Smooth Throttle for UpRev

WhiskeyHotel

Interesting stuff. Doesn't the VVEL vary the valve lift and duration to control power and the throttle butterfly stays wide open nearly all the time? If so, then the power varies more by VVEL rather than butterfly position.

wstar

I've heard that myth often, but I'm pretty sure that's not the case. VVEL very likely does vary the valve lift over different operating conditions, but that's no real substitute for actual throttle plates (which is why you still need ITBs even on the most advanced engines).

The easy way to tell is to log the throttle position over OBD-II, which is what I do on Torque while playing with this stuff. The basic Throttle Position PID comes back as angle data, and it ranges from around 1.0 to 89.6 in my testing so far. Generally speaking, if anything the throttle position has a tendency to stay more closed than you'd expect on stock-ish maps, and only opens up fully when you're at full throttle combined with high RPM.

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wstar

Later today I plan to test some "extreme" maps that will get to the bottom of the mysteries of this table I think. I'm thinking one that ramps to 3800 after the first 4-5 columns or so, and one that never gets higher than about 1500 even at the end. Results should be "interesting", and will confirm whether the table is really just a pedal -> butterfly vs RPM map, or there's something more complicated going on.

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wstar

Ok, so I did my crazy extreme map testing. I need to sit down and think through the results, but they should be informative.

Based on my smooth map from the top post, crazy map #1 was altered so that all of the columns from 37.5% flow onwards (to 100) were all pegged to the value "3800". The result from a driving perspective is that when I reached somewhere around 1/3 gas pedal position, the car would suddenly jump like I nailed the pedal to the floor, the OBD-II throttle position values would jump out to high values (wide open), but the whole jump would be very brief. Basically if I held onto that pedal position, the car would pulse on the throttle between 1/3 and full. It was like it was trying to take off at full throttle, but something else in the ECU held it back a short moment later.

Crazy map #2 was the opposite. From the 37.5% column onwards, all values were pegged to the number "1310". The reaction was somewhat similar. At around 1/3 throttle, the car would suddenly jump in power like I tried to nail the gas hard. However, the OBD-II throttle position sensor would *not* jump to wide open when this happened, just the engine power surged, and power got retarded back pretty quickly like the previous test, although smoother.

I imagine all the throttle jumping around and acting retarded in both scenarios is because there are other tables involved (e.g. VVEL) and the ECU in the overall is either confused by or just flat refuses to follow the contradictory commands with crazy values. But it does seem to confirm that raising the numbers in the table leads the ECU to at least try to open the throttle wider.

I need to think more on all of this to make sense of it though.

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