Hey guys, I need info on your experiences with exhaust sizing on d16's or motors of similar output. I searched and came up with some info, but nothing specific. My engine is stock except for an intake, and I will be adding a 50 shot soon and I will NOT be getting a turbo. I would like to buy a header and full exhaust but I dont know what size I should go with. This is what I have read about sizing.

N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging. There is a happy medium here.

So what is too big or too small for a D16? What is the happy medium? Let me know about what has worked for you, any information will be greatly appreciated.

 

I would go with a 2.25" piping, maybe even 2.5" but thats pushing it for daily driving.

 

are headers easy to find that bolt to 2.25? I've found some that are factory bolt ups, and some with 2.5 in collectors.

 

Get the one with the biggest collector you can find. Usually 2.5" It's very hard to tune an exhaust because the motor breathes in and out more as the rpms go up but the exhaust diameter stays the same. So a certain exhaust is only going to be most efficient at a certain rpm(high rpm range). In your case I would go with 2.25"