Exhaust leak effects?

[IslandTSI]

Well I have been working on my car a bit lately and pulled the top turbo heat shield off and notice a bunch of black soot and grime around the left side of the exhaust manifold. One of the studs is broken off and there is a leak pre turbo between the head and the manifold. I am gonna fis this this winter which isint really the issue.

My real question was what kind of effect would this have been having on the cars performance? It seems to have been running fine but it has seemed to not be quite as fast as it used to be. I still ran a low 14 with basic mods. Would a substantial leak like this effect performance much?

 

[91 Turbo Mitsu]

It would take a fairly substantial pre turbo leak to affect performance and also to the O2 readings would be off slighty because of the fact that the exhaust gases are leaking out.Any exhaust leak is bad but what you need to determine is how bad it is. take the heat shield back off and start the car. Move your hand above the area where the leak is and see if you can feel the exhaust leaking. If not it will probably be ok for a while but you need to fix as soon as you can. With the turbo think about what makes it spin. If you have a leak then those gases arent spinning the hotside. So yes a leak can hurt performance but as I said it would have to be a good sized leak. When you say a broken bolt do you mean the ones bolting the turbo to the manifold. If that is the case you need to fix this asap. Keep me posted. Travis

 

[FORMONTOYA]

The effects of an exhaust leak PRE- front O2 is going to be on your fuel trims. At idle and light cruise you will draw air IN between pulses making the O2 sensor "think" it's running lean, thus adding fuel. At higher RPMs it will actually blow enough air OUT to make the O2 sensor "think" it's running rich, thus pulling fuel, which is not so good.


It just basically screws with your fuel trims, but it shouldn't be enough to mess up anything unless it was just a horrendous leak.

Just fix it.

 

[IslandTSI]

The leak is between the head and the manifold. Its the top left stud that attaches the manifold to the head that snaped off. The car is off the road till spring so it will be fixed before I drive it again.

The reason I notice it is because I had sprayed some degreaser on the block above the manifold last night while changing my oil. Today when i was letting it warm up I could smell the cleaner coming out the exhaust. I took a look at the bolts holding the manifold on one was really loose. Tried tightening it and it snapped.

Wither way i am just gonna use this as an excuse to port my manifold and o2 housing as well as all new gaskets and manifold studs etc.

Hell I might even port the exhaust housing on my t25 while I'm at it. I have all winter

 

[andymoraitis]

In addition to what Jim mentioned, allowing exhaust gas to excape before the turbine will slow spool down and affect top end power since some of the exhaust pulses are escaping. How much depends on the severity of the leak.

Make sure that when you replace the stud that you also replace the manifold to head gasket. I like the Mitsu 4 layer from the EVO. It seals up well and you can find them at the dealer or from a site vendor like SBR.

Good luck,

Andy

 

[IslandTSI]

Here's what it looks like. Looks pretty substantial to me

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[andymoraitis]

Yup, I'd consider that one pretty significant.

 

[92lzerNA]

I was missing 3 exhaust manifold bolts, 2 broken inside the head on missing because it was stripped. My car would hold boost steady at 10psi after doing a headgasket change I installed some stainless studs. Now the car will creep up to around 20psi, could this becaused by not having all of the exhaust leaking any more.

 

[FORMONTOYA]

Just a curious question..........why does the upper hose look collapsed?

 

[IslandTSI]

It collapses when the car is cooled down and there isn't any fluid in it. When it's passing fluid its normal looking.

 

[FORMONTOYA]

Just another curious question...........do you have the coolant overflow blocked off, plugged, or otherwise dis-connected? The only reason I ask is because the hose should NOT collapse like that normally.

 

[IslandTSI]

nope its not blocked off to my knowledge

 

[91 Turbo Mitsu]

Just another curious question...........do you have the coolant overflow blocked off, plugged, or otherwise dis-connected? The only reason I ask is because the hose should NOT collapse like that normally.

You need a new hose. It shouldnt collapse like that. It means it has gotten soft with age. Travis

 

[spyderturbo007]

The effects of an exhaust leak PRE- front O2 is going to be on your fuel trims. At idle and light cruise you will draw air IN between pulses making the O2 sensor "think" it's running rich, thus pulling fuel. At WOT it will actually blow enough air OUT to make the O2 sensor "think" it's running rich, thus pulling fuel, which is not so good.


It just basically screws with your fuel trims, but it shouldn't be enough to mess up anything unless it was just a horrendous leak.

Just fix it.

Jim, I think you might have a typo in there. If the leak is before the front O2 sensor, the additional air drawn in during light cruise will show the ECU a lean condition and your FT's will increase in the positive direction.

Also, at WOT the ECU doesn't look at O2 voltage, so there will be no adverse effects from the leak. Except perhaps the intake sucking up some of the leaked exhaust gas.

 

[FORMONTOYA]

Jim, I think you might have a typo in there. If the leak is before the front O2 sensor, the additional air drawn in during light cruise will show the ECU a lean condition and your FT's will increase in the positive direction.

Also, at WOT the ECU doesn't look at O2 voltage, so there will be no adverse effects from the leak. Except perhaps the intake sucking up some of the leaked exhaust gas.

Thanks, you're correct.......fixed...........

 

[IslandTSI]

Well my thoughts were that exhaust gas hat could be spooling the turbo was just being wasted leaking out to the atmosphere. I can feel it leaking out just with my hand at idle.

Also how well do stud/extractors work? Am i in for a battle here?

 

[FORMONTOYA]

Extractors work great. The real problem is room to maneuver if the head is still on.

I had a stud that was broken in my head, but when I found it, the head was coming off to get freshened up. Once the head was sitting on a bench it was a simple 5 minute job (and 4 of that was gathering tools).

 

[IslandTSI]

Ya I guess I will have to be able to fit a drill in between the head and rad support. I'll get it out somehow. I have no doubt that the majority of the other bolts will snap when I start removing them

 

[crusindregs]

What if the leak was between the ex. manifold and the turbo and it was a decent size leak (1 stud broken). On a 2g with a 16g turbo and stock exhaust could it beneficially relieve some backpressure once the turbo is already spooled up at WOT?