ASK THE COACH
05-10-2011, 12:50 PM
#76
Three Wheelin'
Just noticed this thread, hope Dave and others dont mind me chiming in.
I have spent a decent amount of time coaching/tuning in a relatively high (450 wheel hp) 993 turbo. The car had a lot of corner exit understeer with 4wd. Was fairly stable on entry but a little inconsistent mid corner. The 4wd was a little too simple of a system to really work well on the track. We disconnected the coupler and have been running in 2wd and the car is faster on track. It is more balanced as a whole and more "lively" and fun to drive. I have also spent time in a hi-hp 996 turbo that was very similiar. Its primary problem though was the stock rear suspension links/subframe bushings. The rear of the car would take a very weird "set" on exit and was not very confidence inspiring to roll into the power hard enough, early enough to really put down the super fast times.
[snip]
I have spent a decent amount of time coaching/tuning in a relatively high (450 wheel hp) 993 turbo. The car had a lot of corner exit understeer with 4wd. Was fairly stable on entry but a little inconsistent mid corner. The 4wd was a little too simple of a system to really work well on the track. We disconnected the coupler and have been running in 2wd and the car is faster on track. It is more balanced as a whole and more "lively" and fun to drive. I have also spent time in a hi-hp 996 turbo that was very similiar. Its primary problem though was the stock rear suspension links/subframe bushings. The rear of the car would take a very weird "set" on exit and was not very confidence inspiring to roll into the power hard enough, early enough to really put down the super fast times.
[snip]
Really wish someone had a set of X73 suspension they needed to unload.
05-10-2011, 01:55 PM
#77
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Double declutching
I am about to get my 993's transmission redone. The synchros, I am realizing, are a wear item for a 993.
Both Stan Richardson (at GBox) and Paul Tosi (my mechanic) suggest double declutching.
Though I know the technique of double declutching, I'll bet it's going to be a challenge to get my trailbraking, heel and toe, and double declutch organized.
Suggestions (in addition to practice practice practice)?
Both Stan Richardson (at GBox) and Paul Tosi (my mechanic) suggest double declutching.
Though I know the technique of double declutching, I'll bet it's going to be a challenge to get my trailbraking, heel and toe, and double declutch organized.
Suggestions (in addition to practice practice practice)?
05-10-2011, 04:24 PM
#78
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im sure most of these mechanics and even transmission guys, dont reallly study the dynmaics of the gear box in a racing environment. what are you trying to do by double clutching. we have all seen what chris crevelli does with a close ratio gear box and how easily his skip shifts are from 5th to 3rd. why is that?
synchros do wear, but if you master the match RPM shift, and blip with knowledge of the next gear RPM, that wear factor becomes a minimal one.
double clutching helps spin up the layshaft on a downshift, because it is still spinnning at a slower speed because of the prior gear it was being driven by.
double clutching witout a blip, is totall useless and defeats the purpose. however, there is some that say the act of releasing the clutch , after the blip, spins up the driveshaft, as both the blip rpm now being transfered to the drive line, spins it up , as well as some slight synchro force, to help spin up the layshaft, and driveshaft. when done right, its smooth. if its smooth,there are very few forces that are acting against the wear components.
about 7-10 years ago, in the heat of the battle in races, i would trash my gear box. sometimes not even matching revs, just banging gears. it woud overheat, and get crunchy. fast forward to the last 6 years, same gearbox, no failure or modifications what so ever (testimate to the durability to the borg warner components that are stock on some porsches) and its still running perfect.
So, i think you just learn to perfect the blip downshift and do it later, so there is potentially less wear on the synchros. I also think that double clutching poses a risk for banging into a gear that you might not want to engage, or not want to engage at that time.
synchros do wear, but if you master the match RPM shift, and blip with knowledge of the next gear RPM, that wear factor becomes a minimal one.
double clutching helps spin up the layshaft on a downshift, because it is still spinnning at a slower speed because of the prior gear it was being driven by.
double clutching witout a blip, is totall useless and defeats the purpose. however, there is some that say the act of releasing the clutch , after the blip, spins up the driveshaft, as both the blip rpm now being transfered to the drive line, spins it up , as well as some slight synchro force, to help spin up the layshaft, and driveshaft. when done right, its smooth. if its smooth,there are very few forces that are acting against the wear components.
about 7-10 years ago, in the heat of the battle in races, i would trash my gear box. sometimes not even matching revs, just banging gears. it woud overheat, and get crunchy. fast forward to the last 6 years, same gearbox, no failure or modifications what so ever (testimate to the durability to the borg warner components that are stock on some porsches) and its still running perfect.
So, i think you just learn to perfect the blip downshift and do it later, so there is potentially less wear on the synchros. I also think that double clutching poses a risk for banging into a gear that you might not want to engage, or not want to engage at that time.
I am about to get my 993's transmission redone. The synchros, I am realizing, are a wear item for a 993.
Both Stan Richardson (at GBox) and Paul Tosi (my mechanic) suggest double declutching.
Though I know the technique of double declutching, I'll bet it's going to be a challenge to get my trailbraking, heel and toe, and double declutch organized.
Suggestions (in addition to practice practice practice)?
Both Stan Richardson (at GBox) and Paul Tosi (my mechanic) suggest double declutching.
Though I know the technique of double declutching, I'll bet it's going to be a challenge to get my trailbraking, heel and toe, and double declutch organized.
Suggestions (in addition to practice practice practice)?
05-10-2011, 08:19 PM
#79
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Thread Starter
I am about to get my 993's transmission redone. The synchros, I am realizing, are a wear item for a 993.
Both Stan Richardson (at GBox) and Paul Tosi (my mechanic) suggest double declutching.
Though I know the technique of double declutching, I'll bet it's going to be a challenge to get my trailbraking, heel and toe, and double declutch organized.
Suggestions (in addition to practice practice practice)?
Both Stan Richardson (at GBox) and Paul Tosi (my mechanic) suggest double declutching.
Though I know the technique of double declutching, I'll bet it's going to be a challenge to get my trailbraking, heel and toe, and double declutch organized.
Suggestions (in addition to practice practice practice)?
05-10-2011, 11:20 PM
#80
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Rick, if this is a skill you need to learn, on the advice of your mechanic, and you've never done it before, my first suggestion is start s-l-o-w-l-y, with the car off, in your garage. Then practice slowly, in yoru neighborhood or a parking lot. It is not learned entering T1 at the Glen, going from 5th to 3rd!
I was playing with double declutch today while bringing the Mini to/from its annual trip to the dealer. Its a lot to do even at local road speeds; should be fun at track speed.
05-11-2011, 03:47 AM
#81
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is there a reason you want to do this? maybe im not understanding the end goal.
Yup - like how I learned heel/toe! My wife thought my track obsession was kind of nutty before; seeing me practice heel/toe in the garage confirmed it.
I was playing with double declutch today while bringing the Mini to/from its annual trip to the dealer. Its a lot to do even at local road speeds; should be fun at track speed.
I was playing with double declutch today while bringing the Mini to/from its annual trip to the dealer. Its a lot to do even at local road speeds; should be fun at track speed.
05-12-2011, 09:56 AM
#83
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Had a great conversation with Stan Richardson of GBox (who really impresses me with his ability to communicate technical information to this former liberal arts student).
The transmission is in good shape except for worn out 3rd and 4th synchros and a toasted 1st synchro (interesting as its just a starting gear). Rest of the transmission is good.
The dog rings are a bit off (the cone taper isn't quite right, so its not engaging completely).
Looks like we will stay with the same ratios and work with tire diameter. I'll post about that later.
05-12-2011, 12:03 PM
#84
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Rick, if this is a skill you need to learn, on the advice of your mechanic, and you've never done it before, my first suggestion is start s-l-o-w-l-y, with the car off, in your garage. Then practice slowly, in yoru neighborhood or a parking lot. It is not learned entering T1 at the Glen, going from 5th to 3rd!
I have issues with 2nd gear engaging at downshifting from third, imho issue always was there if I am threshold braking from about of redline on 3rd into mid-range of 2nd gear.
if braking is not that hard there are no issues usually, it goes in fine. when it does not go it feels like I hit a solid metal wall there, it simply does not go at all, like I am pressing something into a metal plate. not sure what is the cultrip - worn clutch, syncros or engine mounts but it looks like double clutch helps a little bit.
05-12-2011, 01:37 PM
#85
Anjin San
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Rick, if this is a skill you need to learn, on the advice of your mechanic, and you've never done it before, my first suggestion is start s-l-o-w-l-y, with the car off, in your garage. Then practice slowly, in yoru neighborhood or a parking lot. It is not learned entering T1 at the Glen, going from 5th to 3rd!
That is fantastic advice. If one can find a rental with manual it might be a good thing to practice on the rental car's tranny.
This thread has become a must read.
05-12-2011, 09:22 PM
#87
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is it ctitical to do full pedal travel during double clutch or is it enough just to 'jerk' it back quickly down to usual point where clutch engages and push it full down again? or is it critical to allow it to travel all the way back? that is kinda slow.
I have issues with 2nd gear engaging at downshifting from third, imho issue always was there if I am threshold braking from about of redline on 3rd into mid-range of 2nd gear.
if braking is not that hard there are no issues usually, it goes in fine. when it does not go it feels like I hit a solid metal wall there, it simply does not go at all, like I am pressing something into a metal plate. not sure what is the cultrip - worn clutch, syncros or engine mounts but it looks like double clutch helps a little bit.
I have issues with 2nd gear engaging at downshifting from third, imho issue always was there if I am threshold braking from about of redline on 3rd into mid-range of 2nd gear.
if braking is not that hard there are no issues usually, it goes in fine. when it does not go it feels like I hit a solid metal wall there, it simply does not go at all, like I am pressing something into a metal plate. not sure what is the cultrip - worn clutch, syncros or engine mounts but it looks like double clutch helps a little bit.
Regarding your downshifts to 2nd gear, sounds like there is a good chance the engine/trans is torqued over a bit at high rpms, perhaps due to worn engine/trans mounts, and gets slightly out of alignment with the shifter mechanism. Either check yoru mounts or just slow down the cadence of your downshifts.
05-12-2011, 09:54 PM
#88
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Actually, its quite common for 2nd gear to get the brunt of the wear. almost always, 2nd gear synchro is in bad shape, alone with first for the reasons I mentioned prior. very unlikely that the engine mounts are worn. they usually collapse with age and the engine doesnt rotate much. if it does, its usually on the initial power application (first fraction of a second) it then would be in equalibriam at peak "blip"rpm and if there was misalignment, that would be negated at the peak and back side of the blip. the throw of the shifter would not be effected. It has nothing to do with the chassis orientation and the engine rocking. I would be wiling to bet, that is not the problem.
and as far as double clutching, you dont really need to push it all the way down to get it out of gear, but you need to leat it all the way out to spin up the drive line to the blip revs and then in again to soften the blow to the synchros on the final step of the shift.
more than likely, he might be able to solve the problem with a later shift in the approach to the turn. if you are familar with borg warner synchros you know about he lock out tendancies when rpms are not matched.
Mark
and as far as double clutching, you dont really need to push it all the way down to get it out of gear, but you need to leat it all the way out to spin up the drive line to the blip revs and then in again to soften the blow to the synchros on the final step of the shift.
more than likely, he might be able to solve the problem with a later shift in the approach to the turn. if you are familar with borg warner synchros you know about he lock out tendancies when rpms are not matched.
Mark
Frankly, IMO, to do double declutching properly, it has to be fast. To make it fast, one often cannot be as picky about the amount of pedal travel. In other words, don't worry about the fact that your legs will most likely push the pedal all the way & release it all the way.
Regarding your downshifts to 2nd gear, sounds like there is a good chance the engine/trans is torqued over a bit at high rpms, perhaps due to worn engine/trans mounts, and gets slightly out of alignment with the shifter mechanism. Either check yoru mounts or just slow down the cadence of your downshifts.
Regarding your downshifts to 2nd gear, sounds like there is a good chance the engine/trans is torqued over a bit at high rpms, perhaps due to worn engine/trans mounts, and gets slightly out of alignment with the shifter mechanism. Either check yoru mounts or just slow down the cadence of your downshifts.
05-13-2011, 03:23 PM
#90
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Confrontational and argumentative posts deleted. Let's keep this thread focused please.
Thanks
Thanks