T_K

iTrader: (5)

Well since, it is measuring volume of air over time, and in order for a smaller pipe to produce the same volume of air over the same amount of time, it would need to have higher velocity, that we already know. Maybe the piping diameter increase of the HFC, 2.75in in this case, over the 2.25in test pipe, is allowing a slow enough air velocity where the cat itself isn't being very restrictive? Maybe 2.5in test pipe is the ideal diameter for a test at 400cfm?

TK

kvjacobz

It can flow more air because of a bigger diameter.

kvjacobz

As RC said, its the flow rate that is important. The exhaust can only flow as much as its most restrictive member. The cats can act as a bottleneck. The velocity does slow down some inside the cat because the cross sectional area has to be increased to increase the flow rate over the same length cat. But this slow down is over a small distance compared to the entire exhaust, so the average velocity throughout the exhaust should be about the same plus the gasses will speed up after the cat when the diameter decreases again.

T_K

iTrader: (5)

Sorry to dig this back up, but it just dawned on me that, if the stock 07 cat flows a little less than a high flow cat, is there some gains to be had by doing some modifications to it? For example if Cheston's 2.75in HFCs flow so well, could that same idea be applied to the stock cats, i.e increasing the diameter of the piping into and out of the stock cat?

TK