[quote]I thought I read somewhere on Yotatech where a guy eliminated his crossover, and ended up going back to stock because he diddnt like the outcome.[quote]
I looked at that. The guy routed it so that only one bank was passing the O2 sensor and I noticed a couple of other design problems.
Tube size selection is important. I have learned by experience not to go too big. I went 2.5" from my Downey headers for a Y pipe then into 2.5" with hi flow cat and open muffler. stinks on the low end but when it gets rolling it pulls and starts to purr at 4000 RPM or 90 mph and it is still pulling past 100mph. Problem with that is that I don't do any 4 wheeling that fast. I think that if I went with a smaller Y pipe from the headers then into the 2.5" at the junction I would have better low end. I am about to put a 3.4 engine in the 4x4. Waiting on the ORS wire harness. Ordered it last week. The exhaust plan for the 3.4 is to use the Tubular exhaust manifold available on 2001 and later. It has a matching tubular crossover that keeps the gases from each side separate until it dumps them out of the crossover into the exhaust pipe. It dumps in at 2.5" then immediately necks down to about 2.25" on back. I will leave this part open with my existing 2.5" system. The tubes in the factory crossover look to be about 1.75" diameter. This plan puts the down pipe on the passenger side. Then I will weld up a section to take it back to the drivers side to meet the existing 2.5" line. I am hoping that this plan will keep low to mid range torque and give some more breathing on the top end for the highway.
After thinking more and reading the thread you referenced I am thinking that even 2" from the manifold is too large and 1.75" would be a better choice for a Y pipe. then into a 2.25 or 2.5 from there back. It looks like my 2wd has a 2" exhaust pipe stock.
A friend of mine runs a salvage. There he got in a motorcycle that has a butterfly valve in the exhaust. It is linked with the throttle and opens wider the more throttle it gets. Basically restricting at low power for torque and open at high power for max hp. I would like to rig it into my exhaust for a test but he wants to try it on a 1200cc Raptor quad he is building.
