hi guys after some experiances basicaly i have a pinto on twin weber 40s with an almost straight through exhaust as its increadibly loud at around 118db at 4k rpm at 1meter away so track days are out of the question mallory park is literaly 25mins away and they have a noise limit of 98/105 depending on who is running it

i have got a motorbike exhaust from a mate for free and have quickly slipped it over the exhaust 4-1 collector and its now at 92-94bd so all good but how will it effect power as i guess its not going to flow as well also what will happen to my jetting as i have it perfect now with the loud exhaust

thanks guys

I may be talking nutsack here (please feel free to correct me people!), but here is my opinion on the situation:

If it's more restrictive then it means the exhaust gas is harder to get out of the system and therefore there may still be some left in the cylinders when you go to put the fuel/air mix into it, you will have the same amount of fuel in there, and therefore the only thing that will change is the amount of oxygen (fresh air), so thats means you will be running richer, which means you wont be able to burn all of the fuel you are putting into the engine, which will result in a decrease in power and a decrease in efficiency (as you are essentially wasting fuel), by how much I couldn't tell you, as it really depends how much lower the flow rate of the new silencer is.

Drive it and see what you think, ideally it could do with a remap to get it running back at an air to fuel ratio (AFR) of 14:1 but it wont do the engine any harm.

[Edited on 18/5/12 by Tatey]

[Edited on 18/5/12 by Tatey]

IMO your going to have to try it....
Only you and the stopwatch will tell if it's 10% down on power.
To get you onm the track (I've found Mallory, the friendly circuit, very friendly ;-) I'm 15 mins away) you've gotta decide if that s a problem.
Fueling will probably be a bit rich with a more restricetd set up, but thats the way to be if any.

Elsy you going ti have to shell out on a BIG jobbie to do it properly

Don't assume because an exhaust is louder it is less restrictive, loads of other factors involved.

You can get straight through exhausts that absorb sound with little gas flow restriction.
In essence large long exhaust cans with a lot of packing round a perforated tube.
The gas flows through, the sound waves are absorbed.