Recently, we added a Mitsubishi Evolution VIII to the test car fleet. This is a caged out road course car. We aren’t real committed to cracking off good lap times this season, but spending more time shaking down the car and assessing what we need to do in order to be competitive for next season of Global Time Attack and Redline Time Attack.
The first few outtings had us break a few things. It was pretty frustrating to have the OEM turbo die on turn 3 of the first lap at Autoclub Speedway in Fontana, CA a couple months back. We were able to redeem ourselves and run the full day recently at the same track. The configuration was the infield-only setup without the high speed Roval. This is a great venue for testing purposes and understanding what the car was doing. On our latest outting, we changed the car over to speed density and E85.
One of the big challenges, has been to fix tip-in and tip-out response of the car. If you know Evo’s/DSM’s, you know that they’re equipped with a MAF of the Karman Vortex (KV) type. This type of MAF is very sensitive to time discrepancies between when the air is measured and it actually arrives at the inlet port. So that BOV needs to open quickly on command by engine conditions. On the street, this isn’t that big of a deal, but when you’re mid corner and you’ve got time slowed down enough in your head that you can throttle modulate a bit mid corner, a bucking car is not what you want to have.
I’m so tired of going to the track and hearing cars flutter on tip-out and then a second later dump some boost. Sure, it is just flutter. Or is it? With a KV MAF that time delay translates into bucking and seriously upsetting the car. That does nothing but kill driver confidence and delay getting back on the throttle. Here’s the mechanism of a slow acting BOV/DV/BPV, whatever you want to call it: You tip-out of the throttle, turbo flutters (no biggie if the MAF doesn’t care), but then a second later when you’re due to tip back in the BOV finally opens. Well, when the BOV opens there is an unloading of the engine. You want that to happen when it is supposed to happen, not later than when it is supposed to happen. That unloading directly impacts how you shift, because the input shaft to the transmission is tied directly to the crank. Trust me, it does matter. And on top of that, the change in engine moment translates into a change in car moment as well. This change will happen whether you are MAF or MAP based in engine calibration.
We had two cars running at the track this past weekend, both with Synchronic technology equipped compressor bypass valves. Rene Garrido of Renown racing was running his Gen 1 RX7 with a 2-rotor turbo and utilizing the Diverter Valve. I was running in the Evo 8 with the stock turbo and our prototype R55 Trident valve that I was track testing (and hell bent on breaking).
If you watch the video, you’ll see just how smooth the valves operate and the impact on the car. If you look closely at my foot during some of the corners, you will see that I’m adding throttle mid corner to get that extra power down. I was not able to get that done before in this car until our recent changes going speed density and eliminating that MAF. In previous iterations of the car, we also had the car setup with the DV sharing a line with the MBC, that’s a different article altogether. Having eliminated that, the car performed much much better from a driver’s perspective.
You’ll need to turn up the volume to hear the RX7, sorry, we were a bit focused on running at the track.