Originally Posted by
jdoug
I just wanted to start a thread on how people tune and find the right pipe length. One question I have is if your engine isn't revving up like it should, then how does one know if the pipe length is the culprit or it just needs some tuning. On my WT .18 I just put my pipe length to 8.5 in. to the convergent cone and tuned from there. I got that measurement from Ron O.
Yes, it screams, but, how do I know that's all I'll get? I suppose I could buy another header and start over with an engine that seems to be tuned in. Another question would be...If I change my pipe length wether its longer or shorter, on an engine that's tuned, would I have to retune with the new pipe length?
Tuned pipes don't turn on and stay on, they have low and max rpm ranges.
The short pipe is for low end power. A short pipe is short so the sound wave has a shorter distance to travel back to the engine so a short pipe will come on at lower RPM and turn off sooner too, top end suffers because the short distance and higher RPM the pipe becomes ineffective and out of time/tune.
A longer pipe the sound wave takes longer to get back to the engine thus the pipe comes on at higher RPM and stays on longer, low end suffers because the longer length is out of time/tune for the lower RPM.
Short is low end power good for short race courses
Long is top end power good for long race courses where you wouldn't want the pipe to pipe out too soon.
Back in the day we had pipe sliders that adjusted the length in sync with the throttle. Off throttle the pipe would be at the shortest length for low end power, and as the engine was throttled up the pipe would lengthen for top end.
Pretty much like the ceeva pipe someone else mentioned except the sliding pipe the whole pipe slid using a ceramic slider
Sealed, also a myth. The raw glasses that the sound wave forces back into the engine just before TDC hangs out at the exhaust port and never really enters the pipe, only the hot oil goes into the pipe so the sound wave doesn't care if it's sealed or not 100% the sound wave will force the glasses back in.
People do play around with the stinger to fine tune a pipe too. A pipe that's slightly larger someone will ventury down the stinger to help keep pipe pressure up to scavenge the hot oil from the engine.