exhaust options

[static]

hey guys, im running a ENTIRE stock m20 exhaust system from the modified down pipes back on a M50TU. my only mods i plan on doing are basically the bolt-on's - 3.5 HFM, s50 cams and maybe a properly done CAI along with software of course....but for now its stock. is my exhaust good for now or restrictive? will it be restrive with those mods?

stock exhaust should be fine for a 2.5, i don't imagine you'd see much gains by opening up the exhaust.
3.5 HFM is totally unnecesary on a 2.5 IMO. Think about it, they used the same 3.0 MAF on all of the M/S5X. So if it was reasonable for 3.2 S52, i'd think it's enough for 2.5L m50. So save your cash for cams and upgrade the retainers when installing cams. Also make some kind of decent heatshield or cold air box. In the summer, you'd see more gain from this than from HFM+exhaust.

[e30_kid89]

hey guys, im running a ENTIRE stock m20 exhaust system from the modified down pipes back on a M50TU. my only mods i plan on doing are basically the bolt-on's - 3.5 HFM, s50 cams and maybe a properly done CAI along with software of course....but for now its stock. is my exhaust good for now or restrictive? will it be restrive with those mods?

[///Mpressive]

Ben's car didn't use the stock cat. It went from an AA track pipe collector to 2.5" pipe (you could put a highflow cat here) then it split to 2x 2" with a flowmaster Y-pipe then connected that to the stock 99 M3 catback with a pair of stock flanges off my old exhaust. Hangers were all custom AFAIK.

It hung a little low, but it was cool.

That's just a big, heavy muffler. It had maybe 1/2 inch clearance above the muffler, it was a tight perfect fit. It would be okay on a plastic bumper car with some type of rear valence to hide it, but you would still be able to see it a little.

I miss that car.

[matt]

Ben's car didn't use the stock cat. It went from an AA track pipe collector to 2.5" pipe (you could put a highflow cat here) then it split to 2x 2" with a flowmaster Y-pipe then connected that to the stock 99 M3 catback with a pair of stock flanges off my old exhaust. Hangers were all custom AFAIK.

It hung a little low, but it was cool.

[static]

You can use an e36 catback no problem. The trick is to redo the part BEFORE the flanges (after the cat). This is how ///Mpressive's car was done, and it was awesome.

hmm, well i don't remember it clearly now (it was a year ago) but the welder pretty much said it can't be done (go figure) and actually showed me what he meant.

in regards to changing the piping upstream from the catback flange, i wouldn't imagine there be too much wiggle room to move the cat pipe around as the tunnel is already pretty restrictive (can do perhaps 3" in each side latterally but not more i imagine)

maybe someone can post pics of Mpressive's setup?

[BigD]

Alex: I'm talking about the motor mount hardpoints in the subframe crossmember - weak.

You can use an e36 catback no problem. The trick is to redo the part BEFORE the flanges (after the cat). This is how ///Mpressive's car was done, and it was awesome.

Cool! Can you give me some more detail? I can't picture what the problem is. From static's post, it sounded like the problem is the pipes from the E36 catback don't follow the E30 underbody exhaust route properly. How does it help to modify the pipes after the cat (by after I assume you mean on the rear axle side? or on the motor side? and modify how?), wouldn't you also have to modify the catback pipes?

Thanks!!
D

[matt]

i tried to get the guy in exhaust shop to use the stock e36m3 catback in it's original state on mine. He basically said the piping angles are just way different, so we ended up just cutting pipes off and doing a custom one all the way to the muff.
You can probably ask a good welder to modify it with some mandrel pieces to make it fit nice.

How is the project going D ?

You can use an e36 catback no problem. The trick is to redo the part BEFORE the flanges (after the cat). This is how ///Mpressive's car was done, and it was awesome.

[static]

good news!

what subframe reinforcements are you talking about?
people succeded in massaging stock e36 exhaust into e30, but honestly, i would strongly advise to bite the bullet and make a full custom mandrel exhaust in a good exhaust shop - otherwise it might end up being a big pain in the ass.

[BigD]

i tried to get the guy in exhaust shop to use the stock e36m3 catback in it's original state on mine. He basically said the piping angles are just way different, so we ended up just cutting pipes off and doing a custom one all the way to the muff.
You can probably ask a good welder to modify it with some mandrel pieces to make it fit nice.

How is the project going D ?

That sucks. Would an E30 muffler bolt up to the E36 cats? How big are the E30 aftermarket muffler pipes (like a stromung?)?

It's going good man! Everything is ready, I've bought all new sensors/seals etc, everything is in, just need to modify the wiring harness, send the injectors for flowmatching/rebuild, and buy a new UUC flywheel and M5 clutch, a rad and maybe, beyond that all I can think of is the OBDI fuel rail and 318 harness cover, everything else is covered, even have an M3 cluster with 49k on it. Once all that is in, the exhaust is the last step. I have THR arms and with some subframe reinforcements for the subframe, I won't need any fucking around with the stock downpipes so I'll just get stock E36 cats. Beyond that, I'm not sure. I really REALLY like this dual muffler, straight through exhaust from UUC but it's a solid waste of $ to have to cut the pipes off and pay an exhaust monkey to do a new pair.

I'm in no rush, the car is wicked fast in the turns and I'm not racing so I don't care how many ricers fly past me in the straights. I'm learning a lot about the car and so is Felicia. One more track day in May, maybe one more in July but I'll probably put it in in time for July.

[static]

Can you tell me (or PM/email) what you had to do to make that fit? That's the exhaust I want to use.

i tried to get the guy in exhaust shop to use the stock e36m3 catback in it's original state on mine. He basically said the piping angles are just way different, so we ended up just cutting pipes off and doing a custom one all the way to the muff.
You can probably ask a good welder to modify it with some mandrel pieces to make it fit nice.

How is the project going D ?

[BigD]

i'm using one of these, modified to fit...

http://www.uucmotorwerks.com/RSC36/

Can you tell me (or PM/email) what you had to do to make that fit? That's the exhaust I want to use.

[matt]

It takes into account a lot of things. I don't even remember most of it now. I think they are having server issues... I can't login either.

[JeffRR]

It's not hard to determine the optimal solution... www.headerdesign.com will get you started.

They must be having trouble with the site, I tried to reg yesterday and today and it doesn't seem to be working.

Anyway, I'm guessing that they run a simulation?
What do they use for inputs?

[matt]

the collector is dual 2"id (almost exact matching the headers) going to a spread oval. its a little tough to see in the pic, but both "primaries" just barely touch and are cut off at 90 degrees....about 2" inside the ovaled collector. that metal v-shape on the outside was just to cover the back side of the collector.

thanks for the tip. what would make a better collector? i will check with header design.

Those are actually secondaries. I personally used the stock BMW secondaries to just past the point where they join going into the cat (off an e36 325i) including the merge. I would probably prefer to use something premade by flowmaster or someone like that. They usually do a prettier job (neatness counts on the inside more than out) and they're pretty cheap.

[Jason89i]

Your collector could use some work. There's nothing wrong with clamps, also.

As for size, 3" is probably OK for a 300hp + euro motor. Run the motor's details through at www.headerdesign.com and it'll give you a better idea.

the collector is dual 2"id (almost exact matching the headers) going to a spread oval. its a little tough to see in the pic, but both "primaries" just barely touch and are cut off at 90 degrees....about 2" inside the ovaled collector. that metal v-shape on the outside was just to cover the back side of the collector.

thanks for the tip. what would make a better collector? i will check with header design.

.....smaller dia dual should be quieter and not as droney as single large dia due to resonance.

i first fired the euro with just the collector on. it was amazingly smooth and quiet. no rumble, no pops, no resonance.

cheers, jason