Inlet length tuning

[tpepmeie]

Little slow this weekend, so I thought I'd share some simulation results of various intake lengths. The stock runner length is a little long, but offers a very good torque curve, yet still allows peak power at 7000 rpm. Here is a simulation showing volumetric efficiency of my 427, using the stock inlet tract length. The green line is volumetric efficiency.



Volumetric efficiency peaks at 6400 rpm, and 5200. The latter being close to the torque peak.

Here is a simulation with a very short runner, sheetmetal type intake. Runner length is some 4.5" shorter than stock. VE peaks at 7200, and again at 6100. The overall peak VE is substantially lower, about 7.5% less. In this config, I would expect hp to peak around 7500.



And here are the two graphs on top of each other.



To better isolate the intake tuning peaks, I have performed this simulation with a "stub" exhaust length, rather than full headers. The headers and collector would smooth out the troughs, and pick up VE by about 3 pct at peak.

So what does it all mean? We'll the stock intake length is about the best for a peak power speed at 7000, although even the best ported setups have at least 20-25cfm flow loss. If we could get the minimal flow loss of the fabricated manifold, but the tuned length of the stock system, that would be as good as it could get.

Todd