Understanding Exhaust Back Pressure for your Turbo Set Up. How to Monitor it and What to Aim for

[@davidarthur6205]

thank you so much for making these videos Jay. no nonsense facts presented clearly in a logical fashion. great work man!

[@realstreetperformance]

Thanks for watching and interacting David

[@Drtyred313]

I can’t explain to you how important this video is…🙏🏾🙏🏾🙏🏾

[@TheCarPassionChannel]

Very valuable information for anyone debating over turbo size!

[@1knowsnothing1]

G Regs! If the price is right, “Main Caps” for 600 please.

[@TheCarPassionChannel]

@@1knowsnothing1 Hahaha

[@realstreetperformance]

Thank you for interacting!

[@davidwisowaty1914]

general rule ive gone by - when you’re turning up the boost while tuning - when the boost starts to taper down in the upper rpm’s you’ve hit your max desired efficiency of your turbine / or hot parts setup. this was nicely described by you with the graph. as always, thank you for teaching us in depth material.

[@chippyjohn1]

your compressor could also be too small

[@1knowsnothing1]

Never overlook the basics! Thanks for the knowledge drop.

[@realstreetperformance]

Thanks for stopping by

[@smooth_ops2942]

When i was about 5 years old and eager to learn fluid dynamics in a vacuum vs atmospheric pressure. My grandfather explained it to me between puffs on his cigarette, and it went something like this but simplified down a little for ease of understanding. Firstly, you have to understand the basics of tangent reflections on uncompromised and unpolydestant substrates which are usually half gated but always full duplexed in a 1bar setup... This is common knowledge that im sure you know but we have to start crawling before we start running. When throughputs are equal from vacuum to pressure or from load to unloaded, preplexed viscositys always stay at a state of bi-lateral stonosis unless ion saturation creates a caustic situation then flow is always at a positive rate. RP1 jet fuel used in space x raptor engines uses a full flow open combustion process which creates around 275psi of throat pressure under 110% full fuel flow. Now this system is a simi-agnastoyic reference based (mechanical) system, it is comprised of dual momentary as well as multi staged pulse sensors for a closed loop ➿ system for dynamic flow control with nano second active duplex modules for total system control from start to finish. Now if you have made it this far reading this mumbo jumbo of word diarrhea that makes zero sense completely... Dont feel bad for wasting your time as i just questioned myself to why the f••k i wasted my time writing it and questioning my life decisions from this point. But if you tried to imagine how any of this would work as you were reading... 👍🏻

[@mohammedabdulla1774]

What are you saying

[@Tonynolie]

I should have known then you started with “When I was about 5 years old and eager to learn fluid dynamics”

[@MBSLC]

Thanks for mentioning the F1 Turbo Era. The BMW 1.5 litre twin - turbo four cylinder engines would make 1,200 hp+ when tuned for race qualifying. The turbo lag was legendary so it was quite a learning curve for the drivers coming from the instant throttle response of the naturally aspirated machines. Great video!

[@chpsuey]

Jay's such a wealth of knowledge

[@RidinDirtyRollinBurnouts]

This is great info I never took into consideration. The fact that one bank runs hotter than the other on a single setup has convinced me to invest in the cooling crossover mod for my car, since my engine is notorious for overheating the back 2 cylinders on forced induction

[@aaronphx420]

Jay is the man! He knows quality and his company is full of it(high quality) :-)

[@rcravincase]

I never paid attention to how the grand national manifolds were setup. I built my own headers and y pipe for a turbo 3800 and was surprised to see gnx power levels at half the boost. Seeing how the are setup, i bet that is why

[@sazzyPheox]

I have a supercharged 3800, is exhaust back pressure important for a supercharger?

[@rcravincase]

@@sazzyPheox yes. Less restriction, less pumping loss, more power

[@GW2_Live]

@@sazzyPheox Supercharger is mechanically driven so much less impact, people obsessing over backpressure usually have other things they should be worrying about first. backpressure is high level stuff IMO

[@FakeJeep]

I've always explained it via "Back pressure bad" "Velocity good" because somewhere, at some point, someone said cars "need" backpressure and then anyone reading that thinks "oh, so back pressure is good". This gets worse to the point that people will argue against larger exhausts because they'll "lose" backpressure and expect to lose power... when their tiny exhaust pipes were making the engine work harder and sacrificing power. Literally had arguments where people thought they'd lose low end torque going from a 1.5" to 2" exhaust because of the above... God my head.

[@rcravincase]

I beleive the "back pressure good" started when people would install a free flowing exhaust and headers and not jet the carb correctly, thus burning valves

[@ACommenterOnYouTube]

Changing the exhaust system diameter only moves the power band to a different area.

[@markrich3271]

Back pressure , drive pressure, boost pressure and crank case pressure aka blow by are all different elements. Just like your intake, different runner lengths and size increase / decrease and move all the pressures associated with a turbo. Just like turbine housing . You can go to large . If you go to small or large it will destroy power.

[@ACommenterOnYouTube]

Well when i removed the stock exhaust manifold and went with a larger diamter 4-1 header, i LOST all my low end torque that i had before but my top end increased dramatically ... So it didnt loose power, it just shifted the power band.

[@FakeJeep]

@@ACommenterOnKZbin definitely depends on setup as the ones above said. For me mine was heavily restricted, so I gained both power and torque going to a larger pipe, but I also didn't go from 1.5 to 3.0 either... Seen a lot of people that just go from 1.5-2 to 4" and murder their low end because they lost velocity and scavenging. It's a balancing act that most companies figure out for you, until you start going custom and higher on power.

[@gadgetdeez7069]

No bullshit advice from this guy. Love it! Keep it coming buddy. :-)

[@MrLangleylad]

Great info ! you lay it out pure and simple that even I can understand it ! 😂 Thanks , I learned something today

[@idus]

I am in the process of building a v6 turbo maniforld to fit in the mazda b2200 and watching this solidified my thoughts on routing. Mistake averted, thanks for explaining this.

[@01sidiropoulos]

I love how simple and correct you talk about engineering.. Keep it up!

[@reubenmorris487]

Too bad Jay is barely presenting the syllabus in these short videos.

[@gammalight1312]

Always something new to learn, thank you!

[@chadbenjamin8118]

Can't enough of this....Thanks for the tech video Jay.

[@Neomustangs]

What a great explaination. Thank you.

[@realstreetperformance]

Thanks for watching and commenting. I appreciate the support

[@7Sin0City2]

Good looking on the informational video!

[@sircefiro]

Thanks, maybe a bit more about exhaust housing & exhaust pipe size effects would be good too

[@marcocoetzee6880]

Thanks for your good advice.

[@nela5596]

Thank you Jay for making these videos, please talk about crappy turbo manifold wastegate position designs but with amazing pretty welds, we have way too many of those around and ppl have no ideas why their car is overboost lol Keep up the great videos!!!

[@jaymeagher1510]

Noted thanks! The worst thing about cheap manifolds or crappy welds is the risk of slag breaking off and killing the turbo. Doesn't get much worse than that!

[@tagperformance]

Jay always coming with the knowledge

[@kammoperformance]

Awesome video!

[@jedpratte]

I see many overlook this. Most set ups are power limited on turbine side and flow not intake side. Played with compounds on diesel trucks many years and learned the impact of exhaust back pressure is huge at high boost levels.

[@turbo32coupe]

Street cars are more fun if you size the turbos for less lag versus more power. If you size the a/r or turbine of the turbo a little small, boost comes up quickly, at the cost of higher back pressure. I run twin Garrett GT28/76 turbos on my 4.6 L cobra motor and get full boost by 2200 rpm. It feels similar to a positive displacement blower, but is more efficient off boost. It makes more power over the entire torque curve than a centrifugal supercharger.

[@jaymeagher1510]

Those are little units! I installed a handful of "Incon" turbo systems on 4.6 Fords and they were always fun to drive. There's certainly a sweet spot, I don't get too caught up in what's happening at less than 4,000rpm these days, I'm just not down there when I'm beating on the car. Thanks

[@mr.c5217]

what size A/R?

[@turbo32coupe]

@@mr.c5217 0.86

[@turbo32coupe]

@@jaymeagher1510 Mine is a street car, makes full boost by 2800 and holds it to 6000. Has a 4R75W and converter that handles the power. I had to turn down the boost to keep the tires from spinning.

[@mr.c5217]

@@turbo32coupe I have twin .73 compressor housings on a 427 I already know I need to go bigger.

[@ThomasTT496Vega]

No one does a technical information video like Jay!

[@kdsboosted4954]

We do this information with charts and dyno run on Richard Holdener live every night at 7

[@Sleeperdude]

Great information thanks for sharing

[@awd_gli9632]

This episode deserves another 30m or so.

[@jaymeagher1510]

We try to keep them as short as possible, but I agree. We could talk about pressure ratios for a long time! Thanks

[@chrisvandy3864]

Awsome video again Jay , wish I lived in the USA 🇺🇸 Cheers Chris QLD Australia 🇦🇺 👍

[@VRMN8R]

Man!!! That was a great explanation Jay, Im turbo stupid and that really made a lot of sense. Thanks for the video.

[@SPTuning]

Great video. I love these tech breakdowns

[@mjaymo]

Brilliant as always thank you

[@BalticSupraRacing]

Awesome video guys. Super easy to follow along.

[@justbeastit]

Great video! Can you do a video on how airflow and power are affected by larger valves and multi angle valve jobs?

[@ACommenterOnYouTube]

Multi angle valve jobs just allow the air to flow smoother around them, larger valves allow more air to pass .... no video is needed

[@ThomasTT496Vega]

Good things will happen! Both increase air flow. When air flow is increased power will go up and boost pressure will go down. Then you can crank the boost back to where it was!

[@justbeastit]

@@ACommenterOnKZbin Thanks, that's fairly obvious but I was looking for more detail about if/how it affects spool up, what power goals it really makes a difference for, etc.

[@ACommenterOnYouTube]

@@justbeastit well next time be specific on your question and dont ask a general question when you need a specific answer ...

[@jaymeagher1510]

I think this is highly dependent on the pressure ratio you're operating the engine at. You also have to consider will the engine benefit from larger valves if the seats are stock sized. Valve jobs should be done with longevity in mind over air flow, thin margin valve jobs are short lived in turbo applications due to heat. Thanks

[@allanmakkink8404]

love the Cleetus McFarland ref lol

[@jaymeagher1510]

He's certainly doing it big and having fun in the process!

[@damianbogle8332]

Great info here as usual Jay.... please continue to pass on your knowledge for us.... 500 years from now someone will be doing a search.... and this info will prove informative...lol

[@BleedingSnow]

Thanks for the clear & educational explanations =)

[@richardknight1258]

Always a fan 🇯🇲

[@snake10566]

So happy with the Cletus reference here.

[@CMReid]

Explained very well! Thanks 👍🏼

[@josephschmier3733]

Thank you BOSS

[@Robert_Mantei]

Excellent video

[@bigdiffas]

Having EMP gauge it is also good insicator if you have some failure going on.. for example boost leak. With boost leak you have to drive turbo harder and that means higher EMP.

[@jonathanmoore5929]

Running a log system on my colorado and i’m fitting back pressure. 40lb on dome to make 25psi of boost and back pressure is at 40

[@danielthompson3849]

Bmw megatron. 1500cc. 83psi of boost. With waste gates removed for Two laps of qualifying at 1400hp If it didn’t melt engine or blow the gearbox case to bits

[@TurbineResearch]

Solid Video 👍

[@FredAllenBurge]

More BP = faster spool and a better street car or daily. But limited in boost pressure and RPM of course. What the aftermarket still badly needs is variable geometry turbine housings🤷‍♂️

[@tagperformance]

They already have that its called variable vane turbochargers

[@3rweldingandfabrication375]

Ford used them starting late 2003 vgt turbo worked good as long as it was maintained to prevent sticking vains

[@GW2_Live]

I have a grand national, thinking about doing a modern turbo manifold setup, a lot would have to be moved, but it's totally doable I think

[@curlracing276]

I had what I think was a super high back pressure issue on my blow through sbf with an on3 88mm turbo with a way too small .96 hotside housing. It made above the advertised power of the turbo but the engine wouldn't make power past 5,800 rpm and would just flatline on the dyno at that rpm. Changed everything we could including valve springs to help it and got it to go to 6,000 rpm. Talked to the carb guy and he suggested it was a back pressure issue which makes sense with the signs we were seeing.

[@turbo32coupe]

I suggest you change the A/R of the exhaust housing to something like 1.3, or switch to a turbo with a bigger turbine

[@turbo32coupe]

Also, if you have high backpressure you need to retard the cam, or increase the LCA to reduce exhaust gas reversion into the intake.

[@curlracing276]

I did go to a bigger housing... 2 this time actually. Went from a single .96 to twin .91s and dual 4" fender exits. Havnt had the chance to run it yet but should free up some exhaust flow and reduce that back pressure.

[@howididitgarage.]

Thank you for your information sir.

[@MrTDM09]

Miss the tech tips videos, Jay!

[@mervynmontague1811]

Very interesting and informative 🇯🇲

[@DanielShipley]

One thing I think Jay left out was a discussion around how camshaft choice can make a big difference. As an example, if you have high backpressure, you can choose a camshaft with lower overlap to prevent blow-back, etc. Maybe the video was intentionally kept short/high-level, so as not to dive into more technical discussion.

[@jaymeagher1510]

You're not wrong and that approach was commonly used in the Grand National world. When you look back and see the turbines they were using on 3.8L engines it's no wonder they were short on exhaust duration. I'd like to have the best running NA configuration with respects to compression ratio, then add boost. Thanks

[@DanielShipley]

@@jaymeagher1510 Yes, we've learned so much in the ensuing years. Back in the early days of turbocharging, outside of the heavily engineered world of F1, backpressure was a complete afterthought on most turbo installations. Now days, we're careful to use equal length headers, split exhaust pulses evenly using split turbine housings, expansion chambers post-turbine, merge collectors, high flow exhaust or dumps, coated hot parts, even "hot valley" designs with the exhaust in the valley of the engine to put the length and heat as close to the turbine as possible, etc. The turbines and compressors have gotten so much better too. One question about building the best NA motor and adding boost: How do you see the trade off's between an engine having high CR and a small chamber VS low CR and a larger chamber? The first will be more responsive, but will be more boost limited with respect to knock. The second will be less responsive, but might have more power potential given the same fuel/knock limitation? Perhaps you would pick based on the application and fuel used? It's an interesting trade-off. Perhaps you could discuss it in a future video?

[@jaymeagher1510]

@@DanielShipley Yes, times have changed. The boost levels are substantially higher these days for the common man. As far as CR that's why I mentioned "respects to compression ratio" as you don't want to build a rattle trap. I'd take the lower compression ratio and slow chambers and enjoy the safety that giving up 30-40hp I'd achieve with the higher CR. We will be doing a compression ratio test this year on the dyno, it should be interesting as we're going to do the test on alcohol and gasoline. Thanks!

[@5PYZ3R]

I need to do some research on this, any sources you recommend? I'm planning to use a small T25 turbo with a big-ish 272 cam on my Honda. initially I was thinking the big cam might help with power on the top end when the turbo starts to fall off, but now that you mentioned this maybe it will have the opposite effect. I already have the cam so I guess I'm going to find out lol.

[@DanielShipley]

@@5PYZ3R Just try to build as minimally restrictive exhaust as possible. If you can make an expansion chamber right out of the turbos on the downpipe, that helps. Oversize the exhaust if possible. Use straight-through mufflers. Use an X-pipe (for a V8) and a split housing on the turbo with the exhaust pulses evenly distributed between the sides. Use a merge collector on the turbo. All those techniques help make the exhaust more efficient and reduce backpressure.

[@jonathanparker5375]

Whoa that helped a ton. 🤯

[@streamlineperformancevideo1926]

Nice Video Jay!

[@Vkandypaint]

Great info thanks!

[@weduhpeople8504]

My built motor on my 2018 Honda Civic type R which has a ewg Garrett 30-770 .82 a/r housing. In had the head port and polished where Tom @ Portflow opened up the fuel tumbling oem design aimed at fuel economy. It’s been opened up to flow 300cfm as opposed to 150-160 cfm. Valves are off the shelf standard size Ferrea valves and single springs. The only thing I didn’t do was replace the camshafts which I plan to do in the near future which I would think with a middle of the road higher lift and duration will help the motor’s efficiency but not moving the powerband to much to the right. Being that the k20c1 is a single port headafold I would think that makes the exhaust gasses have more velocity which helps in response. Would this head design help with efficiency? I also modified a Japanese titanium exhaust with 70mm piping to 80mm ti piping. Im sure that helps reduce back pressure. Im currently at 686 whp 585 ft lbs on Motec M142 which I bought from you, Real Street, port injection, DW300c intank pump to feed a Nuke performance surge tank with a DW300 inside to the di and a Walbro Hell cat 535 to port injection ID1700, 4 port mac solenoid, speed density, Flex fuel but pretty much use full E85 which my gauge says 79% ethanol content.

[@aaronschocke2147]

"...And now you are operating at a 2:1 pressure ratio, and that is not favorable..." *laughs and wipes tear as I throw my GM-8 turbo in the trash*

[@kluc10001]

I love yall thankyou

[@aaronliddell4280]

So would you want to mount the exhaust pressure sensor between the turbine housing and the headers (like in the Y pipe)? Or in the down pipe after the turbine?

[@realstreetperformance]

Between the engine and the turbo

[@ACommenterOnYouTube]

Did you NOT watch this video ??

[@ToolsOutsideTheBox]

Yes yes. Supercharge it AND have a fat turbo!

[@seansackman3909]

Bought a used built 2jz in a Is300, I believe the ECV valve that he had installed and got stuck closed. Didn't realize this and took the car for a spirited drive and found the car to be over boosting, set at 14 and was reaching 17lbs. When I parked I popped the hood and found some smoke from the turbo and oil leaking from the compressor. Just wondering how much damage you figure I did to the turbo? Borg warner efr 9174

[@LynnDisclose]

I got a 10th generation civic hatchback 1.5 turbo, I got muffler delete, vibrant resonater. 2.5 piping from resonater to end of exhaust. And a high flow engine filter. I got a 3inch front pipe that I have not put on yet. I can get a j pipe to eliminate drone right? What do I need for a good set-up

[@marleynugent2236]

Your brain is huge, love your content, just wondering if you have ever had a look at the all mighty Aussie Barra? If not I’d love to see a video on it

[@jaymeagher1510]

Ha! I don't know about huge, outside of cars I'm pretty boring! I've only seen one Barra before. I was taken back on how small the ports are but given the long stroke it's likely OK as it's native design was for low speed power production. Super neat engine to drive around, I bet the response is great. Thanks

[@Dodgevair]

Garrett's turbine exhaust flow charts.....I noticed that you can use Borg Warners turbo selector (Match Bot) to produce exhaust flow numbers (lbs/min) which can then be used in the charts. How do you correctly use that data along with the charts when choosing different A/R housings? I assume you would need to chose a housing where all the points fall below the lines(pressure ratio by turbine flow) in the chart? Or does something else factor in? thanks!

[@samuelmdouglas]

I've always wondered can you use a smaller secondary wastergate to bleed off unwanted exhaust back pressure, still retain your normal wastegate but have one that works directly with your back pressure sensor, even and electric one like the turbosmart e gate that can be controlled by the ecu when the pressure ratios get too high?

[@jaymeagher1510]

You can manage the back pressure with the same gate you're controlling boost with. If you wanted to geek out about it you could just target a pressure ratio and let the rest be what it is. Thanks

[@samuelmdouglas]

@Jay Meagher thanks mate

[@BulliKid]

Can you tell me why the excessive back pressure is more likely to result in knock??

[@thechicanoreview6662]

Great content! Will doing a muffler delete to a stock turbo car ruin the back pressure any way or what would be the cons? Thank you!

[@dannthenitroman]

Absolutely no downside UNLESS it affects the tune outside of the appropriate range.

[@gl5960]

Thanks for the vid. Can an axle back exhaust that has less back pressure than stock cause a reduction in initial acceleration at city speeds in a turbo charged car? This is what I am experiencing since I had an after market axle back to my turbo charged car. Any thoughts on why this might be happening? Thank you.

[@LynnDisclose]

And would a 2.5 straight piping be good rather than a 3inch for 1.5l turbo

[@onurtanriverdi17]

Hello i have watched your video but i have got issue with my car maybe you got some ideas about it. I have got bmw b58 engine gen 1 car. The car completely stock never been tuned recently i had crack on oil filter housing my garage replace the part with oem part how ever after that when i drive the car in sport or sport plus 1-2 mins turbo get glowed( red heat) there is not any power loose or any engine management light computer does not show anything asweel what can be issue have you got any idea about it? Thanks

[@pt0wnweaver227]

Would increased back pressure cause spikes in RPM? I’m running into a weird thing with my truck where I’ll be accelerating in low gears, 2nd primarily, and the rpm’s will jump up beyond the throttle I give while my turbo boost pressure goes down. Any ideas would be appreciated

[@ricepony33]

Love to hear your thoughts on a turbo setup for a road race application.

[@jaymeagher1510]

I think it's certainly gearing and the ability to manage average power. Years ago I tuned a S2000 that the max HP for his weight was 280hp so we used a small turbo and ran more boost down low than at high RPM. It was very effective. The power selection part is much easier than heat management in road racing, the heat can really ruin an event. Thanks

[@ricepony33]

@@jaymeagher1510 Thanks Jay, I would almost think an oversized turbo setup running low boost would reduce the heat.

[@Mugenkidd82]

I'm currently building a turbo b18c1 in my 93 Si.. Head is built, all new valve train by Supertech. Integra Cams, buddy club cam gears, skunk2 alpha rods, intake manny, and 70mm throttle body and Stock crank. For now..Goal HP is 300 on pump gas and 400 on E85. Any suggestions. On turbine size.

[@MarcMonson]

what kind of pressure ratios do your high hp 2jz run?

[@dj4monie]

1:1 and spray it!

[@jaymeagher1510]

@@dj4monie That is the move!

[@jaymeagher1510]

It depends on the turbo and boost level in respects to heat. At some point intercooler comes back into play once you're over 60psi or so. Then you're really trying to manage inlet heat and back pressure. Thanks 1.1 is always nice.

[@fredeg894]

Gems always

[@sfayer90]

Has Jay done any videos on 2jz camshaft selection?

[@jaymeagher1510]

No but I've tested most cams on the market. I use the "272" range for 70mm and less turbines and the BC276 for larger turbos. On the dyno that seemed to offer the best outcomes. Thanks

[@joker8541]

I have a problem, I think, turbocharger. Exhaust back pressure it is 4500hpa? Or this normal

[@MafiaboysWorld]

TL'DR version: Too much back pressure? Add more turbo(s). 😎👍 As Jay said, it's a balancing act. I'm also old enough to remember F1 in the 80s, so I know with my street car that I want stupid quick turbo response but I also want stupid power up top too, so I'm going twin 2860 with .82 rears rather than a single big turbo like a 7675. Maybe I'm wrong with my theory, but I'm doing something individual and that's the point of car building, doing something different and unique. 😎👍

[@christoforos82]

I share your idea and I am doing something similar on my car. However my principle is different. My setup is two stage turbocharging, initially in series and then the big turbo is individual. The small turbo (for low rpm) is KP35 and a bigger is VJ23 (high rpm). The engine is 2L. For this setup to work, it is necessary to have a capable and efficient valve to switch the exhaust gasses between the turbos and the same time the inlets. I think this applies to your setup as well. My set up is built and I performed some runs. I used to run only with VJ23 and achieving boost 0,16bar@2500 and rising slowly until 3700rpm (full throttle) and then rapidly increases. Now with KP35 I get 0,54bar@2500 (full throttle) until 0,6bar@3500 and dies. Then I am switching turbo by pressing of a button on the dash. In the future will be automated. Of course the small turbo kicks in much faster and builds up pressure form around 1300rpm. It sounds awesome also! :)

[@MafiaboysWorld]

@@christoforos82 Nope. Yours is a compound turbo, mine is simultaneous twin turbo. We are not the same. 😎👍

[@mwelke90]

What about High Back Pressure and valves kept open due to stock Valve Springs?

[@jaymeagher1510]

It seems like most of the damage that occurs on exhaust valves is heat related. If you think you're floating the valves you should inspect the valve tips/seats and lock areas. They're generally there to tell you what's happening. Thanks

[@hydrocarbon82]

What he doesn't mention: if you are hitting your power goal (traction, parts strength, etc), have enough fuel system overhead left, and aren't knocking - BACKPRESSURE DOESN'T MATTER. A massive turbo making 600hp will be slower than a small turbo making 600hp, the later just needs more boost due to backpressure. He also doesn't mention those F1 cars didn't use incredibly oversized turbines to minimize backpressure - they picked the right size that hit the HP goal/limit but still spooled before the next corner.

[@AlxGTR]

You did not explain what the main cause of why back pressure is created? What happens when a compressor runs out of efficiency? Wastegate is then closing to try to raise the boost and all of the exhaust flow goes to the turbine. So if we can have the wastegate open all the way to rev limit backpressure will stay low and to make that happen we need a bigger compressor. Turbine housing size is mostly important if we want good response at low rpm and nice driveability. The back pressure sensor is a good way to tell you if you are running out of compressor or if your wastegate is too small.

[@futten3230]

so 1:1 ratio is best but what happens if you have 2:1? MY BUICK 231 seems to land on 2 bars of backpressure no matter the boost i set on the wastegate so i need a turbo with a bigger exhaust housing?

[@turbo32coupe]

Yes, or a bigger turbine. 2:1 is acceptable if it only occurs at the end of the rpm curve. You could retard the cam or increase the LCA to reduce reversion.

[@futten3230]

@@turbo32coupe on my engine it seems like its constant we havent been able to do any rall dyno pulls because of tuning issues as its a blow through carb setup but as soon as the throttles goes on its 30 psi of backpressure vs 7 to 15 psi boost

[@jaymeagher1510]

It's a fairly low reving engine that I would use a no less than a 6766 on and more likely a 6870. With a well matched converter they make great drivers. IMO the large majority of GN engines are under turbo'd with that funky Y pipe insulting the whole show. Thanks

[@futten3230]

@@jaymeagher1510 i m running an automatic specs on the turbo turbine 65 mm ind 56 mm exd compressor 70 mm exd 54mm ind a/r .63

[@jaymeagher1510]

@@futten3230 Yes sir, that's a little turbo! You can easily step up to a larger unit and it will still be very responsive.

[@TRexx47]

Here we go another video .

[@BuyingTickets]

Yeeeee

[@rolandotillit2867]

Too much exhaust back pressure causes sonic choking, two ways to mitigate choking, increase cross sectional area, or reduce gas density.

[@kylecurry6841]

Awesome Jay! Symmetry and/or equal-length exhaust manifold tubing keeps temps more consistent across banks (assuming your engine has banks of cylinders). Question? Wouldn't the pressure from the hotside naturally be higher considering you have high pressure air/fuel now exchanged to hot gases, hence extreme temperature creating a higher pressure then before the Air/Fuel mixture is burned? When it comes to the turbo's cousin, the jet engine, I've always presumed the expanding gases (despite air being compressed prior to meeting the burner) being the driving force keeping things going after the engine is started.

[@jaymeagher1510]

Hello Kyle, the pressure on hot side is clearly higher in the cylinder but once it's in the exhaust port/manifold the pressure ratio is dependent on turbine flow. For example a 7675 on a 3.0 Supra will be under on EBP until 30psi or so of inlet manifold pressure. Thanks

[@kylecurry6841]

@@jaymeagher1510 thanks Jay! Yeah I realized after posting that although thermal energy is at play, temperature and pressure are still two different things

[@eustacebanks6496]

You bird box me every time lol

[@hm-ys4ym]

👍

[@Turbogto_guy]

You never mentioned something very important. The bigger the engine, the worse the problem becomes to control. Richard holdener touts that a 1000hp turbo will make 1000hp on whatever engine, but that’s not true at all. My buddy dynoed his car yesterday, had a turbo capable of making 1200+ but it ran out of steam at 18 psi. Made like 780 at 18 psi and turning it up to 25psi only netted 815hp. He has a 383 cubic in ls engine. A 5.7 or 6.0 would have made more. Hell a 5.3 probably would have made more.

[@turbo32coupe]

To make 1000 hp at 18 psi, you need an engine that makes about 500 hp NA. Very few 383 cu. in can make that. 780 hp suggests the engine only makes 370 hp NA. If it is a Chinese turbo, they never make their advertised flow numbers.

[@Turbogto_guy]

@@turbo32coupe this is a race car. I assure you this engine makes 500hp na at the tires. Big heads. Big cam. E85, yea a big China turbo. I think it’s an 88mm.

[@jaymeagher1510]

It's easily seen in the pressure ratio and I do agree that you can't tie a "1000hp turbo" as a blanket statement. The engine displacement and turbine flow are certainly dancing partners. Thanks

[@ACommenterOnYouTube]

5:00 Today in 2022 .... its STILL being done that way 🤦🏽‍♂️ .... They design it just like that, one side of the engine has a direct path to the turbine while the other side of the engine is T'eed into that 1st collector just like a wastegate dump tube would Tee into a downpipe ... and THATS what causes huge back pressure and boost creeps. It works but its not an efficient design. That last picture of both "headers" should route directly and combine AT the turbine inlet like a twin scroll turbo. Like he said, Cleetus, all that $$ & trying to get into the 7's yet your design is shit 🤦🏽‍♂️

[@jimhiscott2918]

I wish I knew a 10th of what Jay knows. That way maybe I could stop painting the payment with engine parts!

[@pullmyniblets]

Easiest way to stop back pressure....Screamer pipe

[@markrich3271]

That's what waste gates are for too. I don't want to drive a lag monster .

[@Nyfloridaboi]

Idc if I'm on a 1st date and she looks like Jay with a wig on. If she talks to me like that...... I'm taking her home! 😘

[@jaymeagher1510]

All I need is 7 million USD. That's my number!

[@JMAC479]

Backpressure is resistance, backpressure loses power

[@soconoha]

No, thank you, Jay.

[@1986kojikoji]

I dont understand