Stroker M20 exhaust

[tinkerputzer]

Wow glad i found this thread. I normally skip over the exhaust section of this forum.

Excited to see you're going with single 3". This may be of some interest to you. It's a 4 banger but same chassis ;)

http://www.e30m3project.com/e30m3performance/installs/installs-2/exhaust/exh1.htm

Is the placement of the venturi collector close to where the "x" would go in a dual system?

[digger]

Wow glad i found this thread. I normally skip over the exhaust section of this forum.

Excited to see you're going with single 3". This may be of some interest to you. It's a 4 banger but same chassis ;)

http://www.e30m3project.com/e30m3per...haust/exh1.htm

Is the placement of the venturi collector close to where the "x" would go in a dual system?

ill be putting it venturi at 3rd harmonic, x-pipe is 2nd according to pipemax. i could also put the venturi at the 2nd. i wont do any testing of venturi position on this engine perhaps the next it depends how things respond

id seen that article ages ago but forgot about it and thats what i will be doing in effect, i'd be interested to know if the S14 was tuned afterwards as it makes a big difference

[Regnar75]

"knowing this pipemax says 32" is the correct location for the Y-pipe and Burns X-design says 30". So both are in good agreement so that's decided."
this is interesting, does this mean the ideal location of Y pipe on m20 exhaust system would be 30-32 inches from the exhaust port on the head?
"about 400mm when might be better to have used 800mm or 1600mm which are also harmonic lengths" or do you mean even more so like 60+ inches like the s54? this is interesting and i was just planning on rebuilding my exhaust but this is making me think twice about how i should place my Y pipe.

[AWDBOB]

Digger, I'll be running LTs with 2.25" collectors, and a catback with 2.25" piping to a muffler in the back.

What would you recommend for a mid pipe? The end result will be a simple stock bottom end 272 cam M20 with ITBs, I just want to make sure I don't kill the power without enough backpressure.

Is it alright to stay 2.25" duals in the mid pipe? Straight pipe or resonator in there? Just want to make sure I don't lose power.

[digger]

you dont want back pressure, you want good velocity and correct lengths.

i'd use a resonator in the middle section otherwise it's loud/sounds crap IMO. a resonator wont cost hp if you use a hot dog style unless you use a restrictive muffler as a resonator even then it wont be alot.

you need a surprisingly big restriction in the exhaust to cost hp on a lowish hp m20. i did tests once and you need something like a 1" orifice plate in each tailpipe to start to really hurt a 200whp engine.

this kinda means that people are generally using oversized pipes.

[Bullhead]

I have heard of a lot of people using the dynomax ultra bullet muffler for resonators. I am either going this route or using an old school resonator like a glasspack but this is just to save funds. The vibrant resonators aren't cheap but if you have the $ it's a great setup.

[digger]

the vibrant bullet style resonators are quite cheap, the ultra quiet are large OD so clearance is an issue on a lowered car.

[AWDBOB]

the vibrant bullet style resonators are quite cheap, the ultra quiet are large OD so clearance is an issue on a lowered car.

Would there be any negative effects if the pipes aren't crossed?

[digger]

Would there be any negative effects if the pipes aren't crossed?

I can’t say if having no merge at all is an issue as I have not done any tests. I have seen it done and from memory Stuck did this with his M20 and it seemed to work out well. Unless you do a test with a merge and another without a merge you won’t really know the effect of this alone.

Personally I would put a cross over or merge of some sort such as an X-pipe, Y-pipe or H-pipe. BMW usually does this about midway down just behind the gearbox on the 6cyl engines which is seems to give a good allround power curve.

If you were significantly different from stock it might respond to something different but You would need to do a test if you want to better this.

[LJ851]

Would there be any negative effects if the pipes aren't crossed?

My car is currently like this, it does not sound good in my opinion.

[tinkerputzer]

Agreed ^^^ i have bav auto headers straight through to the muffler. It's pretty raspy. I'm waiting to see what digger does before i change anything :)

[digger]

Agreed ^^^ i have bav auto headers straight through to the muffler. It's pretty raspy. I'm waiting to see what digger does before i change anything :)

I've decided to just move the X-pipe (a better X-pipe will be used though) and retain twin system but ill be redoing some of the hacked piping etc. i wanted to retain my custom rear muffler as i liked the sound of a twin system.

i do believe a single 3" or even slightly smaller 2.75" (hard to find cats, mufflers) would be better for absolute best for performance, and simplicity, weight, cost etc if starting from scratch but maybe another day.....

[MaxBell]

Any progress on this? Have you decided what you're doing for resonator/muffler in the center?

I just ordered all mine and went Borla ProXS in the middle, Stromung at the back.

[digger]

two vibrant bottle style resonators which are similar to what i have now and my current muffler which was a custom one made by walker

[digger]

i have moved the X-pipe from 4th to 3rd harmonic and it seems a positive move.

The AFR or timing has not been adjusted at all and you can see that the engine runs alot leaner in parts now and make alot more power in midrange as i was hoping and no loss of topend hp.

i will get it properly tuned in the next couple of weeks and will update as i imagine there will be some additional gains from a tune



im not sure why the operator ran it from such a low rpm but 100km/h is 3400rpm so the peak torque is 220twq 4200rpm give or take and hp 224whp 6100rpm.