DIY Exhaust Mod – Gain of 10+ HP!!!

[nieuwhzn]

So what would happen if the slight bleed holes in chamber 1 and chamber 5 get opened up more? In first order this will let more of the primary exhaust go straight out of the tail pipes. This is almost the same as the exhaust bypass pipes on the PSE. The big difference is that more of the primary exhaust left (yellow) is going to 'hit' the primary exhaust from the right (red). This could lead to these two exhaust sources starting to 'beat' against each other, i.e. drone.

Originally Posted by particlewave

The arrow diagram posted earlier in this thread is incorrect and misleading. This is what's happening:

A) Following the left side (yellow), exhaust enters chamber 2 (with slight bleed off to chamber 1 for mixing with right side (red) exhaust through small holes in inlet pipe). From chamber 2, it is split and goes to chamber 5 and center chamber 3 where it is mixed with the right side (red) exhaust and dumped back into chambers 2 and 4.

B) From chamber 2, exhaust goes to chamber 5. In chamber 5, exhaust is again mixed with right side (red) exhaust, but to a lesser degree than the center chamber (see small holes in inlet pipe).

C) Chamber 5 exits directly to exhaust tip


So, by drilling holes in the exit pipe, you are creating flow from the center mixing chamber directly to exit, essentially creating a small bypass directly from inlet to exit with only the center chamber pipe working as a slight flow restrictor/baffle (similar to the PSE, IIRC...except that the PSE uses an exterior pipe to do the same thing).

[chipmunk]

Originally Posted by nieuwhzn

So what would happen if the slight bleed holes in chamber 1 and chamber 5 get opened up more? In first order this will let more of the primary exhaust go straight out of the tail pipes. This is almost the same as the exhaust bypass pipes on the PSE. The big difference is that more of the primary exhaust left (yellow) is going to 'hit' the primary exhaust from the right (red). This could lead to these two exhaust sources starting to 'beat' against each other, i.e. drone.

In the extreme, opening up the bleed holes in chamber 1 and 5 would effectively give you a free flow system. You would however have to remove the box to get to the ends, or cut holes in the casing.

I am not sure that the mixing of gases causes the resonance. I have just removed a Toyo free flow exhaust from my car due to the resonance (it was so bad my wife refused to travel in it) and there the two pipes and silencer boxes are completely separate ie there is no mixing of exhaust gas from left and right cylinders. I have had resonance before with stainless steel boxes and think it must be something to do with the vibration of the casing. I don't believe that modifying the std box will ever give you resonance, but then that's just my view.

[EssexPorsche]

I would have thought it was quite the opposite.
By design the stock exhaust seems to be designed to ensure the gasses from left and right collide, and therefore, equalize, and therefore not drone.

Where as the after market toyo had no such feature and hence drone?
Who knows?
Jake must have studied this at length...maybe he will chime in?