New gearbox --> Options
01-09-2009, 10:41 PM
#61
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hi Jef,
I do club sport races since 2000. How hard? Allways trying not to loose too much ground on GT3s...
Had the standard 5-speed G50 with LSD before. Losing power because of having one leg in the air isn`t a real issue (at least for me). The advantages I get with a Quaife in a 964 clearly outweight that.
I have never driven a F or G model on track, so I cannot tell if and how strong they tend to understeer.
One last thought: I know someone at Audi, what I hear is they have a clear tendency to torque biasing diffs, as long as the price segment, a certain model is in, does allowe that.
good luck
964sepp
I do club sport races since 2000. How hard? Allways trying not to loose too much ground on GT3s...
Had the standard 5-speed G50 with LSD before. Losing power because of having one leg in the air isn`t a real issue (at least for me). The advantages I get with a Quaife in a 964 clearly outweight that.
I have never driven a F or G model on track, so I cannot tell if and how strong they tend to understeer.
One last thought: I know someone at Audi, what I hear is they have a clear tendency to torque biasing diffs, as long as the price segment, a certain model is in, does allowe that.
good luck
964sepp
Jeff
01-09-2009, 10:47 PM
#62
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I think you're talking about the flat-shift function ? there's a switch on the clutch that tells the ECU that the clutch is down . When the clutch is down and the throtlle is still open (e.g over 75%) the ECU controls the engine rpm with ignition retard and limiters . the engine rpm won't drop below a certain threshold but also can't increase to far either . The result is high air fow through the engine which is also igniting in the exhaust .. this keeps the turbo spinning and producing boost whilst the driver is changing gear . As soon as the next gear is selected and the clutch is realised normal engine power is
restored .
restored .
Jeff
01-09-2009, 10:48 PM
#63
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01-10-2009, 01:03 PM
#64
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Final comments on Torque Bias vs Plate diffs:
1. First of all, either option is way better than an open diff.
2. In my experience, TB diffs do not contribute to unusual handling traits and can be smoother in operation when there is limited grip, i.e. the rain.
3. A new TB diff is going to be better than a worn out (read used) plate diff.
4. A new, good quality, plate diff with the correct locking factors will outperform a TB diff in the same car (assuming decent driver behind the wheel).
We have tried many different diffs, in the end we stopped using all the conventional Porsche plate diffs as we got tired of replacing parts, so we now we only supply & recommend our own carbon plate diff which has custom ramp angles. The advantage of the carbon plates (like a carbon clutch) is that the friction increases when they get hot, unlike all conventional sintered plate diffs which do the opposite, resulting in a higher effective locking factor as the race progresses.
So, the moral of the story is to buy a new diff 'cause all the used ones around will need a rebuild and will cost you the same in the end, and if funds are limited fit a TB diff and it will be still be way better than the open diff.
1. First of all, either option is way better than an open diff.
2. In my experience, TB diffs do not contribute to unusual handling traits and can be smoother in operation when there is limited grip, i.e. the rain.
3. A new TB diff is going to be better than a worn out (read used) plate diff.
4. A new, good quality, plate diff with the correct locking factors will outperform a TB diff in the same car (assuming decent driver behind the wheel).
We have tried many different diffs, in the end we stopped using all the conventional Porsche plate diffs as we got tired of replacing parts, so we now we only supply & recommend our own carbon plate diff which has custom ramp angles. The advantage of the carbon plates (like a carbon clutch) is that the friction increases when they get hot, unlike all conventional sintered plate diffs which do the opposite, resulting in a higher effective locking factor as the race progresses.
So, the moral of the story is to buy a new diff 'cause all the used ones around will need a rebuild and will cost you the same in the end, and if funds are limited fit a TB diff and it will be still be way better than the open diff.
01-10-2009, 01:28 PM
#65
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01-10-2009, 10:38 PM
#68
Nordschleife Master
9A is the old 4 plate and 9C is the new 8 plate. For a 964, it has been my experience that you want the 4 plate version, especially if it is a street car. The preload breakaway torque on the 4 plate is almost 1/3rd that of the 8 plate and about 5 times that of a stock street 2 plate diff. The 8 plate is too much for a street tire and really should be used in a transmission with a cooler. It was designed for the GT3RSR which has 500+hp and runs an extremely wide slick tire.
I currenly run a 9C in my race car and it works well, but I've also run a 9A in my race car and it also worked well. I noticed an increase in the frequency of my transmission cooler pump with the 9C over the 9A which is due to the additional heat produced. Data logging shows about the same amount of wheel speed difference (diff slippage) between the two.
I currenly run a 9C in my race car and it works well, but I've also run a 9A in my race car and it also worked well. I noticed an increase in the frequency of my transmission cooler pump with the 9C over the 9A which is due to the additional heat produced. Data logging shows about the same amount of wheel speed difference (diff slippage) between the two.
01-11-2009, 06:22 AM
#70
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We have tried many different diffs, in the end we stopped using all the conventional Porsche plate diffs as we got tired of replacing parts, so we now we only supply & recommend our own carbon plate diff which has custom ramp angles. The advantage of the carbon plates (like a carbon clutch) is that the friction increases when they get hot, unlike all conventional sintered plate diffs which do the opposite, resulting in a higher effective locking factor as the race progresses.
So, the moral of the story is to buy a new diff 'cause all the used ones around will need a rebuild and will cost you the same in the end, and if funds are limited fit a TB diff and it will be still be way better than the open diff.
So, the moral of the story is to buy a new diff 'cause all the used ones around will need a rebuild and will cost you the same in the end, and if funds are limited fit a TB diff and it will be still be way better than the open diff.
Thanks,
01-11-2009, 11:26 AM
#72
Rennlist Member
9A is the old 4 plate and 9C is the new 8 plate. For a 964, it has been my experience that you want the 4 plate version, especially if it is a street car. The preload breakaway torque on the 4 plate is almost 1/3rd that of the 8 plate and about 5 times that of a stock street 2 plate diff. The 8 plate is too much for a street tire and really should be used in a transmission with a cooler. It was designed for the GT3RSR which has 500+hp and runs an extremely wide slick tire.
I currenly run a 9C in my race car and it works well, but I've also run a 9A in my race car and it also worked well. I noticed an increase in the frequency of my transmission cooler pump with the 9C over the 9A which is due to the additional heat produced. Data logging shows about the same amount of wheel speed difference (diff slippage) between the two.
I currenly run a 9C in my race car and it works well, but I've also run a 9A in my race car and it also worked well. I noticed an increase in the frequency of my transmission cooler pump with the 9C over the 9A which is due to the additional heat produced. Data logging shows about the same amount of wheel speed difference (diff slippage) between the two.
01-11-2009, 01:45 PM
#74
Rennlist Member
BTW, I found a 40/65% differential better for autocross than the 20/100% that my car was supplied with. Turn in is crisper with less understeer and the car doesn't spin the inside rear wheel at all now exiting corners.
01-11-2009, 01:54 PM
#75
here's a disassembled 4 plate, the cross hatched plates are the internally splinned Guard plasma friction disks, the others are externally splined load disks, slippage between them is one of the mechanisms for limiting slip, the notched side plates(aka thrust rings) are where the %/% lockup comes from, the angles generate varying amounts of preload on the plate stack when uder load from acceleration on one side and deceleration on the other
More plates means more friction area, this can be used to increase the amount of breakaway torque or increase longevity, usually a little of each. Breakaway torque is controlled by friction material and assembly pre-load and the dynamily applied preload, these can vary greatly
and assembled, here you can see how the spider gears ride in the sideplates, the angles of the notch(ramps) are not symmetric here, hence the asymmetric lockup figures, you change the %/% lockup by changing the ramp angles.
