Back pressure

[oynot400]

I just got back my spark arrestor from FMF for my pipe. I took it for a test ride and I can't believe the bottom end power it has. After I did all my engine work last winter it blew the S/A right out and I was never happy with the low end power.
So did the S/A give the exhaust enough back pressure to give me my bottom end back? I thought a free flow exhaust would be the best option for my mods. I am thinking now that I was wrong, I will know tomarrow with a little more riding time in.

[Guy400]

Most of the time an increase in exhaust backpressure will increase bottom end torque. However, too much backpressure will cause your engine to lose serious performance. An excess of backpressure will cause increased heat on and around the exhaust valve and seat. It will also substantially increase cylinder temps and this could lead to premature detonation which can cause serious problems (chipped or cracked piston faces among other problems). In your case, the backpressure created by the S/A is a good thing. You'll commonly see advice on this board about not using aftermarket head pipes until you buy cams/bore kits. This is because in stock form your motor won't see "all over" benefit. You'll see an improvement in top end power but likely a loss on the bottom. When the motor is bored/cammed than an aftermarket head pipe will compliment the increase in power the motor now makes.

So to answer your question. Yes, the S/A did give you some low end power back.