Is Bigger Always Better(Exhaust)...?
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SiNFuL
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Is Bigger Always Better(Exhaust)...?
Hey guys, i was originally thinking of getting a Apex'i GTSpec and it has 95mm piping. I was telling a friend w/ a 97 240 this and he said that bigger piping is only better for turbo'd cars, and that smaller piping helps faster flow w/ NA. Is this true? If so, what is the recomended piping for an NA KA24DE? Thanks guys!-Galen
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groundhogday1976
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:: orion ::
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Agreed.
You need velocity and volume from an N/A exhaust - Smaller piping keeps the exhaust gas velocity high and aids scavenging at high RPMs. But too small will choke it out up top and cause unneeded backpressure.
So you have to find a balance...and from my experience, any of the 60mm exhaust will do fine up to ~160rwhp. Past that, a 3"/75mm may add a little up top at the expense of a little low end, but isn't a necessity.
I'd actually say that 2.5" mandrel bent would be ideal...60mm is only 2.36".
And before someone asks about backpressure being "good" or "needed": Backpressure is a result, not a cause. Properly sized piping will add some amount of backpressure, and it's a necessary evil, but as little as possible is best, as long as you don't hurt velocity.
Ok, sorry for the rant...
Later - Brian
You need velocity and volume from an N/A exhaust - Smaller piping keeps the exhaust gas velocity high and aids scavenging at high RPMs. But too small will choke it out up top and cause unneeded backpressure.
So you have to find a balance...and from my experience, any of the 60mm exhaust will do fine up to ~160rwhp. Past that, a 3"/75mm may add a little up top at the expense of a little low end, but isn't a necessity.
I'd actually say that 2.5" mandrel bent would be ideal...60mm is only 2.36".
And before someone asks about backpressure being "good" or "needed": Backpressure is a result, not a cause. Properly sized piping will add some amount of backpressure, and it's a necessary evil, but as little as possible is best, as long as you don't hurt velocity.
Ok, sorry for the rant...
Later - Brian
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:: orion ::
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- Joined: Fri May 23, 2003 4:40 pm
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tinted wrote:Even with a turbo. A bigger exhaust is needed because you are pushing more through the engine. Its not like you get "no" backpressure with a bigger pipe.
Yep...with turbo, you want as little backpressure behind the turbine as possible.
3" is big enough to not cause uneeded backpressure, but still flow all that exhaust gas easily...on a 2.4 liter that is.
So 60mm or 2.5" mandrel for N/A...
75-85mm or 3" mandrel for turbo 2.0-2.5 liter...
Later - Brian