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Thread: 3" vs 2.5" Exhaust?
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11-16-2010 #21
Sorry. I lost this thread for a while. My numbers were at the flywheel. That's what Jim was saying as well. Yes, his stuff is dated but the numbers still appear to hold up pretty well from what I've seen. The oval stuff makes a world of sense. Had it been out there when I did the exhaust the last time I seriously would have used it. I do have a friend who installed it with his car that makes 575hp at the flywheel and it's not acting the least bit restricted. His 3 inch oval has just as much clearance as my 2.5 inch round.
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11-16-2010 #22Thanks. The headers I bought from Thermal Tech in VA, who coated them. They buy raw headers and coat them as part of the sale. The rest of the exhaust I took to a local business who has done powder coating for me in the past. They did a pretty nice job, and they were very reasonable. The finish isn't quite as "polished" "chrome like" as the headers, but it turned out very nice.
'66 GTO Vert Project "Red Ink", 462ci of stroked pontiac power, TKO600, SC&C Stg II+, Tubular lowers, Currectrac Rear suspension, Moser 12bolt w/Truetrack, Wilwood Master and discs all around, too much fun for words...
11-16-2010 #23Yep. I was going to do something else, but after researching it and seeing how much oval is used in NASCAR and other high end competition, I was sold. It's funny how when you're building a car, no matter what there will be stuff that comes out right AFTER you're about done with the build that you wish you could have gotten. In my case, it's the T56 Magnum.
'66 GTO Vert Project "Red Ink", 462ci of stroked pontiac power, TKO600, SC&C Stg II+, Tubular lowers, Currectrac Rear suspension, Moser 12bolt w/Truetrack, Wilwood Master and discs all around, too much fun for words...
11-17-2010 #24another thing to remember when talking horsepower is that a 500hp motor will only be making 500 at about 5-6500rpm! and , unless you are spending most time at the strip will you really notice any differences when running on the street as mostly the rpm's dont get much north of 3500 for any length of time as the speeds will be in the three digit range! a lot of "high powered" motors will only probably be kicking out 350 -400 hp at these rpm's so a 2.5" system will be just fine and easier to package than a 3 ", also, has anybody tried the spiral turbo baffles instead of mufflers? i have fitted several sets now and they sound awesome! no cackle or bark and no resonance either, the system looks good and clean without mufflers and helps out space and ground clearance wise too.
11-18-2010 #25
I think the point of Jim Hand, etc is not that you might be better served with 3" with a 500hp motor when it's actually making 500hp - but more that over the torque curve even from 3500 and up, a motor capable of making or exceeding 500hp may benefit (a little) from 3". In other words, he's not saying that the advantage STARTS when the power peak approaches 500hp. Otherwise, you could make the same argument about a 400hp motor only needing 2" exhaust. Or smaller. The motor is just a big air pump. Think about this. If you have 1000cfm going into the pump, then you heat that 1000cfm significantly, you can seee where both velocity and volume could be impacted at lower than 500hp.
This is a debate that will never go away, however. The differences are pretty small - just like some of the measurements that are out there comparing different X-Pipe designs between themselves, to H-pipes, and to non-crossoever systems. So many variables. If space and packing were a real concern to me, in a 500hp motor I'd go with oval 3" to round 2 1/2" at the tail pipes. There is really no reason not to go that route. That being said, on the street you'll likely see very little difference at all. Of course, on the street you also won't see many of the differences in suspension, etc that we also build into our cars.'66 GTO Vert Project "Red Ink", 462ci of stroked pontiac power, TKO600, SC&C Stg II+, Tubular lowers, Currectrac Rear suspension, Moser 12bolt w/Truetrack, Wilwood Master and discs all around, too much fun for words...
11-18-2010 #26i see what you are saying, i was just trying to give a little info to some that might think it has to be a certain way to work, and in tight spaces a 2.5" will work fine, but a 3" is better if the space is there, it will also be a little noisier usually too, and as you also state, on the street in normal conditions/use most of what we build is not being used to its potential anyway,
11-19-2010 #27With a 500 HP motor a 3" H system with 2.5 tails was no where near the performance of a 3" X and 3" tails. Ultraflows are pretty quiet. Torque Tech's 3" tailpipes fit fine on my car, a little close to the 29.5 slicks.
11-19-2010 #28