3" Exhaust for Euro S50 - Advice and Experience Appreciated

[3MPowered]

Hi guys,

I'm in the process of building an exhaust (myself) for my E30 S50 swap. I've searched and came across this thread: http://www.bimmerforums.com/forum/showthread.php?1221875-N-A-S52-Exhaust-Q-s-Single-3-quot-vs-dual-2-25-quot

Honestly, the thread gave me no real answer.

Also, I've never heard of anyone doing a single 3" exhaust for a Euro S50, and thought that the situation might be different given that the OEM exhaust for a Euro M3 is 2 x 2.5" instead of the NA Spec 2 x 2.25.

My proposed exhaust goes as such:

Y-pipe from the OEM Euro headers to single 3" OD => 18" long high-flow resonator => high-flow cat => 18" long muffler

My goal is to retain/improve the power and torque of the OEM setup while reducing weight and simplifying the fabrication process. Does anyone have any light they can shed on the subject?

[nick325xit 5spd]

I built a dual 2.5" to dual cats to Y pipe to 3" borla proxs resonator to 3" in, dual 2.5" out Flowmaster Super 50. I'm not sure that it actually improves on the power of the OE setup (I've also only run it for about 10 miles), but the noise is quite good.

[digger]

3" is plenty enough size, pay attention to where you merge the twin pipes into the Y-pipe. you don't want it too close to the engine.

also iirc the euro exhaust is twin walled that's why its 2.5" the ID is alot smaller? something along those lines anyway.

[3MPowered]

I built a dual 2.5" to dual cats to Y pipe to 3" borla proxs resonator to 3" in, dual 2.5" out Flowmaster Super 50. I'm not sure that it actually improves on the power of the OE setup (I've also only run it for about 10 miles), but the noise is quite good.

So you built a 2-into-1-into-2? Is that basically a long X-pipe? Sounds interesting, and if the power seemed unchanged then that's about the minimum I can hope for. Thanks for the $0.02.

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3" is plenty enough size, pay attention to where you merge the twin pipes into the Y-pipe. you don't want it too close to the engine.

also iirc the euro exhaust is twin walled that's why its 2.5" the ID is alot smaller? something along those lines anyway.

I was thinking of giving about 6" to 1' of distance between the headers and the Y-pipe merger. I was also considering a flex coupling to dampen vibrations, would this also be a good idea in your opinion?

Is the Euro exhaust ID smaller than 2.5"? I figured I'd know that by now, I honestly hadn't heard that before.

My intent is to not lose power or torque by going single 3", and the general consensus amongst the NA spec guys is that 3" is overkill for an NA spec M3 and will likely lose you power unless you have hot cams or FI. I don't plan on doing either of those things, but I figured the Euro motor could probably put up with a 3" without a noticeable loss of power.

[S14]

I believe the exhaust is dual 60mm. Although I'm not certain if that is inner or outer diameter...

I'll grab a pic of my exhaust. It does a bit of 2 into 1 into 2 deal.

[nick325xit 5spd]

The location of the Y was basically driven by the cats. Depending on how you want to catalyze the car, you can move that up a fair bit.

For some reason, I forgot to take a finished pic under the car.

533101
533102

[tofunin]

Euro exhaust tubing is 60mm. I made a replica euro SS midpipe using 2.5" but I merged it into my 2.25" AA Gen III exhaust since I ran out of money to fund more mandrels, muffler, and tips. I may redo the muffler section down the line but I am pretty happy with the noise except the slight rasp at~2200- and 2800.

[digger]

So you built a 2-into-1-into-2? Is that basically a long X-pipe? Sounds interesting, and if the power seemed unchanged then that's about the minimum I can hope for. Thanks for the $0.02.

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I was thinking of giving about 6" to 1' of distance between the headers and the Y-pipe merger. I was also considering a flex coupling to dampen vibrations, would this also be a good idea in your opinion?

Is the Euro exhaust ID smaller than 2.5"? I figured I'd know that by now, I honestly hadn't heard that before.

My intent is to not lose power or torque by going single 3", and the general consensus amongst the NA spec guys is that 3" is overkill for an NA spec M3 and will likely lose you power unless you have hot cams or FI. I don't plan on doing either of those things, but I figured the Euro motor could probably put up with a 3" without a noticeable loss of power.

only part of the exhaust is twin walled from memory.

3" is smaller than dual 2.25", if you lose torque it will be because the merge is too close. i would place the merge throat at either 28" or 56" (or 14" on race build but loses alot of torque below 3500rpm), the dimensions from end of primary to throat of Y-pipe or x-pipe

this seems to be stock exhaust on e46m3 which is similar engine, bmw put an H-pipe at what looks like something closer to 56" than 28" (eyeballing it) so this wouldnt be a bad place to start

http://rebmw.com/mm5/graphics/00000001/exhaust/e46m3_stockexhaust.jpg

[M3kiwi]

Hope this helps
Final setup V2:
Here's a description of my setup 2.5" twin pipes from the OEM headers. (following same route as OEM system) Merge pipe (approx 10" long) where the exhaust straightens(replaces cats) 2 straight through perforated resonators (replaces small muffler) scorpion muffler

Nov 2012 Exhaust upgrade V1(de-cat): I removed my mid section just before christmas and replaced it with twin 2.5" ,keeping roughly the same curves from the headers into straight through resonators where the small muffler was located. Had the car dyno'ed and compared it to a run when the stock mid section was on. Here we go: Dyno 189.7 kW (CAI, exhaust V:1) with overlay.Lost 48Nm below 3600 rpm, gained 16Nm after that till 5850 then decreased but stayed above earlier run when stock. Lost 5-10 Kw between 2000 -3600 There was a flat spot between 2550-2700 From 3600 up, got a solid 5Kw gain all the way Next I'll put a X pipe in and have it retuned.*

Exhaust V2 (merge pipe added): 1 kW gain so now at 190.8kW But regained 5-10kW between 2600-3500 Also the flat spot between 2550-2700 is gone. The exhaust noise/sound has reduced markedly when cruising no worries now about the police. Unless I plant it**Drone has gone as well.Dyno Results2010 My Base line Dyno 184kW (CAI)Dyno 184.8kW (CAI,Back Box)Dyno 189.7kW (CAI, Back Box, Exhaust V:1)2013 Dyno 190.8kW (CAI, Back Box, Exhaust V:2)Dyno 197.5kW (CAI, Back Box, Exhaust V:2 Mapped)

Photos @ http://bimmersport.co.nz/topic/43521-m3-evo-32-1997-hackar/

[digger]

Hope this helps
Final setup V2:
Here's a description of my setup 2.5" twin pipes from the OEM headers. (following same route as OEM system) Merge pipe (approx 10" long) where the exhaust straightens(replaces cats) 2 straight through perforated resonators (replaces small muffler) scorpion muffler

Nov 2012 Exhaust upgrade V1(de-cat): I removed my mid section just before christmas and replaced it with twin 2.5" ,keeping roughly the same curves from the headers into straight through resonators where the small muffler was located. Had the car dyno'ed and compared it to a run when the stock mid section was on. Here we go: Dyno 189.7 kW (CAI, exhaust V:1) with overlay.Lost 48Nm below 3600 rpm, gained 16Nm after that till 5850 then decreased but stayed above earlier run when stock. Lost 5-10 Kw between 2000 -3600 There was a flat spot between 2550-2700 From 3600 up, got a solid 5Kw gain all the way Next I'll put a X pipe in and have it retuned.*

Exhaust V2 (merge pipe added): 1 kW gain so now at 190.8kW But regained 5-10kW between 2600-3500 Also the flat spot between 2550-2700 is gone. The exhaust noise/sound has reduced markedly when cruising no worries now about the police. Unless I plant it**Drone has gone as well.Dyno Results2010 My Base line Dyno 184kW (CAI)Dyno 184.8kW (CAI,Back Box)Dyno 189.7kW (CAI, Back Box, Exhaust V:1)2013 Dyno 190.8kW (CAI, Back Box, Exhaust V:2)Dyno 197.5kW (CAI, Back Box, Exhaust V:2 Mapped)

Photos @ http://bimmersport.co.nz/topic/43521-m3-evo-32-1997-hackar/

good info what kind of merge did you have with V1 (dyno run xxxx.009)? i cant see from the pic

[3MPowered]

Thanks for the info guys. It sounds like the only surefire way to guarantee no losses of torque for daily driving is to implement as much of a dual system as possible, maybe doing what Nick did and going for a 3" system for the catback section.

The other crappy thing about a dual system is that it will require twice as many exhaust components, effectively doubling the cost. On the upside, some ground clearance is gained over the single 3" system.

Id' like to hear from someone that's actually done a single 3" system on a Euro engine, but maybe there's a reason nobody's attempted one?

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Just gave this a read:

http://www.bimmerforums.com/forum/showthread.php?1557225-Bimmerworld-E46-M3-Race-Exhaust-Review

It's not much to go off of, and yes, it is an S54, but being that the S54 is derived from the Euro S50, the impact of going to a 3" exhaust should be similar. The S54 also has a 2.5" OD exhaust system from the factory, so the similarities keep going.

I'm sure the overall effect will be a shifting of the torque band further up the rev range, with peak torque sitting somewhere around 4000 RPM instead of 3600 RPM. I will try and retain the 2.5" dual as far back as viable, but to keep costs down I think I will merge the exhaust before the resonator and cat. If it doesn't complicate things too much, I may use 2 resonators in the dual section of the exhaust and merge the two pipes after that, similar to Nick's setup above.

I will update this thread in due time with the results, although I won't have a baseline from which to judge whether or not power was lost because it will be the first time I drive my E30 with the S50 in it and I'm sure it will feel more powerful than when the engine was in my E36 :)

[S14]

I had a s50b30 in my e30 sedan. I now have an s50b32 in my e30 M3...

When I was doing my e30 sedan, I measured the headers at 50mm, and thought "perfect, I'll run the e30 M3 groupe A replica exhaust" since it is also dual 50mm. My mistake was not researching what the factory e36 exhaust did after the header flanges (bump up to dual 60mm).

When i finally dyno'd the car, it made 229whp and 251tq... Just about perfectly opposite numbers the motor usually makes. I'm not a scientist, but I believe those numbers would switch if I ran a correct exhaust.

My point is to run the best exhaust for the motor. I had to realize I made a $800 mistake because I thought it would be the cheaper solution!

[M3kiwi]

good info what kind of merge did you have with V1 (dyno run xxxx.009)? i cant see from the pic

V1 had cats removed and replaced with straight pipes to, " straight through resonators where the small muffler was located."

Picture with Dave & Mark in it

The link I left has build pictures and dyno sheets

[3MPowered]

I had a s50b30 in my e30 sedan. I now have an s50b32 in my e30 M3...

When I was doing my e30 sedan, I measured the headers at 50mm, and thought "perfect, I'll run the e30 M3 groupe A replica exhaust" since it is also dual 50mm. My mistake was not researching what the factory e36 exhaust did after the header flanges (bump up to dual 60mm).

When i finally dyno'd the car, it made 229whp and 251tq... Just about perfectly opposite numbers the motor usually makes. I'm not a scientist, but I believe those numbers would switch if I ran a correct exhaust.

My point is to run the best exhaust for the motor. I had to realize I made a $800 mistake because I thought it would be the cheaper solution!

Thats really interesting! I knew there was a correlation between how restrictive an exhaust is and the peak torque figure at a particular RPM, but I never stretched that into thinking you could effectively reverse the power and torque figures using just an exhaust

More low down torque is what these engines need anyways.

[digger]

Thanks for the info guys. It sounds like the only surefire way to guarantee no losses of torque for daily driving is to implement as much of a dual system as possible, maybe doing what Nick did and going for a 3" system for the catback section.

The other crappy thing about a dual system is that it will require twice as many exhaust components, effectively doubling the cost. On the upside, some ground clearance is gained over the single 3" system.

Id' like to hear from someone that's actually done a single 3" system on a Euro engine, but maybe there's a reason nobody's attempted one?

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Just gave this a read:

http://www.bimmerforums.com/forum/showthread.php?1557225-Bimmerworld-E46-M3-Race-Exhaust-Review

It's not much to go off of, and yes, it is an S54, but being that the S54 is derived from the Euro S50, the impact of going to a 3" exhaust should be similar. The S54 also has a 2.5" OD exhaust system from the factory, so the similarities keep going.

I'm sure the overall effect will be a shifting of the torque band further up the rev range, with peak torque sitting somewhere around 4000 RPM instead of 3600 RPM. I will try and retain the 2.5" dual as far back as viable, but to keep costs down I think I will merge the exhaust before the resonator and cat. If it doesn't complicate things too much, I may use 2 resonators in the dual section of the exhaust and merge the two pipes after that, similar to Nick's setup above.

I will update this thread in due time with the results, although I won't have a baseline from which to judge whether or not power was lost because it will be the first time I drive my E30 with the S50 in it and I'm sure it will feel more powerful than when the engine was in my E36 :)

I would not copy the bimmerworld exhaust for a street car. I’ve seen 3 or 4 dynos and they show the same thing they make pretty looking numbers (peak torque and peak hp) but by putting the merge closer to the engine you lose heaps of torque below 4000rpm and you lose the wide powerband. Ive seen like 50 lb-ft torque loss which is like 20-25% at 2500rpm. it works good on a race engine where you never see those rpm but like everything it is a compromise.

edit make it more like 30%, a stock e46m makes about 215-220wtq at 3000rpm
http://www.nexternal.com/bimmerworl/images/E46M_Race_Exhaust_700.JPG

[nick325xit 5spd]

I'm not convinced that the effect of putting the merge at the front is that pronounced. I've build exhausts with the merge up front as well. It was my desire to decently catalyze this exhaust that drove the position of the merge.

[3MPowered]

I will try to leave at least 4' of distance between the headers and the merge if I can help it. I do think that Nick is right that appropriately catalyzing and resonating the exhaust before/after the merge will help to bring the torque curve closer to OEM levels though. After all, if you look at the bimmerworld exhaust there's really nothing there other than tubing. Adding anything to slow exhaust gasses down and create some back pressure should have a mitigating effect on any torque loss.

Then again, I'm no mechanical engineer, so this is all purely speculative.

[nick325xit 5spd]

I will try to leave at least 4' of distance between the headers and the merge if I can help it. I do think that Nick is right that appropriately catalyzing and resonating the exhaust before/after the merge will help to bring the torque curve closer to OEM levels though. After all, if you look at the bimmerworld exhaust there's really nothing there other than tubing. Adding anything to slow exhaust gasses down and create some back pressure should have a mitigating effect on any torque loss.

Then again, I'm no mechanical engineer, so this is all purely speculative.

No. I'm not convinced that having the merge up at the front is as bad as he says.

This has NOTHING whatsoever to with having cats. Backpressure is not good. I run dual (oem E46 M3) cats because I want to car to pass the sniffer test and also because I don't especially like breathing exhaust fumes in large quantities.

[digger]

I'm not convinced that the effect of putting the merge at the front is that pronounced. I've build exhausts with the merge up front as well. It was my desire to decently catalyze this exhaust that drove the position of the merge.

i can show you other BW dynos, and other custom exhaust where the same was done, and one where it was subsequently moved to a more rearward position (gaining the torque back) after initial dyno runs with it being quite close. this case in particular is quite compelling given this proved it wasnt the size of the pipes but the merge location. i did it myself on a non M-car moving the x-pipe closer to engine killed the torque, some years later i then changed back to a more rearward position and gained 20% torque around the 3000-3500rpm mark. i spoke to Larry Meaux (mr pipemax software) and paraphrasing he says too short of a collector length will hurt torque below the peak torque rpm and sometimes it is by alot as its completicated the devil in the details, it seems you do need a fair amount of overlap for the effect to be most pronounced. so your mileage may vary... In v8 land many achieve great results with "collector extensions".

[M3kiwi]

From what I read,
The merge pipe should be located at the hottest point/location on the exhaust.

I checked this when I installed my V1 straight pipes.
Remembering I followed the oem shape the hottest point was at the same location where the the cats had been
If you straighten out the pipes from the headers, then the above is the only way to work out the right location.

Just acouple of other points.
The H cross over on the oem is only for noise reduction (not for performance)
As the s50b32 is straigth 6 and not a V8 the exhaust pulse is not balanced the same, so a straight X pipe won't give the best results.
You want merge pipe with an venturi effect.
As for the straighter design another guy over here did it he also decreased the size of the pipes (next size down ) and got good results. He was less forthcoming with info and didn't post dyno results. I have chatted with him and he's straight up.
Finally don't try and reinvent the wheel, I spent a couple of years trying to find a diy online with no luck most guys who do exhaust mods to this extent are racers, this is because of the cost of fabrication and testing. And they dont want to share
I'm not a racer, but had a couple mates with the fab skills so it only cost me time hrs- no days, of research, materials and dyno runs.
You have my photos get it priced, if you can afford it get it done if not then save. As above do it once and do it right.
;)

[digger]

From what I read,
The merge pipe should be located at the hottest point/location on the exhaust.

I checked this when I installed my V1 straight pipes.
Remembering I followed the oem shape the hottest point was at the same location where the the cats had been
If you straighten out the pipes from the headers, then the above is the only way to work out the right location.

Just acouple of other points.
The H cross over on the oem is only for noise reduction (not for performance)
As the s50b32 is straigth 6 and not a V8 the exhaust pulse is not balanced the same, so a straight X pipe won't give the best results.
You want merge pipe with an venturi effect.
As for the straighter design another guy over here did it he also decreased the size of the pipes (next size down ) and got good results. He was less forthcoming with info and didn't post dyno results. I have chatted with him and he's straight up.
Finally don't try and reinvent the wheel, I spent a couple of years trying to find a diy online with no luck most guys who do exhaust mods to this extent are racers, this is because of the cost of fabrication and testing. And they dont want to share
I'm not a racer, but had a couple mates with the fab skills so it only cost me time hrs- no days, of research, materials and dyno runs.
You have my photos get it priced, if you can afford it get it done if not then save. As above do it once and do it right.
;)

correct when burns does a y-pipe or X-pipe (2 * y-pipe) they use special software to work out the size of the venturi, they will also tell you where it should be placed if you ask. For the last exhaust i had done they told me a number and this was the same number i got from the pipemax calculator

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interesting read ;)

http://www.m3forum.net/m3forum/showpost.php?p=1066764648&postcount=1

i agree with their observations, maybe not so much with their understanding of why the changes occur from a theoretical and physics standpoint

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some more digging

note 4" vs 40" of dual pipes after headers then the merge. A merge close to the engine basically sucks on these things

http://www.m3forum.net/m3forum/showpost.php?p=1066058374&postcount=961

if you have a week to go through same conclusions here

http://www.m3forum.net/m3forum/showthread.php?t=458893

so there is heaps of evidence

[nick325xit 5spd]

Fair enough! You have crushed my uninformed opinion with your evidence! :)

[3MPowered]

correct when burns does a y-pipe or X-pipe (2 * y-pipe) they use special software to work out the size of the venturi, they will also tell you where it should be placed if you ask. For the last exhaust i had done they told me a number and this was the same number i got from the pipemax calculator

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interesting read ;)

http://www.m3forum.net/m3forum/showpost.php?p=1066764648&postcount=1

i agree with their observations, maybe not so much with their understanding of why the changes occur from a theoretical and physics standpoint

- - - Updated - - -

some more digging

note 4" vs 40" of dual pipes after headers then the merge. A merge close to the engine basically sucks on these things

http://www.m3forum.net/m3forum/showpost.php?p=1066058374&postcount=961

if you have a week to go through same conclusions here

http://www.m3forum.net/m3forum/showthread.php?t=458893

so there is heaps of evidence


That's some great info! Thanks for pitching in! A friend has a spare OEM E46 M3 section 1 that he says I'm welcome to try on the E30. If it fits, that may be the best (and cheapest) way to start the exhaust before merging into 3". If the above information is anything to go by, just having that 4 or so feet of dual 2.5" pipe is enough to help retain enough exhaust velocity/back pressure/mojo or whatever it is the gasses need to provide that low down torque.

If the E46 section 1 doesn't fit, I may still end up trying to fab up my own dual section with resonators before merging.

[S14]

crawled on the ground this evening and snapped a few photos. This is not how I would build a euro S50 in an E30 exhaust. It's well made, but now how I would have done it...

Straight off the headers is a pretty standard x-pipe. I'd guess the sexy ones from Burns stainless flows better than this one.
https://c1.staticflickr.com/9/8749/17544384655_3a7715d431_b.jpg (https://flic.kr/p/sJkyjB)Untitled (https://flic.kr/p/sJkyjB) by ericandshovin (https://www.flickr.com/photos/55094281@N03/), on Flickr

after the x-pipe it turns and consolidates.
https://c2.staticflickr.com/6/5444/17358020679_d74287680c_b.jpg (https://flic.kr/p/srSoNB)Untitled (https://flic.kr/p/srSoNB) by ericandshovin (https://www.flickr.com/photos/55094281@N03/), on Flickr

merge to resonator.
https://c4.staticflickr.com/8/7734/17356601628_05d2efecae_b.jpg (https://flic.kr/p/srK7Yd)Untitled (https://flic.kr/p/srK7Yd) by ericandshovin (https://www.flickr.com/photos/55094281@N03/), on Flickr

single back to dual.
https://c1.staticflickr.com/9/8726/17517983116_88c7a418b3_b.jpg (https://flic.kr/p/sG1f4E)Untitled (https://flic.kr/p/sG1f4E) by ericandshovin (https://www.flickr.com/photos/55094281@N03/), on Flickr

dual all the way out. I believe from the clamps back it is an E36 Eismann race catback.
https://c2.staticflickr.com/6/5469/16921776454_f3ce1b6609_b.jpg (https://flic.kr/p/rMjwAs)Untitled (https://flic.kr/p/rMjwAs) by ericandshovin (https://www.flickr.com/photos/55094281@N03/), on Flickr

[3MPowered]

^ Thanks for sharing. Why wouldn't you build your ideal exhaust this way?

[S14]

A few reasons.

- The E36 and I think E46 have the x further back than the E30 M3. This one has the X up close like the E30. I'd probably do it further back.

- I'd probably do dual 2.5 inch all the way through. The 2 to 1 to 2 seams like a recipe for loss.

- the X and the Y in my system don't look like they transition as best they could. I've seen much worse transitions, but I also have a burns stainless 2 to 1 and it is a work of art

- I want to do side pipes

- High quality high flow cats are as good as a straight pipe. I'm no hippie, but cats are a good thing.

- V-band clamps



Overall, it's a well made full stainless system, so it's very low on my priority list of changes/mods, but it is something I've thought about. I've also thought about ways to make it even lighter, and unfortunately I don't think dual 2.5 is good for weight savings.

[nick325xit 5spd]

For what it is worth, my one complaint with my current exhaust setup is that there is annoying drone between 2-2.7k. I'll probably T in a Helmholtz resonator at around 32" long to cut that down. (I've added them in the past and they are extremely effective.)

[3MPowered]

I think you guys have more or less convinced me to fabricating a 2 x 2.5" system all the way back. There can't be much of a weight savings just going single 3" in one section, and the added complication while fabricating probably isn't too bad.

Thanks to everyone for pitching in.