Mighty Car Mods recently posted a video showing a very simple test to determine if a boost leak is worth fixing. They had a BOV on their car that bubbled when they sprayed it with soapy water during a BLT. To measure the amount of air it was leaking they put a condom on the BOV, kept 15psi in the system for 60 seconds, and then tied off the condom to show how much air leaked. They then held up a trash bag full of air saying that's what their engine used in a second, and compared it to the tiny condom to say the loss of air wouldn't hurt performance.

Not very scientific, but do they have a point? Does the loss of air during a static boost test directly relate to the amount of air (and power) that would be lost during a pull? For some reason I was thinking a small leak during a BLT would lose even more while under boost.

Here's the video if anyone wants to watch it:

This is an ok test.

If it was me i would fix every leak possible.

I'm wondering if maybe this is GFB's way of addressing many of the BOV's having terrible leak issues, I bought a GFB knockoff product and it leaks air horribly anything past 10psi, with it installed on the car it rendered a BLT completely pointless, I can get it up to 30 psi to test but it'll just drop back down to 10 within 10-20 seconds

although the semi-atmo dump does make a cool sound it wasn't worth the thought of me having horrible boost leaks

You're not only losing air but depending upon the car you could be messing with the tune. However, a tiny leak is still a tiny leak.

I've fixed small leaks similar to what they've shown and my butt dyno has noticed a difference, on an SD car. But MCM makes it sound like that would be impossible, because it's leaking so little air during a BLT.

I only took physics in high school and I know nothing about fluid dynamics so this might be a stupid question. Using their test as an example, would the BOV leak the same amount of air with a static test that it would under operating conditions making pull, assuming the pressures are the same? That might be an impossible question to answer, but I'd assume it would leak more during a pull. But that's just an uninformed opinion.

Well 30psi during a pull and 30psi during a BLT should be the exact same condition. You're measuring 30psi of pressure in your system. The only difference would maybe be the air is flowing rather than static? Darn, now I'm not sure anymore.

That's what I'm saying, pressure is pressure but when you think about it the waters get a little muddy, at least to a layman like me. And I guess it would depend on the nature of the leak right? If there is a flap of loose RTV that sort of seals during a BLT, it probably wouldn't seal as well under the turbulence of massive amounts of air flowing past it.

I'm also curious about this because small boost leaks don't really affect my car very much but someone had mentioned once that if your MBC is set to 20psi and you're IC setup is leaking boost from every coupler the turbo has to work that much harder just to generate that 20psi.. so it could in example, be generating 25psi but you'll only see 20psi because your MBC is tapped off your j-pipe and your boost gauge is tapped in at the TB and it has a way to travel before it gets from the mbc to the gauge. Does that make sense or am I repeating someone else's bad information?

Vegas smith said:

Well 30psi during a pull and 30psi during a BLT should be the exact same condition. You're measuring 30psi of pressure in your system. The only difference would maybe be the air is flowing rather than static? Darn, now I'm not sure anymore.

Click to expand...

Static conditions are not thr same as dynamic. Fix all leaks. Im curious also how many people make sure their bov pressure source also receives pressure during a blt

This Aussie goofball needs to save his rubbers for his pecker.
As we all know by now even the smallest of leaks can rob us of power. Christ I fnally got around to replacing the throttle shaft seals, which seemed to only leak slightly on one side, and only above 25psi on my 97 and it was a huge difference.