M30 conversion exhaust

Post Fri Oct 03, 2008 4:56 pm

Guys... i take it that the E30 M3 zaust would be ideal for this conversion? and the only mod that needs to be done would be to somehow mate the downpipes to the M3 zaust? i've found one on the bay but, i thought the M3's have a twin tail pipe? does this look good for what i need?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... otohosting

Post Fri Oct 03, 2008 5:39 pm

i did look at that was told that a single 2 1/2 pipe would give more power one of the zoners from finland i think had some power figures using different types of exhausts

Post Fri Oct 03, 2008 5:42 pm

so its a good find then? suppose i can always us a different back box..

Post Fri Oct 03, 2008 5:44 pm

to mate the M3 system to your M30 downpipes, you'll be needing a CAD drawing of the mounting flange to get a local laser / water cutter to knock up for you. about £25 - 30 seems to be the going rate.

i've got a CAD drawing of one here from when i did mine, pm me your email address if you need a copy

Post Fri Oct 03, 2008 5:51 pm

pm sent

Post Sat Oct 04, 2008 9:43 am

not big fan of that exhaust. the standard m30 5 series is twin 2.5inch so why reduce the engine to a single 2.5inch?

i used a twin m3 exhaust and made teh flange myself. you got loads of pics. i also have a 3inch full system which my mate made with me but it hangs a bit low at the flage

personally i would rather have a twin 2inch from a standard 325i than a single 2.5inch. but then twin m3 would be the way to go.

just remember the issue i hade with the down pipes to mount to the m3 flange (what a great word - flange)

Post Sat Oct 04, 2008 10:02 am

not big fan of that exhaust. the standard m30 5 series is twin 2.5inch

No it's not

325i system isn't 2" either - from memory it's 46mm

single 2.5" is ideal for the m30 - I seem to recall reading a post on on flow data on various sizes.

Post Sat Oct 04, 2008 11:26 am

so the 325i system is 46mm/1.8inches, oh well i have never been perfect

the 5 series exhuast is twin pipe and its a bigger bore than the 46mm/1.8 inch 325i system. im pretty sure.

so if bmw made the 5 series with a bigger bore than the 325i it had to be for a reason and why reduce it? maybe they did it to compensate for the cats? bigger silencers???

ok that 2.5 m3 exhaust might do the trick but like i said im not a big fan of that exhaust

Post Sat Oct 04, 2008 12:41 pm

325i system is 41mm ID, M30 is 46mm ID. You need to read into the dynamics of exhaust systems rather than making statements founded purely on guesswork.

As for you not being a big fan of the exhaust I had, fair enough. It was tig welded and used on an m3 race car but hey, your exhaust primarily composed of pigeon shit is sweet-as

Post Sat Oct 04, 2008 1:24 pm

whats the best combination exhaust wise then? i'm going to fabricate mine but not sure whether or not to use 3 inch or 2 1/2 inchpipe

Post Sat Oct 04, 2008 3:52 pm

Theo325 wrote:325i system is 41mm ID, M30 is 46mm ID. You need to read into the dynamics of exhaust systems rather than making statements founded purely on guesswork.

As for you not being a big fan of the exhaust I had, fair enough. It was tig welded and used on an m3 race car but hey, your exhaust primarily composed of pigeon shit is sweet-as

if your going to be an arse, be an arse. as i said the m30 is a bigger bore than the m20 325i.

so i dont like that exhaust, its personal preference.

Post Sat Oct 04, 2008 5:18 pm

well ive made up my mind anyway guys... im gonna get the manifolds on by cutting the flange and rotating it 90degress .. im also gonna try and get the downpipes on and just take the car to the zaust shop to continue it for me... more money, but less headache !!!

Ric325 do the downpipes (or at least one of them go straight on? or do they also need chopping and bending etc??

Post Sat Oct 04, 2008 7:27 pm

i will stop being childish.

my first set of down pipes went on but did hit the steering mech but i think that was due to my engine mounts?

so you could get away with it. i know galls was ok its just tight which most things are with the m30.

the problem with the m3 exhaust is that the m3 flange means the pipes are about an inch apart but theo managed to do it without the amount of pigeon shit i used. maybe he could help and that m3 exhaust could do you nice and save you some penies?

your choice cause it all can be done and any system should work.

Post Sat Oct 04, 2008 7:47 pm

Twin 45-50mm is fine, only go larger if you've already modded the engine for more power(head work/cam/etc).

The out let pipes to a set of Alpina B10 manifolds i owned a while back were 52mm internal bore which was for an M30 pushing 250-260bhp so it's a waste going bigger unless it has a turbo bolted to it.