Thread: What size exhaust are you guys using with NA VE's?

3 inch with cat Sr20ve n1 cams hotshot headers I love it but I might end up taking the cat off has anybody ever rolled straight pipes like the hondas do haha ?
<- straight pipped p10 with n1 cams

No P10 on that video, there are 3 P11 from 2 friends of mine, and other P11 from another guy (on the left), the center and the right was Nico and Pelao.

2.5" until the catalytic and then 3" until the silencer, really good sound when VVL do his job. i'll post videos later.


Regards.

you may be talking about just ve's, i was making the point about all motors in general that there is a limit in size depending on its capability. for example, i can guarantee you a stock ga16 will not perform well with a 3in exhaust

DONT do it! after my spin out i had to take the muffler off so straight pipe ended under the car and it sounded gross, disappointing too lol.

lot of people supporting 3in with hp gains so looks like that is what ill lean towards a little disappointing that my old vibrant can will have to go since its 2.5, i really liked the sound of it.

How about 2.5 but have a e-cutout inplace of the cat... will that gain power as pitting a whole 3inch system?

I meant p11

I'm really sorry to disappoint you, but you're wrong. When/if we were talking about header dimensions then sure. The smaller the diameter that can flow with out restriction will create the most velocity and in turn create the lowest pressure on the back of the valve... But we're not talking about header specs here. The truth is that the exhaust cooling rapidly from the chamber all the way to the exit of the exhaust system wherever that may be. If you have a 2.25 or 2.5in collector you'll have to step that exhaust up to give the gasses enough room to move without restriction, and the further from the choke you get, the larger you will have to step the exhaust pipe to do this properly, so as you can see the longer the exhaust system is the larger it would have to be to truly offer no restrictions... There is no gain in a smaller exhaust unless there is a flaw in the design of the header or some other problem in the set up. I understand the sound thing, but I personally love the way my 3in sounded. Hey, find some graphs of back to back tests..

Peak HP is one thing, what about torque? What was the maximum loss?

I do know for a fact that 3" exhaust on a stock SR20DE (say like, a 96 200SX SE-R) will lose power down low. Not too far to think that it would do the same on the SR20VE motor. Although the peak HP occurs at different locations. A SR20DE with all bolt-ons will make peak HP at circa 7600RPM, but a full bolt on SR20VE will make peak HP closer to 8000RPM. I know so because my VE made peak power at 7960RPM, and my DE with all bolt ons at 7420RPM ish.

I remember SCC magazine put a 3" exhaust on their NA B13 DE and it lost like 8 ft-lbs down lown, but it did gain some up top. And I think that car had an intake. They were about to throw a turbo on it so they wanted to see what it made before hand.

im not sure where you are getting your theory from but that's bogus, im sorry. the larger the exhaust the less it has to flow to escape the piping, and the cooler it gets becoming more dense and even more resistant to flow.

quoted from Mike Kojima and Sarah Frost's book "How to Build Performance Nissan Sport Compacts"

-"Exhaust gas velocity is essential to exploit the scavenging effect from tuned headers. A good velocity exhaust stream keeps the exhaust gas flow high and develops a vacuum behind the closed exhaust valve that helps with scavenging when the exhaust valve opens on the next cycle. This is most important during valve overlap, the part of the 4-stroke cycle where both inatake and exhaust valves are open.
Too-large of exhaust pipe diameter has less exhaust-stream velocity and can lead to sluggish flow at low velocity, less torque, and bad scavenging. A good exhaust for naturally aspirated engines will have low back pressure and high-velocity flow."