Throttle issues, missing the point?
03-12-2010, 03:26 PM
#1
Throttle issues, missing the point?
All those reported instances where 997 begins to "surge" or "buck" at constant throttle, ie accelerate/decelerate (happened to me for 2nd time in 22k miles yesterday) are most probably related to a glitch in the electronic throttle. Remember the tragic death of that young girl last year in the 100+ mph crash at the pkwy toll booth? Consider the # of Porsches on the road compared to Toyotas. Makes you wonder.....
03-13-2010, 01:15 PM
#2
Nordschleife Master
At least you should know how to shift to neutral and shutoff the engine.
03-13-2010, 02:14 PM
#3
Race Director
All those reported instances where 997 begins to "surge" or "buck" at constant throttle, ie accelerate/decelerate (happened to me for 2nd time in 22k miles yesterday) are most probably related to a glitch in the electronic throttle. Remember the tragic death of that young girl last year in the 100+ mph crash at the pkwy toll booth? Consider the # of Porsches on the road compared to Toyotas. Makes you wonder.....
The Porsche e-Gas used the signals from two potentiometers. These are continously monitored by the ECM (engine control module) for plausibility.
If either postion sensor potentiometer failes, the ECM will use the signal of the lower voltage value as a safety measure.
In this mode the max. pedal value is limited to 60% and teh acceleration value is only allowed to increase by 10% per second up to the 60% limit. The pedal valve drops to zero (idle speed default) if the brake pedal is depressed. In addition the cruise control function is disabled.
The throttle valve provides two separate variable voltage signals to the ECM. Potentiometer 1 supplies 05.v to 4.5v while potentiometer 2 supplies 4.5v to 0.5v.
Potentiometer 1 provides the primary throtte position to the ECM. Potentiometer 2 is constantly monitored and check for signal plausibilty as a redudant safety feature.
In the event of a single potentiometer failure the remaining potentiometer is monitored along with the MAF sensor signal. In this mode the amount of torque available is electronically limited based on a fail-safe program map.
Faults on both throttle valve potentiometers cause the fue injectors to be deactivated adn the power to the drive unit turned off. The engine will not run cause the throttle position is unknown.
The throttle control module is tested before every engine start to verify mechanical integrity. The tests include closing spring test, opening spring test,, bypass air position test (emergency running mode).
During driving, the throttle valve control module is continuously monitored. The valve position, ranges, end stages, and voltages are continuously monitored.
In the control module two independent processors continuously monitor each other during operation. (A similar two processor system was used in some railroad track and train controllers I wrote some software for some years ago.)
If a malfunction is detected in either processor, the functioning processor and monitoring circuits in the engine control module can independently deactivate the appropriate final stages (throttle drive or fuel injectors) in the control unit. It can also limit them to predetermined values (to provide a limp home mode).
The Porsche e-Gas system is a very well thought out system. I usually try to avoid "drive by wire" systems just because I do not like the added complexity but I am quite satisfied with the Porsche system. (The VW system on my TDi was very nice and so too was the system on my 2006 GTO.) I like the superb cruise control e-Gas provides and of course the precise and accurate control of the engine's torque output.
The Porsche e-Gas system is not the Toyota system.
Sincerely,
Macster.
03-13-2010, 02:39 PM
#4
Three Wheelin'
How do you know this (are you an LL type)? Just when I get bored to death of "price check", "help me option", etc. threads a nugget like this shows up. Thanks!
03-13-2010, 06:07 PM
#5
I've induced the surge or buck behavior in various cars, sometimes by accident and sometimes on purpose. Just a brief bit of pressure on the accelerator with some release of pressure and a with the right amount of relaxing of the leg/feet muscles the car's motion will cause my leg to develop a rhythm that gives some feed back and the bucking symptom continues.
The Porsche e-Gas used the signals from two potentiometers. These are continously monitored by the ECM (engine control module) for plausibility.
If either postion sensor potentiometer failes, the ECM will use the signal of the lower voltage value as a safety measure.
In this mode the max. pedal value is limited to 60% and teh acceleration value is only allowed to increase by 10% per second up to the 60% limit. The pedal valve drops to zero (idle speed default) if the brake pedal is depressed. In addition the cruise control function is disabled.
The throttle valve provides two separate variable voltage signals to the ECM. Potentiometer 1 supplies 05.v to 4.5v while potentiometer 2 supplies 4.5v to 0.5v.
Potentiometer 1 provides the primary throtte position to the ECM. Potentiometer 2 is constantly monitored and check for signal plausibilty as a redudant safety feature.
In the event of a single potentiometer failure the remaining potentiometer is monitored along with the MAF sensor signal. In this mode the amount of torque available is electronically limited based on a fail-safe program map.
Faults on both throttle valve potentiometers cause the fue injectors to be deactivated adn the power to the drive unit turned off. The engine will not run cause the throttle position is unknown.
The throttle control module is tested before every engine start to verify mechanical integrity. The tests include closing spring test, opening spring test,, bypass air position test (emergency running mode).
During driving, the throttle valve control module is continuously monitored. The valve position, ranges, end stages, and voltages are continuously monitored.
In the control module two independent processors continuously monitor each other during operation. (A similar two processor system was used in some railroad track and train controllers I wrote some software for some years ago.)
If a malfunction is detected in either processor, the functioning processor and monitoring circuits in the engine control module can independently deactivate the appropriate final stages (throttle drive or fuel injectors) in the control unit. It can also limit them to predetermined values (to provide a limp home mode).
The Porsche e-Gas system is a very well thought out system. I usually try to avoid "drive by wire" systems just because I do not like the added complexity but I am quite satisfied with the Porsche system. (The VW system on my TDi was very nice and so too was the system on my 2006 GTO.) I like the superb cruise control e-Gas provides and of course the precise and accurate control of the engine's torque output.
The Porsche e-Gas system is not the Toyota system.
Sincerely,
Macster.
The Porsche e-Gas used the signals from two potentiometers. These are continously monitored by the ECM (engine control module) for plausibility.
If either postion sensor potentiometer failes, the ECM will use the signal of the lower voltage value as a safety measure.
In this mode the max. pedal value is limited to 60% and teh acceleration value is only allowed to increase by 10% per second up to the 60% limit. The pedal valve drops to zero (idle speed default) if the brake pedal is depressed. In addition the cruise control function is disabled.
The throttle valve provides two separate variable voltage signals to the ECM. Potentiometer 1 supplies 05.v to 4.5v while potentiometer 2 supplies 4.5v to 0.5v.
Potentiometer 1 provides the primary throtte position to the ECM. Potentiometer 2 is constantly monitored and check for signal plausibilty as a redudant safety feature.
In the event of a single potentiometer failure the remaining potentiometer is monitored along with the MAF sensor signal. In this mode the amount of torque available is electronically limited based on a fail-safe program map.
Faults on both throttle valve potentiometers cause the fue injectors to be deactivated adn the power to the drive unit turned off. The engine will not run cause the throttle position is unknown.
The throttle control module is tested before every engine start to verify mechanical integrity. The tests include closing spring test, opening spring test,, bypass air position test (emergency running mode).
During driving, the throttle valve control module is continuously monitored. The valve position, ranges, end stages, and voltages are continuously monitored.
In the control module two independent processors continuously monitor each other during operation. (A similar two processor system was used in some railroad track and train controllers I wrote some software for some years ago.)
If a malfunction is detected in either processor, the functioning processor and monitoring circuits in the engine control module can independently deactivate the appropriate final stages (throttle drive or fuel injectors) in the control unit. It can also limit them to predetermined values (to provide a limp home mode).
The Porsche e-Gas system is a very well thought out system. I usually try to avoid "drive by wire" systems just because I do not like the added complexity but I am quite satisfied with the Porsche system. (The VW system on my TDi was very nice and so too was the system on my 2006 GTO.) I like the superb cruise control e-Gas provides and of course the precise and accurate control of the engine's torque output.
The Porsche e-Gas system is not the Toyota system.
Sincerely,
Macster.
03-13-2010, 06:29 PM
#6
Burning Brakes
I've induced the surge or buck behavior in various cars, sometimes by accident and sometimes on purpose. Just a brief bit of pressure on the accelerator with some release of pressure and a with the right amount of relaxing of the leg/feet muscles the car's motion will cause my leg to develop a rhythm that gives some feed back and the bucking symptom continues.
The Porsche e-Gas used the signals from two potentiometers. These are continously monitored by the ECM (engine control module) for plausibility.
If either postion sensor potentiometer failes, the ECM will use the signal of the lower voltage value as a safety measure.
In this mode the max. pedal value is limited to 60% and teh acceleration value is only allowed to increase by 10% per second up to the 60% limit. The pedal valve drops to zero (idle speed default) if the brake pedal is depressed. In addition the cruise control function is disabled.
The throttle valve provides two separate variable voltage signals to the ECM. Potentiometer 1 supplies 05.v to 4.5v while potentiometer 2 supplies 4.5v to 0.5v.
Potentiometer 1 provides the primary throtte position to the ECM. Potentiometer 2 is constantly monitored and check for signal plausibilty as a redudant safety feature.
In the event of a single potentiometer failure the remaining potentiometer is monitored along with the MAF sensor signal. In this mode the amount of torque available is electronically limited based on a fail-safe program map.
Faults on both throttle valve potentiometers cause the fue injectors to be deactivated adn the power to the drive unit turned off. The engine will not run cause the throttle position is unknown.
The throttle control module is tested before every engine start to verify mechanical integrity. The tests include closing spring test, opening spring test,, bypass air position test (emergency running mode).
During driving, the throttle valve control module is continuously monitored. The valve position, ranges, end stages, and voltages are continuously monitored.
In the control module two independent processors continuously monitor each other during operation. (A similar two processor system was used in some railroad track and train controllers I wrote some software for some years ago.)
If a malfunction is detected in either processor, the functioning processor and monitoring circuits in the engine control module can independently deactivate the appropriate final stages (throttle drive or fuel injectors) in the control unit. It can also limit them to predetermined values (to provide a limp home mode).
The Porsche e-Gas system is a very well thought out system. I usually try to avoid "drive by wire" systems just because I do not like the added complexity but I am quite satisfied with the Porsche system. (The VW system on my TDi was very nice and so too was the system on my 2006 GTO.) I like the superb cruise control e-Gas provides and of course the precise and accurate control of the engine's torque output.
The Porsche e-Gas system is not the Toyota system.
Sincerely,
Macster.
The Porsche e-Gas used the signals from two potentiometers. These are continously monitored by the ECM (engine control module) for plausibility.
If either postion sensor potentiometer failes, the ECM will use the signal of the lower voltage value as a safety measure.
In this mode the max. pedal value is limited to 60% and teh acceleration value is only allowed to increase by 10% per second up to the 60% limit. The pedal valve drops to zero (idle speed default) if the brake pedal is depressed. In addition the cruise control function is disabled.
The throttle valve provides two separate variable voltage signals to the ECM. Potentiometer 1 supplies 05.v to 4.5v while potentiometer 2 supplies 4.5v to 0.5v.
Potentiometer 1 provides the primary throtte position to the ECM. Potentiometer 2 is constantly monitored and check for signal plausibilty as a redudant safety feature.
In the event of a single potentiometer failure the remaining potentiometer is monitored along with the MAF sensor signal. In this mode the amount of torque available is electronically limited based on a fail-safe program map.
Faults on both throttle valve potentiometers cause the fue injectors to be deactivated adn the power to the drive unit turned off. The engine will not run cause the throttle position is unknown.
The throttle control module is tested before every engine start to verify mechanical integrity. The tests include closing spring test, opening spring test,, bypass air position test (emergency running mode).
During driving, the throttle valve control module is continuously monitored. The valve position, ranges, end stages, and voltages are continuously monitored.
In the control module two independent processors continuously monitor each other during operation. (A similar two processor system was used in some railroad track and train controllers I wrote some software for some years ago.)
If a malfunction is detected in either processor, the functioning processor and monitoring circuits in the engine control module can independently deactivate the appropriate final stages (throttle drive or fuel injectors) in the control unit. It can also limit them to predetermined values (to provide a limp home mode).
The Porsche e-Gas system is a very well thought out system. I usually try to avoid "drive by wire" systems just because I do not like the added complexity but I am quite satisfied with the Porsche system. (The VW system on my TDi was very nice and so too was the system on my 2006 GTO.) I like the superb cruise control e-Gas provides and of course the precise and accurate control of the engine's torque output.
The Porsche e-Gas system is not the Toyota system.
Sincerely,
Macster.
03-13-2010, 11:54 PM
#7
Race Director
Also, I have some experience writing safety critical software/firmware -- software/firware which if it doesn't work right property damage, human injury even death possible -- for railroad track and train controllers which are responsible for opening/closing switches and controlling signaling lights that control sections of railroad tracks.
Sincerely,
Macster.
