rayop wrote: ↑Sun Apr 22, 2018 6:07 am
I recently had my 1990 Nissan 300zx 2+2 NA exhaust changed from factory to Top Speed headers, Magnaflow cats, and Billy Boat Cat back system (x pipe, resonated). Let me say, there is such a horsepower gain since this swap that to those that say it doesn't...they are dead wrong!
Holy Zombie Thread Revival!
I have never seen proof that headers do much for an NA other than sounding a bit better for all of that hassle, and my Z guy agrees even for a TT unless over 600HP. There's no NA restriction issues to combat/improve really so that's why there isn't much gain...cone filters also claim 5-7 HP but I've seen proof they change nothing really other than ease of maintenance. Changing out the cats and mufflers for larger internal diameter tubing makes things free-flowing as possible, but also can disrupt the exhaust scavenging aspects of the exhaust and actually lose much of the low-end response, and only give a tad of extra power at the top...a bad trade off generally, plus that RASP.
Stock to 2 1/4 diameter tubing, high flow cats, and improved mufflers is the best bet for an NA and generally smooths things out nicely, and still sounds good. This is what I did with my NA after initially trying all of the "fad" stuff, and had to dial things back to this point to make it run decently at all and most of all not sound like a crappy Honda.