Finished my 3 in exhaust (B5 passat)

[Al]

Re: Finished my 3 in exhaust (B5 passat)

This site is going downhill.

Agreed!

[Mister T]

Re: Finished my 3 in exhaust (B5 passat)

unless your previous exhaust was the size of a straw, you shouldnt be spooling that much sooner with your 3". Im sure it did spool sooner, but there is no way it was 1200 rpm sooner.

Hey, I'm as surprised as you are (or in disbelief for that matter). The best means I have of comparing the before and after is the PSI before and after the 2-3 shift. There's a massive gap there and shifting at 6500 in 2nd dropped be back into 3rd gear around 4000.

With my previous setup, I'd get back into boost at about 15 PSI @ 4000 and slowly climb to 21-22 PSI @ around 5000-5200. Now when I make the shift and get back on it I'm back into boost immediately in 3rd. Same if I laid into the throttle at 4000 RPM in 3rd. On the 3-4 shift where it dropped me into boost at 5000 RPM however, it would boost immediately (on the 2.5 in one).

The one explanation I have is that there was about a foot of 2 inch exhaust left on account of the tip transmission being in place when the 2.5 in was put in. The only other contributing factor I can think of is the fact that my manifold had two cracks in it. However I would think that those cracks would probably have sealed themselves off by means of expansion once things heated up.

[Remedys]

Re: Finished my 3 in exhaust (B5 passat)

That makes sense but one thing, I would not assume that the cracks in your manifold close off under heat, when metal expands under heat the growth tends to go away from the crack propagation point and will make the crack larger when heated. Just something for everybody to keep in mind, it is one of those things where you might think your okay when you’re really making things worse.

[J-hop]

Re: Finished my 3 in exhaust (B5 passat)

well a larger exhaust will reduce back pressure which would act on your turbine wheel causing the turbo to slow down between shifts, this is why by going to a larger exhaust you are able to get back into boost right away.

don't know who designed your original exhaust but yea that was a bad idea to bottle neck it down to 2"s, especially when you are running that much boost.

BTW i really hope this isn't on a stock turbo!!!!