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Alright, so the electronics of the auto rev match and the suspension operate on the same network in CAN bus. When the signal from the suspension is broken, the rev matching stops working.
I'm not typically one to compare against another company's products. What I will say is simply factual and logical based on the data, and that is our final drive reduction is more aggressive than that of any of the individual gearing solutions. This means more acceleration/thrust. We are going to release some graphs today/tomorrow to show you exactly where you are getting the improvements in the various gears. We are also doing a thrust comparison to the 997.2 GT3RS and the results so far have been quite interesting...
Oh we plenty of early adopters, a half a dozen just in the last few days haha. Expect to start seeing an influx of feedback late November once they have arrived and been installed : )
That being said, once the first batch is all spoken for the next round of pre-orders will likely then be in the February time frame so don't wait too long!
Come November we have made plans to hit Sebring and record video and track data back to back on a few fellows' cars that will be joining us for our hosted track day. We'll also throw in some acceleration testing as well.
To note, this mechanical upgrade has no effect on the software function of the rev match feature. It will operate the same as always : )
When Porsche released the last GT3 manual transmission car (997.2) they shortened the ratio in the RS 13% (from 3.44 to 3.89). Why? Simply to improve the acceleration and on track performance, which helped contribute to the RS’s 7 second improvement over the GT3 on the Nürburgring. The 19% reduction in the GT4 final drive ratio (from 3.89 to 4.62) will have a similar effect on the GT4’s performance, improving 0-60 time by approximately 4/10ths of a second and improving lap times on most longer/fast US tracks by at least a second. As an example, the GT4’s top speed with the 4.62 ratio on the back straight at Sebring will be 2-3 mph faster and only 2-3mph off the top speed of the more powerful 997.2 GT3 RS. Virtually all of that 2-3mph gain will have occurred at the point of initial acceleration i.e. coming out of turn 16 onto the back straight. This gain (advantage) is maintained for the majority of the back straight until the GT4 with the 4.62 ratio shifts into 6th where an additional slight gain occurs over the GT4 with the standard ratio.
The 1st chart compares thrust vs speed of a 997.2 GT3 RS and a GT4 with our 4.62 ratio and bolt-ons (est. 40hp increase). The 2nd series of charts compares the thrust vs speed of a GT4 with the 4.62 ratio and a GT4 with the 3.89 standard ratio. In this example, both cars have equal power upgrades.
From studying these charts what can we learn? Firstly, let’s compare the GT4 with the 4.62 ratio to the GT3 RS. The GT4 will now be slightly faster 0-60 than the RS, even though the RS has a horsepower advantage (450hp), and the GT4 will still be fractionally ahead at 90mph. After that, the RS’s extra horsepower allows it to pull slightly ahead and by the time it gets to 150mph it’s 2-3mph faster than the GT4 with the 4.62 gearing, as opposed to being 4-5mph faster than a GT4 with standard gearing. How is this achieved? The GT3 RS is doing the acceleration run from 90-150mph using three gears, the GT4 is now doing it using four gears. The additional gear and the shorter ratios allow the GT4 to nearly maintain the same terminal velocity and forward thrust as the more powerful GT3 RS up to 150mph. As the speed increases beyond that, the RS’s additional horsepower will allow it to pull a bigger advantage.
The second series of charts compares the thrust vs speed of the GT4 4.62 ratio versus the standard 3.89 ratio, both with equal bolt-on upgrades. As you can see with these charts, the GT4 with the 4.62 ratio will have a noticeably faster 0-60 time. It will also have an additional gain in the 75-110mph acceleration range, which is the critical acceleration range coming out of most of the slower corners on track. This allows the car with the shorter ratio to pull out 1-2 car lengths, which it will maintain down the length of the straight. These incremental improvements exiting the corners is how the car with the shorter ratio is able to improve its overall lap time. From 110mph to 145mph the forward thrust is virtually equal. Above 145mph, the car with the shorter final drive ratio has a slight edge. This equates to not only a faster GT4 but one that is more engaging and fun to drive : )
John,
Are you able to post a plot of the mathematical difference in thrust (vs speed) for the stock vs revised GT4 gearing options? I think it’d be slightly easier to make sense of than the overlaid plots. Thanks.
Originally Posted by AutoQuest Motorsports
When Porsche released the last GT3 manual transmission car (997.2) they shortened the ratio in the RS 13% (from 3.44 to 3.89). Why? Simply to improve the acceleration and on track performance, which helped contribute to the RS’s 7 second improvement over the GT3 on the Nürburgring. The 19% reduction in the GT4 final drive ratio (from 3.89 to 4.62) will have a similar effect on the GT4’s performance, improving 0-60 time by approximately 4/10ths of a second and improving lap times on most longer/fast US tracks by at least a second. As an example, the GT4’s top speed with the 4.62 ratio on the back straight at Sebring will be 2-3 mph faster and only 2-3mph off the top speed of the more powerful 997.2 GT3 RS. Virtually all of that 2-3mph gain will have occurred at the point of initial acceleration i.e. coming out of turn 16 onto the back straight. This gain (advantage) is maintained for the majority of the back straight until the GT4 with the 4.62 ratio shifts into 6th where an additional slight gain occurs over the GT4 with the standard ratio.
The 1st chart compares thrust vs speed of a 997.2 GT3 RS and a GT4 with our 4.62 ratio and bolt-ons (est. 40hp increase). The 2nd series of charts compares the thrust vs speed of a GT4 with the 4.62 ratio and a GT4 with the 3.89 standard ratio. In this example, both cars have equal power upgrades.
From studying these charts what can we learn? Firstly, let’s compare the GT4 with the 4.62 ratio to the GT3 RS. The GT4 will now be slightly faster 0-60 than the RS, even though the RS has a horsepower advantage (450hp), and the GT4 will still be fractionally ahead at 90mph. After that, the RS’s extra horsepower allows it to pull slightly ahead and by the time it gets to 150mph it’s 2-3mph faster than the GT4 with the 4.62 gearing, as opposed to being 4-5mph faster than a GT4 with standard gearing. How is this achieved? The GT3 RS is doing the acceleration run from 90-150mph using three gears, the GT4 is now doing it using four gears. The additional gear and the shorter ratios allow the GT4 to nearly maintain the same terminal velocity and forward thrust as the more powerful GT3 RS up to 150mph. As the speed increases beyond that, the RS’s additional horsepower will allow it to pull a bigger advantage.
The second series of charts compares the thrust vs speed of the GT4 4.62 ratio versus the standard 3.89 ratio, both with equal bolt-on upgrades. As you can see with these charts, the GT4 with the 4.62 ratio will have a noticeably faster 0-60 time. It will also have an additional gain in the 75-110mph acceleration range, which is the critical acceleration range coming out of most of the slower corners on track. This allows the car with the shorter ratio to pull out 1-2 car lengths, which it will maintain down the length of the straight. These incremental improvements exiting the corners is how the car with the shorter ratio is able to improve its overall lap time. From 110mph to 145mph the forward thrust is virtually equal. Above 145mph, the car with the shorter final drive ratio has a slight edge. This equates to not only a faster GT4 but one that is more engaging and fun to drive : )
These are great charts, thanks John! I went to a 20% shorter final drive ratio on my old 200mph geared BMW and it was a night a day difference. Yes there was more shifting around town but I enjoyed it and it really made the car feel like it lost 500 lbs, almost jumpy even, and I got to see redline a lot more often. If this is anything similar, it's probably going to be the most dramatic single mod to the way the car feels in street driving.
While I understand changing gearing doesn't increase power and isn't inherently faster, it does make the car feel much more responsive in gear and gives us more options to stay in the top of the powerband at speeds we're more likely to see in the US. Looking forward to reviews and perspectives from people in the first run of these!
These are great charts, thanks John! I went to a 20% shorter final drive ratio on my old 200mph geared BMW and it was a night a day difference. Yes there was more shifting around town but I enjoyed it and it really made the car feel like it lost 500 lbs, almost jumpy even, and I got to see redline a lot more often. If this is anything similar, it's probably going to be the most dramatic single mod to the way the car feels in street driving.
While I understand changing gearing doesn't increase power and isn't inherently faster, it does make the car feel much more responsive in gear and gives us more options to stay in the top of the powerband at speeds we're more likely to see in the US. Looking forward to reviews and perspectives from people in the first run of these!
Thanks for the kind words Andy, I'm glad to hear you've experienced a final drive change in the past : ) We have done numerous 997 GT3's from 3.44 to 4.0 ratio with great success, to do a similar change on the GT4 was a no brainer.
Originally Posted by Gilou Panizzi
Can't wait to see some videos of this mod !!
You most certainly shall : )
Last edited by AutoQuest Motorsports; 10-25-2017 at 12:21 PM.
This is the best solution so far for the 981's long gearing problem that a lot of people don't want to face upfront....including Porsche.
The shorter FD increases engine torque to the wheels commensurately because of the higher ratio torque multiplier effect and therefore you accelerate faster.
The shorter FD increases engine torque to the wheels commensurately because of the higher ratio torque multiplier effect and therefore you accelerate faster.
10-13-2017, 07:19 AM
