Exhaust for NA race motor
#1
Exhaust for NA race motor
I came across a used Borla SM exhaust for a good price. The exhaust is 2.25" pipe diameter and I plan on running RB NA header which has a slightly bigger outlet 2 3/8 pipe diameter which according to RB had a wall thickness of .0625 which then puts ID of the pipe at 2.25. The Borla SM exhaust has a small section between Header and muffler that is 2" in size. I think they did this for SM rules or stock manifold flange fitment. Since my used exhaust has a missing flange, I was thinking of just replacing the front pipe with 2.25". For a NA motor in the 130-159whp range, is this exhaust appropriate with proper 2.25" match or still a bottleneck and I should instead look for the RB 2 3/8 race midpipe & muffler? Perhaps I am overthinking this as the difference is negligible and only will be known on a dyno. Any thoughts?
#8
Cpt. Slow
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Everyone needs to remember, that Spec Miatas...suck. A lot. They run terrible suspension that is cheap and only works on smooth tracks. They have EXTREMELY loud exhaust because lighter is better, and every .5hp is a HUGE advantage in the incredibly tight front pack, or mid pack, or back field.
So stop comparing to SM, please. It only shows ignorance.
My enduro team ran a quiet (street friendly) 2" OD Borla exhaust, made 148hp. If you're a little bigger diameter, and a little less restricted muffler, yes, I'm sure it'll be a TINY bit more powerful. But we had to spend 2 hours at a time in the car, so we loved it and it made great power. Please consider your circumstances before making exhuast decisions, don't just buy the one that makes the most noise or the most power.
So stop comparing to SM, please. It only shows ignorance.
My enduro team ran a quiet (street friendly) 2" OD Borla exhaust, made 148hp. If you're a little bigger diameter, and a little less restricted muffler, yes, I'm sure it'll be a TINY bit more powerful. But we had to spend 2 hours at a time in the car, so we loved it and it made great power. Please consider your circumstances before making exhuast decisions, don't just buy the one that makes the most noise or the most power.
#9
I am in complete agreement with you that SM dictates tight rules and within such confines, the SM crowd looks to lightest less restriction to stock exhausts. I happen to come across a local deal on the almost new Borla exhaust with an optional muffler. Given the $$ I spent on this exhaust and the fact that I need to change a small front section of the pipe that mates up to the flange of the header, I figured I should be ok on both functional and sound wise with the optional muffler, unless this system is too restrictive and then I'll just list it. Thanks all!
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