13b-rotary-vw

I'm am left building my own exhaust system. I'll be using stainless, but mild steel is still an option. I am going to have to make my own segmented radius bends.

What I need to know is:

What are the differences between using 2.5 inch or smaller primaries?
What length should theses primaries be before they reach the "Y"?
What length and diameter should the secondary be?

Keep in mind that this is going on a carbureted 13b 6port, that is in a 64' volkswagen beetle, high horse power is not the main goal and sound level is preferred to be kept at a minimum (trying to keep the cops off my back).

Distributor questions:

Can I run a crank angle sensor with it's zero advance on a carbed set up?
I know how to run the electronics and I might even be able to build my own electronic advance.

The real question is do I really need to have timing advanced at all? I've heard of people "locking their dizzy" on turbo setup's. And how much do the trailing timing effect performance, I get mixed answers with this one, some say it helps the low end some say the top???

If anyone can help I would greatly appreciate it, this project is on the tightest budget and everything counts...Thanks to all...

diabolical1

iTrader: (3)

your exhaust questions will be purely conjecture on my part, but i'll share my thoughts. you probably want to go with less than your proposed 2.5" primaries - and i'd say so for a couple reasons. since the exhaust ports are probably nowhere near 2.5", keep them inline with the ports (roughly 2"). velocity and noise would be my other reasons. a bigger collector promotes better flow, but obviously it also means more noise. i'd start with 2.5".

also, since you're putting this in a Beetle, i'd be more concerned with length, since you'll be limited. since this is all going to be custom, maybe you can get some more specific information from other forum members - in particular GtoRx7. because he builds exhausts to your specs - i can't speak for him, but maybe he can help your figure out the ballpark of where you'll need to be. he's a nice guy - at least, anytime i've ever had communication with him he has been. you will need your intake length handy.

for the timing questions: simplicity would dictate running an actual distributor - not a crank angle sensor. if you don't plan to turbocharge, i wouldn't lock it. i'd get some jets, venturis, an EGR setup, a timing light and have at it. get a notebook (or spreadsheet) and put in the time for tuning.

you could run a crank angle sensor, but a timing-only computer would be needed. personally, if you're going to go that far, i'd just spring for a MegaSquirt II or III and do fuel as well. you'd probably end up spending as much for jets/venturis as you would the fuel injector hardware.

i wish i could be of more help. i hope something i said yields some progress.