DIY Exhaust Mod – Gain of 10+ HP!!!

[MidMotor2TrunkToter]

............who will be the first to go 3 or 4 holes in each pipe? Larger holes? .......... The sound is good now but could it be better?

[tonkasdog]

Hi guys, first post on 986, I have been following this thread with an open mind and decided to go ahead after all the good reviews. Went & bought a 14mm by 250mm all purpose drill bit as my oval pipe is spot welded on. Pushed the drill bit as far back as it would go and let rip. 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

[cWadeb]

A tad embarrassing but I'm missing something so simple I can't see it. Went out to drill a couple of holes inside the exhaust tips into the muffler chamber per the example in the earlier post.
No deal: the angle of the drill wouldn't let the bit bite, it just keeps wanting to move around, attempted to use smaller bit with the idea of working up to the 1/2" but no luck.
How did you do it?

Thanks

[tonkasdog]

Hi, I had the same problem, I started with a standard cordless drill & the bit just spun all over the inside of the pipe. I got a bigger mains powered drill, put all my weight behind it & pushed like f**k! This is why I had to go more to the back of the pipe as there is no way I could have put a hole where crioas did with the tail pipe on, couldn't get the angle. Does anyone know what is directly behind the hole I've made as per my previous post?

[blue2000s]

Originally Posted by cWadeb

A tad embarrassing but I'm missing something so simple I can't see it. Went out to drill a couple of holes inside the exhaust tips into the muffler chamber per the example in the earlier post.
No deal: the angle of the drill wouldn't let the bit bite, it just keeps wanting to move around, attempted to use smaller bit with the idea of working up to the 1/2" but no luck.
How did you do it?

Thanks

You will want to use a center punch to place a "dent" where you want the drill to go through the wall. Any hardware store has them.

[crios]

Center punch as suggested by blue2000s, or/and you'll have to push in and to an angle, agaist the wall to use as leverage, leaving some cuts on the pipe. You can also cover up the drill with ducktape where it hits the wall to help prevent these cuts. Go slow, into you establish a groove where the drill will stay in place.

See pic below:

[MidMotor2TrunkToter]

Don't be a :chicken:! Still interested to hear if anyone is enough of a rebel to drill more than 2 holes per side.

Lov'n the Crios! :dance:

[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??