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Exhaust Gurus? Will settle for exhaust-experienced.

Discussion pertaining to positive pressure E28s.
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Joe in FL
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Exhaust Gurus? Will settle for exhaust-experienced.

Post by Joe in FL »

Though many of us seem to like it loud, I'd like to go a little more stealthy with my theoretical turbo exhaust setup. Here are the criteria:

Stock (or close to stock) noise levels at idle and cruise
An even, mellow sound, without all the fanfare when you get on it
Adequate flow for a 2.7l M20 making 350rwhp.

I've thought about a couple (or a few) flowmaster-type deals in series along a 3" pipe, but not sure if these would give me that "engine is at the other end of a looong tunnel" sound you hear on so many Detroit dogs.

TIA for any ideas

Joe
Skeen
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Post by Skeen »

I personally like Magnaflow better than Flowmaster, but that's splitting hairs. I don't know what else you can do besides use more mufflers...you might try to find something that's not a "straight-through" muffler. Remember that the stock system just used two mufflers and a cat, so something similar would probably yield similar results even though most aftermarket cats are much smaller than the OEM equipment (and thus keep the noise down more).
T_C_D
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Post by T_C_D »

Joe,

You have no hope of running an exhaust adequate for 350rwhp and keeping it near stock noise levels. I run two mufflers on the 325i and it still drones at lower RPM.

Sorry but I don't see it happening.

Todd
Jesse
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Post by Jesse »

Run a muffler from the turbo to the tail pipe.
bahnstormer
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Post by bahnstormer »

lately people have been using those electic exhaust switches

u have a flap that sends air one way or another....

altho tuning for that must be a bitch....
Yellow2
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Post by Yellow2 »

Throw 2 muffler back to back like 2 magnaflows. Get a precat or something to help quiet the noise, jsut get it all 3" :laugh:
///ARINUTS...
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Post by ///ARINUTS... »

I use a dynomax super turbo muffler on my E30 Turbo. It's decent. I think I might put another muffler in series to make it a bit quiter and to make it look like I have a cat. I like the "sleeper" effect. but like Todd said , you will never be able to get stock like sound/ noise level, with the flow needed for 350hp.
Monotalonawd
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Post by Monotalonawd »

bahnstormer wrote:lately people have been using those electic exhaust switches

u have a flap that sends air one way or another....

altho tuning for that must be a bitch....
That's what I did to my 535i. I reused the two stock mufflers but added an electric cutout to a section of 3" dia exhaust pipe right after the downpipe. I could have made the exit at a less pronounced angle but the exhaust gases will always find the easiest way out nonetheless. I really appreciate that mod!

I got pulled over a little bit too often for excessive exhaust noise with my other cars in the past, not gonna happen again this time! :laugh:

Image
Velocewest
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Post by Velocewest »

Monotalonawd, the cutout rocks! I can't believe everyone hasn't bought one of these yet. :banana:

Quick Time Performance
T_C_D
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Post by T_C_D »

Velocewest wrote:Monotalonawd, the cutout rocks! I can't believe everyone hasn't bought one of these yet. :banana:

Quick Time Performance
At $400 it's hardly a bargain.

Todd
FastFiver
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Post by FastFiver »

T_C_D wrote: At $400 it's hardly a bargain.

Todd
No doubt, although I would consider it if I had a lease vehicle or wanted to keep it fairly stock looking with the exhaust. TCD's exhaust will give me plenty of breathing, that I'm sure of.
Velocewest
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Post by Velocewest »

T_C_D wrote:
At $400 it's hardly a bargain.

Todd
Single 3" is only $200, and includes the switch and wiring. That's less than a good high-flow Kat. Short of firing up my vintage big-ass-amp stereo with all the windows in the house open and the Stone's "Beggars Banquet" cranked to 11, there aren't too many ways I'm guaranteed to piss off my neighbors two streets away for $200... :evil: :D
Monotalonawd
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Post by Monotalonawd »

T_C_D wrote:
At $400 it's hardly a bargain.

Todd
Wow!!! $400... I wouldn't have bought that if it was that expensive! :D I got mine for around $100 back then, now it is $117. Got it from here: http://www.mccordcg.com/mpp/order.htm

I just love the sound when letting off the gas pedal from 6000 rpm in second gear just before entering my appartment parking lot... the neighbors also! :laugh:
M635CSi
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Post by M635CSi »

Wouldn't it have been better to design the cutout with the straight through section valved, and the 45 degree bend to the muffler?

I’m also wondering how well that (butterfly valve) would seal if you have a stock (back pressure) exhaust system.
Monotalonawd
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Post by Monotalonawd »

M635CSi wrote:Wouldn't it have been better to design the cutout with the straight through section valved, and the 45 degree bend to the muffler?

I’m also wondering how well that (butterfly valve) would seal if you have a stock (back pressure) exhaust system.
Since I'll be re-doing my downpipe to accomodate my new custom turbo manifold, I'll try to switch the cutout emplacement to have it really straight through.

But give me a chance, I'm not that good with a welder so I chose the easiest configuration. :laugh: Not much space between the tranny and the floorpan!

If you look at a FlowTech Y-pipe cutout (Summit Racing), the exhaust does take the same path as mine, but at a less pronounced angle, that is. That's where I got my inspiration! The cutout acts as a "pressure reliever", what can't go through the muffler WILL find its way out, regardless of exit angle. Here's a custom install on a 2002 Vette I found on the McCord site:
Image

And I do have the stock BMW exhaust system with the resonator and rear muffler; the 3" pipe is only replacing the "too restrictive" cat converter! It seals perfect; and over time, the carbon build-up helps too! :D
M635CSi
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Post by M635CSi »

Monotalonawd wrote:
M635CSi wrote:Wouldn't it have been better to design the cutout with the straight through section valved, and the 45 degree bend to the muffler?

I’m also wondering how well that (butterfly valve) would seal if you have a stock (back pressure) exhaust system.
Since I'll be re-doing my downpipe to accomodate my new custom turbo manifold, I'll try to switch the cutout emplacement to have it really straight through.

But give me a chance, I'm not that good with a welder so I chose the easiest configuration. :laugh: Not much space between the tranny and the floorpan!

If you look at a FlowTech Y-pipe cutout (Summit Racing), the exhaust does take the same path as mine, but at a less pronounced angle, that is. That's where I got my inspiration! The cutout acts as a "pressure reliever", what can't go through the muffler WILL find its way out, regardless of exit angle. Here's a custom install on a 2002 Vette I found on the McCord site:

And I do have the stock BMW exhaust system with the resonator and rear muffler; the 3" pipe is only replacing the "too restrictive" cat converter! It seals perfect; and over time, the carbon build-up helps too! :D
That's WILD. I like it!!
j9fd3s
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Post by j9fd3s »

coming from the rotary world, quiet and power is possible, but it takes a lot of mufflers!

on a turbo car you want at least 3" (less backpressure the better), with a rotary you need to worry about heat, and thus most mufflers dont cut it long term.

we usually end up running a racing beat 3" presilencer ( http://www.racingbeat.com/resultset.asp ... mber=16434 ), as its durable and quiet, in the center, and then "season to taste" with the rear muffler.

borla makes something similar, but its not as quiet.

on the rx7's you need 2 mufflers to keep it quiet enough to drive on the street, 1 is loud and droney

mike
M635CSi
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Post by M635CSi »

j9fd3s wrote:coming from the rotary world, quiet and power is possible, but it takes a lot of mufflers!

on a turbo car you want at least 3" (less backpressure the better), with a rotary you need to worry about heat, and thus most mufflers dont cut it long term.

we usually end up running a racing beat 3" presilencer ( http://www.racingbeat.com/resultset.asp ... mber=16434 ), as its durable and quiet, in the center, and then "season to taste" with the rear muffler.

borla makes something similar, but its not as quiet.

on the rx7's you need 2 mufflers to keep it quiet enough to drive on the street, 1 is loud and droney

mike
Back in 1985, I put a 13B from an RX4 in the back of my '71 911E. It was a great car and solved the problem I had with Porsche at the time; the maintenance costs and expense of making them go fast. Porsches really weren't very fast (power wise) until they started with their turbo cars.

The Rotary was the answer. I made up a header with parts from Racing Beat and used two 24" bullet mufflers plus a SuperTrapp muffler in series. Because of the fast attack time and extreme exhaust overlap, the Rotary exhaust is VERY hot and very hard on mufflers.

It was a great car. Back then, you could pick up a good used rotary engine from the junk yard for about $150 and they would spin to 8,000 with no problem. They would pull like an electric motor and with VERY simple modifications would make about 50 hp more than the 911S was making at the time.
Velocewest
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Post by Velocewest »


Back in 1985, I put a 13B from an RX4 in the back of my '71 911E.
That just had to drive the P-car zealots CRAZY!

Good job! :lol:
M635CSi
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Post by M635CSi »

Velocewest wrote:

Back in 1985, I put a 13B from an RX4 in the back of my '71 911E.
That just had to drive the P-car zealots CRAZY!

Good job! :lol:
Thanks!

Yes, it made the P-guys nuts because they suffer from a common delusion among car enthusiasts; that their chosen brand somehow has the market cornered on good engineering.

I liked (like) the early 911 styling but that's all. Porsche tried all kinds of things to remedy the problem of hanging something as heavy as an engine on the wrong side of the rear wheels. First, they put lead weights (no kidding!) in the front bumper, next, they stretched the rear swing arms making the car longer, then, they tried making the engine out of magnesium to lighten it; all pretty much to no avail.

The 13B engine was lighter, simpler, cheaper and shorter than the Porsche six. Putting a radiator in the front of a 911 improved the car's balance.

Of all the cars I've owned, that was certainly the one that was most "me". I built it during a time when you could have fun with cars and not worry about the "resale value". I wasn't hung up on "brand purity" because, when you get right down to it, the make of a car is just a label they sew on...
bmwm3n528
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Post by bmwm3n528 »

...Back from the dead.

This McCord Power Plate is really got me interested. I'm just trying to think how you'd want to design it to where it'd be the most beneficial.

Eisenmann makes a sport exhaust system for Porsche "Tequipment" line that does something similar. Has a switch wired in to where you can shut it up, when necessary. This, for me, is perfect...As our cars are sedans, and should remain somewhat tolerable/comfortable for long jaunts.
PDX5
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Slightly off topic

Post by PDX5 »

I think I might have a use for my stripped m20 super e throttle body :laugh:

But seriously... it'll be slightly ghetto because I'll probably use a wire to pull the flap open instead of a cool switch. Plus, my exhaust is already rusted from sitting in the garage, so I'll weld on a cut out and bolt that TB on.

The TB will be able to handle the heat, right?

Muwhahaha! Somebody stop me :laugh:

Anyway, if it doesn't work, I'll buy another OEM exhaust and be happy for another 20 years...
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