Quote:
Originally Posted by davidimurray
Generally - you cannot make extra power/torque by tuning runner lengths, but you can move the position of the peak on the performance curves. ..........Generally, the longer the runners, the lower down the RPM range your peak will be,
As your losses are based around the air velocity travelling through the system, but you have to size your diameter for a particular velocity. So in an ideal world you would have variable length and diameter intake runners!!
|
I beg to differ.
Shorter runners will result in LOWER rpm HP whereas the longer runners will make HP in Higher rpm range.
IOW, for a town car shorter runners would be ideal and for racing engines longer runners would be more suitable. Ever wondered why racing engines have such beautiful long curved runner to inlets?
Basically an ideal plenum for a car to be used in town a good plenum design would be;
Plenum volume: 80 - 100% of engine volumetric capacity - normally aspired engines.
Runner lengths: anything from 200 - 300mm - measured from valve seat edge to runner inlet at plenum.
Runner diameter: 110 - 120% of inlet valve diameter.
General shape of plenum: Round or oval tapered down from TB - taper starts between 1st and 2nd intake from TB and runs well past last intake. Minimum diameter at the narrowest end of plenum must be about 1.5 times the diameter of the runners.
Just my 2 cents worth