In several threads I've seen people mention cross-overs, "X" pipes and in one case an "H" pipe. I understand the need for bigger pipes and duals to reduce resistance to air flow, but what does the cross-over or "X" do to improve horsepower and why/how does it do it?
X-pipe takes advantage of the engines pulses or scavanges. a h-pipe doesn't make more HP(on open headers) but it balances out the exhaust and provides somewhat of a gain on mufflers cars.
It all starts with overlap in cam timing. This is when the intake valve is open when the exhaust valve is open a tad bit. This creates a suction. This is typically on opposing cylinders. This helps scavenge exhaust out and free up some HP. The HP is just as effective as an x pipe from what I have seen on cars below 6500k past that x pipe wins hands down. Nascar use the x pipes because they see way past 6500rpm.
Use an H pipe. They are much cheaper. They mellow the sound and increase torque a little within a certain range. X pipes cost much more and DO make additional power in a narrow range. HOWEVER, the inventer of the X pipe said himself that they only make a very slight increase on Nascar engines running at super high rpm. They will NOT be cost effective or noticable on the street. If a Nascar engine needs to turn 9k with a 130+% VE and only gains a 4% power increase at peak, what will you gain on a 6k engine with 95% VE at peak? It won't be the full 4%... and even if it was, that's 4 HP per 100. If you get 300 at the flywheel, then you might see an additional 12, if your engine is running at 130+% VE. And that's at peak. The X pipe is not known for low rpm gains or significant torque gains like the H pipe is. This is from Dr Gas (forgot his proper name) himself. I guess he sells them for street cars cuz he knows there's a sucker born every minute...
Thank you for the information. Is it feasible to manufacture the H using clamps and T's or are all the extra joints going to defeat the purpose? (I don't see myself shelling out a lot of cash for what would possibly not be significant gains just going down the road).
