Need Exhaust Flow
Thread Starter
Teching In
Joined: Apr 2005
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From: Home of the Hawks
Need Exhaust Flow Has the required exhaust flow for a bolt on car been measured? I am hoping to start my bolt on project this coming fall after my wife and I get a house. There are many comments on which cat-back system seem to flow the best and those that don't. I know that I want to go with QTP headers, especially now that all have the the spike in the collector. From that point on there are so many different options that I'm curious which is the best from there back. I'm not so worried about how loud the car is, or what the exhaust note will actually be, just no rasp. I want to get the exhaust right from the start and not have it be the restriction down the road. I was leaning toward td's out the back with 18" chambered mufflers, but I also had another thought which was a little different. Using two straight throught dynomax mufflers,but not bullets, right after the axle to the tips that I already have. The reason I asked if the flow has been measured is because the advetised flow for the straight through muffler is over 1100 cfm, which I believe is more than enough, even after a cam and heads, but does anyone actually know how sweet thunders flow? The other set-up that I wonder about is a 3" y-pipe to a 2 1/2" dual in dual out dynomax which is shown flowing around 900 cfm. Last question, will the addition of cats make any difference with the flow? I am under the impression that cats are the way to keep rasp out of the exhaust.
Thread Starter
Teching In
Joined: Apr 2005
Posts: 32
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From: Home of the Hawks
Illuzion,
I see that you have sweet thunders, but have 3" duels. Why 3" and not 2 1/2", because they both have the smaller baffles? Do you have crossover in there as well, an X or H pipe or two pipes going back seperate? I've also seen it said on here that 3" is too much until over 500 rwhp. So does the 3" in that case effect the scavaging in the exhaust or in my case would I need the 3" because of the cats? I also wonder when I could drop down to 2 1/2 pipe for cleareance at the rear axle, either over the top or under.
I see that you have sweet thunders, but have 3" duels. Why 3" and not 2 1/2", because they both have the smaller baffles? Do you have crossover in there as well, an X or H pipe or two pipes going back seperate? I've also seen it said on here that 3" is too much until over 500 rwhp. So does the 3" in that case effect the scavaging in the exhaust or in my case would I need the 3" because of the cats? I also wonder when I could drop down to 2 1/2 pipe for cleareance at the rear axle, either over the top or under.
TECH Regular
Joined: Oct 2005
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David Vizard did an exhaust article recently for PHR which is linked from a post somewhere on the forum. He says that 2.2 CFM per HP (per pipe) will virtually eliminate backpressure and support a 'zero HP loss' system. He also says straight exhaust tubing flows ~ 115 CFM/sq. in.
Originally Posted by MadBill
David Vizard did an exhaust article recently for PHR which is linked from a post somewhere on the forum. He says that 2.2 CFM per HP (per pipe) will virtually eliminate backpressure and support a 'zero HP loss' system. He also says straight exhaust tubing flows ~ 115 CFM/sq. in.
the Vizard article is at the end of the exhaust guide in the external forum or my sig
