I learned something about mufflers today

[ELVA164]

Well, I don't know maybe it has something to do with giving the engine the proper back pressure.

This. It sounds like the turbo exhaust was probably quite a bit larger and more free-flowing, but if you go too far with that it robs the engine of back pressure. With too little back pressure, the engine struggles to maintain a healthy idle and loses performance across the rpm band (but especially high up). Generally speaking and if working within a healthy spec, a smaller pipe allows for better top end and a larger pipe gives more midrange power. Going too far either way hurts more than helps.

[CoreyZ]

This. It sounds like the turbo exhaust was probably quite a bit larger and more free-flowing, but if you go too far with that it robs the engine of back pressure. With too little back pressure, the engine struggles to maintain a healthy idle and loses performance across the rpm band (but especially high up). Generally speaking and if working within a healthy spec, a smaller pipe allows for better top end and a larger pipe gives more midrange power. Going too far either way hurts more than helps.

This is incorrect, AFAIK. Back pressure isn't a good thing. It's a bad thing. The notion that some back pressure is good comes from the good ole days of carbs. When you put a free flowing exhaust on an old carbed motor without adjusting for it, the increased flow will cause the car to run leaner, running a risk of burned valves, ect.

You want as little back pressure as possible, particularly for high rpm power. What you don't want is slow exhaust gas velocity. Too large a pipe slows the exhaust gasses, which has numerous negative effects on performance.

[Exodus_2pt0]

This is incorrect, AFAIK. Back pressure isn't a good thing. It's a bad thing. The notion that some back pressure is good comes from the good ole days of carbs. When you put a free flowing exhaust on an old carbed motor without adjusting for it, the increased flow will cause the car to run leaner, running a risk of burned valves, ect.

You want as little back pressure as possible, particularly for high rpm power. What you don't want is slow exhaust gas velocity. Too large a pipe slows the exhaust gasses, which has numerous negative effects on performance.

I wish we could just kill "Backpressure" as a word and remove it from all vocabulary related to engines.

[Deathtoll]

Well to be perfectly honest the muffler looked almost exactly like the old one except it didn't say Super Turbo. The pipes all look like they are the same size. I'm begining to beleieve that there was something wrong with the old one. When he removed it I could have sworm I heard stuff rattling around inside.

I've driven it a bit more since the muffler was replaced and it feels no different than before other than being quieter and smoother. I can really hear the S52 snarl like it should without getting all that extra noise. I can also hear the transmission and all the other little sounds the car makes. It's pretty cool.

[nokincy]

This is incorrect, AFAIK. Back pressure isn't a good thing. It's a bad thing. The notion that some back pressure is good comes from the good ole days of carbs. When you put a free flowing exhaust on an old carbed motor without adjusting for it, the increased flow will cause the car to run leaner, running a risk of burned valves, ect.

You want as little back pressure as possible, particularly for high rpm power. What you don't want is slow exhaust gas velocity. Too large a pipe slows the exhaust gasses, which has numerous negative effects on performance.

You want to have zero back pressure. Back pressure is when there is something causing exhaust gases to flow back on itself slowing the exit of gases which inherently is bad. Gas velocity is what you're referring to.

[Deathtoll]

I believe the diameter of the exhaust I currently have is the stock diameter of a 99 e36 m3 coupe.

[AndrewBird]

I bet the exhaust was rubbing/rattling on something before you replaced it and causing your vibrations. Replacing it moved the exhaust to where it should be and now it no longer rattles.

[Deathtoll]

I bet the exhaust was rubbing/rattling on something before you replaced it and causing your vibrations. Replacing it moved the exhaust to where it should be and now it no longer rattles.

That's quite possible. never thought of it that way.
But the whole car was shaking not just anthing clanging together.

[JasonC]

The clanging you heard in the old muffler wad a baffle that came loose.

[Click]

Currently running the guy on the bottom. Idle is fine. Sometimes the idle is jumpy, but it does that with muffler on too.



Small enough to have good gas velocity, straight enough to be interested in teh opposite sex, and -10 or 15 pounds because racecar.

[MR 325]

I believe the diameter of the exhaust I currently have is the stock diameter of a 99 e36 m3 coupe.

Your car has single 2.5" exhaust.

[e30trooper]

Time for a non off brand muffler. Look into getting a spintech or magnaflow. Id say look for a remus but prices could be a bit high. BTW who did you goto? I paid $50 just for a cut/weld to put my remus on.

[dashboardmonkey]

I run a magnaflow on single 2 1/2 in system on my swap. Not very loud at all. My intake is louder lol

[JasonC]

Hell, i run basically open headers on the Corvair and Firehawk. My truck is the normal one with a Thrush chambered muffler lol.

[e30Nicko]

All I know is my car used to feel like one of those massage chairs at idle.

Free massage...