Originally posted by BBRTuning
View Post
Yeah, done this test a few times in a few different ways. You just won't beat the CSL airbox with any sort of open velocity stacks, even for peak power. It gets even worse if you then add individual filters for each stack. The absolute worst thing you can do is run those "rock stopper" stainless mesh filters on each stack. Not only do you have almost zero filtration, you actually have very little flow surface area. The filtration surface area of the CSL filter is massive in comparison, and remember that only one cylinder at a time is in the meat of its intake stroke, so you essentially have the entire CSL filter area providing airflow for each cylinder.
Recently had a pretty serious S54 on the dyno 12:1 (limited by racing class), 296/288 high lift cams, Emtron standalone ECU. We made a genuine ~385whp SAE @ 8600 RPM with a Turner airbox on this car. Since it's a proper race car, we knew we'd never run actual open stacks because that's just silly unless it's a show car when things like carbon airboxes exist, but we WERE interested in figuring out if there was a better trumpet length for this engine setup than what the Turner CSL box comes with, so we decided to dyno the car with various length open trumpets, starting with one that matches the CSL box length. Each time I adjusted the tune to match the trumpets. The results were so bad that I didn't even bother to take pictures of the dyno graphs. Peak power with the open trumpet "CSL length" was almost the same, but low and midrange torque suffered significantly. Additionally, both the shorter and longer trumpet lengths not only lost low/midrange, but the top end was also worse, showing losses between 5-10whp depending on the configuration, and up to 20 ft-lbs. We were shocked as we expected the shorter runner length to provide some top-end benefit at the expense of low-end. It either told us that the open stacks are just straight up worse in every way, or that there was no advantage for the RPM range we're running in to go any shorter than the Turner CSL runner length.
Since this topic comes up often and no one seems to believe that engineers (and all motorsport/race teams) know what they're doing, I guess I'll need to export all the graphs from this test, once I get back to that particular dyno and post it for everyone's enjoyment..
Comment