Posted 16 October 2009 - 10:15 PM
G'day Andrew! Ok, here goes, especially for you mate. Hopefully it's of use to you:
System #1
CAE Tri-Y's (CH12's) : yes, the 1-5/8" primary versions, with tiny 2" ?? collectors, I've forgotten.
Running a twin 2-1/4" system with twin Redback mufflers
Chassis dyno the car usually made around 220rwkW.
This was early on in my drag racing days, I still ran an 11.99 with this setup, with 3.5 diff gears.
System #2
Custom made 4-into-1's : 1-7/8" primaries, 3" collectors
Running a twin 3" system with twin straight-through mufflers
Chassis dyno made highest power ever at 245rwkW.
This is the system I had when I ran my 11.77's, & still with the old hydraulic baby cam too, but 3.7 gears. It was an animal exhaust! Sounded insane.
System #3 (Current)
Custom made Tri-Y's : 1-3/4" primaries, 2" secondaries, 2-1/2" collectors
Running a twin 2-1/2" system with twin Supercat mufflers (expansion chamber style)
Chassis dyno produced around 235rwkW
Back to running 11.9's so far, Note: this is also when I changed to the bigger solid cam and forged pistons when the engine was freshened. Either the extractors are robbing me of power, or the cam is badly matched to the rest of my combo (I suspect both are contributing). After the rebuild I expected huge improvements, but went back to where I was earlier.
We are only talking tenths here, and very small amounts of dyno power, but yes, there are some definite performance edges it seems with those 4-into-1's.
PS. My mate (Mischa) is running 4-into-1's fairly similar to the ones I had (System2 above). I can't remember his exact sizes, but they are very similar). Actually went for a ride in his SLR earlier tonight, it feels crazy. They had it on the dyno this afternoon and have already hit 300rwkW still on a safe tune. Go the 383 Chevs! Send him a PM if you want to discuss his setup (LXV8 on these forums).
Oh yeah - lastly, no I don't race with my downturn 'dump' pipes off the extractors - they are what I run on the street (they dump at the diff after the mufflers). I have run open pipes once at Heathcote, but it made no difference to my E.T. It was actually slower off the line and felt worse, so since then I've always raced with the system on. I will have to give your collector extension idea a go next time, thanks for the advice.
Stay tuned for extractor photos....