaks. - The hot side of the turbo gets cooled down due to the longer pipes, even with heat wrap or ceramic coating to try and keep the heat inside the pipes. - Mid-mounts (turbo is below and rear of the engine) has been the best single-turbo setup, with proper heat protection. (from the perspective of front-engine cars) My tuner has tuned over 6000 cars and has seen about every type of setup possible. And he says they're a stupid setup because of all the wasted energy, the same size turbo in a mid-mount simply makes more power and has better response in the real world.

[@Lofi.z34]

You mentioned these at the end of your video and I think should have been further highlighted. There's no sugarcoating it, it's a stupid setup.

[@kiddovr3147]

I mounted my Turbo Charger hanging out my passenger window.

[@dylanmorgan5589]

My God you've done it.

[@Reesetrain44]

free cold air intake!

[@shroomsneed3021]

16:10 the relation between heat loss and diameter is linear. At 16:20 . the 2*pi*r^2 is to calculate the area of the the two caps of a cylinder. in a tube without caps such as an exhaust pipe, you are only interested in the surface area of the "wrap" or the tube section. which is calculated by pi*base diameter*length of the cylinder. so the relationship between the diameter and surface area, and thus heat transfer is linear

[@urano1988]

yeah, pretty rough mistake considering the end-caps!

[@anonino_sem_nome]

Consider that when you double the area, exhaust gas will have 4 times more volume to expand and therefore highly decreasing its temperature.

[@stuntvist]

It will still mess with your throttle response though. Many F1 teams have transitioned to a water-air intercooler setup to reduce overall induction system length. Some of the recently demo'd engines seemingly didn't even care about having equal length exhaust manifolds if it meant a shorter overall exhaust valve to turbine distance which arguably is more due to packaging reasons but does also help throttle response. But most importantly, a shorter (and straighter) intake system will incur less pressure loss. The only important "quality" of air for a combustion engine is the oxygen content; since the engine can only consume x volume of air at y pressure, the increase in air volume won't do much or anything at all to increase air density (thus oxygen content) in the combustion chamber and pressure becomes the deciding factor. If you have more pressure loss in your induction system, you will have more turbo lag by default to make the same power as the pressure at the turbo has to be higher to compensate for the losses. This doesn't mean rear mount systems are stupid or make your car undrivable, it's just that they will incur a noticable dip over an equal power setup in terms of responsiveness. The one other benefit for rear mount systems I can think of is that the turbo inlet air temperature is going to be lower than typical engine bay setups. Yes, this can be avoided if you duct your intake correctly, but often people just run a filter directly on the turbo inlet to reduce cost and complexity. Otherwise, great vid.

[@phillgizmo8934]

What pressure losses? If your pipe is sealed, it can be as long as a gas pipeline of million meters, as long as it's filled with "technical gas" for pressure, you get an immediate outcome on the other end when you put some in on this side. Technical gas kind a stays always in the sealed pipe.

[@SupraSav]

The only quality of air that is important is oxygen content? Ok.. So when the intake charge is hotter than expect from, say a heat-soaked intercooler, and you start running into detonation; would you argue that the temperature of the intake charge is not relevant? Oxygen content is not the only relevant thing. Don't spread ignorance.

[@fastinradfordable]

There is NO WAY Intake temps under the car are less than in front of the car

[@stuntvist]

@@SupraSav Hotter intake charge means less oxygen content because hot air is much less dense than cold air. Detonation and pre-ignition from hot intake air temps is due to said temps dramatically affecting final combustion chamber temperatures. It's also one of the main ways HCCI engines control ignition timing, hotter IAT for more advanced timing and colder IAT for retarded timing, with a fairly narrow operating window for usable performance.

[@stuntvist]

@@phillgizmo8934 It's technically not a sealed system and even if it was the fact that you're actively forcing a fluid (air) through it changes the dynamics completely. Any extra length, bends, restrictions (intercooler core, throttle etc) will alter the flow of the air through the system and potentially reduce final air pressure depending on what that piece is or is designed to do.

[@acarzt]

The added travel time for exhaust and intake is ~ 0.1s (100ms) which any gamer will tell you, is absolutely detectable. So you cannot claim that there is NO turbo lag. It is negligible, but not 0. Also, the exhaust gases will decelerate over that distance vs straight off the cylinder head which will affect how quickly the turbo spools up. As you mentioned, you can plan for and accommodate these things but if you just do a direct comparison of the same turbo, same exhaust pipe size, etc. the one in the engine bay will spool quicker (less lag). The differences would be easily demonstrable on a dyno. Which would be much more interesting than a whiteboard comparison.

[@thedingothatateyourbaby9811]

I worked for a shop called CIN Motorsports from 2006-2008. We were the first to install a rear mount turbo kit (from STS) on a 350z. Then the 2nd 350z and then the 3rd 350z. Nobody was doing it back then. No less lag than a front mounted single and all 3 Zs sounded AMAZING.

[@halsnyder296]

I love your explanations!

[@jimmysealander7453]

Great video although i do disagree that a bigger turbo makes more power per default! It will however have a greater potential for higher airflow and thereby power IF the engine can handle and sustain that additional flow. There was a time (in Sweden) when turboing with old semi-truck turbos was popular and cheap, although the engines would not be able to produce enough exhaust to spool the turbine. So adding a smaller turbo would, at that point, outpower the bigger turbo. Although thanks, really like your contents!

[@cannaroe1213]

Turbos are technically engines (heat pumps) in their own right, and can be defined in horsepower like an engine (compressor maps are basically dynographs for turbos). If you have a smaller turbo that makes more power on a trickle of fuel (exhaust) than a big turbo that doesn't spin up with that amount of fuel, well it's probably true the car doesn't move as much, but the bigger turbo should always makes more power for the same RPM at peak efficiency. The AR ratio (one axis on compressor map, equivalent to torque) is defined by the intake/volute circumference difference. You'd never say a 6.6L Duramax makes less power than a 1L Miata, so long as you're stuck with miata injectors. It's like, yah, of course.

[@nickrider5220]

Very interesting info. The first thing I thought was that the turbos and intakes will be prone to damage and water ingress.....I'd driven through 30cm of floodwater this morning, it looks like I would've been stranded if I had a turbo like the ones shown !

[@frankcooke1692]

But if you had to turbos you could go fast enough to skim over the surface of the water.

[@kermitthehermit9588]

Never drive through flood water.

[@jaredlancaster4137]

​@@kermitthehermit9588never say never. Generalizations like that are not helpful. Definitely take extreme care driving through flood water.

[@frankcooke1692]

@@jaredlancaster4137 There is very little difference between 'extreme care' and 'reckless abandon', in any practical sense. Nobody drives into a flooded road with the intention if being up to their neck in water.

[@jaredlancaster4137]

@@frankcooke1692 the difference is checking the depth before you drive into it. I'd say thats a very practical difference.

[@dysfunctionalveteran836]

I've been subscribed to your channel for about 6 months. I enjoy how informative and in-depth your content is. Thank you.

[@michaelcloss565]

Man I fell in love with this video as soon as you described how boost pressure works. How much "boost" you are running is almost irrelevant besides as a comparison on that same car. Can't tell you how many times dudes have been like "I'm pushing 32 psi you are only pushing 16 you're about to get smoked." Well my turbo is much larger therefore moving much more air making more power. All that 32 psi is telling me is how much resistance you have.

[@devlinrawlings3322]

This video feels like a more fun university lecture

[@mickwolf1077]

You explained the boost threshold well, i see it like by having the exhaust longer and losing heat, that'd make the gasses more dense and less volume which means less flow. not what you want to feed your turbo.

[@imblackmagic1209]

the volume stays the same, the thing that drops is the pressure, remember the ideal gas formula, pV=nRT, the pressure is directly related to the temperature in that formula, the gas will occupy all the volume it is allowed to, and the piping has a fixed volume it can take, so at the end of the day, less temperature is less pressure, and the turbo needs that pressure as well you can also add bernoulli's principle into the mix to add in the flow of air in the pipe related to the pressure it's an interesting topic

[@terjejohnsen3651]

Oil to turbo shouldnt be big problem use a Oil cooler and a tank with eletrick pump and you can have a closed setup.

[@mrb.5610]

Complicated. You'll need a high pressure pump for the turbo AND a scavange pump for the drain. More things yo go wrong ! Plus something not mentioned is the extra weight of the installation - especially hanging behind the rear axle. It won't improve acceleration times or handling !

[@DarrenBoxhall]

Hahahahh, what?

[@vintagespeed]

lots of guys run water tanks in the back for heat exchangers so why not? you'd have to monitor that oil pressure in addition.

[@aaronnoyb]

​@@mrb.5610I ran a bed mounted turbo on a 5.7 LS for a few years, single 6-8psi oil pump was all that was required, no scavenging or high pressure pump required. As he said in the video, remote mount turbos run much cooler, so the oil isn't required to do as much cooling, just lubricating. Oil drain ran down into to a 3 quart tank, directly below the turbo, pump mounted below that, discharged through a power steering cooler, then through the turbo. A pressure switch would activate a warning light on the dash, if pressure dropped below 4psi, only a couple seconds on cold start. Ran some super duper expensive oil, specced by the turbo supplier, didn't change it the entire time I had the truck. I carried a blanking plate, so I could remove the turbo core and block off the turbine housing, if something went wrong with the oil system and never needed it. After this video, I think I need to build another one.

[@jiijijjijiijiij]

​@@aaronnoyb As someone who likes the idea of a closed loop as a solution and was wondering what would be required for it, this is really useful info. Thank you.

[@ronaldkiplagat6034]

Even my lecturer didn't explain this much man you're extra ordinary

[@leanspo]

First of all: Happy New Year!! 🥂 Damn! I don't have a car, I'm not planning to buy one anytime soon and I guess I'll never tune it up for track, BUT I enjoy so much with your videos and I'm always glad to learn something new! Keep it up! Cheers!

[@chuckschillingvideos]

I'm thinking that it might be beneficial in a rear-mounted turbo to implement an entirely separate dedicated dry sump and electrically driven pump to drive the oil to feed the turbo.

[@otomoravec1732]

absolutely, great idea

[@DevotedGamer1]

One major problem of the remote rear-mounted turbo is the absorption of dust and debris from the ground into the turbo and damaging them

[@markproper9791]

Nice one! Another benefit is that you could actually run a VGT (variable geometry turbocharger) on a petrol setup. You mentioned the VGT but did'nt elaborate on the fact that you only find them on diesel engines because the exhaust temperature is lower than on a petrol engine. Since they wont survive petrol exhaust gas temps. Would make a lot of sense to remote mount a VGT if the exhaust temperature is about 200-300 Celcius lower, and fix the downside of the raised boost threshold. might even improve it.

[@kirillryzhkov2208]

Porsche utilizes VGT and have for some time now..

[@m4r_y0]

Thank you for all this info, I have some comments: 1) I agree about all the lag arguments, but would also add that air is compressible. That means when you press the pedal, the engine spins, the gas in the pipe will simultaneously compress and move outwards (water for example will immediately start to move). So I think this will also lead to some time delay, and obviously I don’t have data/measurements 2) the 2*pi*r^2 part of the equation is for the beginning and end of the pipe, which are arguably irrelevant in this case of dissipating heat to the surrounding air

[@firstNamelastName-ho6lv]

I'm pretty sure the compression of air just means that it will max out at the speed of sound in air, which is still too fast to be perceptible in 4 meters.

[@jacopovisentin]

Generally speaking you can make the assumption that a flow is incompressible if its Mach number is smaller than 0.3. If we use an exhaust speed of 120 m/s like he did in the video we get around Mach 0.35 so the compressibility is not negligible but would still have a pretty small impact on the end result

[@firstNamelastName-ho6lv]

Yeah I agree, people have felt lag and I think it's all the "imperceptible" different lags building up. When you just add the 2 types of lag he talks about, it comes to 1/10th of a second which is perceptible imo.

[@tyranneous]

Great video... currently in the process of fitting a rear mount turbo to a mk2 golf (it's a long story), mostly just to find out if it'll work. My hypothesis around mitigating issues was exactly as you said - size the turbo appropriately and wrap the exhaust to retain heat - and I've not gone large with the exhaust pipe until after the turbo. A point about the length of the boost pipes - yes, they come from the rear of the car, but traditional engine-bay mounted turbo boost pipes tend to take a trip at least one full circuit around the engine bay. If you add up that distance, including via the intercooler, you aren't far off the boost pipe length coming from the rear of the vehicle... as long as the vehicle isn't a stretch limo of course! One thing I'm doing that's very custom is that I've written/built a boost and oil pressure control system based on an Arduino board (complete with sensors for oil pressure, boost pressure, etc.) so I can match the desired oil pressure best for the turbo, but it means I can run a separate oil system from the engine. If the turbo fails (it's very cheap but readily replaceable!) then the engine doesn't lose oil pressure, and doesn't end up with any additional heat in the oil from the turbo.

[@hilmurleaf8146]

I think they should put a metal mesh screen over the air filter for better protection for the air filter so dirty air doesn't blow in easily

[@woodstockresinworks2972]

Brilliant vid!! It’s the vid I’ve been waiting for for 3 years! I built my own rear mount turbo set up in my 306 and have endless idiotic and depressing conversations with people who don’t know what they’re talking about! I shall now just reference this video. Thank you!!! 😀

[@pxgstudios]

First time seeing your videos. Its very clear why you have 1M subscribers. Concise, straight to the point, well educated!

[@Djsj1313]

I had a sts remote turbo kit on my 04 z06 there was no lag, no problems and it made 550hp to the wheels and sounded amazing!!

[@damianblazevic1518]

I was watching this and waiting to see whwre you were going with this. You nailed it. keep the pipe small and as hot as possible. the turbo will always lag when its cold. ceramic coat and wrap over the top works very well. count to 30 and you'll hear the boost build up and it'll stay on boost. nice work.

[@dagra55]

I never thought about a rear turbo set up, but bc I want to keep my a/c in my 97 using a K20 this might be a better way to go. The only real drawback I can see, other than mildly more complicated, is the increased boost threshold. But it's a civic....so I'm committed to all the RiP'uMs. Bc of the higher rev limit I can build back what's lost, cook the RPMs, and still build a considerable amount of boost. It will always be my daily and eventually, pre turbo, I'm lifting it 3" so clearance isn't an issue. With enough complicated math on the air volume you can fine tune piping diameter for best results. Also increased noise‽ The entire purpose of a turbo is for the whistles, whooshes, and most importantly the STUUUtUuuutuututuus. Great video this offered a solution to my build complications.

[@kasotty]

Nice I was actually debating between turbo and supercharger, this makes my life so much easier. Thank you

[@tksperformance8789]

Modern turbos surely help eliminate lag but not without being combined with modern turbo engines which much higher compression ratios and better flowing cylinder heads.

I've always been on the fence about remote mounting due to what I assumed would be a rubberband effect. Not so much lag but the the length of piping and the times when the throttle is moving, there would be moments when all of the piping isn't charged uniformly, this making tuning a remote setup to be streetable hectic. After watching this video, I'm now more open to the idea of remote mounting 😃

[@eVerProductions1]

Damn dude you really blew up and I’m happy for you!! I remember back 2 ish years ago you just explaining engine stuff and your mr2 project and now you almsot have 1million subs

[@turbojoe9554]

big problem with long piping is condensation and therefore rust. Water is a normal byproduct of combustion of gasoline. You see this on cool days, as steam out of the tail pipe. The longer the pipe the more surface area there is to dissipate exhaust heat, thus it's entirely possible to get a good bit of water in the system. Cars driven on short trips will puddle the exhaust system; leading to problems.

[@FullBoostJ4]

I did a super budget rear mount turbo build on my Lexus LS400, even with my (very) limited gabrication skills, it was highly satisfactory and ran a reasonable 6lb of boost with very little lag. Now I'm going to do it again bigger, better and twin!!

[@HBLOS14]

This man is so intelligent and explains things so well he makes you feel like an auto engineer

[@Bruuhhhhhh]

I love how easy to understand you managed to explain the entire topic and the reasonings behind it. Amazing stuff !

[@michaelncounselor5412]

One of the best explanations I've ever heard. Bravo my good man.

[@64BitMatt]

Thank you!!! ive been getting so much pushback on wanting to rear mount my turbos!! now i'll send them this!

[@d4a]

They likely won't listen 🤣But send it anyway, you never know. There will definitely some kind of reaction 😁

[@NBC_NCO]

I have a buddy with a 2004 Corvette and has a twin turbos rear mount setup. He Dynoed over 1,100 rwhp. His primary reason was to keep the engine clean and easy to perform maintenance.

[@ekyu88]

Thank you for your exceptionally clear explanation of turbo addon to engines. This is very rare so keep up the good work!

[@J4NOObs]

dont normally sat this but im only 3 mins in and ive already learned so much lol

[@TheNotsnot]

Completely unrelated to content, but a big attaboy nonetheless: I'm partially deaf in one ear. -30dB, with a hard cutoff above 1kHz. Generally I can't understand people talking to just my bad ear. However, you speak so clearly that i can completely understand you using only that bad ear. Kudos!

[@It_Is_I_I]

I hadn't even considered the possibility of a rear turbo, this genuinely opens a world of possibilities

[@BoogieManSince1977]

Your vids are quite honestly, Spectacularly good and clear and well reasoned, love your work, thanks

[@bavarianstreettool]

Just listened to Christoph Waltz tell me about remote mount turbos for 20 minutes and loved every second.

[@caywo_]

I still can't believe how good you are at explaining. You're amazing!

[@xenasloan6859]

just love this guy's intellect, delivery and subjects...