lsx24

iTrader: (45)

Sorry I don't buy that. Are you saying a 500 rwhp setup will not scavenge as much as one with 400 rwhp? Or are you saying a 500 rwhp setup does not scavenge? I find both of those hard to believe...just like long tube headers, it doesn't matter what hp you are at, it will still scavenge a proportionate amount.

Ragtop 99

iTrader: (7)

Problem is, you're making the arguement without any evidence that you can get scavenging improvements on an lS1 exhaust, as typically installed.

I'm not saying it might not exist, I just haven't seen anyone demonstrate it. If it were consistently good for say 10 rwtq, I think it would have been demonstrated by now.

lsx24

iTrader: (45)

If you're talking about demonstrated gains from duals with crossover, over ypipe configuration, I have some myself with a before after:



I gained 20 lb/ft of tq, over my ypipe setup. All of it was in the midrange rpm, with the Bassani True Dual system. The xpipe crossover is the component responsible for the midrange gains, with it's scavenging effect.

Ragtop 99

iTrader: (7)

You went from stock cats & Y-pipe to high flow cats. Had you had high flow cats, a real Y-pipe with a true merge and a 3.5" catback, I'd fully agree it was all due to the X-pipe

lsx24

iTrader: (45)

I see what you're saying, regarding having a consistant data point, such that you can see clearly how duals may or may not effect the power output. However I respectfully disagree based on logic:

Stock cats to high flow cats are a linear change. It will effect hp gained/lost in a consistant way, by allowing better breathing at high rpm. Since I didn't gain any hp up top, you can conclude that it made no difference adding high-flow cats to my setup, as they would not be able to account for a 20 lb/ft change in tq in the midrange since they are a linear addition.

Similarly, adding a good flowing y-merge connection is a linear modification. You would again see better breathing (mostly up top) with a better merge collector. Since again I didn't see any top end hp improvements, it's safe to say adding a better merge collector would not add more hp in my instance (since duals are way better flowing than the stock merge).

Therefore, the only variable left to account for the increased midrange tq is either the lack/removal of backpressure or the crossover. Duals have very little (if any) backpressure, and since it's also a linear modification, we know it didn't help my situation. The crossover is NOT a linear improvement, as I gained tons of hp under the curve but none in high rpms.

Ragtop 99

iTrader: (7)

Most people would expect a full exhaust system to be a linear gain using the term as I think you are, so I'm not sure why you show only a hump in the middle. I think an X-pipe is helpful, but I can't jump to the conclusion that an X-pipe creates a surge in mid-range torque to the exclusion of low and high end.

I have tested this assumption. My headers came with a crappy Y-pipe, kinda like the one that comes with pacesetters, and it then went into a 3" catback. I ran the car for quite a while with the crappy y-pipe. I then redid the system with a 3" true merge into 3.5" I-Pipe into a 3.5" cut-out then narrowed down to 3" to go over the axle to my D/D exhaust. Even with the cut-out closed (which is how I drove it 99% of the time), I ended up having to update the VE table on the low end, including my idle VE. That's pretty conclusive to me that the change went accross the board.

When a true merge is used, the exhaust pulses come together much more efficently than the stock system.

I think duals are great and twin 2.5" has more capacity than a single 3". My point is that a properly design Y-Pipe sytem will hang with duals.