The TRUTH About Boost Leaks: Find Out How Much HP You're REALLY Losing! (Suprising Results!)

We all know boost leaks are bad and can wreak havoc on any forced induction system, but at what point will you start to see a measurable power loss. In Todays video we answer an age old question, what happens when you have a boost leak in your charge system? We tested it and the results were so interesting!
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[@BrianCrofoot]

Turbo speed can go crazy with boost leaks which is very important when you’re already pushing the turbo speeds up near peak recommended rpm’s. This is a badass video. Loving your guys content lately!

[@jeffkoch8612]

It NEEDS to be noted that any car running a MAF will see much more substantial losses, even at 1/8 or smaller leak.. This is only applicable to cars running speed density engine management; which no modern turbo cars run from the factory. Small leaks are HUGE on MAF cars

[@ninjatech123]

Beat me to it!

[@danielwelsh1114]

Mote data to compare would be to log the duty cycle the waste gate solenoid is operating at, at each hole increment.

[@DrCrunkMusic]

Yeah and compare that at set rpms. We can see how efficient it's operating with the leak rather than peak output. Great comment

[@nyftn]

i was thinking something similar .

[@pharmztko]

Makes sense,, I’d be curious to see how much more of a difference those leaks would make when you’re pushing 40-50psi boost vs just 15psi boost

[@Ajhowardz32]

Me aswell because my 2JZ had a missing bolt on the compressor housing, 2 leaks at Vaccum lines, and I only made 538 at 31psi on E85 I just got the leaks fixed just waiting to go back to the dyno to see what I’ll make with my leaks fixed

[@StavTech]

way more, this test makes it seems not as bad as it can be due to the low boost they ran

[@PRZJ91]

I think that psi would over spin the turbo and cause it to explode plus the engine would end up knocking because of excessive backpressure and tbh doing that on purpose is just bad lol they don’t wanna blow up the motor so no need doing it at that high of boost pressure.

[@Baard2000]

​@@StavTechyou are completely right. I do mainly tractor pull diesel head preparation. If a piece of gasket is blown out of e.g. 20 mm width and 1.25 mm thickness .... power is gone. They run 6.5 bars up to 10 bars with a single turbo...... one bit air gone and the engine runs so fat it is flushed with diesel instead of burning it...

[@StavTech]

@@Baard2000 exactly. From personal experience of boost leaks on tuned cars, it’s generally way way worse than this video makes it seem

[@theatomproject007]

The area of a circle is not linear so going from 1/4" to 1/2" is expected to be much more than double the loss. Just note that it's easy to see a 1/2" hole as an obvious boost leak, but 0.19635in^2 is an extremely small crescent of a 2.5" boost pipe. I think (If my maths are working today) it would be a gap of about 0.075in in a 2.5" boost pipe to create a crescent opening with the equivalent area of a 1/2" circle. This is a great example of another valid reason for running a turbo shaft speed sensor on a high end Turbo engine. When all other environmental conditions are the same, you can expect shaft speed to be the same for any given boost value. If that is not the case then you have a boost leak. It's that simple. Also complementing it is the exhaust back pressure sensor as again, all things being equal, if the ratio is higher than normal then you probably have a boost leak. And Finally having a shaft speed sensor affords you the ability to "ride the efficiency islands" through boost control to get better performance out of the turbo. Boost isn't the whole story, if you are just making extra heat inside the Turbo, it's a waste.

[@bootneylee9802]

I would assume this is what tends to wear turbos out faster, unchecked boost leaks. Those rpms are insane.

[@TurboEverything]

This is cool as hell!!! Neat to see what happens when you start introducing boost leaks

[@supraguy4246]

AWESOME info! i always wondered about this, more content like this please

[@misterlith]

Awesome video, cheers for going to the effort! I've anecdotally worked out boost leaks (and roughly whats happening when they happen) with cars that don't have EMAP or turbine speed data but from that angle as well, it feels like it might possibly be interesting or useful to mention how the things would look for those of us who don't have that extra data. What I did manage to spot in the video is the closed loop (/ boost solenoid duty) ramping up to maintain target boost until it looked like you may have had an integral clamp on the PID - and lambda stayed consistently around .77. I tend to keep an eye on if closed loop needs to work harder when there isn't some atmospheric condition to justify it, and lambda going richer than target randomly... I'd be curious how much closed loop had to work to keep that there.

[@hseriesonlymonctonnb1181]

Do exhaust restrictions next ! Love this series just got my first dyno !

[@loverboy8476]

Excellent video series!

[@Nonexsisting]

What a great video. I appreciate everything you guys do

[@coultl6556]

Love this! Bring more real world data!

[@TurboJohnRacing]

Interesting test! Thanks for sharing the data...... Very interesting the straight gate on charge pipe instead of wastegates in normal location is basically this from what I can tell.

[@lukk4273]

Thank you for doing this. I can see how the cold side boost control method could work well on promods especially if the turbos are spec'd for it.

[@krazyd27]

Great video. Another age old test would be bumping up fuel pump pressure to get more flow out of an injector

[@DrCrunkMusic]

Depends on what your turbo is capable of as to the exact value of wen you start to notice as the ecu will try to target the correct boost. Sometimes you can achieve that with a leak, the turbo is just working a lot harder and often spinning a lot faster under the reduced pressure load. Very cool video 👌

[@notsponsored103]

The biggest lesson here was what happens when the pressure ratio across the head goes in favour of the exhaust. The last test made the same charge pressure at the intake valve as the base line test, so where was the power lost? Dirty inert exhaust gases return to the cylinder during valve overlap, leaving less room for the clean intake mixture. Exhaust pressure was a whole atmosphere higher than the charge air pressure. It's like having 15psi of boost in the exhaust and 0psi in the intake. To compensate for the leak, the compressor works harder. This, in turn, generates more heat in the intake charge, reducing the air density further. Less air density = less oxygen + dirty mixture = way less power.

[@mattmorrison6958]

For sure, and residual exhaust usually shows up in calculated VE and corrected fueling, so it'd be interesting to see if the % VE change lined up with the % power lost at those rpm points (if IAT wasn't too much higher on top of that)

[@ernburn6340]

How do the EGT's look? Do they change? What about boost leaks on a diesel? Awesome vid✊️

[@baby-sharkgto4902]

Awesome video! Please do a centrifugal supercharger if you get the chance 👍

[@zeroyon9]

A test of the impact of different duration cams on the 2JZ would be great. Lots of cam dyno tests exist but mostly V8. Very little back to back on a twin cam turbo motor making 600+

[@notch4u]

Great test guys. Awesome vid. Was logging turbo speed with my EFR since it was available. Curious what the IATs were and how they were affected thru ought. Also curious if you had a MAF in front of the turbo strictly for monitoring, how much air loss their was as the leak increased, over the sealed setup.

[@exothermal.sprocket]

I suppose at some point you will approach safe turbo RPM speed before things are dangerous. Your approach to this study is so much more refreshing than the stuff Motor Trend Engine Masters was doing, just how the production is put together and the thoughtful communications.

[@garage79r]

Great data

[@rossjuniper3610]

More like this please!

[@FILIPINOTUNER]

The fluttering went away with that last one at least. 😆

[@kmartkid6312]

Video also shows that even though the psi can be matched flow also matters since a good chunk is flowing out.

[@Razonics13]

Nice! I’d be interested to see the same test with me leak in the exhaust; pre-turbo

[@mattmorrison6958]

The wastegate is a pre-turbo hole/leak in manifold to begin with, so when/where target boost is reached, peak power and drive pressure will likely end up pretty similar. Spool/response/midrange will take a hit for sure though

[@StreetRacingLifeStyle]

This would be interesting with VVT as it can attempt to alter boost. Also try a hotside leak to simulate cracked manifolds or bad gaskets

[@chrisnl6791]

Hey thanks for this . Can we have a video testing with a controlled boost pressure while changing the fuel types such as gasoline, e85, e-100 and methanol fuels ⛽️

[@naiahhaian]

"if you're trying to make power dont drill holes in your intake" - solid advice

[@alexiegomez1691]

So a good boost controller and stand alone still will spin the Turbo faster to compensate for the parameters ✍🏼

[@MotorSwapDan]

Excellent

[@Pizzaschnitzer]

how do you think about a fixed circulation hose as prevention on turbochargers with very small exhaust turbines? they help the charger to gemain in flow.

[@brandonsmith6136]

I would love to see the affects of down pipe sizing does bigger always equal better is there a point where the exhaust slows down too much in the big pipe and a smaller down pipe for might be a better idea for more velocity

[@802Garage]

Please do some testing on "copper" vs platinum vs iridium vs ruthenium spark plugs! I have seen it documented that changing to a modern style of plug can have a similar effect to increasing timing very slightly. It should also mean better spark at high boost levels. Would be interesting to see if there is any difference on a dyno.

[@AJv-kb2pc]

Bro named him Wilson like cast away 🤣

[@rhetericalpha]

I think placement of the boost leak can play a roll as well. Like on a bend/90° area where air can flow right into it. Like a wastegate you don't fabricate it to be perpendicular to the flow of exhaust gases but in the stream. What if the boost leak is more so on a bend where the air flows right into it

[@wolfaja755]

With smaller turbos and bigger boost a small boost leak can cause a dramatic change in horsepower. You end up running into an issue of maxing out the useful turbo rpm band and loosing a large amount of boost. I was running 23psi however, with a boost leak caused by a flange being damaged and leaking by I was only hitting 14psi. I saw a dramatic increase in back pressure and a sharp increase in turbo rpm but it was outside of the turbos effective band. Because I’m a man of science I did a dyno with the boost leak and found a 35% drop in power. The turbo also built boost a lot slower pushing my boost threshold from 3000 to 4500rpm. The leak itself was basically a slit spanning a little less than an inch around a flange that attaches from boost pipe and the intercooler. Because I had to special order the part it took a while to fix the issue. The damage caused by this was the o ring on the flange being destroyed and no bitches.

[@starion707]

Can you guy do a test on 3.5in round down pipe and exhaust vs 3.5in oval down pipe and exhaust

[@Plumbing_Nation]

And I'm overly worried about a small clamp leak. Lol

[@StavTech]

Should be. On most setups it's worse than this makes it look.

[@lukk4273]

Dont forget when the bov line pops off not only the line leaks but the bov valve itself will open too without pressure to hold it closed. So its like over an inch leak lol

[@GarageSupra]

Man thats a well built 2J, I can't believe it makes 150hp more than mine at 1.5psi less boost with a 1" hole in the intake LOL. ( I have a faily stock 2j with a 6262 gen 2 only running 13psi)

[@LiveWire-it8zr]

Depends where the boost leaks are and if your fuel management can adjust/deal with them. If not, you have way worse problems than just a boost leak.

[@BaseSRKI]

Very Cool

[@DieLaughing69]

I to see it tested after MAP or EGT. I apologize if that's ignorant to anyone, but I feel it may make the issue more clear

[@bunky8077]

Cooler pipe diameter, how small until power loss and how big until boost response is affected

[@jacopowell4151]

What will the difference be closer to the intake manifold? More loss or the same?

[@vaugr1917]

Makes me wonder what power would be at highest recorded turbo speed with and without the boost leak

[@yackemup]

Backpressurw is going up because the speed of the turbo is increasing. You have a hole in one side and the turbo is making up for that hole by spinning faster all while the exhaust side doesn't have a hole and gets to experience the increase in backpressure

[@FastPaull]

So this just proves what I and many others have thought for years. A tiny leak around a boot isn't doing shit to hurt power or the turbo itself. You need an unrealistically large leak to effect power. Especially on high horsepower stuff.

[@jeffkoch8612]

False. If you are running a MAF, even a 1/16” leak will cause noticeable losses. This is true for vehicles running speed density, ergo no maf. If you have a maf, this doesn’t apply to your car.

[@FastPaull]

@jeffkoch8612 Yes, with a MAF car, a small leak will effect power, however that's due to the ECU freaking out. Not the overall size of the leak itself. Having a leak with a MAF car isn't even a case of losing power. In most cases, the car will barely even run. I had a Vibrant airflow straightener in a charge pipe turn sideways close to the MAF (blow through HPX) and it didn't even want to start. Not even leak related.

[@jeffkoch8612]

@@FastPaull I know, I build and tune them.. My point being that this video should’ve had a disclaimer, as MOST turbo owners who watch this now think boost leaks don’t matter, when in fact on most turbo cars they matter a lot.. The average turbo car owner doesn’t run speed density.

[@FastPaull]

@jeffkoch8612 I build and tune them too.. Yes, I agree they should've put a disclaimer. However. MAF car people will quickly realize that boost leaks do matter cause their shit won't run, so it's kind of a moot point.

[@NBSV1]

A small leak doesn’t matter much since the engine is consuming so much air at wide open compared to what a small leak is flowing. To me leaks around a boot can lead to meaning the clamp is loose and the boot may blow off. But, I’ve fixed noticeable boost leaks before and the owners didn’t notice an improvement in power.

[@steffytheking]

The smaller the turbo the bigger the difference will be due to the lower cfm. So the ratio of produced vs lost cfm would be higher. Shaft speed is also more affected on a smaller turbo vs larger turbo. Also even a tiny leak can cause big problems on a draw through maf setup. Blow through less so depending on position and even less for map sensor based system.

[@dieselboy740]

Only wide open throttle testing. Partial throttle efficiency and drive ability is going to be the most affected.

[@jdm.flair2020]

Wow i thought it would make a way bigger difference. My little 4 banger had a few boost leaks on some couplers and it ran rich up top and had a lot less torque. I fixed the leaks and it instantly blew the tires of in second gear. My boost leaks must have been huge😂

[@LolBlopsPlayer]

I dont know if yall did but did you make multiple pull with each whole to make sure the number where average and more accurate

[@bigddb92]

Exhaust leak next

[@diambo4life]

Really should have tested this at higher boost and replicated what most people try to do when the boost is down....they turn up the boost even more. So, we needed to see what happens when you try to get that 12psi boost reading back to 15psi (with the leak present) and what happens to the turbo shaft speed and back pressure.

[@roysampson182]

Even with a 1/4" hole the idle would be terrible if you were running a mass airflow sensor.

[@Echelonperformance]

Crazy thing is I wa shaving my turbo actually lifting off the manifold ( 2 bolts fell out) car wouldn’t make over 32psi. And still pulled 730whp and 716 tq I can’t even imagine how much power I was losing at the time😭😭🤦🏾‍♂️🤦🏾‍♂️.

[@Slowpoke99s10]

What about exhaust leaks before the turbo??

[@user-nf3oq2ge3g]

This is a good test actually. But I prefer no leaks. But your ebcs naturally bleeds off pressure to increase boost in a Subaru so you have to calculate for the loss. In your psi boost curve, and how to smoothly translate.

[@lilpickleracing]

i actually did this test by accident one time, i forgot to tighten my 90 elbow to the intake and left bolts finger tight made a pass with the procharger normally making 35 psi and with a 3/4 tall gap 4 long x4 wide still made 15 psi

[@Thumper68]

You can move a lot of air through 3/4” and larger the results are as I expected

[@abarth99]

That’s why you need to data log your waste gate position with a sensor.

[@robsnodgrass915]

Everytime I change out a blown turbo I try to clean the intercooler, but they all leak water.

[@finnroen2334]

Did you consider monitoring airflow into the turbo, charge Air temperature out of the turbo and EGT? .;) Is that the 1800 hp PTE 8685 hp turbo? If so it has unrealistic overcapacity for this test. In a more realistic test, boost leaks sabotages a lot, detonating engines and melting turbine wheels.

[@jefferyholcombe5189]

Just like you turned the boost down, problem is that with the velocity of the air going strait threw the pipe, the air is not going to make a right turn and exit threw the holes you made. You want to see results, drill your holes on a bend in the outside corner and your result's will be massively different!

[@rossjuniper3610]

Would have been relevevant to log air intake temp too.

[@racenightsolutions5626]

You should try it on a elbow and see if it’s different

[@21jordanlee]

Never thought i would see a glory hole in a boost leak comparison, 😂😂

[@Haaspeed]

Im here for turbo wheel speed 😅

[@v8consumption]

Do pre turbo leaks

[@blankyable]

Please test twin scroll vs open scroll with the only variable being the back housing. Same exhaust manifold(equal length so the TS turbo works), same everything else. I have never seen a definitive test where the only variable is the housing. There are so many people, especially in the subaru world I am in that swear by it, but all of the fast guys I see run open scroll turbos.

[@mattmorrison6958]

Subarus seem to be a trickier one there, since their inherently long runners mean less blowdown interference to begin with (where much of the benefit comes from on other platforms), but going divided does essentially cut the (already large) manifold volume in half as far as what each firing cylinder sees. Would be interesting with the different underlying factors

[@SomeOne_86]

I'm really shocked by how little the small holes affected the power. I thought even a tiny leak would make a big difference.

[@croustibat682]

the turbo easily compensates at low boost like this, by turning faster and keeping good efficiency. If it were running closer to what the turbo can do, the efficiency would go down and a small leak would have a similar effect to a big leak on low boost.

[@SomeOne_86]

@@croustibat682 That makes a lot of sense. Thank you for the explanation, I didn't really understand that from the video.

[@adrianlivesey4375]

if this was MAF based it would get very scary very quick rather than a MAP based tune

[@derekcruz7576]

Engine Masters did that

[@crazysvt03]

Is it down on power at the end even with 15.6 psi because the back pressure is so high ( the exhaust cant get out of the cylinder ) or is it something else?

[@kmartkid6312]

Turbos flow air not just compress it. Pressure is the same but you are loosing air flow and volume when it leaves the hole. Since the turbo has to fill that void it has to be spun harder and faster putting more stress on the exhaust impeller leading from the exhaust manifold.

[@mattmorrison6958]

Yes, the compressor is likely falling further off of its efficiency islands, leading to higher IAT which is partly taken care of by the intercooler, but all that extra work required in airflow shows up in the drive pressure, which ends up hurting VE and cylinder filling (more residual exhaust)

[@AdaneEdmund]

Do Exhaust Leaks affect anything pre/post turbo?

[@AllmoneyinJ]

No

[@lukk4273]

I actually thought the backpressure would of been higher with those boost leaks. Wonder if the ait went up too cause that seems like alot of power loss over a few pounds of backpressure. edit: Missed it also dropped boost too

[@user-kw7zb8qw1u]

1866 barometer 900000 rail pressure would

[@brianermeling2764]

Exhaust leaks have a more significant effect.

[@GarageSupra]

Only if its before the turbo/gate.

[@StavTech]

Shame did it at such low boost and such a small turbo, makes the results seem not as bad as they can be, and doesn't show the difference in spool either too. I bet this video gets used as reference by people arguing that boost leaks aren't a big deal, despite anyone with actual real world experience knows it is...

[@aaronschocke2147]

Yep. Seat of the pants and time slips show my truck dropping from 550 wheel to approximately 360ish wheel....if that. Found three pretty wack boost leaks, but they only showed up over 6psi. After that, I noticied three of my boot clambs had broken and the boots would swell and push past the clamps and vent. They didn't look like much, but at full flow from my shop compressor, when I brought it up to 14psi and let off, it only took about two seconds to drop to 6psi 😂 That's with some pretty hefty pipes and a big intercooler. Plenty of volume to hold air and POOF. Gone. Lol. It bad enough that the max boost I could sustain was about 21psi. It's a good thing I went with the billet wheel because I have NO idea what that shaft speed was!!!!! 😂😂😂😂

[@tkello001]

Nonsense. Boost leaks destroy turbos regardless of the effect on boost and power. You can tell by the oil mist that shows up at the boost leak areas.

[@mihailpetrovici5044]

Ya'll just hate that engine or something🤣🤣🤣🤣

[@user-kw7zb8qw1u]

Whats destroyes the turbo is the back pressure

[@sneezinhatch]

True you need some back pressure depending on compression ,engine size, and what your doing with the set up

[@sethhughes2163]

lol... I have to tell on a good customer of mine. ( it's factual, and had the chance to never have happened ) So here goes: Joey S. has a dual turbo 73' Vega, you know how you've almost got your car perf. upgrades within an hour of being done and he says to me... " Hey... instead of welding that last section in... I'm just gonna' run some flex hose on it " ( Rear mounted? Under car, single small 68mm turdski... ) and there were 4 more guys in the shop working... and WE ALL BUSTED OUT LAUGHING SIMULTANEOUSLY! The guys lit into him as you can imagine... right? So I'm trying to stop laughing and finally get out " Hey, I'll do it before lunch and... " and he cut me off cuz the guys really got him SORE and he said something like " no, I just had talked about doing a couple different things... and y'all go on and I'll get it " We'll it was like okay bro, no sweat... and we finished what we were all doing and when I was done I went in the office to just kinda get away... SO, long story short, he was so pissed he didn't even roll a bead or two on the charge pipe, forgot all about the v- band section, that I hab finished and safety- wired the flex on the charge pipe and the v- band. Loaded the car with the guys and that night he called.to apologize which there was no need... but to did not make ANY boost. It defies logic but his wife had been giving him a rash about the car and that was normal... bet in the end Monday morning the dude gave me a big hug and said he was sorry... and then he busted out laughing and said " How could you let me do that "? And we were good and in an hour or so we fixed him up and we've been as good of friends as we ever had been! BUT... he's not the first... including myself when I got my first car at 16 in 76' ... a 69' Chevelle SS and the next week built an L88 and dropped it in with a " double ring input M~22 Mucie " Rock Crusher " begind it, with a MOROSO BRUTE STRENGTH POSI WITH A ZOOM 4:88 R&P... and I wanted to go just two house down to the corner and ce right back... with the drivers door off... yep, I did it... so did all the dudes in the shop that day!

[@MrMajood1994]

2jzhub

[@jubthreesixnine688]

Moist

[@TheAscendedMaster]

You should have cut different sized slits instead of holes since most boost leaks are between gaskets and flanges.

[@alexiegomez1691]

13:20 = Western 304🤷🏻‍♂️😂