Can a 5" down pipe clear the firewall?
See commentsThe fact that they "run on compression" has nothing to do with why they don't need back pressure.
Running on compression allows the diesel engine to function without having a consistent fuel to air ratio (like a gasser needs). The back pressure affects this mixture on a gasser engine and is therefore necessary for the engine to function properly. On a diesel the back pressure plays no part in how the engine runs because the fuel to air ratio does not matter (to an extent).
But bigger isn't always better. At lower volume flow /power levels, a larger exhaust diameter will cause the gas to stall and eddy and actually cause more back pressure than a smaller diameter pipe.
I am sorry but this is just simply wrong unless the larger pipe is followed up by another smaller diameter pipe. If it is 5" straight out then it will flow better in every scenario than a 4" or 3". If it were a 4" into a 5" and then back into a 4" then it could have a negative affect on flow. Try exhaling slowly through a small straw and see how long it takes you to deplete your lungs...now try exhaling slowly through a 1" PVC pipe and time it. If you truly put the same effort into exhaling using each then the 1" PVC pipe will deplete your lungs quicker.
This is 100% correct. Needing backpressure on a gasser is a myth, a popular one at that. Scavenging is what you want.no engine wants backpressure
Is this a redundant question? Cause I actually don't know. Would a 4" allow the hx35 to spool faster?no engine wants backpressure
and exhaust systems have bends in them
do some data logging on a mild truck with a little HX35 with 4" and then 5" exhaust and get back with me on the initial spool-up results