Exhaust Systems: Opinions?

[fastpat]

You would not get a significant increase in horsepower by running only pipes to the rear of the car. It would not be worth your time, money, or the hatred of everyone with one mile of where you live.

Not to mention the fact that it would sound like crap. It would be cheaper to buy a beater for $100.00. and every time you get the urge to hear unmuffled exhaust just fire that up and drive it around for 10 minutes. Then return to normal and enjoy your good car. :p

[Guest]

on the other hand i like how my car sounds without a cat.. but i have a resonator.. its not too loud.... i dont know what supersprint exhaust sounds like WITH a cat....

[shifty]

[QUOTE="88 535is south florida"]on the other hand i like how my car sounds without a cat.. but i have a resonator.. its not too loud.... i dont know what supersprint exhaust sounds like WITH a cat....[/QUOTE]

I like the sound of a 535i without a cat, too. Sounds suh-weet!

I'm thinking about doing the same with my eta. It's time for a new cat-back, and I'm thinking about going a little farther upstream and just having the cat gutted. . . or removed altogether, a pipe welded in its place, and the proper flange welded on the end.

[BMWJustin]

Hartge headers, straight pipes to the muffler, and no cat. Its fairly loud but I love it, at idle its not too bad but when you hit the gas it roars. If you dont want to do something that extreme the B&B exhaust is a great system with a cat. If you can, and you probably already have, try to get a ride with someone with one or more of these combo's.
Good Luck
Justin

[Guest]

My deceased 533i had Euro manifolds and downpipes with a crossover for the O2 sensor bung, dual 2-1/4" cats then pipes to a Euro M5 rear muffler. IMO, this system was perfect, not too loud, no weird cabin resonance at 2-3k rpm and sounded GREAT at RPM. The downside is cost of the components and the fabrication work.

This system went into the Euro M5 with a custom X-pipe at the output of the headers. It was OK but not exactly what I wanted. So the next iteration of the exhaust for the rebuilt engine will be Euro downpipes from the headers to an X-pipe with O2 sensor bung in front of a dual in/out metallic substrate catalytic convertor, then dual pipes into the Euro M5 rear muffler.

Rich

[shifty]

[QUOTE="BMWJustin"]Hartge headers, straight pipes to the muffler, and no cat. Its fairly loud but I love it, at idle its not too bad but when you hit the gas it roars. If you dont want to do something that extreme the B&B exhaust is a great system with a cat. If you can, and you probably already have, try to get a ride with someone with one or more of these combo's.
Good Luck
Justin[/QUOTE]

Justin, I bet that thing sounds awesome! What muffler is it? Stock Euro 535i?

The B&B sounds pretty good except for the BOOMINESS in the trunk at idle. Peter C, an Aussie living in Dallas, had the B&B on his 535iS last time I was there, and it was loud even with dynamat in his trunk. I think I remember him taking the thing off and selling it because of that.

I wonder if extending the pipes farther out the back would decrease some of that boominess, though. . .

[shifty]

[QUOTE="Rich Euro M5"]My deceased 533i had Euro manifolds and downpipes with a crossover for the O2 sensor bung, dual 2-1/4" cats then pipes to a Euro M5 rear muffler. IMO, this system was perfect, not too loud, no weird cabin resonance at 2-3k rpm and sounded GREAT at RPM.[/QUOTE]

Rich, I'll never forget the sound of that exhaust when you revved it up that time at Dave's! That must've been back in 2001, geez. . .

[Walt]

Stebro fittment isn't all that bad.

I had them make mine with an extra resomator, instead of the cat and include flanges to mate with the headers.

Great sound (quieter than supersprint), good performance and nice looking.

They are, however, dicks to deal with and slower than you can imagine.

Walt

[Al Canuck]

Friend of mine had a Stebro system on his 87 535i. It was WAY too loud for his taste, so he took it off, and went back to stock. He then sold it to another friend, who put it on his 533i. That car was so bloody loud that he managed to get a provincial vehicle safety inspection issued by the RCMP. I could hear his 533 coming from a mile away. It would vibrate the door at my shop, and you could barely talk in the car. Sounded great, but louder than hell.

My 535i has a PO installed, $150 muffler shop system. It hangs too low, is 1 piece from manifolds to muffler, and consists of a single 2" pipe, but besides all the crappy stuff, the cheapass muffler has a great note.

Al

[Nick C.]

Ok i want to hear someone with a Stebro. I don't believe that its so loud . Ok B&B with a stock everything else is not loud at all. Its really personal preference. I could try to make a clip/moovie if you like to show you. I got my B&B because it was SUPPOSED to be %) the loudest for the E28's. Well i was kinda disappointed when i started the car for the first time. Didn't hit me like i expected. BUT, the build quality is GREAT. Everything is SS. Looks good and it should be the last system you ever have to buy. The sound is ok, the droning is the best part ,lol. SuperSprint looks real good but im not sure how long it lasts. I got an almost new bosal sitting in my basement and while it doesn't look appealing to the eye it did have a little sound for a stock exhaust.

BTW BMWJustin i am dying to hear a clip of your car. If you have anything please post it.

[stuartinmn]

My M535 has a home brew system that was installed by the previous owner. It has the euro exhaust manifold and downpipes plumbed into a factory cat and front muffler, followed by dual pipes to the rear with two Cherry Bomb glasspacks side by side at the very end. It isn't as goofy as you'd think. I've always like the sound - it has a real deep tone with no resonance inside the car. Here's a link to a short sound clip I made last summer (it's kind of muffled, I did it with my digital camera sitting on the passenger seat.) http://home.mn.rr.com/stuartstephens/Audio.wma


[Edit by stuart in mn on [TIME]1109217637[/TIME]]

[fastpat]

[QUOTE="88 535is south florida"]on the other hand i like how my car sounds without a cat.. but i have a resonator.. its not too loud.... i dont know what supersprint exhaust sounds like WITH a cat....[/QUOTE]

[QUOTE="Shifty"]I like the sound of a 535i without a cat, too. Sounds suh-weet!

I'm thinking about doing the same with my eta. It's time for a new cat-back, and I'm thinking about going a little farther upstream and just having the cat gutted. . . or removed altogether, a pipe welded in its place, and the proper flange welded on the end.[/QUOTE]

You're just trying to goad me, I know it.
(@) The only people that gut catalytic converters on an e28 are the un- or under educated in how a cat works, and why there's nothing to be gained by removing the inards of a BMW cat.

I suppose these notions gained popularity during the production of General Motors cats that were loaded with beads/ the exhaust came in below the beads and was passed over the beads and out of the top of the bead stack. The actual flow was randon and quite poor, and worsened during the life of the cat.

I don't know of a cat built like that now, and BMW cats are among the best, essentially restricting nothing if used with the engine displacement for which they're designed. :@

Gutting a catalytic converter is the functional equivalent of running 13 x 10 inch wheels on your e28 that have been rattle can sprayed green and gold with 225/50-13 tires mounted on them. ~0

Do I really need say more?


[Edit by fastpat on [TIME]1109218245[/TIME]]

[shifty]

[QUOTE="Nick C."]Ok i want to hear someone with a Stebro. I don't believe that its so loud . Ok B&B with a stock everything else is not loud at all. Its really personal preference. I could try to make a clip/moovie if you like to show you. I got my B&B because it was SUPPOSED to be %) the loudest for the E28's. Well i was kinda disappointed when i started the car for the first time. Didn't hit me like i expected. BUT, the build quality is GREAT. Everything is SS. Looks good and it should be the last system you ever have to buy. The sound is ok, the droning is the best part ,lol. SuperSprint looks real good but im not sure how long it lasts. I got an almost new bosal sitting in my basement and while it doesn't look appealing to the eye it did have a little sound for a stock exhaust.

BTW BMWJustin i am dying to hear a clip of your car. If you have anything please post it. [/QUOTE]

You think the droning is the BEST part? Holy crap! Everyone says that's the worst.

Maybe you need to talk to Raj about the system he had on his 5er a couple of years back. That's probably what you're looking for.

[shifty]

You're just trying to goad me, I know it.
(@) The only people that gut catalytic converters on an e28 are the un- or under educated in how a cat works, and why there's nothing to be gained by removing the inards of a BMW cat.

I'm not looking for an increase in performance on my eta by doing away with the cat. The engine is completely stock, so there's no reason to try to increase the flow of the exhaust even if the cat WAS the bottleneck in the current system.

All I want is a better sound, and, if the 535i's without a cat that I've heard are any indication, I know it'll sound better without a cat.

Gutting a catalytic converter is the functional equivalent of running 13 x 10 inch wheels on your e28 that have been rattle can sprayed green and gold with 225/50-13 tires mounted on them. ~0

What the hell's wrong with that? I LOVE 13" wheels sprayed green and gold!

But seriously, Pat, I appreciate the information. It sounds to me like the misconception with catalytic converters is similar to that with reducing the backpressure in the exhaust system. The problems that arise from reducing the backpressure in the exhaust system only existed in carbureted cars. Nowadays, the only negativity that you get from reducing backpressure is increased airflow which, in turn, leans out the mixture. This can, of course, be solved by enriching the mixture which, of course, increases power (more air/fuel flow at the right mixture = more power).

[doug]

[QUOTE="Shifty"]The problems that arise from reducing the backpressure in the exhaust system only existed in carbureted cars. Nowadays, the only negativity that you get from reducing backpressure is increased airflow which, in turn, leans out the mixture. This can, of course, be solved by enriching the mixture which, of course, increases power (more air/fuel flow at the right mixture = more power).[/QUOTE]

So is that the current concensus? I've been passively involved in some spirited debates about backpressure, and in the end I tend to agree with Shifty's viewpoint: less is better. But how, if at all, is that related to the issue of pipe size? It's tempting to think 'less backpressure is better' equates to 'bigger piping is better.' But doesn't exhaust size affect the shape of the power band? Is there a body of wisdom associated with exhaust sizing for the m30 and/or m20?

[Shawn D.]

[QUOTE="Shifty"]The problems that arise from reducing the backpressure in the exhaust system only existed in carbureted cars. Nowadays, the only negativity that you get from reducing backpressure is increased airflow which, in turn, leans out the mixture. This can, of course, be solved by enriching the mixture which, of course, increases power (more air/fuel flow at the right mixture = more power).[/QUOTE]

[QUOTE="dotrp"]So is that the current concensus? I've been passively involved in some spirited debates about backpressure, and in the end I tend to agree with Shifty's viewpoint: less is better. But how, if at all, is that related to the issue of pipe size? It's tempting to think 'less backpressure is better' equates to 'bigger piping is better.' But doesn't exhaust size affect the shape of the power band? Is there a body of wisdom associated with exhaust sizing for the m30 and/or m20?[/QUOTE]

Shifty is not entirely correct, in that neither "leaning" nor "enriching" the mixture detracts from or improves power until you know whether or not the mixture is correct in the first place. Mixtures that are too rich will decrease power just as lean mixtures will, albeit being safer for the engine in terms of combustion temperatures.

As for exhaust size, for a normally-aspirated engine, the exhaust should be sized for best scavenging for the RPM range you're interested in. This is a combination of exhaust pulse timing and momentum along with backpressure. For a turbo engine, zero backpressure is the goal, as there's really no scavenging per se in a turbo engine (turbo guys, I know you'll correct me on this if I'm incorrect). There's lots of exhaust theory out there -- have a look on the internet.

I did some figurin' on E28 exhaust sizes and have a spreadsheet for it:
"Shawn D.'s Exhaust Calculator" Note that this is very simplistic -- just a general examination to get you in the ballpark.

[Edit by Shawn D. on [TIME]1109260507[/TIME]]

[shifty]

[QUOTE="Shawn D."]Shifty is not entirely correct, in that neither "leaning" nor "enriching" the mixture detracts from or improves power until you know whether or not the mixture is correct in the first place. Mixtures that are too rich will decrease power just as lean mixtures will, albeit being safer for the engine in terms of combustion temperatures.[/QUOTE]

Shawn, my comment on leaning and enriching the mixture was assuming the engine is set up properly in the first place. Of course if you're running stoichiometric, you're already too lean for max power, or if you're running the right mixture for max power and you lean out a little you'll be closer to stoich but too lean for max power.

[Shawn D.]

[QUOTE="Shawn D."]Shifty is not entirely correct, in that neither "leaning" nor "enriching" the mixture detracts from or improves power until you know whether or not the mixture is correct in the first place. Mixtures that are too rich will decrease power just as lean mixtures will, albeit being safer for the engine in terms of combustion temperatures.[/QUOTE]

[QUOTE="Shifty"]Shawn, my comment on leaning and enriching the mixture was assuming the engine is set up properly in the first place. Of course if you're running stoichiometric, you're already too lean for max power, or if you're running the right mixture for max power and you lean out a little you'll be closer to stoich but too lean for max power.[/QUOTE]

Very good, my friend -- you is on your way to becomin' a true guru!

[fastpat]

[QUOTE="Shifty"]The problems that arise from reducing the backpressure in the exhaust system only existed in carbureted cars. Nowadays, the only negativity that you get from reducing backpressure is increased airflow which, in turn, leans out the mixture. This can, of course, be solved by enriching the mixture which, of course, increases power (more air/fuel flow at the right mixture = more power).[/QUOTE]

[QUOTE="dotrp"]So is that the current concensus? I've been passively involved in some spirited debates about backpressure, and in the end I tend to agree with Shifty's viewpoint: less is better. But how, if at all, is that related to the issue of pipe size? It's tempting to think 'less backpressure is better' equates to 'bigger piping is better.' But doesn't exhaust size affect the shape of the power band? Is there a body of wisdom associated with exhaust sizing for the m30 and/or m20?[/QUOTE]

Try How to Build Horsepower by David Vizard. This guy has written about exhausts for years and is among the most knowledgeable on the subject.

[Velocewest]

If you want to spend too much, Metric Mechanic makes an exhaust they call system 300. The PO of my car dropped the $1,000 for this setup. :~ That's SS system money.

http://www.metricmechanic.com/pg104.htm

I think the muffler is actually off the 524td. It flows well, and is pretty quiet at all RPM's. For the money I would have just gone to my favorite local exhaust shop and had a custom system built. Probably would have been about $600 with an equivalent cat and a nice Magnflow.

[jim_in_fl]

Just came across this recently:

Hot Rod exhaust system test

In their tests, on a "mild" 454, a dual 3" system picked up around 13 hp and 15 ft/lb tq across the entire range over a dual 2.5" system.

Also, people have recorded gains of 5-7 whp, with no low-end losses, going from 2.5" to 3" exhaust on a 240SX (2.4L 16v 4-banger) with intake and header.