Possible exhaust leak?
 

I recently switched over to a catless UEL header (Tsudo) and I'm noticing a few things that kind of point me toward a possible exhaust leak, however I'm also not ruling out a possible tune misconfiguration too which might be causing some of my problems so I figured I'd turn to the community for help on this. I've researched just about as much as I possibly can, gone through sound clips of cars with the same header/different headers, watched clips of cars with leaks and I can't seem to figure out if it's "just the way it sounds now" or if it is indeed a leak somewhere.

At cold start you can hear a clear woosh of air through the system, this is also present at mid-high acceleration around 2.5-3K rev's and higher, but seems to dissipate once you cross the 4K rev boundary. The best I can describe is that under acceleration it gives the car a clear "putt putt" sound along with the boxer rumble, it just doesn't seem to sound right based upon everything else I've seen/heard with these cars. I've been back under the car and checked the gaskets, made sure everything is tightened down and I can't seem to see anything, but it's still bugging me with regards to the sound.

Current setup from front to back is as follows:

Grimmspeed CAI
Tsudo UEL
Tsudo Overpipe
Stock Catted Front Pipe
Invidia N1 Catback with resonator.

I'm running the OFT stage 2 93 Oct tune, with the Quiet cold start modification and am getting ready to try and dial the tune in using Wayno's threads on the topic once I can figure out if things are running correctly or not. Currently I only have the data log that I'm going to link in this post, however I plan on pulling another on my drive home from work tonight so I'll post an update then. What bugs me about the logs is the crazy LTFT value (between 0 and negative 5).

http://datazap.me/u/stumcewing/log-1...8?log=0&data=1

Any help to troubleshoot and resolve this would be greatly appreciated!

Couldn't get your log to load, could be because I'm at work.

In regards to a possible leak, what I do, depending on how lazy I am is either use my hand (with a glove on) to feel for a leak around gaskets or put soapy water onto the joint. You can then feel or see the bubbles. Another option is to hold a piece of paper up to the joint to see if it's leaking or not.

Keep in mind, due to thinner materials and no heat shield, there will be some extra noises. I feel like I've seen somewhere that the "whoosh" noise is normal for some, if not all headers.

Hope this helped a little bit, and if not, maybe someone else will find it handy.

Yeah, I'd seen the thread describing the woosh. Which at the time put me at ease, but the log values kind of throw me as does the "putt putt, I'm a tractor" noise between the 2-3K. I don't get why I'd be seeing such crazy negative LTFT within the log though I am running the stock Stg 2 MAF scaling for the Grimmspeed, which might be what is causing the datalog values, so I'd contemplated switching back to stock airbox and seeing if that changed anything.

Put a Gruppe-S uel on my car last weekend and Im seeing the same LTFT numbers you are.. Going to go back under the car and to make sure everything is torqued correctly. Curious for others to chime in. Debating on doubling up the gaskets

ltft of 5% or less is fine,you will get a bigger variance in ltft arround idle due big changes in intake air temp under bonnet in traffic.

with exhaust leaks you wuold normally expect much higher long term fuel trims like 10% or more at lower rpm and idle.

if you have exhaust leak o2 sensor sees fresh air and then ecu thinks its lean, so it adds fuel vie ltft, so you generally see high positive fuel trims, your are not overly high and their negitive.

log it again after a day or two of driving

You might want to re-think that.

Most times I have tried that, it didn't turn out well ..... :sigh:


humfrz

Steve, Thank you for the advice Sir. I was hoping to do another log tonight however I realized too late that I had left the OFT on my dining table this morning. I'm going to do a couple more runs tomorrow and see what I can come up with. I've also gone back in and added the modified Grimmspeed values for the MAF scaling to see if that adjusts anything as well with regards to the way the logs come out. I'm definitely going to keep updating this as I pull more logs to see if I can get it narrowed down a bit more. I did a somewhat spirited highway run tonight and, whilst the sound it still there, it did seem to dissipate a little the further I ran it on the highway. I'm pretty certain that the 10F temps out here right now aren't helping things along at all either, what with the extended cold starts and longer warmup times.

dont get too anal about getting rearly low ltft. anything below +/- 5% is fine and you might see up to +/- 7 % at idle with big temp changes, if you can get it lower great, but it rearly wont make much difference.

if you adjusting maf then try to do it at average temps for your climate as big changes in temps will cause fuel trims to shift.

do your scaling at similar temps else you will chase your tail

So as an update. I stripped down the Grimmspeed intake on my day off and reinstalled it all, that seems to have cured some of the "putt putt" noise I was getting, plus it sounds better now and the ltft is definitely back into the positive (between 5.2 and negative 1 for the most part). Still seemingly getting gassed a little when the car is stationary, so I'm going to recheck the gaskets on the mid-pipe and the mufflers over the weekend. Sounds awesome though now.

http://i1148.photobucket.com/albums/...psbtfw0qfw.mp4 <------- click for vid

Thanks for the help and advice everyone.

those LTFT numbers are nothing..when I had a very small leak at the header/overpipe connection I had 10-12% positive LTFT just at idle. Also, I've had the OFT and JDL UEL and both have that "wooshing" noise you're talking about. Many people have it and complain about it. It's just due to thinner/lighter material and no heat shield.
It's never a bad idea to retorque the header bolts after putting some miles on them though.

As another update: the N1 had a minor leak at the gasket where the mid pipe meets the axel back. It's taken care of most of the noise at this point. Now I'm hearing what everyone describes as the normal whooshing noise and not the putt putt that I was getting from the leak. Guess it does pay to check the rear sections again even if you didn't change them recently.


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