Would a 3.5" y pipe with a 3.5" to 3" reducer on the end create the same back pressure as a 3 inch y pipe?

 

anyone else? what's the difference b/w a 3 inch pipe and a 3.5 inch pipe with a 3 inch nozzle on the end, in terms of backpressure?

 

I did quite a bit of exhaust testing on my c4 Vette. I found that the point of restriction was simply that. once it was opened up...the rest of the system worked fine. in my case, I went from 3.5 psi of backpressure at wot 5500rpm to .8psi through Random cats and straight through dynomax mufflers. That's about as good as it gets for a full length exhaust. I'd highly recommend that people do this testing before spending money on exhaust systems. Turns out the factory system was fine at my hp level with the exception of the mufflers themselves.