I have never done a boost leak test on my car so i dont know if i have one, but I read all the time that whenever someones car is not running right, everyone tells him to make sure he does not have a boost leak. How big a deal could it be if you have a small leak at one of the pipes? I mean just enough to make a small hissing sound. I would think it would have to be a major leak before you could tell a difference in performance.

 

Its a BIG DEAL... You have to understand that turbo's make boost (pressurized air) in order to make power. The more boost( given everything is in order ex. Timing, A/F ratio)the more power. So if you are losing boost, you are losing power.

 

In round figures, if you leak 10% of the air that "should" go into the engine, you'll drop your a/f ratio by just over a full point. The car is still going to run, it's just going to run rich and lose some power. You're guess is as good as mine as to what a 10% leak looks likes or sounds like. I'd say it's substantial, a lot more than would leak around a hose clamp on an intercooler hose that stays on, but leaks a little bit.

 

Depends on how small a leak it is!

Seriously though, any boost leak is performance you are throwing away. Since we're all willing to part with $1,000's to get more power, leaking it away no matter how little is pretty backwards. Most of the time it should be pretty easy to fix so at the very leat you might as well do it. Besides, a small leak now can turn into a bigger one later.

Having said that, there's no reason why one should religiously check for boost leaks when there's no apparent reason. You could if you have the time, but unless you're running insane boost I wouldn't think you need to.

 

People talk about leaks and still running the same amount boost as they always did and that the turbo was having to work harder to keep the boost up. I dont see the turbo having to work harder to be true....the same amount of air goes through the turbo anytime, it is the wastegate that regulates the amount of air that comes through. So a small leak should have no effect on turbo spool or overall power as long as you can maintain a constant level of boost. A big leak would be another story...i mean a leak large enough for you to loose boost over. Anyone see where i am going with this. A small leak should have no noticable effect.

 

If you dont have a boost leak the wastegate would be further open to achive the same boost level which means less back pressure.

Typically on stock turbo engines a boost leak means more boost taper as the smalish stock turbo is just about maxed out in the higher rpms

Additionaly, on MAF sensor equiped cars a leak of any kind equals additiobnal injector on time and too rich a mixture

Boost leaks on a turbo motor are power parasites

 

wrong..

the same amount of air does not go through the turbo at anytime and the wastegate does not regulate the amount of air that comes through. the wastegate regulate the amount of exhaust gas that enters the turbo. more exhaust gas entering the turbo means the turbine wheel and compressor wheel will spin faster which means more air is sucked through the turbo. if you have a small boost leak and your psi didn't drop, that means that your turbo has to work harder to maintain the same psi plus the air lose through the leak. if your turbo has to work harder, that means that your charged air is also hotter. with MAF type ecu, the leak will effect fuel map because the air is calculated before the turbo, so the ecu thinks the engine is getting more air than it actually does because it doesn't know about the leak. with MAP type ecu, a leak does not effect fuel map because what psi the MAP sensor read is what the engine actually get, but air temp will still be effected.