DIY Exhaust Mod – Gain of 10+ HP!!!

[Mike_Yi]

Originally Posted by tonkasdog

When I shine a light down the pipe you can see the hole at the back but you can also see more metal directly behind the hole, it's even scored by the drill bit & I'm sure I would of gone through this if I'd carried on pushing. Does anyone know what this will be and should I drill through this as well? The sound is better and I'll be taking it out later to test drive. Cheers

I'd bet that you are seeing the outer shell of the muffler. DO NOT drill through that.

I'll be borrowing one of my Dad's long drill bits early next week.

BTW, I would guess that you are only hearing the difference in sound at low RPM because at higher RPM, the volume and velocity of the air keeps it moving through the big holes in the existing pipes as opposed to the tiny drilled holes. At slower speed, there is less air moving, and it can get through the smaller holes.

I'll put a DB meter on it before and after to see what difference in sound level it makes.

[23109VC]

i have a pedro mod on my car and I notice one sound from the muffler at lower rpm and then a totally different sound at higher rpm.

i wonder if the pedro mufflers could also have an issue where at certain rpms, the amount of air that actually makes it into the bypass pipes changes? i notice the sound of my pedro muffler is different at low rpm vs higher rpm - which could be the result of air flow/velocity allowing more air to get into the bypass pipes, but at high rpm less can make it due to more of it flowing out the "real" muffler piping and less can divert/escape into the bypass pipes??