A clutch for big torque
12-18-2002, 08:59 AM
#1
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A clutch for big torque
When my motor was first built, the GT2/RS type single mass flywheel package was fitted with torsion damped organic plate. First and second gear were fine but in third and upwards, when the peak torque was hit around 4500rpm, it would let go and the clutch would slip. If I avoided peak torque in the higher gears, for example a maximum acceleration run thro' the gears, there wouldn't be a problem since 4500rpm was not touched in the last 4 gears.
RS Tuning said my options were either they would remap the ECU to reduce the torque or to either fit a sintered disc or just avoid peak torque in the higher gears.
Option 1 was not an option.
One of the great thrills of this engine is to rev it from 3000 thro' to 7000 in third gear, feeling that massive slug of torque assaulting your senses, so option 3 was out.
I opted for option 2 and after speaking to Todd Knighton of Protomotive, fitted one of his sintered torsion sprung discs. This held the torque no problem and whilst it was "as described" by Todd, ie MUCH easier to drive than the race rigid sinter disc, it was still difficult to drive in stop go traffic resulting in the tt being left at home if a city trip was being made.
During my recent engine rebuild I spoke to FVD who recommended a set up of their 980NM (725lb/ft) pressure plate with an RS/GT2 torsion organic disc.
When the pressure plate arrived it had a sticker hand written on the box with "980NM" but the pressure plate had stamped on it part#3082999750.
This is the # for the Sachs unit which Sachs recommend for 993 upgrades and it is rated on their web site (www.sachs-race-engineering.de) for the following torque:
With "organic disc" 595NM
With "Organic special face" 695NM
With "Sinter disc" 765NM
I was naturally a bit sceptical because it didn't look any different from a stock pressure plate with that part# and even with a sinter disc it was only rated to 765NM.
I can report that the clutch is beautifully progressive and user friendly and does appear to be able to cope with the peak torque in the higher gears. It is still quite new and hopefully it won't lose any of its bite, but I can highly recommend the set up for any single mass flywheeled 993tts due for clutch replacement.
RS Tuning said my options were either they would remap the ECU to reduce the torque or to either fit a sintered disc or just avoid peak torque in the higher gears.
Option 1 was not an option.
One of the great thrills of this engine is to rev it from 3000 thro' to 7000 in third gear, feeling that massive slug of torque assaulting your senses, so option 3 was out.
I opted for option 2 and after speaking to Todd Knighton of Protomotive, fitted one of his sintered torsion sprung discs. This held the torque no problem and whilst it was "as described" by Todd, ie MUCH easier to drive than the race rigid sinter disc, it was still difficult to drive in stop go traffic resulting in the tt being left at home if a city trip was being made.
During my recent engine rebuild I spoke to FVD who recommended a set up of their 980NM (725lb/ft) pressure plate with an RS/GT2 torsion organic disc.
When the pressure plate arrived it had a sticker hand written on the box with "980NM" but the pressure plate had stamped on it part#3082999750.
This is the # for the Sachs unit which Sachs recommend for 993 upgrades and it is rated on their web site (www.sachs-race-engineering.de) for the following torque:
With "organic disc" 595NM
With "Organic special face" 695NM
With "Sinter disc" 765NM
I was naturally a bit sceptical because it didn't look any different from a stock pressure plate with that part# and even with a sinter disc it was only rated to 765NM.
I can report that the clutch is beautifully progressive and user friendly and does appear to be able to cope with the peak torque in the higher gears. It is still quite new and hopefully it won't lose any of its bite, but I can highly recommend the set up for any single mass flywheeled 993tts due for clutch replacement.
12-21-2002, 12:59 AM
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Burning Brakes
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TB
Thanks for the info. The sinter disc material is dreadful on the street as you have discovered. Like you I went with a semi race set up which I kept for one week after a stop and go drive to Los Angesles. Is it possible that the pressure plate has been modified by FVD or Sach? My pressure plate looked stock till the Clutchmaster engineer pointed out the differences.
I am running a GT2 unit modified with 20% more clamping force. This has held up reasonably well with good driveability as I have about 8000 track miles. The stock units can only hold up to 520 lbs ft. of torque and starts slipping under high torque loads in 3rd and 4th gear at 4000-4500rpm. My motor dynoed at 798 NM and I went thur 2 clutches before I found a fix. I had to go the custom built route at that time as no one offered an off the shelf pressure plate and disc. It looks like you have found one. Did you upgrade to the 3.8 on your rebuild? Thanks again for the post.
Thanks for the info. The sinter disc material is dreadful on the street as you have discovered. Like you I went with a semi race set up which I kept for one week after a stop and go drive to Los Angesles. Is it possible that the pressure plate has been modified by FVD or Sach? My pressure plate looked stock till the Clutchmaster engineer pointed out the differences.
I am running a GT2 unit modified with 20% more clamping force. This has held up reasonably well with good driveability as I have about 8000 track miles. The stock units can only hold up to 520 lbs ft. of torque and starts slipping under high torque loads in 3rd and 4th gear at 4000-4500rpm. My motor dynoed at 798 NM and I went thur 2 clutches before I found a fix. I had to go the custom built route at that time as no one offered an off the shelf pressure plate and disc. It looks like you have found one. Did you upgrade to the 3.8 on your rebuild? Thanks again for the post.
12-21-2002, 12:00 PM
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Jim
I'm sure the "980NM" pressure plate must have been modified it just wasn't obvious which bits to a layman like me.
The only actual mods I had done to the RST spec engine were the carillo rods - I didn't want to go through the time and extra expense of getting a different spec motor re dynoed. The purpose of the rebuild was to do a "secret" mod involving turning the pistons on one side which usually liberates an extra 5% power, once the motor was broken open, it turns out RST had already done the mod (despite denying that it works).
This clutch seems to be holding even in the current low UK temps (3degC/38degF) which are giving bigger than DIN torque
Do you know what level of boost is giving you the 798NM ?
I'm sure the "980NM" pressure plate must have been modified it just wasn't obvious which bits to a layman like me.
The only actual mods I had done to the RST spec engine were the carillo rods - I didn't want to go through the time and extra expense of getting a different spec motor re dynoed. The purpose of the rebuild was to do a "secret" mod involving turning the pistons on one side which usually liberates an extra 5% power, once the motor was broken open, it turns out RST had already done the mod (despite denying that it works).
This clutch seems to be holding even in the current low UK temps (3degC/38degF) which are giving bigger than DIN torque
Do you know what level of boost is giving you the 798NM ?
12-21-2002, 02:26 PM
#4
Burning Brakes
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TB
The dyno figures indicated 798 NM at 4543rpms and boost 1.25 bar. This is using 100 octane race gas. Interestesly, this is max boost as it starts droping off down to 1.0 at 6000 rpm.
I believe that the twin plug set-up is responsible for 50 NM of that torque.
The carillo rods are a good insurance policy for these modified engines. It seems that around 520
hp these engines need a little beefing up in the clutch and rod department.
The dyno figures indicated 798 NM at 4543rpms and boost 1.25 bar. This is using 100 octane race gas. Interestesly, this is max boost as it starts droping off down to 1.0 at 6000 rpm.
I believe that the twin plug set-up is responsible for 50 NM of that torque.
The carillo rods are a good insurance policy for these modified engines. It seems that around 520
hp these engines need a little beefing up in the clutch and rod department.
12-26-2002, 01:46 PM
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[quote]Originally posted by Jim Brady:
<strong>TB
Thanks for the info. The sinter disc material is dreadful on the street as you have discovered. Like you I went with a semi race set up which I kept for one week after a stop and go drive to Los Angesles. Is it possible that the pressure plate has been modified by FVD or Sach? My pressure plate looked stock till the Clutchmaster engineer pointed out the differences.
I am running a GT2 unit modified with 20% more clamping force. This has held up reasonably well with good driveability as I have about 8000 track miles. The stock units can only hold up to 520 lbs ft. of torque and starts slipping under high torque loads in 3rd and 4th gear at 4000-4500rpm. My motor dynoed at 798 NM and I went thur 2 clutches before I found a fix. I had to go the custom built route at that time as no one offered an off the shelf pressure plate and disc. It looks like you have found one. Did you upgrade to the 3.8 on your rebuild? Thanks again for the post.</strong><hr></blockquote>
<strong>TB
Thanks for the info. The sinter disc material is dreadful on the street as you have discovered. Like you I went with a semi race set up which I kept for one week after a stop and go drive to Los Angesles. Is it possible that the pressure plate has been modified by FVD or Sach? My pressure plate looked stock till the Clutchmaster engineer pointed out the differences.
I am running a GT2 unit modified with 20% more clamping force. This has held up reasonably well with good driveability as I have about 8000 track miles. The stock units can only hold up to 520 lbs ft. of torque and starts slipping under high torque loads in 3rd and 4th gear at 4000-4500rpm. My motor dynoed at 798 NM and I went thur 2 clutches before I found a fix. I had to go the custom built route at that time as no one offered an off the shelf pressure plate and disc. It looks like you have found one. Did you upgrade to the 3.8 on your rebuild? Thanks again for the post.</strong><hr></blockquote>
12-26-2002, 01:52 PM
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[quote]Originally posted by Michael Beard:
[QB][/QB]<hr></blockquote>
I have a 1996 993TT with the 450 HP powerkit, GT2 lightweight flywheel and clutch setup and a few other modifications.
I put the powerkit in about 1500 miles ago and the clutch setup about 5000 miles ago. I drive the car preaty hard and I think the clutch is loosing its grip above 4000 RPM. I can do a slow take off in first and to thru the gears really hard and when I come to a stop, I can smell the clutch and the car doesn't seem to pull as hard as it used to.
Do you think the added HP has affected the clutch that much? With this setup, what would you recommend?
[QB][/QB]<hr></blockquote>
I have a 1996 993TT with the 450 HP powerkit, GT2 lightweight flywheel and clutch setup and a few other modifications.
I put the powerkit in about 1500 miles ago and the clutch setup about 5000 miles ago. I drive the car preaty hard and I think the clutch is loosing its grip above 4000 RPM. I can do a slow take off in first and to thru the gears really hard and when I come to a stop, I can smell the clutch and the car doesn't seem to pull as hard as it used to.
Do you think the added HP has affected the clutch that much? With this setup, what would you recommend?
