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Discussion Starter · #1 ·
i would like 2 do my exhaust, from headers back so id like 2 start my planin and saving now, so is a 3inch exhaust going to be too much?
 

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what kind of engine are you wanting to build......boost nitrous stroker?
 

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¡ʇsnq ɹo uʍop ǝpısdn
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yes

unless your upwards of... i think 500 horses ... i can't remember there is a recommendation chart somewhere... unless your upwards of 500 3 inch is over kill... i have 2.5 inch on my little sixxer and for the little cfm it has its way over kill...

side note... if you do a single turbo 3 inch is average size
 

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The Boss is in
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Yeah thats too much unless you got the motor I would say 450 HP and you could get away with 3in but anything less is over kill
 

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you can run 3" on a stocker, just make sure you get a good set of mufflers to create back pressure
 

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Discussion Starter · #9 ·
Its just a regular stock engine, I planned on running duals obviously but I wanted 2 avoid mufflers and cats, is a n x pipe going 2 be enough back pressure?
 

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+1 back pressure is a myth..... I learned this on here .... go to the sticky on the dyno info and you will see some numbers.....from what I have heard here you do NOT need back pressure like a lot of people seem to think
 

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3" isn't going to hurt you but dollar per horsepower is probably not to your advantage with a mild set up. The only thing you need to worry about when it comes to back pressure is eliminating it. Contrary to popular belief you do not need back pressure. If you did these exhaust companies wouldn't be spending thousands of dollars every year designing better exhaust systems that eliminate more and more back pressure. Back pressure is an obstruction.
 

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on a pretty well stock engine that would take some of his low end torque though wouldnt it
 

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on a pretty well stock engine that would take some of his low end torque though wouldnt it
I put a 3" exhaust on a stock GT that I had back in the early 90s and it didn't hurt anything. It was a noticeable improvement.
 

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This is from Magnaflow's website:


"BACKPRESSURE = TORQUE?
An old hot-rodder's tall tale: Engines need some backpressure to work properly and make torque. That is not true. What engines need is low backpressure, but high exhaust stream velocity. A fast-moving but free-flowing gas column in the exhaust helps create a rarefaction or a negative pressure wave behind the exhaust valve as it opens. This vacuum helps scavenge the cylinder of exhaust gas faster and more thoroughly with less pumping losses. An exhaust pipe that is too big in diameter has low backpressure but lower velocity. The low velocity reduces the effectiveness of this scavenging effect, which has the greatest impact on low-end torque.

Low backpressure and high exhaust stream velocity can be achieved by running straight-through free-flowing mufflers and small pipe diameters. The only two exceptions to this are turbocharged engines and engines optimized for large amounts of nitrous oxide. Both of these devices vastly increase the exhaust gas volume and simply need larger pipes to get rid of it all."
 

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I put 3" on my 83 had a cam but stock other then that and had dynamax on it didnt feel any diffrent but was really really deep
 

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Its just a regular stock engine, I planned on running duals obviously but I wanted 2 avoid mufflers and cats, is a n x pipe going 2 be enough back pressure?
wtf no mufflers?your car is going to sound like ****!
 
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