Xpost: Downshifting (mostly to 2nd) issues on track...
#1
Thread Starter
Rennlist Member
Xpost: Downshifting (mostly to 2nd) issues on track...
From 997 Forum, I might have better luck here, as more guys track. This is the issue on a 15K miles 997.1 C4S on track.
I've reported in the past that I've had some issues with shifting in/out of 2nd. It has been much worse on track and during my last track day of the season, I kinda narrowed it down.
After 2nd session when the car was hot and track dried a bit (was a very wet day), I had major issues downshifting into 2nd on a hard braking zone, with sharp right turn, on a down hill. It was either very hard to get into it (proper brake, heel/toe, downshift), or a couple of times I actually could NOT get into 2nd at all, and had to slow down and get into 3rd...
Then on the last few sessions of the day I realized WHY! The point of engagement into 2nd was SHIFTED to the right!!! So, basically it was not at the far left bottom of the gear, but somewhere between typical 2nd and 4th slots! So, over the last few laps I basically re-adjusted where I put it into 2nd, and it was fine.
After track day was over and driving back on street, the shifting is fine, just at the same engagement point as before?!
What could cause this? Anyone has encountered the same?
My first suspects are:
(1) Linkage needs adjustment, or it's loose,
(2) Engine mounts either have issues or just not solid enough for track use, hence the movement of engine on a downhill, SHIFTS the engagement point.
(3) Synchros might have issues?
Thanks!
PS. GREAT trackday at Pacific Raceway, was my first time going there and it was amazing, incredibly wet at the beginining and I almost completely lost the car on turn 1, at 120 Mph, but I saved it.
I've reported in the past that I've had some issues with shifting in/out of 2nd. It has been much worse on track and during my last track day of the season, I kinda narrowed it down.
After 2nd session when the car was hot and track dried a bit (was a very wet day), I had major issues downshifting into 2nd on a hard braking zone, with sharp right turn, on a down hill. It was either very hard to get into it (proper brake, heel/toe, downshift), or a couple of times I actually could NOT get into 2nd at all, and had to slow down and get into 3rd...
Then on the last few sessions of the day I realized WHY! The point of engagement into 2nd was SHIFTED to the right!!! So, basically it was not at the far left bottom of the gear, but somewhere between typical 2nd and 4th slots! So, over the last few laps I basically re-adjusted where I put it into 2nd, and it was fine.
After track day was over and driving back on street, the shifting is fine, just at the same engagement point as before?!
What could cause this? Anyone has encountered the same?
My first suspects are:
(1) Linkage needs adjustment, or it's loose,
(2) Engine mounts either have issues or just not solid enough for track use, hence the movement of engine on a downhill, SHIFTS the engagement point.
(3) Synchros might have issues?
Thanks!
PS. GREAT trackday at Pacific Raceway, was my first time going there and it was amazing, incredibly wet at the beginining and I almost completely lost the car on turn 1, at 120 Mph, but I saved it.
#2
Rennlist Member
Most likely option #2
Some semi-solid engine mounts may cure your problems
Some semi-solid engine mounts may cure your problems
#4
I know exactly what you meant, as this same second gear issue also happened to both my RS and club coupe while at track for multiple times. Somehow at the track, the second gear was not at the far left bottom corner, but slight right of the far left.
I don't know what causes this either. My RS has dynamic engine mount, so does this rule out the engine mount problem?
I don't know what causes this either. My RS has dynamic engine mount, so does this rule out the engine mount problem?
#5
Rennlist Member
I know exactly what you meant, as this same second gear issue also happened to both my RS and club coupe while at track for multiple times. Somehow at the track, the second gear was not at the far left bottom corner, but slight right of the far left.
I don't know what causes this either. My RS has dynamic engine mount, so does this rule out the engine mount problem?
I don't know what causes this either. My RS has dynamic engine mount, so does this rule out the engine mount problem?
For a more technical version, let's try this: Second gear is never at the far left bottom corner of the linkage in a street Porsche. The linkage pattern is:
R 1 3 5
-- 2 4 6
The left column is not present in a car built to one of the racing formulas unless the regulations require reverse. Then the whole column is blocked mechanically in some fashion and demonstrating the existence of reverse to tech inspection requires some action we wouldn't perform accidentally on track. Ferrari used to do that with their street cars, probably to remind people the cars were 'bred' for racing. Come to think of it, that statement dates me badly I suppose. I think most serious race formulas these days permit sequential linkages or computer-shifted transmissions with paddle controls.
In a road car, the left column is made difficult to reach with detente springs, but if we get pumped up on the race track and start using too much force with shifting, then the force the springs use to resist us is trivial. That lets us get the lever into the leftmost position if we also have a mental image of second being in the left bottom corner. Of course, nothing happens when we pull back in that position. I haven't tested a GT3 yet, but I dropped in over here to prepare for a test in a couple of weeks. I'm curious: does Porsche do anything special on the GT3 linkage to make this shift into the empty position less likely?
Problem goes away, of course, if you remind yourself to use light force on the shift. The detente springs aren't really weak, we just use a lot of force on the shift if we hurry while pumped up on adrenalin. As a back-up, since we all get pumped sometimes, it helps to not picture second being in the corner, but picture it correctly as being in the next position over from the column that holds reverse and... and limbo. I've got to admit I did this also the first time I took a street Porsche on a race track. When racing cars that have no reverse, or tuck it away on the right side of the linkage, it's easy to get into the habit of treating the 3-2 shift as a pull back into the nearside corner. Clearly, that isn't correct with street Porsches.
Incidentally, that suggestion about shifting before turn-in only works if you're driving pretty tamely. Once you learn trail braking, you're carrying enough extra speed at turn-in (that goes away in the trail braking phase) that in many corners you will be above the rpm for the downshift until after turn in. Admittedly, it is easier to heel-and-toe while at maximum braking, but 'easier' and 'faster' rarely cohabitate.
Gary
#6
Thread Starter
Rennlist Member
I know exactly what you meant, as this same second gear issue also happened to both my RS and club coupe while at track for multiple times. Somehow at the track, the second gear was not at the far left bottom corner, but slight right of the far left.
I don't know what causes this either. My RS has dynamic engine mount, so does this rule out the engine mount problem?
I don't know what causes this either. My RS has dynamic engine mount, so does this rule out the engine mount problem?
#7
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http://www.suncoastparts.com/product//PKRSMOUNTKIT.html
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#8
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From: Somewhere in a galaxy far, far away....
Pull drain plug on tranny. Inspect for filings.
Engine mounts may or may not help.
966 Cup shifter cables are always a good way to refresh the tired street cables.
MB Euro on 7th can help you with this. Bernie has done multiple transmissions.
Engine mounts may or may not help.
966 Cup shifter cables are always a good way to refresh the tired street cables.
MB Euro on 7th can help you with this. Bernie has done multiple transmissions.
#9
Rennlist Member
I put wevo semi solid mounts on my car. Cured the inability to shift properly from 2-3 on a hard right hand decreasing radium corner. Great mod. Can't tell the diff in ride or noise.
#10
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Like this unit? Would these cause vibration and comfort issues on street?
http://www.suncoastparts.com/product//PKRSMOUNTKIT.html
http://www.suncoastparts.com/product//PKRSMOUNTKIT.html
No real difference in sound or vibration.
#12
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From: Vancouver, BC, Canada
I have the wevo mounts and I still had the odd shifting problem until Kees explained how I should be shifting. Much like Gary's post above - if you tense up and try to do things fast then you may run into problems. Be relaxed. Shift slowly and deliberately. That will get the job done.
Cheers,
Cheers,
#15
Thread Starter
Rennlist Member
How does the Cup shifter cable would be different than 997? Scan told me stock cables are literally wearable and snap very frequently and needs replacement.