My "exhaust leak or normal?" thread

[GTLEGACY007]

So i've seen several threads on the matter, but i'm having trouble nailing this down on my particular vehicle. Stock, while boosting, I couldn't hear the turbo at all. I'm now at stage 2, with a catless up, catted dp, and catback on the car, all with fresh gaskets.

 

Any time i'm in boost now I hear a whistle coming from the turbo area. I've seen some threads on this which state that this is completely normal, that it's just the sound of the turbo, which I was never able to hear before. Other threads seem to suggest the cause of this could be an exhaust leak, at either the turbo to dp (seems least likely), turbo to up (more likely), or up to manifold (most likely).

 

So my question is, at what level of a "whistle" would one assume it's an exhaust leak vs. just the typical spool of the turbo? This noise can be audibly, clearly heard any time the car is in boost, over the radio, on the freeway, any time the car is in boost. When i'm in boost, I can hear the whistle louder than the sound of exhaust. I suppose a good question in more laymans terms would be, to those of you with an exhaust-leak free stg. 2 set up, what do you hear in-car during heavy acceleration, "vroooooOOOOMMM" or "whissssssSSSTLE"? lol. Thanks in advance.

[TSiWRX]

Nearly impossible to quantify, unfortunately - you're in CA, so I'd assume that there are plenty of Subaru enthusiasts in your local area.

 

Have someone familiar with "Stage II" BL/BPs (other Subarus? fine - but remember, the amount of sound deadening in the BL/BP is different from that of the Imprezas or Foresters) take a ride with you.

 

Yes, the better breathing tracts that you've changed your car to, plus the higher boost levels, will return with more in-cabin turbo soundtract, and yes, it can well be louder than the exhaust as well as the radio.

 

But it's truly hard to quantify....

 

And to judge based on observed boost or datalogging is also virtually impossible: while not common, it's also far from uncommon that nothing manifests in terms of those two measures until a REALLY BIG leak is present.

[Ridgeracer]

What you could also check for is sot marks around flanges of the UP, DP, and turbo..Some leaks can be smelled in the cabin air especially when the car is cold. You can sniff around those parts when the engine is cold to pinpoint.

[TSiWRX]

^ Very good points!

 

On a totally cold car, 007, you'll have a good 3-5 minutes to feel around, without risk of getting scalded.

 

Just don't attempt to re-enact the scene from Kung-Fu, and you'll be fine.

 

Oh - and typically, an exhaust leak will make the car sound more like a tractor, a boost leak will sound more like a whistle. However, that's not to say that an exhaust leak can't occur in "just the right way" as to sound like a whistle, either.

[LosAngelesLGT]

What you could also check for is sot marks around flanges of the UP, DP, and turbo..Some leaks can be smelled in the cabin air especially when the car is cold. You can sniff around those parts when the engine is cold to pinpoint.

 

You can literally put your hands around the flanges and feel for air passage before things get hot. I hope the UP was torqued to the turbo before anything else. You do not want a up to turbo leak. That would suck. My whistle and leak was from the collector (header) to my up.

 

I solved this with a grimspeed 12 layer gasket that is basically 3 oem gaskets and makes it easy to mate up. You should try this gasket if the leak is in this area which is very common.

 

That you have whistle makes me think it is at the collector (header) to up because it is a 2-hole-flange connection. The two bolt connection is like the jaw in your mouth where a 3 bolt+ flange cannot open the same way. A 3 bolt flange can whistle as air passes the gasket but the 2 flange sure sang for me!!!

[TSiWRX]

^ Mine, at that location, went from no extra sounds to a friggin' tractor-pull.

 

To-blame? Yours truly. I failed to re-torque after heat-cycling (I honestly have no idea why/how I missed that one, but I did). Better technique the second time around means now going on four years without problems.

[GTLEGACY007]

Hmm... looks like I have some poking around to do. A major leak of any kind would at least result on some type of reduction in power, correct? This is one of the things that leads me to believe all is well, as the car pulls like crazy , considering the stock straight to stage 2 transformation

[TSiWRX]

A major leak of any kind would at least result on some type of reduction in power, correct?

 

^ You'd be surprised at how big of a pre-turbo leak you can have, and still make target boost. Trust me.

 

Post-turbo, it simply doesn't matter. Actually, without a DP, you'd probably go faster!