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Originally Posted by Jason@Nameless
Ok so we just got the car off the dyno this morning (tested the same design as previously tested, but without the midpipe) and the car is making the exact same power as before. I'll have the graphs here shortly to compare. So good news and bad news. Bad news is that the car didn't pick up any extra power over the weekend. Good news is, you don't need a midpipe to make this level of power.
Now, on top of this discussion, we have been working with a number of Australian customers and frequenting their message boards for the GT86 as well as some of the ECU Tuning forums and there have been some rumors of the torque dip being exaggerated on the dyno vs. on the street based on the load that the dyno puts onto the car vs. the load the car sees on the street. If that is the case, then there may be some increase power from ECU learning that doesn't translate to the dyno, but again, that's total speculation and it should be an equal improvement no matter what system you run.
Next steps on this car are to work on some more designs including our intake as well as getting a catless version of this stepped header tested out on the car asap. We have also been discussing some other, rather wild, options for the car that we'll share after we get another look under the car to evaluate the feasibility of the routing for these alternate header designs. We have also investigated the feasibility of getting the maximum amount of power out of the car by having an alternate exhaust length (electric cutout or race day side exit design). The tuned length of the primaries and secondaries on the header as well as the collector diameters are not the only dial to turn in order to bias torque, midrange or high end horsepower. The collector and muffler/tailpipe combo harmonics also have the ability to impact power levels. But we're talking exhausts that are half of the length of the car vs. anything the full length.
More to come.
Jason
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I'm not so sure about this. From the Open ECU thread (
http://www.ft86club.com/forums/showthread.php?t=8691 ) jedibow's logs from highway pulls show a dip in Absolute Load in the range of the torque dip, as well as advanced timing. This would indicate that cylinder filling is not as good as elsewhere in the range.
Copy pasta of another of my posts in that thread:
(From a bike tuning book
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Where the pipe produces a flat spot, cylinder filling sags and so does flame speed, thus requiring more advance.
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So it is probably there on the street, too.
I personally don't think the 'dip' is a huge issue given that the car is geared to pretty much avoid it at max RPM shifts, and has the low peak for grunt when putting around town and short shifting. But placebo effect for some drivers maybe? They've seen the dip, so they 'feel' the dip?