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Discussion Starter #1 (Edited)
I'm wondering if I can find 8-10rwhp going from the 2.5" catted Bassani X pipe to a 3" catted Dr. Gas X-pipe. The cats would be high flow units, such as those sold by ATI for turbo applications.

Right now, I have a 2.5" Bassani X-pipe. The BBK LT's have 3" collectors and my cat back is all 3". However, the inlet to the cat-back has been reduced down to 2.5" to match uip with the 2.5" Bassani X-pipe. So, going to the 3" x-pipe would allow me to open up the inklet of the car back to 3". The Dr. Gas crossover would have to be in about the same downstream location as the Bassani crossover (behind thetranny cross member).

Any input would be greatly appreciated.
 

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Somewhere in the stuff I save (can't find it), I have a chart for exhaust size for approximate HP. This takes into account HP and TQ. You notice Ford uses 2 1/4" for 320 HP Cobra, and even the newer 390 HP Cobra. The 2 1/4" gives good TQ and noise suppresion for that HP levels, without costing much HP. Most of us have stepped up to 2 1/2" systems at the expense of drone (especially with OR X's, and H's) for a little extra power (but not much thru stock type manifolds). The better systems are mandrel bent, but a few bends and crimps in stock pipes don't hurt as much as people think, because exhaust gases can speed up and slow down as they move along, it's not the same principal as water thru a water hose. Actually, when I had a 2 1/2" Borla system at the 400 RW area, I complained to Borla about noise, and they sent me some "chokers", that basically choked down the exhaust to about 1 3/4" in one spot, and I didn't lose any power. Got a lot quieter though. Sold that for my Bassani set up with 2 1/2" catted X making about 464 RWTQ last time on the dyno, so it's not hurting me. With LT's, maybe would have to rethink the system.

I'm currently using a 2 1/2" system at the 550 RW area, (maybe could use 3" system now), and I know Jake lamotta still uses a 2 1/2" catback with crimps and bends (not sure if it is even mandrel bent) at his HP level, and he runs 9.80's now with probably 700 RW.

Edit addition...Ford did choose the 2 1/2" system for the 2000 R which is an off the floor race car (well...almost) at the 380 HP level. .
















So...without having exact info, that why I said I'm guessing you would lose TQ, and maybe HP with 3" all the way. I figure the 2 1/2" X pipe basically gives you a 2 1/2" system, and I figure that is large enough. MHO though.
 

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Discussion Starter #5 (Edited)
Ralph Greene said:
Somewhere in the stuff I save (can't find it), I have a chart for exhaust size for approximate HP. This takes into account HP and TQ. You notice Ford uses 2 1/4" for 320 HP Cobra, and even the newer 390 HP Cobra. The 2 1/4" gives good TQ and noise suppresion for that HP levels, without costing much HP. Most of us have stepped up to 2 1/2" systems at the expense of drone (especially with OR X's, and H's) for a little extra power (but not much thru stock type manifolds). The better systems are mandrel bent, but a few bends and crimps in stock pipes don't hurt as much as people think, because exhaust gases can speed up and slow down as they move along, it's not the same principal as water thru a water hose. Actually, when I had a 2 1/2" Borla system at the 400 RW area, I complained to Borla about noise, and they sent me some "chokers", that basically choked down the exhaust to about 1 3/4" in one spot, and I didn't lose any power. Got a lot quieter though. Sold that for my Bassani set up with 2 1/2" catted X making about 464 RWTQ last time on the dyno, so it's not hurting me. With LT's, maybe would have to rethink the system.

I'm currently using a 2 1/2" system at the 550 RW area, (maybe could use 3" system now), and I know Jake lamotta still uses a 2 1/2" catback with crimps and bends (not sure if it is even mandrel bent) at his HP level, and he runs 9.80's now with probably 700 RW.

Edit addition...Ford did choose the 2 1/2" system for the 2000 R which is an off the floor race car (well...almost) at the 380 HP level.

So...without having exact info, that why I said I'm guessing you would lose TQ, and maybe HP with 3" all the way. I figure the 2 1/2" X pipe basically gives you a 2 1/2" system, and I figure that is large enough. MHO though.
Ralph - Thanks for the additional information. I agree that there are many factors to consider in choosing an exhaust system, tube diameter being one of them (other factors including restrictions associated with cats, coupling transitions, bends, etc.).

I'm just wondering if O/R X pipe gains could be achieved via a true high-flow 3" cat and matching pipe/ X crossover relative to the fairly restrictive 2.5" pre-heater type cats that I presently have.

I guess to take the guess work out, I'll just give it a try.
 

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David,

I have an off-road BBK H if you want to try it. It is matched to the LTs.

Chris
 
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