Matt Sharp
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10-22-2004, 03:15 PM
Join Date: Oct 2004
Location: Tallassee, AL
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Matt Sharp
#2
10-22-2004, 05:06 PM
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Join Date: Jul 2004
Location: Athens, TX
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Matt,
I debated between true duals and a single to dual setup for several weeks before deciding...
The problem with most dual systems is that nothing is done to equalize the exhaust pulses from one cylinder bank to the other. To solve the problem, most go with an equalizer (H-pipe) or an X-pipe. An old hot rodder trick is to get underneath the vehicle with a can of spray paint and paint the exhaust pipe, then take a short drive. Once the engine is warmed up, shut her down and look to see which area the paint burned off...this is where the exhaust gasses are hottest, and where the equalizer or X pipe should be placed to increase exhaust gas scavenging. The fundemental problem with trying to do this on our trucks is that the X or H pipe has to be located so far downstream, that a fair amount of the gains associated with the crossover or equalizer pipe are lost. (My opinion and observation)
Another consideration is the fact that the transfer case, transmission, and fuel tank(s) make running a true dual exhaust difficult. You'll probably have to decide either to run the driver's side pipe under the driveshaft to run parallel with the passenger pipe, or you'll have to run it outside the frame rail.
For me, the bottom line was that larger diameter (2 1/4") head pipes into a 3" Y followed by a Hi-flow cat and Mangaflow 3" single in/ dual 2 1/4 out muffler would ****ion much like a true dual setup with an X or equalizer pipe, without the expense of dual cats or mufflers. Granted, a properly designed true-dual setup on a high-horsepower vehicle is (arguably) superior to a single, but with the difficulty of running true duals on our trucks and the fact that all but the hottest 302's will not outflow a single 3" pipe, a single to dual tailpipe system made more sense for me...and I noticed a big difference in performance over the stock 1 7/8" head pipes and 2.5" single exhaust.
As for mileage, if you keep your foot out of it, and stay on top of your tuning, you shouldn't notice much of a difference. The tendency, however, is that after adding some kind of speed part or something that makes it run/sound better, we are more inclined to get our foot into it more than normal.
When I got my truck back in June, I was getting 12.5 mpg. After the tranny rebuild, 14.7; After the headers & exhaust; 17.5 (with the A/C on). I have yet to check it after the FIPK, Coil, wires, cap, rotor, and plugs, but I'm sure I'd be getting close to 18.5...(combination highway, country road, and in town driving)
I debated between true duals and a single to dual setup for several weeks before deciding...
The problem with most dual systems is that nothing is done to equalize the exhaust pulses from one cylinder bank to the other. To solve the problem, most go with an equalizer (H-pipe) or an X-pipe. An old hot rodder trick is to get underneath the vehicle with a can of spray paint and paint the exhaust pipe, then take a short drive. Once the engine is warmed up, shut her down and look to see which area the paint burned off...this is where the exhaust gasses are hottest, and where the equalizer or X pipe should be placed to increase exhaust gas scavenging. The fundemental problem with trying to do this on our trucks is that the X or H pipe has to be located so far downstream, that a fair amount of the gains associated with the crossover or equalizer pipe are lost. (My opinion and observation)
Another consideration is the fact that the transfer case, transmission, and fuel tank(s) make running a true dual exhaust difficult. You'll probably have to decide either to run the driver's side pipe under the driveshaft to run parallel with the passenger pipe, or you'll have to run it outside the frame rail.
For me, the bottom line was that larger diameter (2 1/4") head pipes into a 3" Y followed by a Hi-flow cat and Mangaflow 3" single in/ dual 2 1/4 out muffler would ****ion much like a true dual setup with an X or equalizer pipe, without the expense of dual cats or mufflers. Granted, a properly designed true-dual setup on a high-horsepower vehicle is (arguably) superior to a single, but with the difficulty of running true duals on our trucks and the fact that all but the hottest 302's will not outflow a single 3" pipe, a single to dual tailpipe system made more sense for me...and I noticed a big difference in performance over the stock 1 7/8" head pipes and 2.5" single exhaust.
As for mileage, if you keep your foot out of it, and stay on top of your tuning, you shouldn't notice much of a difference. The tendency, however, is that after adding some kind of speed part or something that makes it run/sound better, we are more inclined to get our foot into it more than normal.
When I got my truck back in June, I was getting 12.5 mpg. After the tranny rebuild, 14.7; After the headers & exhaust; 17.5 (with the A/C on). I have yet to check it after the FIPK, Coil, wires, cap, rotor, and plugs, but I'm sure I'd be getting close to 18.5...(combination highway, country road, and in town driving)
