E28 M5 proformance exhaust (rear box) options?

[BM WORLD 1264]

finally completed my engine rebuild and tunning etc in my E28 M535i fitted with a M88 engine thats been bored out ,stroked and hot cams ,HC pistons etc etc 3.65L .

have had it all retuned on a rolling dyno etc

also have fitted a 4" millar maf unit to it.

manage to get about 30kw (40hp) more at the wheels than a std m5 engine puts out

see build project here.

http://www.bimmersport.co.nz/forums/index....showtopic=31734

i am just wonder what rear mufflers are around that fit in the back of the e28

as the the turner guy (and exhaust guy) both think the current exhaust system is a bit restrictive ,

power comes up nice and strong to 5300rpm then pretty much holds that untill 7000rpm

we think with all the mods etc it should still keep climbing upwards to say about 6500rpm etc.

whats around that has a twin in twin out type that can fit into the rear of the e28.

was looking at replacing the front pipe section with larger pipes 2-2.5" and 2 coby(hot dog ) type mufflers then to a new back box with larger inlets and outlets .

exhaust shop guy says he can do a Y conector then go into a large single inlet and out let type 3"?? . but i am not sure about that , might make it a bit loud and not look quite right etc.

the rear muffler thats in there now has twin 45-50mm inlets and outlets and about 150-160mm diameter

but theres not alot more room to go in width in the back of the e28 only about 220mm etc

current exhaust setup

have seen mufflers like these here in NZ

http://www.trademe.co.nz/Browse/Listing.aspx?id=449610295

http://www.trademe.co.nz/Browse/Listing.aspx?id=449466620

they are about 204mm wide so not alot of clearance to the sides

any info or thoughts would be great

thanks brent

Edited February 20, 2012 by Brent HARTGE535i

[No name user 379]

hay brent if ive got this right and not picking but the m88 stock was 286hp which working back and converting to kw wheel its 248hp wheel or 185.8kw, ive seen a few mates cars come off gavins dyno and 15% to the wheels is pretty much bang on just a thought for work done it doesnt seem to add up unless the motor for the 160kw was tied but still makes the power same as a stock m5/m635.

something isnt right there should be alot more in it and not just in need of the exhaust, cam timing to tune is too soft?

http://en.wikipedia.org/wiki/BMW_M88

[BM WORLD 1264]

hay brent if ive got this right and not picking but the m88 stock was 286hp which working back and converting to kw wheel its 248hp wheel or 185.8kw, ive seen a few mates cars come off gavins dyno and 15% to the wheels is pretty much bang on just a thought for work done it doesnt seem to add up unless the motor for the 160kw was tied but still makes the power same as a stock m5/m635.

something isnt right there should be alot more in it and not just in need of the exhaust, cam timing to tune is too soft?

http://en.wikipedia.org/wiki/BMW_M88

it goes like a cut cat ,

pulls away easily from std e28 m5 e24 m6 and e36 m3 etc

and that was before some of the engine work and the millar maf and remap etc

so i dont think it has that problem.

have asked gavin what other cars get on his dyno

e30 325i 90-100rkw

my e36 325i & 328i both at 112rwkw

std e28 m535i 635csi 110-120rwkw (218hp flywheel)

std e36 m3 about 160rwkw

std e34 540i about 150-160rwkw etc

my e34 544i 4.4L after remap 192rwkw

std e34 3.6L m5 about 180rwkw (315hp at the flywheel)

3.2L M3 ABOUT 190KW+

so i think its on the right track ,

its just that its been held back a bit (at the top end of the revs) by a 20 year old exhaust system

from a fairly std e28 528i 535i etc

thanks brent

Edited February 20, 2012 by Brent HARTGE535i

[No name user 379]

i dont dought it doesnt go and its around the same power as my m50b25 with similar work but its still about the same as the engine was stock im sure there must be more in the tune or somewhere, be interesting what an exhaust does that factory 286hp was on a factory exhaust so bmw says.

188kwx1.15=216.2kwx1.34=289.7hp

[Neal 512]

You could try and copy an old hartge or remus otherwise check out the link below.

http://www.supersprint.com/en/prod-298-684..._m5_286_hp.aspx

[BM WORLD 1264]

i dont dought it doesnt go and its around the same power as my m50b25 with similar work but its still about the same as the engine was stock im sure there must be more in the tune or somewhere, be interesting what an exhaust does that factory 286hp was on a factory exhaust so bmw says.

188kwx1.15=216.2kwx1.34=289.7hp

dont get me wrong i am very happy with the power and torque it makes.

gavin was also very pleased with the results he has got from it.

said it makes more torque than his e34 m5 powered e30 race car thats currently doing very well in the bmw open class race series

and he has sleightly more power than my engine makes on his dyno but he has a proper headers on it and a much larger pipes and more free flowing exhaust system (2 times 2.5" coby's and powerpro rear muffler)

than in my e28

also e34 have a pretty large intake system /throttle bodies , intake valves etc.

so i think with a little more tweaking with a freer flower exhaust system it should release a little more peak power etc.

my mates std e34 m5 makes about 180rwkw ,

but the e34 m5 run larger header pipes and more of a extractor set up and the exhaust is also has a larger pipe set up etc

i dont think a stock e28 m5 system would be of any use either

and i am reluctant to spend 400 pounds or 700-800usd etc on some of these after market ones because they probably still go for a sleightly quieter setup to keep people happy etc.

[No name user 379]

Ive seen his car go and power to weight is a good thing im basing my findings on what i do day in day out and wouldn't it nice to find another 30-40hp hiding that maybe over looked? im sure you would be even happier

hay just trying to help Brent there's many ways of doing things....A

Edited February 20, 2012 by crunchy

[BM WORLD 1264]

Ive seen his car go and power to weight is a good thing im basing my findings on what i do day in day out and wouldn't it nice to find another 30-40hp hiding that maybe over looked? im sure you would be even happier

hay just trying to help Brent there's many ways of doing things....A

ok thanks for your input.

i am just basing my findings on what i have seen on the same dyno with different cars/engines i have had and others i know who use the same dyno.

ok so when you make a 300- 350hp turbo engine what size exhaust do you use to get the gases out for top end power

say if was a single pipe or twin pipe set up

Edited February 20, 2012 by Brent HARTGE535i

[No name user 379]

Thats not how tuning works or how to make power try this little formula i use to make headers

p=primary header length

p= 850xed( 180 deg plus number deg the exhaust valve opens before tdc) / eng rpm you want to work it best at ( and i dont mean 9k!

This gives the primary length header id should match port id and running 6-3-2-1 gives a broader power band and helps cylinder scavenging also running stepped tubed headers gives a greater power band.

Where the 3-1 come together you need to run a merge cone also coming into a merge collector stepping down then up again around 7-10 deg the actually main system for yours a single 3" is fine and n/a will do 350hp turbo ill push 900hp.

Now cam position is also important and i dont mean drop it in the hole and its all go there's free power to be had there as in what center line is each cam sitting at? plus or mins a few deg makes massive differences between good and great power.

Ive never been a fan of generic cams unless the head is done to suit reverse engineer it by doing the head first or at-least flow bench test it to see where it works the best,just cause it has cams doesnt mean it work better.

eg: if a head has peak flow at 10mm lift and the cam is 10.5 you can drop air out of suspension killing power big time short of me designing what you have if you dont have answers for any of that then who knows what you may have or could end up with.

ps: exhaust isnt the only thing that limits topend where would you like me to start on that topic?

Seriously unless you build an engine from the start knowing what your trying to achieve even the calculator wont help you, even with an error of 10% your still pretty much the same power as the motor was stock no matter what way you look at it.

Edited February 22, 2012 by crunchy

[E30-323ti 66]

Something like this Brent would fill the gap.

Flowmaster HP

A single 2.5" might be a bit small, but you could always put 2 beside eachother being 4" thick.

Also have a look at magna flow mufflers.

With want you have done to the motor, it seems a shame to not have some nice headers and free-flowing exhaust.

[tcbaurpower 5]

I would be interested to see how this works out for you Brent. What works for your beast can only be good for a little 3.5L and mine could use an upgrade.

[BM WORLD 1264]

I would be interested to see how this works out for you Brent. What works for your beast can only be good for a little 3.5L and mine could use an upgrade.

yes is working very well .

nice improvement over a std e28 535i etc.

heres a short video clip of mine at taupo last year before the millar maf upgrade and remap

and my mates e28 m535i with schrick cam etc following me

[No name user 379]

whats the weight differance between the two cars? i noticed at the topend he pulls you back in

[BM WORLD 1264]

whats the weight differance between the two cars? i noticed at the topend he pulls you back in

they weigh the same ,diffs are the same ratio , same brakes (e34 540i type),

but he has sleightly better suspension setup than me with coil overs and can corner a bit faster than me with better turn in etc with adjustable camber plates etc.

same sway bars , same bilstein shocks (sleightly different valving though)

only difference is I just didn't bother rushing up and braking at the last minute just ease off and braked normally,

so i just let him catch me on the corners the i pull away again,

at one stage i just left the car in third gear the whole way around the track.

[No name user 379]

oh really? doing a comparison for e34/e28 there's 265lb difference unless there's different curb weights model based if you changed the diff ratio you could make better use of the gearbox staying in 3rd points too a tall rear end.

[BM WORLD 1264]

oh really? doing a comparison for e34/e28 there's 265lb difference unless there's different curb weights model based if you changed the diff ratio you could make better use of the gearbox staying in 3rd points too a tall rear end.

its a red e28 m535i vs my silver e28 m535i with m5 engine not a e34.

so same weight.

yes i am looking at fitting a 3.91 diff soon , just to help it along a bit and will also help that i have 7000rpm to play with now (only had 6500rpm before)

both cars run the getrag 260 gearbox.

at taupo i use mostly 3rd and 4th gear , only need 2nd if someone holds me up in a corner.

at hampton and puke i just get into 5th on the back straight

[No name user 379]

ah my bad didn't see that yes i need the same but a large case around 3.5 upwards the medium 4.1 im running is great with 8500rpm but im not aware of a large case that ratio.

[E30-323ti 66]

I recall looking into that yrs ago, IIRC there was a E32 that has a 4.27 large case diff.

I'll have the link saved somewhere, all the E46 M3 guys in the US were all excited and swapping their R&P's for them.

You'll have the 3.08 at the moment won't you Brent??

[BM WORLD 1264]

I recall looking into that yrs ago, IIRC there was a E32 that has a 4.27 large case diff.

I'll have the link saved somewhere, all the E46 M3 guys in the US were all excited and swapping their R&P's for them.

You'll have the 3.08 at the moment won't you Brent??

yes large case diffs any higher than 3.91 are pretty rare. the 3.91 ratio i have came from a e32 735i , also used in e34 m5 etc

teh later e34 and e32 735i 535i used medium case diffs to cut back on weight and cost etc and they where a bit of a overkill for the 211hp they had.

i can get you a 3.07 if you need , thats a factory ratio for these euro spec e28 535i etc .

also have 3.25 from a e23 735i etc

will probably sell the 3.73 lsd in the future