Tonight was my first real test drive after installing a 70 mm exhaust just a couple of days ago. When I punched it at around 80 mph (6th gear), the boost hit around 10-11 psi and a loud swooshing sound was heard. The boost level began to drop and now I can't get it to go over 7-8 psi. My ECU is tuned by EVOMS at the 580 level so that I get sport mode boost all the time. Would increasing the exhaust diameter from 60 to 70 mm (both with 200 cell cats) do something to cause a loss in boost? Any suggestions/advice would be appreciated, TIA.

 

First to check is the intercooler hoses,pull it around see if any losing.Then the Y-pipe joint as well..Might be something like those poped out.

 

Ahh, the familiar swishing sound. I "have that t-shirt."

It is a likely a leak and it could be as easy as a loose hose or a blown hose or intercooler. I've experienced all three issues.

The first, easiest check is the short, single hose off the Y-pipe that connects to the plenum. Mine has popped off more than once. Make sure that it's securely clamped on at both ends. Mine has come off at the far side going into the plenum more than once.

If your using EVOMS cup intercoolers you may have the drivers side hose from that intercooler only partially connected. when my car was on the lift I noticed that and found that the hose didn't easily mate with the intercooler so it was almost off (see picture). I had the metal tube on that intercooler cut and re-welded in a more aligned position to accept the hose.

The fact that your getting some boost could mean that one of the intercooler hoses is blown or not seated well due to a loose clamp. Another possibility could be that an intercooler is leaking.

A pressure or smoke test can diagnose your boost loss but first check the hose at the Y-pipe as it is easy to slip on and re-clamp by the owner. When mine has come off all the way I've experienced no boost so I kind of doubt that it's the problem but it's so easy to check that you may as well do it. It may be that it's not all the way off.

 

Also change the gas and get diverter valves

 

Increasing your exhaust diameter reduces your backpressure and should make you spool faster. It should not affect boost.

My guess is that a hose came loose...as others have stated.

You can try and replace the BRVs (not diverter valves) like Shotcaller said, but I doubt that they are the problem.

 

Many thanks for the informative info and pics. I'm wondering if I should take it to the dealer or back to the shop that installed the exhaust? I'm leaning toward the shop but the dealer is just down the road and 15 mi closer. It would be an interesting warranty test but do I want to expose my mods to the dealer for this?

 

Before you take your car anywhere, pop the decklid and take a look inside. The Y pipe is connected to hoses on the left and right. Take a look and a quick shake...make sure they are connected. Slip your hand under the Y pipe as it enters the hose connection to the throttle body assembly...make sure it is connected and not loose. These are pretty easy fixes, and all you need is a screwdriver to reattach and tighten the hoses.

Beyond that, you'll either need a ramp, jack, or lift to look under the car at the other hoses.

If you do need to go back, go to the tuner if your dealer is mod-unfriendly.

 

Thanks Bobby! I'll poke around and see what I find and let you know.

 

I just had the same problem yesterday, and I have been on this forum checking out what possible problems it can be. I am taking it into the dealer this week to check it out.

BTW, I did check my hoses yesterday by tugging at the intercooler hoses behind the fender wall, but nothing seemed loose. I also checked my y-pipe connection as well. In addition, my idle in neutral is a bit rough and actually stalled twice yesterday. I haven't gotten any CEL yet, but maybe I haven't driven the car far or long enough for the computer to cycle itself???

Hopefully, it's an easy fix...

 

Loud swooshes should be heard on basketball courts, not turbos. Another clue I forgot to mention, is that my car sat idle for 3 days after installing the exhaust. When I tried to start it, instead of starting right up on the first crank, it took three tries which has never happened before even after sitting for a week. Also, no cel. Is that normal, not to get a cel for boost loss?

 

I was driving the TT on Friday and was hitting 1.2 bar solid thru the gears then all of sudden I had the same swooshing noise. I was down to .7 bar but at least the swooshing told me of a leak vs something much worse like a blown or frozen turbo.

I went over to Stuttgart Performance in Costa Mesa and it was a simple hose that came off at the end of the Y pipe. A road test by the Stuttgart tech replicated the problem so they replaced the Y pipe hose and now Im perfect. They did this for free as I am one of their customers; top notch guys over there.

Id much rather go there than the dealer. They even completed the TSB (turbo lube) too while I waited!!

 

I'd not risk the dealership relationship right now as 1) they may be mod-unfriendly and 2) it is likely not an expensive fix so it's not worth coming to them with a small issue and risking their disposition toward your mods from then, on forward. A loose hose may not cost you anything even if your exhaust shop fixes it.

The place where you just had the exhaust work done will likely be more receptive to making you happy since they just took your money. Also, the quicker rise in boost with the larger diameter exhaust could have 'shocked' a loose hose to come off so they may see it partially as their responsibility to ensure that all the hoses are clamped on tightly. It's not hard for them to do a few simple initial checks.

check the hose at the Y-pipe first yourself (bring along a stubby philips(?) for the clamp screw). It may be just that simple.

 

Vic, was your Y pressure pipe one of IPD's new designs or the OEM one?

 

Its the IPD one- have had it on with no probs for about 6 months along with the 82mm TB.

 

How about diverters?? Very possible due to boost hoses as well.