My first M30 swap details

[m10man]

Why a single "2.5 ? by calculation that is the same diameter as a stock 325i exhaust i.e 2x "1.75, the 735i comes with a double "2 as stock
why would you want a smaller exhaust,

It produces more torque on the 3.5 engine and about 5hp more top end. Lighter and dampens the exhaust pulses to produces a quieter system eliminating the need for the centre resonator. Also allow the exhaust to run hotter so that the whole system lasts longer.

[m10man]

with a gtech pro???

Unfortunately I only have the earlier G-tech - I want to buy one of the new G-tech pro RR's though. Knowing my exact weight should help in getting an accurate HP figure too.

[Gunni]

Why a single "2.5 ? by calculation that is the same diameter as a stock 325i exhaust i.e 2x "1.75, the 735i comes with a double "2 as stock
why would you want a smaller exhaust,

It produces more torque on the 3.5 engine and about 5hp more top end. Lighter and dampens the exhaust pulses to produces a quieter system eliminating the need for the centre resonator. Also allow the exhaust to run hotter so that the whole system lasts longer.

how can a smaller exhaust make more torque AND more high end Hp?
beeing smaller then stock even,

besides the M30 has a weak high end while having a in you face low end and mid range,

[m10man]

I will find the dyno report for you, but the 3.5 bmw six definately likes the 21/2 inch single system more than the dual 2 inch. With exhausts bigger is not always better - it is all about flow and finding the optimum size to match the engines exhaust pulse.

[TW166Y]

Drivershaft : M20B20 non modded

sorry dude i never saw this before, are you saying here that a 320 propshaft will work instead of an m3 one or a half/half make up prop in engine pos 3, if so thats great stuff! and waaaaay cheaper

[gareth]

only with a m10 gearbox on a m30. it won't fit with a M30 box.

[TW166Y]

only with a m10 gearbox on a m30. it won't fit with a M30 box.

what do i need then an m3 prop or a made up one?

[bigdek]

either dude.

m3 prop usuall Ԛ£80 - Ԛ£150.

when did mine i found a specialist who cut and joined the front of the m30 prop to the rear of the m20 for Ԛ£40

which is very cheap.

[TW166Y]

dek could you get hold of this fella again and also was that balanced too?

[bigdek]

hes in glasgow m8

did evodans as well i'm sure

[m-dtech]

there is propshaft company in falkirk not far from where i live.

im sure fuzzy used them for his cossie conversion.

m

[TW166Y]

ill have to see if i can find an engineering company close to me i suppose, either that or i drop on an m3 one

[DanThe]

I got a quote of Ԛ£100 the other day Twigg, down the road from me. Reading the above posts though I need to keep looking

[DanThe]

I got a quote of Ԛ£100 the other day Twigg, down the road from me. Reading the above posts though I need to keep looking

[TW166Y]

how comes you need one dan? you doing a m30 too

[DanThe]

Nope, 6 spd for my M50

[TW166Y]

Nope, 6 spd for my M50

[m10man]

Found the exhaust comparison figures. A lot of guys here in oz with the ford 4.1 straight six (which incidently was designed by BMW) fantasise about putting a dual system on but discover they lose performance so go back to a single. But here are the figures:

Comparison done on a 1988 E34 535i.
Flow Test
2x42mm (1 3/4 inch) exhaust flow = 235cfm
1x65mm (2 1/2 inch) exhaust flow = 300cfm

Acceleration Test 60-80mph
2x42mm exhaust
3rd gear = 4.9 sec
4th gear = 7.2 sec
5th gear = 10.7

1x65mm exhuast
3rd gear = 4.4 sec
4th gear = 6.7 sec
5th gear = 10.25

For those of you who want to make a comparison with your 335i the E34 M5 did these figures:
3rd gear = 4.0 sec
4th gear = 5.2 sec
5th gear = 8.0

and just for interest if you put a single 65mm (21/2 inch) system on the M5 it then does:
3rd gear = 3.4 sec
4th gear = 4.9 sec
5th gear = 6.9

Hope this inspires some of you to experiment with a single 2 1/2 inch system.

[DRIFTBOY]

That is very interesting!

And annoying for me - I wanted to try a single pipe on my 335i but was talked out of it by a couple of mates!

Might start again with my exhaust now, I can't get my wonky back box straight so a single pipe would sort that too!

[gareth]

i wonder why bmw did the twin pipe then? maybe a comination of ground clearance and noise level?

[Andy335Touring]

So where do you put the Y-peice in to make it go from 2 to 1 ?

Is 2" = 42mm a typo ?

Just to add some info to this i worked out the surface area's.

2 x 50mm I/D = 3927mm2

To get the same surface area you need a single tube with an I/D of between 70-71mm

1 x 2 1/2" or 63mm I/D = 3117mm2

or if you use 65mm I/D = 3318mm2

My guess is you are getting similar positive effects to fitting an X-pipe to a twin system with a using a single pipe/Y-peice ?

[m10man]

So where do you put the Y-peice in to make it go from 2 to 1 ?

Where the first connection is just past the gearbox.

[m10man]

Is 2" = 42mm a typo ?

Yes Andy, it be 44mm - I have corrected that.

[Andy335Touring]

I'll hope fully put my X-pipe just in front of that mount but before the down pipe flange.

My WBO2 sensor is down stream from that so it will help it to read the gas's from all 6 cylinders rather than just the 3 that it see's now.

[Andy335Touring]

Is 2" = 42mm a typo ?

Yes Andy, it be 44mm - I have corrected that.

Two inches is fifty point some thing MM ?

[m10man]

Yeah 2 inch is 50.8mm so the stock E34 pipe is 1 3/4 inch. I have changed that too.

Looking at that photo Andy - are you running an O2 sensor? Are you running a Kat aswell? I am thinking of getting the O2 sensor and wiring and running it - it has to be better as the ECU then knows exactly what the engine is doing as far as fuel/air mixture. I dont want to run a Kat though.

[DRIFTBOY]

Just a thought though. -

I assume the twin systems they tested were the standard ones. ?

The single pipe systems obviously weren't standard, so I wonder what silencers they used, as they are the main restrictor in an exhaust system, not the size of the pipe (unless it's a pea-shooter - literally!).

I'm not saying this isn't true (I hope it is, it would make my life easier!), I just wonder how accurate and scientific the test was.

[Gunni]

My 2 x "2 exhaust is custom with a custom rear muffler,
the stock system is almost a silencer and kat front to back,

[TW166Y]

gunni how much did that cost you again? why does this 02 censor need to be ran and where is it located when i start pulling the car to bits?

[Gunni]

Mine was expensive, well compared to local standards I guess, 540pounds from the exhaust manifolds and back
with custom muffler in the back

I didnԚ´t put a O2 in this car, but might tough

[Andy335Touring]

Yeah 2 inch is 50.8mm so the stock E34 pipe is 1 3/4 inch. I have changed that too.

ah, right, gotcha now

I must admit that i've not measured my down pipes before, i think my Scorpion M3 exhaust is a tad over 50mm O/D so i guess it's around 48mm I/D ?

Looking at that photo Andy - are you running an O2 sensor? Are you running a Kat aswell? I am thinking of getting the O2 sensor and wiring and running it - it has to be better as the ECU then knows exactly what the engine is doing as far as fuel/air mixture. I dont want to run a Kat though.

Yes, it's for my Inovate WBO2 that is to help me tune my stand alone ECU(if i had a lap top at the mo that is )

So i'm told you can't put an O2 sensor on a Cat ready Motronic ECU that didn't actually have an O2 sensor as standard because the programing of the ECU isn't there to make use of it ?

[Gunni]

All Motronic 1.3 ecuԚ´s have the O2 input, it may just be the rom it self in the ecu that has the 02 signal turned off,
using a KAT chip would make it usable again

[TW166Y]

now im really lost

[Andy335Touring]

now im really lost

Ignore O2 sensors, you won't need one

[gareth]

this shows the bore sizes and spacings of the M3 system (taken from a scoripon stainless one like andys)
http://img.photobucket.com/albums/v382/ ... d23494.jpg
46mm bore... can't imagine it being a lot different to the standard M3 one.