Need advice on exhaust for DASC car

[Christian]

I need some advice on a new exhaust setup. Any input would be appreciated.

Setup:
Z3 w/ M44
- Downing Atlanta supercharger @ 9 psi
- 3" MAF from S50 6 cylinder
- Larger injectors
- Technique Tuning Stage III software
- Supersprint cat-back (average pipe diameter 2.0 inches)
- E36 M3 clutch w/ Fidanza lightweight flywheel
- Last dyno: 181 rwhp (~100 degree ambient temp, 80% humidity)

My Goal:
- Gain 10+ hp above 5500 rpm
- A small decrease in low end torque is acceptable
- Keep exhaust at or near current Supersprint volume and tone (I dislike really loud exhausts)
- Make exhaust free flowing enough to handle increase boost in the future

My plan:
- Install 4-1 header (Supersprint copy): I know the stock header is very good, but I think the larger primaries and collector will help for a forced induction motor.
- Install resonator in place of catalytic converter (Vibrant Ultra Quiet)
- Install mandrel bent pipe and a larger rear muffler, probably a Magnaflow

I can't decide on the exhaust pipe diameter that I should run. I'm thinking 2.5", but I know that some guys stay with 2", while others go up to 3". Does anyone have any experience with different exhaust setups on forced induction M42/M44 motors? Any input would be appreciated.

[HuGo]

When I had my DASC i got the (still have) 2.25" Stromung exhaust. I felt a difference for sure towards the higher end. I was running at 10lbs of boost. I loved the sound. I had no exhaust leaks or anything. I'm pretty sure a 2.5" would be a good idea if you plan on getting bigger headers.

BTW, don't listen to what marko has to say. You're just going to here garbage.

[Marv17]

nice. any pics on the setup under the hood? is there anything else done besides the supercharger??
just to say something i've read that the bigger diameter exhaust can cause a loss in hp because of less back pressure. not sure if that helps in your decision.

marko! whats your input on this?

[marko]

I had a 2.25 stromung as well & thought it sucked... lost bottom end & the car felt slower off the line than with the stock one.
Sounded horrible to boot (drone)... & the exhaust tip is simply retarded.
Swithched to a 2 inch... low end feels better, & it isn't as loud (but the exh. tip is STILL retarded).
Also, stromung exhausts dont fit properly... both of my stromung exhausts had severe leak issues as well as subframe clearing issues.

P.S. take Hugo's suggestions with a grain of salt... he has neon lights under his car & is a VIP member of most people's 'ignore list'.

good luck... M

Originally Posted by Christian

I need some advice on a new exhaust setup. Any input would be appreciated.

Setup:
Z3 w/ M44
- Downing Atlanta supercharger @ 9 psi
- 3" MAF from S50 6 cylinder
- Larger injectors
- Technique Tuning Stage III software
- Supersprint cat-back (average pipe diameter 2.0 inches)
- E36 M3 clutch w/ Fidanza lightweight flywheel
- Last dyno: 181 rwhp (~100 degree ambient temp, 80% humidity)

My Goal:
- Gain 10+ hp above 5500 rpm
- A small decrease in low end torque is acceptable
- Keep exhaust at or near current Supersprint volume and tone (I dislike really loud exhausts)
- Make exhaust free flowing enough to handle increase boost in the future

My plan:
- Install 4-1 header (Supersprint copy): I know the stock header is very good, but I think the larger primaries and collector will help for a forced induction motor.
- Install resonator in place of catalytic converter (Vibrant Ultra Quiet)
- Install mandrel bent pipe and a larger rear muffler, probably a Magnaflow

I can't decide on the exhaust pipe diameter that I should run. I'm thinking 2.5", but I know that some guys stay with 2", while others go up to 3". Does anyone have any experience with different exhaust setups on forced induction M42/M44 motors? Any input would be appreciated.

[HuGo]

Originally Posted by marko

I had a 2.25 stromung as well & thought it sucked... lost bottom end & the car felt slower off the line than with the stock one.
Sounded horrible to boot (drone)... & the exhaust tip is simply retarded.
Swithched to a 2 inch... low end feels better, & it isn't as loud (but the exh. tip is STILL retarded).
Also, stromung exhausts dont fit properly... both of my stromung exhausts had severe leak issues as well as subframe clearing issues.

P.S. take Hugo's suggestions with a grain of salt... he has neon lights under his car & is a VIP member of most people's 'ignore list'.

good luck... M

Subframe clearence was perfectly fine. I put mine on with NO PROBLEMS. No exhaust leaks. The tip sorta is retarted ill give ya that one. Tip sticks out to much. Not anymore since i cut mine for the swap. But like i said, the stromung exhaust did make a difference especially with the stg 3 tuning.

I think you're confusing me with TiFreak Marko. Those neons have been LONG and i mean LONG gone. Atleast use something in present time not something I had when I first joined the forum The VIP thing, well it does feel pretty good

[marko]

Truth be told, increased exhaust diameter & mendrel bends do almost always result in a better flow & less restriction... I.E. additional horsepower.

Top end vs. bottom end is always a compromise - but that would be to the driver/owner to determnine where they want their optimal powerband.

In fact 2.25 diameter exhaust did wonders for my NA 2 litter GTI, some years ago - but for some reason it simply did not work out that way with the Stromung on my blown Ti.

I think rather than guess the result (which is what most of us do) - it may be prudent to employ a company such as the one linked below - and have them make you a custom system with a proper back box, which will insure good HP results and a desired sound.
http://www.mufflex-performance.com/

[mohaughn]

I'm with Marko on the fit of the stromung. Mine had to be dented to not hit the subframe. I would also say that some of the hangers are a bit out of alignment on mine as I had to cut the rear valence to get the exhaust to hang properly. It is loud inside of the car, but for a track car, I don't really care about that. Luckily, it doesn't have the ricer sound outside of the car..

I don't think you can get a stromung made for the Ti anymore, the group buy was supposed to be the last batch of them. Probably better off, and much cheaper to get something made custom locally.

[DustenT]

I have a stock 318ti exhaust mid section with a gutted cat if you want to fab something. BTW...running with a gutted cat is a horrible idea. Besides the obvious environmental issues, the noise is unbearable.

[Christian]

Thanks for the input guys.

My fake Supersprint header arrived today, and looks surprisingly good for $100.00. Although I haven't installed it yet, the collector runs farther back than the stock header, so I'm debating two options.

1. Have a 2.5" custom mid pipe with cat delete (resonator in it's place). Have this connected to my current Supersprint cat-back.

2. Have a 2.5" full exhaust made w/ cat delete, resonator, and Magnaflow muffler. I'll probably choose option 1 first, and move onto option 2 if I gain power w/ option 1. The car is pretty torquey with the DASC, so I don't mind losing a bit of low end if I can pick it up (and then some) on the high end.

Marv: I don't have any pics on this computer. Besides the engine mods I listed in my first post, I have Ground Control/Koni suspension, front strut brace, race roll bar w/ harness bar, 17" SSR Integral wheels. I think that's about it.

Dusten: I may PM you about the mid-pipe w/ gutted cat. I'm going to install the new header and go from there.