Launching a 996t
Discussion
As some of you will have read I am currently hillclimbing my 996t. Its a great car for the job except in one area that I just cant get around, the standing starts.
The best 0-64' I have managed so far is 2.28 which was at Gurston and slightly downhill.
At the recent Shelsley which is on a fair slope my best was 2.38, where as some of the Evo's and Scoobies can regularly do around a 2.10 ish, [ GTR almost a 2 dead!!! ] the 997 t in my class has done a similar low 2.
I consider myself a decent pilot with quite a bit or motorsport experience in different cars and the 996t is by far the hardest car to get off the line.
Too many revs and it tramps itself silly to such an extent the cup holder pops out! too few and it will bog. Dumping the clutch is not on, I have to side step it for my best results.
In the grand scheme of things its not a big deal, but to regularly loose 2 to 3 tenths to 64' I could do without.
Anyone have any ideas how this can be improved / possible fault with the car etc ??????
FYI the 997T in my class also has similar issues but not as bad.
Thanks in advance for any help
cheers.
The best 0-64' I have managed so far is 2.28 which was at Gurston and slightly downhill.
At the recent Shelsley which is on a fair slope my best was 2.38, where as some of the Evo's and Scoobies can regularly do around a 2.10 ish, [ GTR almost a 2 dead!!! ] the 997 t in my class has done a similar low 2.
I consider myself a decent pilot with quite a bit or motorsport experience in different cars and the 996t is by far the hardest car to get off the line.
Too many revs and it tramps itself silly to such an extent the cup holder pops out! too few and it will bog. Dumping the clutch is not on, I have to side step it for my best results.
In the grand scheme of things its not a big deal, but to regularly loose 2 to 3 tenths to 64' I could do without.
Anyone have any ideas how this can be improved / possible fault with the car etc ??????
FYI the 997T in my class also has similar issues but not as bad.
Thanks in advance for any help
cheers.
It might be worth digging out contemporary road tests (from the likes of Evo, Autocar etc.) who often describe the techniques they found worked best when figuring the car's 0-60mph. 
Other than that, just experiment with a variety of techniques yourself: get hold of a VBox or similar, find a quiet, straight stretch of tarmac and time launches using a selection of launch revs.
Other than that, just experiment with a variety of techniques yourself: get hold of a VBox or similar, find a quiet, straight stretch of tarmac and time launches using a selection of launch revs.
Mark A S said:
IMI A said:
Not much more you can do apart from maybe even stickier tyres and running lower tyre pressures at the rear.
Thanks, but we can't run anything softer TBH and lowering the pressures would upset where it excels,,,,,,,,,, the bendy bits 
Interesting you mention the difference to the 997 in your class. Maybe you can find something in the drive train differences between the two?
You mention the rear axle diff - have you done anything with the centre diff?
I found this in the original 997 turbo brochure (page 44) http://coochas.com/brochures/Resources/911_997_tur...
"In the previous 911 Turbo (Type 996), a viscous multi-disk clutch responded to relative front/rear speed differences to determine how much torque to apply at either axle. The new 911 Turbo, by contrast, employs an electronically controlled multi- disk clutch that responds to traction changes almost instantaneously... The sensor data is analyzed in real time, enabling immediate adjustments in the torque split between the front and rear axles."
Obviously a healthy dose of marketing speak in there but basically (and I am no expert in this) I think the computer actuated system in the 997 can respond faster to a loss of rear wheel traction than the viscous coupling in the 996.
Maybe you can do something with the oil in the viscous coupling to make it better suited to the fast starts? Or maybe replace it for a torsen diff? The latter would be a lot of work but I suspect more effective for getting the power down.
BTW I think 2.4 secs is already mighty impressive, well done
Hope this is in some way helpful
You mention the rear axle diff - have you done anything with the centre diff?
I found this in the original 997 turbo brochure (page 44) http://coochas.com/brochures/Resources/911_997_tur...
"In the previous 911 Turbo (Type 996), a viscous multi-disk clutch responded to relative front/rear speed differences to determine how much torque to apply at either axle. The new 911 Turbo, by contrast, employs an electronically controlled multi- disk clutch that responds to traction changes almost instantaneously... The sensor data is analyzed in real time, enabling immediate adjustments in the torque split between the front and rear axles."
Obviously a healthy dose of marketing speak in there but basically (and I am no expert in this) I think the computer actuated system in the 997 can respond faster to a loss of rear wheel traction than the viscous coupling in the 996.
Maybe you can do something with the oil in the viscous coupling to make it better suited to the fast starts? Or maybe replace it for a torsen diff? The latter would be a lot of work but I suspect more effective for getting the power down.
BTW I think 2.4 secs is already mighty impressive, well done
Hope this is in some way helpful
Thanks all, much appreciated Car is not short of traction, if the Tramping could be eliminated I am sure it would be faster off the line, I don't appear to be able to find anyone who knows how to avoid the tramping,,,,,,,,,,,,,,,, yet!
Can't use a sequential box in the regs, besides, it would spoil its nice road manners which are still VERY nice.
cheers
Car is not short of traction, if the Tramping could be eliminated I am sure it would be faster off the line, I don't appear to be able to find anyone who knows how to avoid the tramping,,,,,,,,,,,,,,,, yet!Can't use a sequential box in the regs, besides, it would spoil its nice road manners which are still VERY nice.
cheers
I sprint an Evo that regularly gets very low 2's and sometimes 2.0 ish (if I'm very lucky). I don't for one minute purport to be an expert, but it may be useful if you were to share your launch technique on here.
My method is to lift the clutch to biting point while holding the car on the handbrake, bring up the revs and then release the hand brake and clutch simultaneously while at the same time flooring the throttle. Its not a failproof method but tends to work for me.
My method is to lift the clutch to biting point while holding the car on the handbrake, bring up the revs and then release the hand brake and clutch simultaneously while at the same time flooring the throttle. Its not a failproof method but tends to work for me.
I used to hillclimb an Escort Cosworth with around 350 bhp back in the mid 90's that was quite easy to get off the line, regular 2.1 and like you sometimes a 2 dead.
The 996t is not easy at all mainly due to the tramping, its this I need to get to the bottom of.
Best starts are not dumping the clutch but side stepping it whilst revving it up to around 3k ish then trying to control the tramping!
cheers
The 996t is not easy at all mainly due to the tramping, its this I need to get to the bottom of.
Best starts are not dumping the clutch but side stepping it whilst revving it up to around 3k ish then trying to control the tramping!
cheers
Mark A S said:
I used to hillclimb an Escort Cosworth with around 350 bhp back in the mid 90's that was quite easy to get off the line, regular 2.1 and like you sometimes a 2 dead.
The 996t is not easy at all mainly due to the tramping, its this I need to get to the bottom of.
Best starts are not dumping the clutch but side stepping it whilst revving it up to around 3k ish then trying to control the tramping!
cheers
thats interesting - 997 needs 3800 to 4000 rpm but still only 1 in 10 starts are perfect - at Brunters anyway. Best 0-60 time I've achieved is 3.6 secs so your car is really moving. I've never suffered axle tramp in the 997The 996t is not easy at all mainly due to the tramping, its this I need to get to the bottom of.
Best starts are not dumping the clutch but side stepping it whilst revving it up to around 3k ish then trying to control the tramping!
cheers
Just a thought, but would a momentary, slight lift of the throttle, once you're moving work to stop tramp? The Griff I had needed a similar technique - granny starts were never any use, and full-on clutch drops just lit up the rear tyres, but a little bit of finesse on the throttle could bring the tyres back to the ideal grip/spin rate. You sort of had to lift until it felt right and then get straight back on the throttle.
Edited by Digga on Thursday 20th August 15:58
IMI A said:
thats interesting - 997 needs 3800 to 4000 rpm but still only 1 in 10 starts are perfect - at Brunters anyway. Best 0-60 time I've achieved is 3.6 secs so your car is really moving. I've never suffered axle tramp in the 997
Is the time quoted for 64 feet not 0-60?I was shown the off-thrttle technique. so when it's tramping just do a straight off/on with the throttle.
Dunno, might work
If in the grand scheme of things if it is not that big of a deal then why worry about?
I'd focus on being as smooth and quick off the line as consistently as I could be and instead of worrying about a possible less than spectacular start make the most of the rest of the run.
You state the car's best in the twistie bits. Well, wring the most out of it in these areas of which in most hillclimbs there are a number of turns while there is only one start.
I've seen a number of videos of hillclimb starts and rally starts and the like and while some launches are impressive a number are rather lame. Some of these by drivers I'm sure that are above your pay grade.
While I've not hillclimbed my 2003 Turbo and have not bothered to do any drag race starts as I know the car - and this is true of a number of cars I've owned -- is just not going to win any awards from its starting line elapsed numbers I have perfected a quick launch technique. I've never tested it against the clock but on the street at least it suits me and the car.
What I have found gets the car off the line reasonably quick and with the least amount of abuse to the drivetrain -- which granted is important to me but it may not be that big of a factor in your situation -- is to just brings revs up to 1K or so and smoothly release the clutch then once the car is moving and the clutch fully engaged giving the car the whip. It is important to note here I think that my car has the stock flywheel which while not the lightest thing around helps get the card moving without a lot of revs necessary to keep from killing the engine.
Forget about any viscous fluid tweaking. For one thing the torque transmitted to the front diff is zilch when the vehicle is stationary and there is nothing you can do to change that.
As the vehicle gains speed the torque transfer climbs from 5% to a max of 40% but my info is this number only arrives at around 150mph+.
Furthermore, AFAIK there is no choice of fluids for the coupling. The fluid is a special fluid that as the two sets of discs in the coupling spin at different speeds -- due to the tire size differences -- this heats the fluid and the fluid as it heats up gets more viscous and this works to transfer torque between the set of discs connected to the rear diff (transmission) and the discs connected to the front diff.
The 997 AWD system is different in that the discs are actually in contact and the force of this contact is controlled by the DME which can increase or decrease this contact amount to change the amount of torque transmitted to the front diff.
In videos of 996 Turbos (and 996 C4s) in the snow one can see while the rear wheels are spinning like crazy while the driver is spinning donuts in the snow the front tires are not spinning at all and in some cases the inside front tire is nearly stationary as the donut is a very tight one.
OTOH, videos of 997s with the new AWD system one can see for instance in hard launches in marginal traction condtions the front tires actually spin (along with the rear tires) from a dead start thus indicating the front tires receive torque immediately.
However, I do not think your car would really benefit from this system were it possible to adapt it to your car.
Focus on smoothness and consistency of your start. Know you have left the starting light as good as you can and turn your full attention to the track in frotn of you, not what you have left behind.
I'd focus on being as smooth and quick off the line as consistently as I could be and instead of worrying about a possible less than spectacular start make the most of the rest of the run.
You state the car's best in the twistie bits. Well, wring the most out of it in these areas of which in most hillclimbs there are a number of turns while there is only one start.
I've seen a number of videos of hillclimb starts and rally starts and the like and while some launches are impressive a number are rather lame. Some of these by drivers I'm sure that are above your pay grade.
While I've not hillclimbed my 2003 Turbo and have not bothered to do any drag race starts as I know the car - and this is true of a number of cars I've owned -- is just not going to win any awards from its starting line elapsed numbers I have perfected a quick launch technique. I've never tested it against the clock but on the street at least it suits me and the car.
What I have found gets the car off the line reasonably quick and with the least amount of abuse to the drivetrain -- which granted is important to me but it may not be that big of a factor in your situation -- is to just brings revs up to 1K or so and smoothly release the clutch then once the car is moving and the clutch fully engaged giving the car the whip. It is important to note here I think that my car has the stock flywheel which while not the lightest thing around helps get the card moving without a lot of revs necessary to keep from killing the engine.
Forget about any viscous fluid tweaking. For one thing the torque transmitted to the front diff is zilch when the vehicle is stationary and there is nothing you can do to change that.
As the vehicle gains speed the torque transfer climbs from 5% to a max of 40% but my info is this number only arrives at around 150mph+.
Furthermore, AFAIK there is no choice of fluids for the coupling. The fluid is a special fluid that as the two sets of discs in the coupling spin at different speeds -- due to the tire size differences -- this heats the fluid and the fluid as it heats up gets more viscous and this works to transfer torque between the set of discs connected to the rear diff (transmission) and the discs connected to the front diff.
The 997 AWD system is different in that the discs are actually in contact and the force of this contact is controlled by the DME which can increase or decrease this contact amount to change the amount of torque transmitted to the front diff.
In videos of 996 Turbos (and 996 C4s) in the snow one can see while the rear wheels are spinning like crazy while the driver is spinning donuts in the snow the front tires are not spinning at all and in some cases the inside front tire is nearly stationary as the donut is a very tight one.
OTOH, videos of 997s with the new AWD system one can see for instance in hard launches in marginal traction condtions the front tires actually spin (along with the rear tires) from a dead start thus indicating the front tires receive torque immediately.
However, I do not think your car would really benefit from this system were it possible to adapt it to your car.
Focus on smoothness and consistency of your start. Know you have left the starting light as good as you can and turn your full attention to the track in frotn of you, not what you have left behind.
To avoid any confusion, I am talking about 0 to 64 foot times that are common at hillclimbs / sprints etc. [ I have no idea what my 0 to 60 mph is ]
When I say 3000 rpm, I am not looking at the rev counter, just on feel as I have done quite a few starts now [ average 5 / event ] too many revs though and it tramps too much. I do back it off to control, but its not like a V8, if you back off a fraction too much it will bog due to the immense traction available and dropping boost.
Matt at Fearnsport has looked over the car and confirmed all is in order, no slackness anywhere in the drivetrain/ suspension etc so maybe its just the way they are, it looks like the 997's have a more sophisticated system to allow smoother starts, maybe I just ought to dump the front diff and drive shafts
When I say 3000 rpm, I am not looking at the rev counter, just on feel as I have done quite a few starts now [ average 5 / event ] too many revs though and it tramps too much. I do back it off to control, but its not like a V8, if you back off a fraction too much it will bog due to the immense traction available and dropping boost.
Matt at Fearnsport has looked over the car and confirmed all is in order, no slackness anywhere in the drivetrain/ suspension etc so maybe its just the way they are, it looks like the 997's have a more sophisticated system to allow smoother starts, maybe I just ought to dump the front diff and drive shafts
Kawasicki said:
Tramping - excitation of powertrain at eigenfrequency.
Stiffer engine mounts.
Could you explain that in user friendly English please Stiffer engine mounts.
Its something I have thought about, I suppose with stiffer mounts whilst they will help, on the road the effect will be to make more of a harshness whilst cruising?
Using a road car is always going to be a bit of a compromise, so with 5 x 1st in class and 2 records I perhaps ought to just accept it as is, as no car is perfect.
cheers
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