What just happened to my exhaust?

[95_GTO]

So for the last 4 months or so, my exhaust has been loud and raspy with more of a growl. Its a stock exhaust. I thought all this time its been a hole or leak somewhere that has been causing this. However, last night I took the car out on the highway and had it up to 130mph. After getting off the highway, I noticed that when accelerating, the exhaust was quiet and smooth, back to the way it used to be. Not only that, but my car seemed to have more pep to it. I was so happy to have my exhaust fixed.

Today though, while driving and enjoying the sound of my exhaust, I stopped at a stoplight. As soon as it turned green I hit the gas, and for some reason my exhaust went back to the loud, raspy tone it was. So whats causing this? Any thoughts? I would like to get my exhaust back to the way it was, quiet and smooth. Its a 95 SL.

[dpartinvr4]

does it have active exhaust?

[x2percentmilk]

will bet on an exhaust leak

[95_GTO]

does it have active exhaust?
No, its only a SL


will bet on an exhaust leak
But where? And why would it go away and then come back?

[x2percentmilk]

ive had exhaust leaks at the flanges go away and come back when the pipes heat up and cool, other leaks could be flex pipe tears that move around and seal or open slightly.

[IPD]

ive had exhaust leaks at the flanges go away and come back when the pipes heat up and cool, other leaks could be flex pipe tears that move around and seal or open slightly.

this. my money's on a flex-pipe leak though. that's the first thing to go when it shits the bed. (it's where mine started leaking). in any event, look at replacing the downpipe before you mess with the catback.

[ntcmpjg]

Well Eric from FSR said it best when these cars out of no were gain power and seem faster then before it means something bad is going to happen.


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[95_GTO]

Well, driving to school this morning, my exhaust was back to being quiet. I'm guessing its going to go back to being loud once I drive it a bit, but I'll wait to see what happens.

[95_GTO]

Well here's another update: When the car sits for a period of time, such as overnight, the next time it is driven, it is smooth and quiet. However, after driving for a period of time, it will go back to being loud and raspy. Except when I take it on the highway doing around 65-70mph, it goes back to being smooth and quiet, until I get off the highway,doing 25-35mph, it returns to loud and raspy. Hopefully this update can narrow down the problem more.

[IPD]

i still think it's an exhaust leak; and probably one on the downpipe. cold pipes will be contracted. when it warms up, i would expect them to expand; which may "open" or exacerbate any leaks that are present. i'm not necessarily surprised that it's quieter on the highway. could be the increased airflow leaks less because of the velocity. could be the additional wind surrounding it effects it. could be a lot of different things.

[dpartinvr4]

i still think it's an exhaust leak; adn probably one on the downpipe. cold pipes will be contracted. when it warms up, i would expect them to expadn; which may "open" or exacerbate any leaks that are present. i'm not necessarily surprised that it's quieter on the highway. could be the increased airflow leaks less because of the velocity. could be the additional wind surrounding it effects it. could be a lot of different things.
increased velocity would cause a drop in pressure, which would cause the pipe to suck air in, rather than push air out." of the leak"

[colt45 gto]

sounds like the baffles have collapsed, the lead foot may have dislodged some baffling but this has blown clear. the wadding used the the exhaust is held by steel mesh (perforated steel) if this has corroded over the year it will no longer hold the wadding that can adn will move into the flow of the gasses.

make sense?

[Emilie@GZP]

Have you ever driven one of tehse cars with no downpipe? tehy're slow turds. Turn teh car on, and stick your head under tehre by teh front wheel (or as close to "under" as you can get). If you hear a farting noise, you have a nasty little exhaust leak. I'd be willing to bet at teh flex section. I'd also be willing to bet, that if it is leaking at teh flex section, you have beat taco motor mounts (9 times out of 10, it's teh rear motor mount that's teh culprit). I'd get that puppy changed. A shit rear motor mount will trash even a brand new downpipe in a matter of months...... ask me how I know this :lol:

[gametrainer]

I replaced the stock exhaust on my '92 RT/TT about a month ago with the Ebay M2 exhaust. While removing the stock DP we noticed that it came off with only about a 1/4 inch piece of tubing holding on right before the front flex section.
Prior to replacing it, there was no indication that there was anything wrong with the stock DP. Stealth has 103,000 miles on it.

[95_GTO]

sounds like the baffles have collapsed, the lead foot may have dislodged some baffling but this has blown clear. the wadding used the the exhaust is held by steel mesh (perforated steel) if this has corroded over the year it will no longer hold the wadding that can adn will move into the flow of the gasses.

make sense?

I believe it does. Where is this wadding? What can I do to clear this up?


Have you ever driven one of tehse cars with no downpipe? tehy're slow turds. Turn teh car on, and stick your head under tehre by teh front wheel (or as close to "under" as you can get). If you hear a farting noise, you have a nasty little exhaust leak. I'd be willing to bet at teh flex section. I'd also be willing to bet, that if it is leaking at teh flex section, you have beat taco motor mounts (9 times out of 10, it's teh rear motor mount that's teh culprit). I'd get that puppy changed. A shit rear motor mount will trash even a brand new downpipe in a matter of months...... ask me how I know this :lol:

How do you know that? :confused: Never driven one with no downpipe. Perhaps thats why when its loud and raspy, hp seems a little down. When it was smooth, I noticed a little bit more pick up in acceleration. What signs do I look for on a trashed motor mount? Whats the estimated cost in getting that fixed?

[colt45 gto]

I believe it does. Where is this wadding? What can I do to clear this up?
the wadding is in the mufflers, when the mufflers are working right it will create back preassure which an N/A needs. as for it getting a bit more umph when its quiet? i can not explane this unless its getting the right amount of back presssure?
you need a mechanic to check it over to see exactly whats wrong. forum speculation is never the right answer.

[IPD]

the wadding is in the mufflers, when the mufflers are working right it will create back preassure which an N/A needs. as for it getting a bit more umph when its quiet? i can not explane this unless its getting the right amount of back presssure?
you need a mechanic to check it over to see exactly whats wrong. forum speculation is never the right answer.

really? REALLY? the backpressure myth AGAIN? roflmfao.

[colt45 gto]

really? REALLY? the backpressure myth AGAIN? roflmfao.
pretty smart aint ya? not really!

riddle me this.....
out of three motor bikes i have had and 2 N/A cars all 3 ran worse with straight through pipes on.

the VFR's actually lost 11 BHP (on dyno's) and run like ruptures with race cans until they was retuned with bigger jets in the carbs and set up right then they gained 20 BHP over stock.

you can put straight exhausts on cars if you like but its only the noise that makes you believe its actually better, a stock tuned engine will run worse without the right setup.

for forced induction its totaly different they run better with straight through systems.

it might be a different story if he had induction and had the car tuned for a bigger exhaust system but a stock setup will fall flat.

[IPD]

colt, please....for the love of god...go search for one of the HUNDREDS of ig3pete's posts on the subject.

backpressure is BAD. delta pressure GOOD.

[colt45 gto]

sorry no. i know from expireince i dont need to read about it. like i said. bikes run on dyno's before and after they are tuned for restriction so with full flow they run weak.

and you didn't riddle me the answer because you can't.

[Emilie@GZP]

How do you know that? :confused: Never driven one with no downpipe. Perhaps thats why when its loud and raspy, hp seems a little down. When it was smooth, I noticed a little bit more pick up in acceleration. What signs do I look for on a trashed motor mount? Whats the estimated cost in getting that fixed?
I know that because I replaced the dp on my stealth with one in perfect condition. My motor mounts were shot. Within a couple of months, the replacement dp was cracked at the flex section. We replaced the rear motor mount and installed another downpipe, and over a year later, still perfect.

If you haven't replaced the rear motormount or any of your motormounts, then your rear one is guaranteed to be shot, and the rest are probably pretty tired looking too. Rev the engine, if it rocks back and forth noticeably, your mounts are beat. It's a bitch of a job, don't know the cost off the top of my head.

[IPD]

sorry no. i know from expireince i dont need to read about it. like i said. bikes run on dyno's before and after they are tuned for restriction so with full flow they run weak.

and you didn't riddle me the answer because you can't.

keep that shit up and i'll nominate you AND steve68 to be on global ignore. backpressure is BAD. period. maybe going without a manifold or using straight pipes isn't as "effective" as an OEM exhaust; if your only measure of efficacy is low-end torque. that's very likely because OEM, exhaust gasses are merged so that the preceeding one creates a vacuum behind it as it exits the exhaust; helping to pull the next cylinder's exhaust charge out behind it. you run a "lakes pipes" off each cylinder individually; or run a manifold/header which doesn't effectively merge the exhaust flows...and you "lose" power--(when really, you're just improving high-rpm efficiency).

if backpressure was what built power; everyone with a 3/s would be driving around with 1/2" exhaust pipes.

http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/168578-exhaust-straight-scoop-backpressure.html

you are a retard.

p.s.

wait...did you say bikes with CARBS? yeah...no wonder why you're so damn confused. let me guess...you never re-tuned the carbs AFTER you swapped exhausts? :rolleyes: a "stock tuned engine" is just that; at stock tuned engine. if you can't modify the fuel intake to automatically compensate for variances in the exhaust--well...then you can't run a "stock tuned engine" with anything other than that "stock exhaust".

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

why you could be considered a "knowledgeable expert" on this platform (let alone any other) is beyond me. i'm a fucking idiot with the car-knowledge of a 7th grader, and i know better. jeez.

[mb3000]

:popcorn2:

[colt45 gto]

I know that because I replaced the dp on my stealth with one in perfect condition. My motor mounts were shot. Within a couple of months, the replacement dp was cracked at the flex section. We replaced the rear motor mount and installed another downpipe, and over a year later, still perfect.

If you haven't replaced the rear motormount or any of your motormounts, then your rear one is guaranteed to be shot, and the rest are probably pretty tired looking too. Rev the engine, if it rocks back and forth noticeably, your mounts are beat. It's a bitch of a job, don't know the cost off the top of my head.

i agree completely with the motor mounts they will put excess stress on the flex sections. but this doesn't explane why its quiet one minute and loud the next. could be a compelation of both diagnostics?

i know IPD came out with some shit but he went on ignore yesterday so i have no clue what shit he came out with, i bet he completely ignored the fact i had 3 bikes on dyno's in the past. so i chose to also ignore what he has to say. i should have ignored him as soon as i signed up here tbh.

[IPD]

roflmfao. the "i'm a moron who has been demonstrated to be talking out his own ass, so i'm putting my nemesis on ignore so that i can pretend i'm still right" defense.

to anyone else who is still paying attention, read what i posted--please. backpressure is a MYTH. i really don't care if you like me or not; the truth is what matters.

[mb3000]

Colt, if you are talking about a 2 stroke "bike" engines than yes, they do need back pressure.

[IPD]

Colt, if you are talking about a 2 stroke "bike" engines than yes, they do need back pressure.

agreed. but that's a FAR, FAR cry from a 6g72. even if it was a 4-stroke he's referring to....not changing the carb to compensate for the increased exhaust flow (from a more open exhaust) is going to cause it to run LEAN. this is precisely what was mentioned in my links. EFI doesn't have this problem, as it will automatically adjust.

[Amphiron]

Everything that I've read about exhaust theory and learned in college brings me to the same conclusion:
Open exhaust = more high end torque but less power in the low RPM range
Closed exhaust = more low end torque but less power in the high RPM range and this don't mean CLOSING THE EXHAUST off completely it means a typical EFI will favor a nice tuned 3" exhaust system as opposed to running demolition derby style headers.
I really wish I could find the write up about this but this was said to be the basic rule of thumb when it comes to F1 exhaust design. I think I actually got it from a topic on 3si.
Heres another good write up stating that running a giant exhaust isn't necessarily gonna give you more power.
Exhaust Theory (http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm)

[95_GTO]

For those still paying attention despite the derail, I crawled underneath my car today and found a big leak where I was told it was going to be, in the flex section. I patched it up with some exhaust wrap for now until I can do a more permanent fix to the problem. The exhaust is back to being quite and smooth.

http://i726.photobucket.com/albums/ww262/greentalon_95upload/3000gt/3000GT%20Misc/exhaust2.jpg

[IPD]

i called it in post 6. :)

[colt45 gto]

Colt, if you are talking about a 2 stroke "bike" engines than yes, they do need back pressure.

i didn't know they made VFR750's in 2 stroke? no sir deffinately 4 stroke engines.

[colt45 gto]

For those still paying attention despite the derail, I crawled underneath my car today and found a big leak where I was told it was going to be, in the flex section. I patched it up with some exhaust wrap for now until I can do a more permanent fix to the problem. The exhaust is back to being quite and smooth.

http://i726.photobucket.com/albums/ww262/greentalon_95upload/3000gt/3000GT%20Misc/exhaust2.jpg
and feels better too i bet.