For eveyone else reading this thread, please don't follow in OP's footsteps. Placing the collector too close to the manifold like he proposes will cause the exhaust gasses to back up into the combustion chamber at lower rpm when scavaging and exhaust gas speeds are lower. It's called exhaust reversion, and race teams don't care much about it considering they don't spend any time on the street.
Just to be sure, I'll post a few examples:
http://www.r3vlimited.com/board/showthread.php?t=317505
Exhaust from run 3 notice the x-pipe is closer to the engine
Run 3 to run 4 was a cam timing change (advanced 8 degrees). i did a cam belt change at the same time and thought maybe the timing shifted a few degrees. while i found good gains the shape of the torque curves shows that this was not the problem. the real problem is the relocation of the x-pipe
Quote:
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Originally Posted by Loftygoals
So I posted my dyno a few weeks ago:
http://www.m3forum.net/m3forum/showp...&postcount=949
On the suggestion of some of the forum members, I reworked my 3.5" exhaust.
Original Config:
eBay Headers
4" of 2.25 Dual Pipes
Merge to 3.5"
3.5" Resonator
3.5" Race Muffler
New Config:
eBay Headers
40" of 2.5" Dual Pipe
Dual 2.5" Resonators
Merge to 3.5"
3.5" Resonator
Basically, I moved the merge back to just before the rear subframe on my MZ3 Coupe. This forced me to change to dual resonators before the merge.
The other modification I made was I switched from the stock water pump setup to an electric pump.
The results, we awesome:
Sorry for the lack of Torque readings, but the dyno wasn't picking up RPMs for my base line pulls. But you can clearly see there is a lot more power down low. Up top didn't change, despite the electric pump. This leads me to believe either the readings were a little varied from the last time I was on the dyno, or that the exhaust changes zapped a little top end power, but the electric water pump made up for it.
Then I did a little playing with the ECU settings and tune. I wanted to richen it up a bit up top:
This compares my dyno from a few weeks ago to my exhaust changes and a little tuning.
I'm happy overall, but I think with some better tuning that I can pick up a lot more power up top. |
3.5 race exhausr vs stock collector placement 3.5" exhaust
