G-Tech Pro - Competition
11-29-2003, 12:17 PM
#16
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another gtech run
I just did quarter mile run with my new Gtech Pro meter. It's really fun to see the data on the computer so one car can be compared to another.
Here's my run with the Gtech Pro.
gtech run
Here's my run with the Gtech Pro.
gtech run
11-29-2003, 03:40 PM
#17
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One more time.
http://us.f1f.yahoofs.com/bc/578e3c5...qH2y_AuwgoT.iC
http://us.f1f.yahoofs.com/bc/578e3c5...qH2y_AuwgoT.iC
Last edited by MBailey; 12-01-2003 at 11:29 AM.
11-30-2003, 02:39 AM
#22
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MBailey, My Rx-7 has a couple after market parts.
My exhaust consists of a down pipe which I goofed with a bit to improve flow, stock main cat which I goofed with to improve flow, and an after market HKS cat back. I also modified the stock intake to improve its flow and forced air from the nose of the car. I have an after market computer(Power FC) set a touch higher than stock boost.
The car is sort of light too, starting with a curb weight around 2850 lbs. From there I shaved off a hundred pounds or so by replacing the stock exhaust parts with lighter after market items, having the spare tire removed, and a mini battery installed. It should be about 800 lbs lighter than the 911tt, but with a bit less power, so the power to weight ratio is similar.
My exhaust consists of a down pipe which I goofed with a bit to improve flow, stock main cat which I goofed with to improve flow, and an after market HKS cat back. I also modified the stock intake to improve its flow and forced air from the nose of the car. I have an after market computer(Power FC) set a touch higher than stock boost.
The car is sort of light too, starting with a curb weight around 2850 lbs. From there I shaved off a hundred pounds or so by replacing the stock exhaust parts with lighter after market items, having the spare tire removed, and a mini battery installed. It should be about 800 lbs lighter than the 911tt, but with a bit less power, so the power to weight ratio is similar.
11-30-2003, 10:43 AM
#23
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Greg,
What is your feeling on what your HP is at the rear wheels? Was stock something like 255? Back in 95 I had a supra TT and it had 320 but was almost as heavy as what I have now. Icould never get below 14.0 in the quarter in that car. What did the stock RX-7s run in the quarter?
What is your feeling on what your HP is at the rear wheels? Was stock something like 255? Back in 95 I had a supra TT and it had 320 but was almost as heavy as what I have now. Icould never get below 14.0 in the quarter in that car. What did the stock RX-7s run in the quarter?
11-30-2003, 09:56 PM
#24
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2003 911tt X50 G-tech Pro run
According to the Gtech meter, 1rst gear for my Rx-7 displays a little under 300 wheel HP. The 255 HP for the stock 1993-1995 Rx-7 would be fly wheel HP. Given a half way decent launch, the stock Rx-7 of this vintage should do a mid to high 13 in the quarter with trap speed in the low 100s.
This evening my friend (forum member Greg@Simple.net) tested his stock 2003 911tt X50 with my Gtech Pro meter. Here's his run.
This evening my friend (forum member Greg@Simple.net) tested his stock 2003 911tt X50 with my Gtech Pro meter. Here's his run.
12-01-2003, 04:26 AM
#25
Instructor
Re: 2003 911tt X50 G-tech Pro run
Originally posted by greg schroeder
According to the Gtech meter, 1rst gear for my Rx-7 displays a little under 300 wheel HP. The 255 HP for the stock 1993-1995 Rx-7 would be fly wheel HP. Given a half way decent launch, the stock Rx-7 of this vintage should do a mid to high 13 in the quarter with trap speed in the low 100s.
This evening my friend (forum member Greg@Simple.net) tested his stock 2003 911tt X50 with my Gtech Pro meter. Here's his run.
[[/IMG]
According to the Gtech meter, 1rst gear for my Rx-7 displays a little under 300 wheel HP. The 255 HP for the stock 1993-1995 Rx-7 would be fly wheel HP. Given a half way decent launch, the stock Rx-7 of this vintage should do a mid to high 13 in the quarter with trap speed in the low 100s.
This evening my friend (forum member Greg@Simple.net) tested his stock 2003 911tt X50 with my Gtech Pro meter. Here's his run.
[[/IMG]
I think you either have a problem with you G-tech or your useing it improperly. From my calculations if your car in makeing 300 rwhp with a combined weight of aprox 2850 with you in the car your, trap speed would be aprox 110 mph. To run 125mph you would need a big set of blowers for that. Not posible with stock turbo's. Same with the 996 tt, the mph is way too high.
12-01-2003, 08:19 AM
#26
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G tech mph at the end of the quarter is always somewhat higher than at the strip since the g-tech calculates speed at the exact end of the quarter rather than an average over the last few yards like the light beams do. In my experiance this translates to 3-4mph faster. I think Gregs HP is probably more than 300 because with gasoline and him on board it probably weighs more than 2850lbs.
I think an X50 can pull 120 mph in the quarter.
I think an X50 can pull 120 mph in the quarter.
12-01-2003, 11:31 AM
#27
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With me in it my Rx-7 could weigh 2850 instead of 2950. Entering the lower figure into the G-tech meter would render lower HP readings.
After reviewing the data again on the computer I realize my max HP is not in 1rst for the Rx-7, but rather was shown in 3rd gear. Loss of traction due to wheel spin and wind resistance might bring HP figures down a bit for the G-tech when compared to a dyno. Some say they are seeing the G-tech HP figures to be more conservative than Dynojet. This is nothing new though. Dynojets read higher than other dynos too.
Here are the G-tech Charts for "HP and TQ vs RPM" , "HP vs Time" for both the 2003 911tt X50 and 1993 Rx-7 with mods. I'm not sure why the max number displayed on the right of the "HP and TQ vs RPM" looks a bit different than what the large graph shows for the Rx-7. Perhaps it's the inertia of the flywheel at shifts when the clutch come in contact.
HP and TQ vs RPM
HP vs Time
After reviewing the data again on the computer I realize my max HP is not in 1rst for the Rx-7, but rather was shown in 3rd gear. Loss of traction due to wheel spin and wind resistance might bring HP figures down a bit for the G-tech when compared to a dyno. Some say they are seeing the G-tech HP figures to be more conservative than Dynojet. This is nothing new though. Dynojets read higher than other dynos too.
Here are the G-tech Charts for "HP and TQ vs RPM" , "HP vs Time" for both the 2003 911tt X50 and 1993 Rx-7 with mods. I'm not sure why the max number displayed on the right of the "HP and TQ vs RPM" looks a bit different than what the large graph shows for the Rx-7. Perhaps it's the inertia of the flywheel at shifts when the clutch come in contact.
HP and TQ vs RPM
HP vs Time
12-01-2003, 12:05 PM
#28
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ANY device that uses acceleration to calculate speed and distance over time suffers from a really big bugaboo -- gravity interference.
To calculate velocity from acceleration, one integrates over time. To calculate distance from acceleration, one double integrates over time. Integration or double integration (integrating the previous integration) allows offset errors to accumulate without bound.
What are offset errors? As a practical matter, it is impossible to separate the effects of gravity from the effects of acceleration due to force from the engine -- except by direction. Gravity acts in a direction pointing to the center of the earth. Gas-pedal acceleration acts in a direction parallel to the road surface. The only way to remove gravity from the g-signal input is to ensure that the g-measurement system has the ability to null-out the gravity signal by orienting the g-sensing axis exactly 90 degrees from straight up. This is not so easy as it might sound (understatement of the millennium).
If the sensor is mounted to a sprung vehicle, the gas-pedal acceleration will cause some suspension squat and some gravity will sneak into the measurement. If the track surface is not perfectly flat (flat means without incline or decline), errors due to gravity intrude. Any influence that de-tunes the "null" of 90 degrees to perpendicular of the sensor can cause trouble by falling prey to gravity's presence.
Then there's always zero-drift in the accelerometer itself. It may just decide to report .03 g when there is actually 0.00000 g to be measured.
Any continuous input from gravity or sensor drift corrupts the integration by supplying a false (positive or negative) impression of the engine's ability to speed-up the vehicle. This corruption is especially evident when measuring small value accelerations. Smaller accelerations occur when testing in higher gears or slower cars.
The only way to make g-sensing work for 1/4 mile times is to apply a bunch of fudge factors to compensate for all the different ways gravity and sensor drift can mess up the readings. The resulting accuracy is totally dependent on the instrument designer's creativity and the user's tolerance for undiscovered measurement errors.
/soapbox
To calculate velocity from acceleration, one integrates over time. To calculate distance from acceleration, one double integrates over time. Integration or double integration (integrating the previous integration) allows offset errors to accumulate without bound.
What are offset errors? As a practical matter, it is impossible to separate the effects of gravity from the effects of acceleration due to force from the engine -- except by direction. Gravity acts in a direction pointing to the center of the earth. Gas-pedal acceleration acts in a direction parallel to the road surface. The only way to remove gravity from the g-signal input is to ensure that the g-measurement system has the ability to null-out the gravity signal by orienting the g-sensing axis exactly 90 degrees from straight up. This is not so easy as it might sound (understatement of the millennium).
If the sensor is mounted to a sprung vehicle, the gas-pedal acceleration will cause some suspension squat and some gravity will sneak into the measurement. If the track surface is not perfectly flat (flat means without incline or decline), errors due to gravity intrude. Any influence that de-tunes the "null" of 90 degrees to perpendicular of the sensor can cause trouble by falling prey to gravity's presence.
Then there's always zero-drift in the accelerometer itself. It may just decide to report .03 g when there is actually 0.00000 g to be measured.
Any continuous input from gravity or sensor drift corrupts the integration by supplying a false (positive or negative) impression of the engine's ability to speed-up the vehicle. This corruption is especially evident when measuring small value accelerations. Smaller accelerations occur when testing in higher gears or slower cars.
The only way to make g-sensing work for 1/4 mile times is to apply a bunch of fudge factors to compensate for all the different ways gravity and sensor drift can mess up the readings. The resulting accuracy is totally dependent on the instrument designer's creativity and the user's tolerance for undiscovered measurement errors.
/soapbox
12-01-2003, 02:12 PM
#29
Instructor
Originally posted by greg schroeder
With me in it my Rx-7 could weigh 2850 instead of 2950. Entering the lower figure into the G-tech meter would render lower HP readings.
After reviewing the data again on the computer I realize my max HP is not in 1rst for the Rx-7, but rather was shown in 3rd gear. Loss of traction due to wheel spin and wind resistance might bring HP figures down a bit for the G-tech when compared to a dyno. Some say they are seeing the G-tech HP figures to be more conservative than Dynojet. This is nothing new though. Dynojets read higher than other dynos too.
Here are the G-tech Charts for "HP and TQ vs RPM" , "HP vs Time" for both the 2003 911tt X50 and 1993 Rx-7 with mods. I'm not sure why the max number displayed on the right of the "HP and TQ vs RPM" looks a bit different than what the large graph shows for the Rx-7. Perhaps it's the inertia of the flywheel at shifts when the clutch come in contact.
With me in it my Rx-7 could weigh 2850 instead of 2950. Entering the lower figure into the G-tech meter would render lower HP readings.
After reviewing the data again on the computer I realize my max HP is not in 1rst for the Rx-7, but rather was shown in 3rd gear. Loss of traction due to wheel spin and wind resistance might bring HP figures down a bit for the G-tech when compared to a dyno. Some say they are seeing the G-tech HP figures to be more conservative than Dynojet. This is nothing new though. Dynojets read higher than other dynos too.
Here are the G-tech Charts for "HP and TQ vs RPM" , "HP vs Time" for both the 2003 911tt X50 and 1993 Rx-7 with mods. I'm not sure why the max number displayed on the right of the "HP and TQ vs RPM" looks a bit different than what the large graph shows for the Rx-7. Perhaps it's the inertia of the flywheel at shifts when the clutch come in contact.
12-01-2003, 02:39 PM
#30
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Biiing,
The results on the G-tech X50 are almost identical to Motor Trends results as far as quarter time. The speed difference is caused by the G-tech measuring speed at the very end of the quarter rather than averaging the last few yards. I cant vouch for the RX-7 result.
http://www.motortrend.com/roadtests/...he/index1.html
The results on the G-tech X50 are almost identical to Motor Trends results as far as quarter time. The speed difference is caused by the G-tech measuring speed at the very end of the quarter rather than averaging the last few yards. I cant vouch for the RX-7 result.
http://www.motortrend.com/roadtests/...he/index1.html