GT3 gear ratios
Discussion
all the talk earlier of gearboxes coupled with an inability to sleep (not because of gearbox talk) had me dig out my gear ratio charts and quickly calculate some more info for various gear ratios in the GT3 models to see how they shaped up in comparison with each other and the ratios in my 996 Cup.
i just calculated speeds in mph at 7000rpm and rounded to nearest mph, firstly to allow a direct comparison without varying redlines fogging things and secondly because i already had gear charts for most of the cars showing speeds at 7000rpm. its just to allow a comparo, not see who can go the fastest
for those of you of a nerdy disposition, enjoy!!! for everyone else, theres plenty other threads
03-05 996 Cup:..........1st-45mph,..2nd-70mph,..3rd-96mph,....4th-106mph,..5th-127mph,..6th-153mph
996.1GT3:.................1st-41mph,..2nd-73mph,..3rd-101mph,..4th-130mph,..5th-162mph,..6th-192mph
996.2GT3&RS:...........1st-41mph,..2nd-73mph,..3rd-101mph,..4th-130mph,..5th-157mph,..6th-184mph
997.1GT3&RS&.2GT3:..1st-42mph,..2nd-70mph,..3rd-97mph,....4th-123mph,..5th-150mph,..6th-172mph
997.2 GT3RS:............1st-37mph,..2nd-63mph,..3rd-87mph,....4th-111mph,..5th-135mph,..6th-162mph
2008 997 Cup...........1st-43mph,..2nd-65mph,..3rd-81mph,....4th-99mph,....5th-122mph,..6th-149mph
heres what this means in terms of shifting in the 997 cup. in combination with that engine the cars is always cooking. this highlights the benefits of the short ratios. the next gear doesnt see you drop significant rpm.
i just calculated speeds in mph at 7000rpm and rounded to nearest mph, firstly to allow a direct comparison without varying redlines fogging things and secondly because i already had gear charts for most of the cars showing speeds at 7000rpm. its just to allow a comparo, not see who can go the fastest
for those of you of a nerdy disposition, enjoy!!! for everyone else, theres plenty other threads
03-05 996 Cup:..........1st-45mph,..2nd-70mph,..3rd-96mph,....4th-106mph,..5th-127mph,..6th-153mph
996.1GT3:.................1st-41mph,..2nd-73mph,..3rd-101mph,..4th-130mph,..5th-162mph,..6th-192mph
996.2GT3&RS:...........1st-41mph,..2nd-73mph,..3rd-101mph,..4th-130mph,..5th-157mph,..6th-184mph
997.1GT3&RS&.2GT3:..1st-42mph,..2nd-70mph,..3rd-97mph,....4th-123mph,..5th-150mph,..6th-172mph
997.2 GT3RS:............1st-37mph,..2nd-63mph,..3rd-87mph,....4th-111mph,..5th-135mph,..6th-162mph
2008 997 Cup...........1st-43mph,..2nd-65mph,..3rd-81mph,....4th-99mph,....5th-122mph,..6th-149mph
heres what this means in terms of shifting in the 997 cup. in combination with that engine the cars is always cooking. this highlights the benefits of the short ratios. the next gear doesnt see you drop significant rpm.
Edited by fioran0 on Sunday 19th February 00:04
the 8/32 (4.0) final drive change is applied as a percentage drop to each gear so has the effect of very slightly closing the gear spacing as larger speeds are reduced more than lower ones. it mainly just lowers the speed across the board though. the cup has completely different ratios fitted to keep the spacing shorter between gears.
with an 8/32 fitted you get:
6.1GT3......1st-34mph,...2nd-63mph,...3rd-83mph,...4th-106mph,...5th-133mph,...6th-157mph
6.2GT3......1st-34mph,...2nd-63mph,...3rd-83mph,...4th-106mph,...5th-130mph,...6th-152mph
changing to an 8/32 on the street boxes helps shorten things down so that 4,5 and 6 can be brought into use easier but at the expense of a much shortened 1,2 and 3.
with an 8/32 fitted you get:
6.1GT3......1st-34mph,...2nd-63mph,...3rd-83mph,...4th-106mph,...5th-133mph,...6th-157mph
6.2GT3......1st-34mph,...2nd-63mph,...3rd-83mph,...4th-106mph,...5th-130mph,...6th-152mph
changing to an 8/32 on the street boxes helps shorten things down so that 4,5 and 6 can be brought into use easier but at the expense of a much shortened 1,2 and 3.
Edited by fioran0 on Saturday 18th February 11:26
the 7/35 R&P was for the GT3R/RS though can be fitted in the Cups however not if you want to race in a standard class. regs need the 8/32.
inspection required after 10hrs racing and its not to be used for any races longer than 12hrs. replacement depends on inspection results. 8/32 is recommended to be replaced after 8000km with regular inspections.
the GT3R/RS ran the same 1,2 and 3 as the cup but then had a shorter 4th, longer 5th and longer 6th.
not quite sure the porsche motorsport dept in weissach have hillclimbs on their schedule board, though i accept that this would be a good use for it (though perhaps not the car).
inspection required after 10hrs racing and its not to be used for any races longer than 12hrs. replacement depends on inspection results. 8/32 is recommended to be replaced after 8000km with regular inspections.
the GT3R/RS ran the same 1,2 and 3 as the cup but then had a shorter 4th, longer 5th and longer 6th.
not quite sure the porsche motorsport dept in weissach have hillclimbs on their schedule board, though i accept that this would be a good use for it (though perhaps not the car).
Edited by fioran0 on Saturday 18th February 11:35
Too long for a road car, no.
They could do with being closer together and shorter for track driving, something Porsche has been creeping towards as increased rev ranges offset some of the road compromise this brings. A lot of folks run 8/32 final drive to change this.
0-60 times mean nothing unless you drag strip.
They could do with being closer together and shorter for track driving, something Porsche has been creeping towards as increased rev ranges offset some of the road compromise this brings. A lot of folks run 8/32 final drive to change this.
0-60 times mean nothing unless you drag strip.
mrdemon said:
if they are to long for track work they are way to long for B road driving.
Good for the ring though lol
Really? I dont see how the two are mutually inclusive at all and often find the opposite to be true. You got unrestricted one way only B roads round by you? Good for the ring though lol
Edited by fioran0 on Saturday 18th February 14:20
You don't have data overlay do you. Would be very interesting to look at.
The GT3 engines have a very small range where they are properly firing. Generally longer gears might save you a shift but cost on others where you are forced to accept a sub optimal rev level post shift.
Without a data overlay there's no way to check but its as feasible that the ratios benefit you elsewhere by a greater margin than you lose having to grab 6th on that one occasion (ie the 3-4 change which chugs big time), that the 5th gear ratio that forces you to take 6th gains more by starting off at a higher rpm and accelerating quicker than a 5th ratio that starts lower down the rev range but let's you hold it til the end, or that it is infact a pain and costing you on that track and layout.
The GT3 engines have a very small range where they are properly firing. Generally longer gears might save you a shift but cost on others where you are forced to accept a sub optimal rev level post shift.
Without a data overlay there's no way to check but its as feasible that the ratios benefit you elsewhere by a greater margin than you lose having to grab 6th on that one occasion (ie the 3-4 change which chugs big time), that the 5th gear ratio that forces you to take 6th gains more by starting off at a higher rpm and accelerating quicker than a 5th ratio that starts lower down the rev range but let's you hold it til the end, or that it is infact a pain and costing you on that track and layout.
Edited by fioran0 on Saturday 18th February 21:49
mrdemon said:
why do you think the new car has 7 gears and PDK :-)
it's bound to be a GT3 option.
Hmmmm..... What will be on the new GT3?it's bound to be a GT3 option.
You do know the 7MT transmission is the PDK box with a clutch and a fancy shift input converter to arrange the "manual" gear selection into a proper order. That's it.
I've heard from several places that only the cup is going to be 911 (991) based and that the RSR etc will be on the coming 961 platform and have 8 cylinders.
Would certainly save the awkward moment when you are trying to float wet sump to street folks and dry sump is still being used on race cars.
If this is remotely true then the very top of the pile of things this means is the removal of all of the homologation rules which define in some way what the GT3 be mechanically and puts all bets off.
PDK, 9A1 and a sported up C2S. Potentially.
Not quite rear engined V8 RSR. Awesome.
Edited by fioran0 on Sunday 19th February 11:40
Thanks for that. It's great (and rare) when folk can post up data.
I see the data putting the 7.1 ahead in terms of time as you say but the overlays show the 7.2 out dragging it by a decent margin and both have two shifts.
The 7.1 starts ahead and on the throttle earlier, gets a cleaner second shift and rolls into the brakes but still only is 0.1 ahead.
I do see how another 1-200 yds on the straight would see you need another shift on the 7.2 (your point on silverstone) but then another 100yds again would see the 7.1 need a shift. thats the eternal compromise of using the same gearbox everywhere. there will always be "if only there was/wasnt another 100yds"
I still think the shorter gears would give more benefits over an average lap.
Did you stay clear on both to point 11? Can you show the overlays to this point or did you have to lift?
What are you using for your data?
Edit: reread that and it sounds a bit barking (orders not mad). I promise it was interest/excitement and not all red faced.
I see the data putting the 7.1 ahead in terms of time as you say but the overlays show the 7.2 out dragging it by a decent margin and both have two shifts.
The 7.1 starts ahead and on the throttle earlier, gets a cleaner second shift and rolls into the brakes but still only is 0.1 ahead.
I do see how another 1-200 yds on the straight would see you need another shift on the 7.2 (your point on silverstone) but then another 100yds again would see the 7.1 need a shift. thats the eternal compromise of using the same gearbox everywhere. there will always be "if only there was/wasnt another 100yds"
I still think the shorter gears would give more benefits over an average lap.
Did you stay clear on both to point 11? Can you show the overlays to this point or did you have to lift?
What are you using for your data?
Edit: reread that and it sounds a bit barking (orders not mad). I promise it was interest/excitement and not all red faced.
Edited by fioran0 on Sunday 19th February 01:07
Steve Rance said:
Yep I think that a cup final drive is a really usable and cost effective upgrade to a 996gt3. Maybe pound for pound one of the best.
steve, apologies, i totally missed your post. absolutely agree (once you get over and then adjust to the whoosh that is first gear lol)Ken.
Thanks for the info and further posts. Great stuff.
What data can you read from your system. It sounds very interesting indeed.
That 6RS trace was good to see too. The new 7.2 RS is the first car imho that's equal too or better than the 6GT3 in terms of lap times/pace assuming all are stock and even still it needs really worked to achieve. That it needs better gearing and 3.8 to do it speaks volumes. Especially when you factor on its improved aero aswell.
As Steve mentions in detail, Its a ball dropped rather than the power of the 6 (which I love).
The paradox is that in cup form where it's just the raw cars the 7 obliterates the 6. the 7 platform is so much better but you can't tell due to PASM.
Now with a suspension change on a street 7 everything changes.
Thanks for the info and further posts. Great stuff.
What data can you read from your system. It sounds very interesting indeed.
That 6RS trace was good to see too. The new 7.2 RS is the first car imho that's equal too or better than the 6GT3 in terms of lap times/pace assuming all are stock and even still it needs really worked to achieve. That it needs better gearing and 3.8 to do it speaks volumes. Especially when you factor on its improved aero aswell.
As Steve mentions in detail, Its a ball dropped rather than the power of the 6 (which I love).
The paradox is that in cup form where it's just the raw cars the 7 obliterates the 6. the 7 platform is so much better but you can't tell due to PASM.
Now with a suspension change on a street 7 everything changes.
If you don't normalise the RPM to something common when doing the above sort of analysis, you can't really gain much of an insight into relative gearing.
You only see maximum (theoretical) in gear speeds. This can be useful but it isn't the whole story. How the gearing of one car relates to a second car is lost as a result of the difference in applied RPMs
The GT4 has shorter gear ratios in every gear but 1st when compared to a 996.2 GT3 ( assuming GT3 is running stock 3.44 final drive) but when combined to its huge bling wheels ends up losing out.
For the same RPM in each of the 6 gears, the GT4 ends up pulling higher kph than the GT3. The gap is pretty small in 5th and 6th but fairly significant in the other gears.
Those with a GT4 need to get them onto smaller wheels.
You only see maximum (theoretical) in gear speeds. This can be useful but it isn't the whole story. How the gearing of one car relates to a second car is lost as a result of the difference in applied RPMs
The GT4 has shorter gear ratios in every gear but 1st when compared to a 996.2 GT3 ( assuming GT3 is running stock 3.44 final drive) but when combined to its huge bling wheels ends up losing out.
For the same RPM in each of the 6 gears, the GT4 ends up pulling higher kph than the GT3. The gap is pretty small in 5th and 6th but fairly significant in the other gears.
Those with a GT4 need to get them onto smaller wheels.
In a short answer - yes. With a bigger rim and tire radius you suffer in two areas; acceleration is reduced due to the larger diameter and road speed for a given RPM increases.
I can only assume market reasons are behind the bigger rear tire on the 991 RS though I will be kind and say perhaps the aero needs it.
I haven't got the ratios for the RS, and despite a quite google didn't come up with any. Ive limited options for finding out at 11.30pm on a Friday night
Interestingly, the spread of the individual gear ratios on the 991 GT3 are pretty much identical to the 996 GT3 gear ratios. The PDK obviously has 7 gears so benefits from a reduced drop between each gear. The different spacing makes direct comparisons trickier, however the upper and lower limits are 3.75 - 0.84 on the 991 versus 3.82 - 0.85 on the 996.
The 991 however benefits from a shorter final drive at 3.97 versus the 3.44 used OEM in the 996 so total gear ratio is shorter as a result.
For a 996 GT3 with a 4.00 R&P though things change - a touch of advantage to the 996 in overall ratios, and an advantage back to the PDK for having 1 extra cog in between to help drops.
The tire diameter difference is pretty remarkable though. 27.2" diameter tire on the 991, 25" on the 996, and a massive 28.7" on the 991 RS
As a result, 7000RPM in 3rd gear in the 991 GT3 is ~ 133.4 km/h, the 996.2 GT3 it is ~ 155.80 km/h, and a 996.2 GT3 with a 4.0 R&P is ~ 122.5 km/h. The GT4 is ~164.8km/h
The tire diameter increase of around 5.5% on the 991 RS (versus the 991 GT3) would hurt gearing by the same 5.5% though. The question for the RS is whether the ratios have been dropped by an equivalent (or greater) amount.
I can only assume market reasons are behind the bigger rear tire on the 991 RS though I will be kind and say perhaps the aero needs it.
I haven't got the ratios for the RS, and despite a quite google didn't come up with any. Ive limited options for finding out at 11.30pm on a Friday night
Interestingly, the spread of the individual gear ratios on the 991 GT3 are pretty much identical to the 996 GT3 gear ratios. The PDK obviously has 7 gears so benefits from a reduced drop between each gear. The different spacing makes direct comparisons trickier, however the upper and lower limits are 3.75 - 0.84 on the 991 versus 3.82 - 0.85 on the 996.
The 991 however benefits from a shorter final drive at 3.97 versus the 3.44 used OEM in the 996 so total gear ratio is shorter as a result.
For a 996 GT3 with a 4.00 R&P though things change - a touch of advantage to the 996 in overall ratios, and an advantage back to the PDK for having 1 extra cog in between to help drops.
The tire diameter difference is pretty remarkable though. 27.2" diameter tire on the 991, 25" on the 996, and a massive 28.7" on the 991 RS
As a result, 7000RPM in 3rd gear in the 991 GT3 is ~ 133.4 km/h, the 996.2 GT3 it is ~ 155.80 km/h, and a 996.2 GT3 with a 4.0 R&P is ~ 122.5 km/h. The GT4 is ~164.8km/h
The tire diameter increase of around 5.5% on the 991 RS (versus the 991 GT3) would hurt gearing by the same 5.5% though. The question for the RS is whether the ratios have been dropped by an equivalent (or greater) amount.
Edited by fioran0 on Saturday 16th January 00:14
Just to follow this up. Here are the effective gear ratios for the 996 GT3, the 991 GT3 and the GT4 when normalised for rear tires.
Cay GT4 - 11.92, 7.03, 5.08, 4.07, 3.42, 2.92
996 GT3- 13.14, 7.40, 5.37, 4.16, 3.44, 2.92
991 GT3- 13.67, 8.68, 6.27, 4.89, 4.05, 3.50, 3.06
Interestingly, 2-6 on the 991 GT3 when looking at its normalised effective gearing is very close to the 2-6 on a 996 GT3 when fitted with a 4.0 R&P.
With the R&P on the 991 RS being adjusted to offset the increased tire size, its effective normalised gearing should be the same as for the regular 991 GT3.
Cay GT4 - 11.92, 7.03, 5.08, 4.07, 3.42, 2.92
996 GT3- 13.14, 7.40, 5.37, 4.16, 3.44, 2.92
991 GT3- 13.67, 8.68, 6.27, 4.89, 4.05, 3.50, 3.06
Interestingly, 2-6 on the 991 GT3 when looking at its normalised effective gearing is very close to the 2-6 on a 996 GT3 when fitted with a 4.0 R&P.
With the R&P on the 991 RS being adjusted to offset the increased tire size, its effective normalised gearing should be the same as for the regular 991 GT3.
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