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Jay’s Tech Tips #16: Boost Leak Test

September 6, 2019

Hi, I’m Jay from Real Street Performance. Today, we’re going to talk about doing a boost leak check, and why it’s important on your forced inducted vehicle. On a force inducted engine, boost is power. So you want to make sure that the system is not leaking air because if it’s losing boost, it’s going to be losing power. Depending on the system and how its set up, having a boost leak is detrimental in a few different ways. On a turbocharged car, if you have a boost leak, the turbocharger will just speed up to meet the same boost target most of the time. And that’s going to increase back pressure and the workload on the turbocharger. In addition to that, if you have a mass airflow sensor car it’s accounting for a certain amount of air. And if that air doesn’t pass through the entire system and leave the tailpipe, then the fueling is going to be off. On a map sensor based car, the boostics will typically make for an erratic map signal which will change injector pulse width and the timing. And make that an erratic situation which is harder to tune, making for an engine that doesn’t run as well. So in order to do this test, you’re going to make yourself a tool or if you could probably purchases through a vendor online. But the idea is to cap the inlet of the turbocharger and fill the system with air. And then start fishing around for air leaks. So you can use a spray bottle full of soapy water. You can use the smoke machine if you have access to that. Or just use your ears if it’s quiet. So unless you have an engine that has a tremendous amount of overlap where both valves are open at the same time, you can just feed air into the turbocharger, and just listen. If you need to use a spray bottle with some soap in it you can do that and spray around. But generally you can hear the leaks and go chase them down. Whether it be a coupler or a vacuum line or maybe the intercooler core is split. But if you just beat air into the system, and then just take a listen. You can generally fish out where they are. This car has these quick couplers on the boost control solenoid with a nylon line. And one of the seals is leaking on that. So that’ll be the first thing we address. This is something you want to do before tuning. Hopefully you’re enjoying these little Tech Tips and you’re getting some information that helps you with your build. Tune in next week for another tech tip. You could subscribe below or like us on Facebook. Thanks.


  • Reply Gabriel Dalcomune January 27, 2015 at 12:27 am

    Compression test coming up? 

  • Reply Steven Barnette January 27, 2015 at 2:06 am

    Jay is the new Turbo Yoda. Thanks again, guys! Awesome series.

  • Reply PIPnorcali January 27, 2015 at 5:59 pm

    Keep up the good work

  • Reply TwasButNowAint January 28, 2016 at 5:59 pm

    Quick question: Will a boost leak create sputtering at low boost? Once the boost is high enough the sputter quits. Thanks

  • Reply Sebastian Steele June 25, 2017 at 3:33 pm

    could you use this same setup by covering the turbo inlet and instead of just air use some sort of homemade smoke machine or is that only good for the vac side?

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