exhaust tertiary length

[jonny]

Hi,

I am having trouble in packaging my exhaust. I have calculated some primary and secondary lengths and managed to package them into the car. Unfortunately due to space constraints, the distance from where the secondary ends to where the muffler starts is quite long, about 200-250mm. I'm wondering whether at this length will the tertiary lengths be of negative effect on the performance??
Anyone has data to support or deny this?

[jonny]

Hi,

I am having trouble in packaging my exhaust. I have calculated some primary and secondary lengths and managed to package them into the car. Unfortunately due to space constraints, the distance from where the secondary ends to where the muffler starts is quite long, about 200-250mm. I'm wondering whether at this length will the tertiary lengths be of negative effect on the performance??
Anyone has data to support or deny this?

[Jersey Tom]

Its all wave theory. At each junction (primary to secondary, etc), some part of your wave is reflected, and some is transmitted. The big performance modifier is the primary junction. The tertiary to muffer and muffler to end lengths I dont think have quite as much effect.. just not enough wave left to reflect. Would be somethin to run an experiment on in Ricardo Wave..

[Wesley]

Don't forget that you can tune lengths for pressure waves nth harmonics - it's just that, like Tom said, you'll get less and less reflection with a longer pipe as the wave amplitude decays during transit.

[jonny]

How do you calculate the nth harmonic for the reflectrions? Cant seem to find any reliable ones on the net...

[Wesley]

I think Advanced Engine Technology by Heisler has a good introduction to tuning exhaust lengths, and it should have all the equations you need to get started.

Or you might be able to search it on the forums, I'm willing to bet it's been discussed before.