Whos makes best decat??

[BenR]

4

 

[MarkM]

BenR and fmp.

What sort of increase/decrease in power will incorrect silencer positioning cause. Is it a case of lose and gain across the rev range or do you lose throughout the rev range from poor positioning. Are you talking a couple of bhp or is it significant.

What effect does an increase in bore size have over gas flow.

 

[Danith]

This is a very simplistic look at exhaust pulse tuning, and there are far too many generalisations.

Firstly the size of the crossectional change has a greather bearing on the amplitude of the refracted negative sign that will travel back towards the head, so ultimately opening to atmosphere has the greatest result, a perforated silencer will do very little, especially the high efficiency ones.

Then you have to take into account exhuast temps as this will effect density of the gasses, and the speed of sound which the pulse will travel at. This is changed when the car has moving air under the vehicle.

And these pulse tuning effects will invariably lead to a corresponding trough to the peak in the power graph you have just created, so you need to know where you want to place the peak. IMO, for road cars its best to try and cancel out the effects and work with manifolding.

Its a complex area and not something an exhaust place, even like btb, can pump out correct numbers straight off.

YEAH THATS WHAT I THOUGHT :S

 

[BenR]

BenR and fmp.

What sort of increase/decrease in power will incorrect silencer positioning cause. Is it a case of lose and gain across the rev range or do you lose throughout the rev range from poor positioning. Are you talking a couple of bhp or is it significant.

What effect does an increase in bore size have over gas flow.

i'd go as far to say that changes are near immesurable in that the changes are so small.

And changes would be tradeoffs, gain in one area will lead to a loss in another, as always is the case with pulse tuning. If you play with them then you need to set up beneficial pulses in areas of the rpm range where you will most use them, and then take the hit for the loss in another area, you try to place this loss somewhere that is least harmfull.