Quote:
Originally Posted by BongoBennie
I have been so concerned about if the runners were going to be long enough and never really thought about making them longer, the Geo manifold is a work of art in this respect.. I would definitely have to wind the primaries a bit tighter than that though... How much longer are they than stock? And that truck, how bad ass! Hood work does seem the most logical, Im just worried about people messing with it where I park for work, seeing that hood will give people the impression there is a K20 inside although Id like to see their face when they pop the hood.....
Back to runner length.... 16" stock length..... what are the effects of adding 4"? adding 10"?
adding length is much more doable.
|
A reasonable estimation for runner length was developed by empirical testing by Chrysler in the 50's. Simplified version is:
N x L = 84,000
N is the tuned engine rpm
L is the length in inches from the opening of the runner to the valve head.
Assuming you have another 2" from port to valve, that gives you 18" for your stock intake manifold. The above equation puts you at a torque peak of 4700rpm based on my assumption. Which probably isn't too far off,
Wikipedia puts the peak torque of the Honda Fit's L15A1 engine at 4800rpm
Adding 4" puts you at overall runner length of 22" which gives a peak torque at about 3800rpm.
Adding 10" puts you at overall runner length of 28" which gives a peak torque at about 3000rpm.
Keep in mind this is simplified, but it should be good enough for an estimate.