Cold winter weather and excessive torque
02-08-2007, 11:39 AM
#16
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Like you say, I do not think that there is a problem with the hardware and in truth it should be much better than a cable, but my experience does not back this up.
The only hard info I have came from trying to iron out running glitches on a supercharged 996 3.6 engine which ran a Giac chip with a ZF Engineering centrifugal blower. The engine put down around 500hp at the flywheel at the limiter, but had a flat spot between 1600 to 2000rpm where the car would just not accelerate if you gave it more than 20% throttle. For reasons that I would rather not say, the owner would not accept our explaination of it being a modified car and hence just drop a gear, he insisted in driving it in the sub 2000rpm range so we had to investigate the problem.
We put it on the dyno and looked at the actual values to see what was happening. From memory rhe results from 1600 to 1900rpm were something like:
Foot pedal 10% = throttle plate 10%
FP 25% = TP 25%
FP 50% = TP 25%
FP 75% = TP 25%
FP 100% = TP25%
Hence the ecu would just not let you open the throttle more than 25% below 2000rpm, at which point this car ran lean an dropped into a torque "hole", you could run it flat to the boards on the dyno and it did not have enough torque to accelerate the rollers!
Giac would not help with the mapping of their protected chip so in the end we had to give up trying to help the customer because we could not do anything for him. He sold the car in the end and the new owner loves it, simply accepting the need to change gear to avoid the hole.
The only hard info I have came from trying to iron out running glitches on a supercharged 996 3.6 engine which ran a Giac chip with a ZF Engineering centrifugal blower. The engine put down around 500hp at the flywheel at the limiter, but had a flat spot between 1600 to 2000rpm where the car would just not accelerate if you gave it more than 20% throttle. For reasons that I would rather not say, the owner would not accept our explaination of it being a modified car and hence just drop a gear, he insisted in driving it in the sub 2000rpm range so we had to investigate the problem.
We put it on the dyno and looked at the actual values to see what was happening. From memory rhe results from 1600 to 1900rpm were something like:
Foot pedal 10% = throttle plate 10%
FP 25% = TP 25%
FP 50% = TP 25%
FP 75% = TP 25%
FP 100% = TP25%
Hence the ecu would just not let you open the throttle more than 25% below 2000rpm, at which point this car ran lean an dropped into a torque "hole", you could run it flat to the boards on the dyno and it did not have enough torque to accelerate the rollers!
Giac would not help with the mapping of their protected chip so in the end we had to give up trying to help the customer because we could not do anything for him. He sold the car in the end and the new owner loves it, simply accepting the need to change gear to avoid the hole.
02-08-2007, 11:09 PM
#17
Three Wheelin'
Join Date: Dec 2004
Location: Halifax, Nova Scotia , Canada
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Colin ,
Those results are wrong for a standard 996 or any other ME7 DBW system.
Sounds like the car had a problem .
Your GT3 experience was suprising. The throttle control is biased in the sport direction on that model . Was the car on slicks in the rain ??
Geoff
Those results are wrong for a standard 996 or any other ME7 DBW system.
Sounds like the car had a problem .
Your GT3 experience was suprising. The throttle control is biased in the sport direction on that model . Was the car on slicks in the rain ??
Geoff
02-15-2007, 12:03 AM
#18
Drifting
TB,
I pulled some old data on the laps we ran with and without Racelogic TC. It has been so long that I forgot we were able to get faster lap times by running the car w/o TC in the dry, albeit the standard deviation was greater w/o TC. During qualy, it was better to run w/o TC, however in a race, it was better to run TC. It's also interesting to note that with a junior driver, the TC was faster in all cases, although not by as huge a margin as I'd expected (0.2 seconds on average in the SupraTT).
Things changed dramatically in the wet however with lap times being blistering fast with TC and super consistent as compared to without TC. Lap times improvements of 0.4 seconds on average even with a good driver at the wheel and 0.7 seconds with a novice driver. The SupraTT was a real pig to drive in the wet as it was converted to single turbo, had tons of lag and no rear wheel grip. I used to drive circles around it with my stock-engine 993TT on wet tracks.
I pulled some old data on the laps we ran with and without Racelogic TC. It has been so long that I forgot we were able to get faster lap times by running the car w/o TC in the dry, albeit the standard deviation was greater w/o TC. During qualy, it was better to run w/o TC, however in a race, it was better to run TC. It's also interesting to note that with a junior driver, the TC was faster in all cases, although not by as huge a margin as I'd expected (0.2 seconds on average in the SupraTT).
Things changed dramatically in the wet however with lap times being blistering fast with TC and super consistent as compared to without TC. Lap times improvements of 0.4 seconds on average even with a good driver at the wheel and 0.7 seconds with a novice driver. The SupraTT was a real pig to drive in the wet as it was converted to single turbo, had tons of lag and no rear wheel grip. I used to drive circles around it with my stock-engine 993TT on wet tracks.
