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Hey all,
I have a really weird issue that came up at the track this weekend. 01 ZO6, cam, mild tune, Kooks headers, no cats, Billy Boat exhaust. Had the car close to 4 years now and I can get a whiff of exhaust if sitting still since it has no cats...okay, not an issue. Had the car to the track 3-4 wks ago and after I got home I noticed a metallic rattling in the driver side muffler, figure it is a baffle coming loose - annoying, but not pressing. So at track this weekend and rattle is there, run all day Saturday with no issues. First session on Sunday, golden...actually run a PR. Second session I go back out and about 3rd lap I come out of a carousel corner and notice the car sounds a smidge louder...take the next turn onto a straight and get pummeled by, what seems like, raw exhaust in the cabin. Eyes watering and this is blasting along at 100+ with windows open. Pull off into pits and jack up car, can't find anything loose in exhaust, can't hear ANY kind of leak around motor/collectors...no smell of exhaust outside of what has been norm for past 4 yrs and tailpipes are burbling exhaust out of all four tips...like normal. Take the car back out for third session, and first two laps are normal...get up to full speed on third lap and get to hammering on it and again, cabin is saturated with exhaust fumes, windows open, 100+, eyes watering, feels 20 degrees warmer in cabin than outside (I'd almost say it felt like the heater was on), and we get a black flag. Into pits, smell subsides...crank vent fan up and is normal sitting there for 5-10 min. Go back out and within a lap the same thing...once I get the car spun up for a bit (revving above 4K for any kind of sustained period) it just is blasting into the cabin, but can't identify from where...can't see anything in cabin, but smell is overwhelming and hard to breathe even. Try a lap or two and decide this is stupid unsafe and go to pits and park car.
We jacked it up six ways to sideways looking at exhaust, can't find any kind of leak, no carbon trails at the collector or at the axle back attachment. NO sounds near the motor like at header or collector to indicate a leak, idling and even with revving it seems normal. I got home a short bit ago and haven't put the car up to where I can actually get underneath and look at exhaust. I am kind of wondering if that baffle that was loose is broken off and possibly partially blocking exhaust (??) It would allow low pressure exhaust to get out, but once I start leaning on it hard it either blocks out completely or builds back pressure. The only problem with that is if it is building all that back pressure how is it getting into the cabin if there are no leaks along the exhaust?
I know enough to be dangerous with my car and trying to learn as much as I can as fast as I can since I'm tracking it more and more, I haven't got any good working theories on this and hoping maybe someone can help me figure this out. I truly suspect it is rooted in that bad muffler since it didn't start until there was a slight increase in sound, guessing that is when the baffle finally let loose, or moved, or whatever. How exhaust is getting into the cabin is out of my scope and I don't want to just buy a new muffler and come to find out it is something else...not sure what else it would be and/or that whatever else it is happened at nearly the same time the baffle let go on the track, but strange things happen and I'm wholly open to learning something new.
Any thoughts, ideas, or direction would greatly appreciated. Thank you all in advance!
That is top of the driver side exhaust can...right under the little well in the back and there are body vents somewhere close to that. The hole is darn near fist sized so when I'm pushing a ton of exhaust leaning on the car it just blew straight up into the cabin...windows open so body vents would be open too. Wonder if the baffle let loose and blocked exhaust causing it to build pressure and blow out or if when it let loose it just weakened the metal and broke it. Rest of the exhaust is solid, no issues, scoring, anything...
Quick update for all since this was a weird one...been tied up so irritatingly slow to get this resolved, but it's done now. Anyway...here is the culprit of the issue...
And for anyone who doesn't think exhaust gases are hot...here is the fallout of blowing that exhaust for about 6-7 laps...
Yep, that is the 'foam' bumper on the frame...MELTED that stuff like butter!!
The worst part though, aside from having to shell out for a new exhaust...was I'm pretty sure that extra heat in the area compromised my left rear tire too. Check out the inner edge of the tread...
Overall, too darned expensive of a failure...exhaust, tire(s)...how do you even blow out a muffler like that?!?
Anyway...for your entertainment/consumption, my best advice is if you have something similar - PARK! The secondary damage is what upsets me the most.
Count your blessings. Could have been MUCH worse had you blown that tire and bounced into a wall or another vehicle. Good lesson learned and good of you to pass this info on to other folks. Track racing our cars gets pricey, it's the unexpected stuff that we need to be prepared for.
You are absolutely right...could have been much worse. There was that part of me that was like "toughen up Wade, it's just exhaust smell - who needs Oxygen anyway! LOL Just keep going..."
Glad I listened to my more rational side and erred on the side of caution to park it when I did..bit of a wake up call when I saw the tire (had the tire failed...THAT would have been expensive!).
Overwhelming Exhaust smell
