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Ignition Timing Corrections During AX Runs

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Old Jul 17, 2018 | 06:32 AM
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Default Ignition Timing Corrections During AX Runs

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Old Jul 17, 2018 | 02:13 PM
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Are you sure this is unusual, and not within normal operating parameters? Have you compared to the factory map, or within typical street driving?
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Old Jul 17, 2018 | 07:43 PM
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Old Jul 17, 2018 | 11:58 PM
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Originally Posted by Dan991C4
I'm looking for all opportunities for that 0.10 of a second Autocross time improvements that isn't cheating.
You'll find more time in your driving than you will in that knock control.
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Old Jul 18, 2018 | 12:46 AM
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Old Jul 18, 2018 | 10:08 AM
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I'm with KJ in the sense that this is a forest for the trees thing. You have access to information that a consumer really shouldn't have, and are reading too much into it. The same thing would happen if you were able to chart, say, a suspension bushing deflecting during a run, or if you put an LVDT on each of your shock shafts. Getting lost in the minutia is fine if you are an F1 team with millions of dollars on the line and that's your livelihood. In AX it can both make you crazy and suck all the fun out of it.

I think you'd see about 1000x more benefit on the clock if you were to simply shore up your apexes on the right hand side of the car, there appears to be a lot of extra distance you cover in several RH turns.

Also it's tough to tell without a view of the steering wheel, but looks like you double input on steering through the slalom, or at least use jagged inputs. Not sure if your car is a PDK and it's doing PDK things, but sounds like you may be treating the throttle pedal like an on/off switch. Starting application earlier and squeezing into it will be less shock on the car/chassis/tires and you'll be able to carve a more accurate line. Can you record a throttle position trace?
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Old Jul 18, 2018 | 10:53 AM
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Old Jul 18, 2018 | 03:02 PM
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KJ and Burglar: Which part of "I'm looking for all opportunities to improve that .1 second.." did you not underst, oh, wait...
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Old Jul 19, 2018 | 10:48 AM
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Us autocrossers can be real jerks. I love it.
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Old Jul 19, 2018 | 09:20 PM
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I got a report from the Porsche calibrators that the logs look fine. It is not uncommon to see timing corrections particularly on large throttle delta and Cyl 6 is always the most prone. The fuel combustion chemistry calculus shows slower burning fuel can reduce the timing corrections due to spark knock detected by the sensors.

The Torco fuel additive looks like a well established trusted chemical that slows fuel combustion and safe when used in moderation. I normally run with six gallons of fuel in the tank for the max weight reduction term in the Autocross equation. Bumping up to 97 octane should be about 12 oz. I should see a reduction in timing retardation on the next logs and the max engine power term in the Autocross equation in perfect happiness.
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Old Jul 20, 2018 | 12:23 AM
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Very good, Dan991C4. Glad you got your answer.

As for the rest of you knuckleheads, let's just all agree not to mention the latest octane limit rule discussion, OK?
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Old Jul 20, 2018 | 09:16 PM
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I'm in SSP because of the IPD plenum so I can make my own grade gasoline.
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Old Jul 23, 2018 | 07:58 AM
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The acceleration was much smoother off the line by bumping up the octane. The G force gage showed a -0.1 G drop in max (bottom number) off of what I normally see even on different design courses. I'll need to look at my physics book to see if this is a good assumption.

Another factor may be the temperature was about right for the P Zero Corsa (PZC4) tires to work well too shown in the gage's high lateral G max.

I'm probable going to work on toe settings next. I think I might be out a little to much in the front. Understeer is still there but way reduced with the stiffer rear sway bar.

Test III -



G-Force Gage
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Old Jul 26, 2018 | 02:51 PM
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As long as that G-force meter is repeatable, I suppose it could be helpful... but from the look of how high the values are, i don't think it's very accurate, unless those are spikes while going over bumps or something.
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Old Jul 27, 2018 | 01:01 PM
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Those numbers are about right as peaks (not sustained) with the tire he's running. I saw roughly the same lateral numbers on VW GTI I autocrossed recently on BFGs. V-box 20hz gps data.

Its hard to use such peak data, however, as it is so fleeting dynamically and difficult to reproduce.
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