add another 1000rpm onto that

Thanks FordFairmont - you are correct my Gregories says 3800RPM for the BBM changeover.
Can anyone confirm or dispute that the factory cats on the I6 flow reasonably freely? If they do then perhaps all you need is to match up to that. I have noticed that the best performing exhaust is not always the largest diameter.

Cheers,
C

True i was only planning on folllowing the standard ratio of each pipe = cc of cylinder until it goes into 2 pipes then hopefully the cc of those should equal the cc of the pipes attached to it. Same ratio i use to use in an o
d sigma race car. If this wont work on these cars let me know as i am new to fuel injected cars. I would like more info bout those other companies extractors you are talking about. Will be easier to copy thhen to make from scratch. wont be back at work for a whilie yet. Waiting for work to resume.


I plan to buid the initial pipes out of 2'' into 3'' for the twins with a 3'' final length. Will be hard work but hopefully all will work out nicely.

Hmm, very interesting, after all, moding' cars is an experiment.

Just that 2" and 3" outlet sounds pretty big. The gas velocity would be slower IMHO and would make the engine work harder to pump out the gas / fill the pipe / and leave the system, yeah?

It is the length of the various sections that is critical although the diameter and hence the capacity come into play also. The idea is that the exhaust gas pressure fronts from any one cylinder improve the scavenging on other cylinder(s) .
The simplest way would be to have all the primaries collect at the appropriate length from the exhaust valves. You see this a lot in motorcycle 4 into 1 pipes. The downside I imagine is that the beneficial effects will be over a narrow rev range and divided by the number of cylinders. To improve this extractors are designed to work with pairs or groups of 3 cylinders, hence the 6-3-1 and 6-2-1 designs which give more combinations of interactions between cylinders and give a better result for street cars.

Hey guys stupid question but extractors from a EB 6 should fit onto a el xr6? and how much are gaskets for them aswell? cheers