964 C4 Cup conversion
06-08-2008, 08:23 PM
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964 C4 Cup conversion
Am considering transforming my C4 to cup specs, is the 4 to 2 wheel drive conversion as simple as removing the front drive shafts and conecting axel or will it require me sourcing a normal c2 drivetrain?
06-08-2008, 08:36 PM
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The short answer is NO. Unlike the 993 where you can just disconnect the front diff., the 964 requires more work than is probably worth it. Thoughothers have attempted it. Joel Reiser was supposedly converting a customers car either last year or in 06'. Contact him and you may get a much more complete answer.
06-08-2008, 09:24 PM
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To do it right you'd need a C2 G50 transmission, a C2 ABS brain and connector plug spliced into the removed C4 PDAS plug, and a fabricated shifter plate or one cut from a C2 tunnel welded into the tunnel.
06-09-2008, 08:53 AM
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and a fabricated shifter plate or one cut from a C2 tunnel welded into the tunnel.
06-09-2008, 10:56 PM
#6
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Just did the conversion last month. Not as simple as the Panorama article made it out to be, but no too difficult either. Main issue is cost. I had local race shop here in Charleston SC do the conversion. They are friends and always do a great job, at a fair price.
Biggest price was parts.
Here is a list of parts from my experience, with prices:
1) G50 transmission used - $3500
2) LSD - $1600
3) shifter console reinforcement - $100
4) Shifter rod, misc parts for shifter - $100
For the most part, the Panorama article was correct, but we found a few differences in my 89 C4:
1) My original C4 rear axles were from 944 - had to by new 964 C2 for the G50 box as mine did not match the flanges on the G50 box. +$900
2) My "new" C4 light weight flywheel/ KEP pressure plate/ and KEP clutch did not fit the 93 G50 bell housing - had to change the entire set out for a Cup clutch and flywheel package. +$1800
3) speedo does not work from 89 version.
4) flywheel sensor had to be changed to match the new flywheel.
5) 89 starter is different - had to upgrade to newer model starter to fit new G50 bellhousing
Total parts bill was $7500 - $8000.
I don't know, but the later C4 may have more parts in common with the C2, but mine seems to be a bit of a crossover.
Hope this helps. By the way, I LOVE the car on the track!
Dave J
Biggest price was parts.
Here is a list of parts from my experience, with prices:
1) G50 transmission used - $3500
2) LSD - $1600
3) shifter console reinforcement - $100
4) Shifter rod, misc parts for shifter - $100
For the most part, the Panorama article was correct, but we found a few differences in my 89 C4:
1) My original C4 rear axles were from 944 - had to by new 964 C2 for the G50 box as mine did not match the flanges on the G50 box. +$900
2) My "new" C4 light weight flywheel/ KEP pressure plate/ and KEP clutch did not fit the 93 G50 bell housing - had to change the entire set out for a Cup clutch and flywheel package. +$1800
3) speedo does not work from 89 version.
4) flywheel sensor had to be changed to match the new flywheel.
5) 89 starter is different - had to upgrade to newer model starter to fit new G50 bellhousing
Total parts bill was $7500 - $8000.
I don't know, but the later C4 may have more parts in common with the C2, but mine seems to be a bit of a crossover.
Hope this helps. By the way, I LOVE the car on the track!
Dave J
06-09-2008, 11:04 PM
#7
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Garrett - I did not get a new C2 ABS brain - I left my C4 brain attached to the accelerometers, disconnected/ plugged the hydraulics from the PDAS pump, - so far it works fine - ABS still works, and PDAS error lights do not come on.
Anything I'm missing or overlooking? I would like to remove the accelerometers all together, and figured that I could replace them with a resistor, but haven't figured out the specifics yet.
Dave J
Anything I'm missing or overlooking? I would like to remove the accelerometers all together, and figured that I could replace them with a resistor, but haven't figured out the specifics yet.
Dave J
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06-10-2008, 12:05 AM
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I'm curious to ask: Which one you prefer the car with C2 or C4 (although you may have some placebo effect after all the money spent)? Please describe the differences...
06-11-2008, 12:53 AM
#9
Racer
The car is a track only car. I raced it for the last 2 years as a C4 in both PCA and NASA . As I learned the car on the track as a C4, I was very comfortable with it in that configuration. I have had to do a bit of adjusting in my driving style to learn how to control the car as a C2.
As a C4, the car was very stable on the track. As expected ,it had a tendency to understeer - and I had learned how to adjust and anticipate the understeer. I would turn into a corner sooner, trail brake more, and apex a bit earlier than the rear wheel drive cars that I was racing against. After apex, getting on the power was simple and predictable - the car would straighten out and had a very slight push , but was very stable- never any power oversteer. I found that the car as a C4 had most trouble on the low speed turns - 90 deg or more. The front end would get "bound up" and I would have to fight the front end oround the slow, tight corners.
As for the car in the C2 configuration, I am really just beginning to learn it - Its been on the track about 3 days since the change. Hopefully by the end of June, I'll have a bit more mastery of it.
However, I do notice many subtle differences even now. First, the car turns in much more quickly than before. I'm still expecting the car to push , but it doesn't now. I can turn in a bit later, and the car goes where I point it now. ALso, the car is a bit less stable and the power must be applied more easily or the back end will step - In fact, I've had to loosen the rear sway bar to keep the rear under. Now take these observations for what the are worth - only 3 days on the track and I'm by no means an expert.
My initial impression about the difference between the C4 vs C2 is that the C4 is more stable and predictible but at the expense of quickness around the slower speed , tight turns. The C2 is more unstable, but allows more potential for quickness and responsiveness. Again, just my impression!!
Why did I change it ??? Well, 1) I like to tinker on the car, and 2) PCA doesn't allow much options for the C4 (I raced it in the old stock F class - E now???) where as the C2 can run as a stock C2, RSA, or Cup Car.
Dave J
As a C4, the car was very stable on the track. As expected ,it had a tendency to understeer - and I had learned how to adjust and anticipate the understeer. I would turn into a corner sooner, trail brake more, and apex a bit earlier than the rear wheel drive cars that I was racing against. After apex, getting on the power was simple and predictable - the car would straighten out and had a very slight push , but was very stable- never any power oversteer. I found that the car as a C4 had most trouble on the low speed turns - 90 deg or more. The front end would get "bound up" and I would have to fight the front end oround the slow, tight corners.
As for the car in the C2 configuration, I am really just beginning to learn it - Its been on the track about 3 days since the change. Hopefully by the end of June, I'll have a bit more mastery of it.
However, I do notice many subtle differences even now. First, the car turns in much more quickly than before. I'm still expecting the car to push , but it doesn't now. I can turn in a bit later, and the car goes where I point it now. ALso, the car is a bit less stable and the power must be applied more easily or the back end will step - In fact, I've had to loosen the rear sway bar to keep the rear under. Now take these observations for what the are worth - only 3 days on the track and I'm by no means an expert.
My initial impression about the difference between the C4 vs C2 is that the C4 is more stable and predictible but at the expense of quickness around the slower speed , tight turns. The C2 is more unstable, but allows more potential for quickness and responsiveness. Again, just my impression!!
Why did I change it ??? Well, 1) I like to tinker on the car, and 2) PCA doesn't allow much options for the C4 (I raced it in the old stock F class - E now???) where as the C2 can run as a stock C2, RSA, or Cup Car.
Dave J
07-13-2008, 12:57 AM
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I am not very familiar with the 964 C4, but why do you need to buy a G50 gearbox? Can't you just remove the front housing where the torque tube mates to the gearbox and add a C2 shifter assembly like I have done on my 993? You can save yourself a good $5k by not buying the gearbox, it is worth exploring.
07-14-2008, 07:32 AM
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The 964C4 trans is different to the 993 in that all output torque has to be directed through the front differential, where it is then split between front and rear through an epicyclic gearbox and clutch arrangement, which unfortunately means that if you remove the front diff you lose drive to both the front and rear wheels. From what I remember of the system, there is just no easy way to eliminate the front drive whilst maintaining 100% drive to the rear, hence why it is always cheaper to sell the C4 trans and buy a C2 version.
The 1989 only 964 C2 & C4 use a gearbox mounted speedo sender, much the same as a 3.2 Carrera. From 1990 onwards this was deleted by using the ABS sensor from the front wheel - the ABS signal is converted to the required speedo signal using a frequency change module which looks like a relay and is located in the main fuseboard. Unfortunately for 1989 owners the belhousing design of the gearbox also differs to the later cars because it used a 3.2/930 derived flywheel and clutch. You cannot convert this belhousing to the later design because the starter motor is also located approximately 2mm closer to the axis of the input shaft (ask me how I know.....). My recommendation for any owners of 1989 model cars contemplating this change is to fit a 1989 C2 gearbox to avoid all these issues, however finding one will probably be the hardest part of the conversion!
The 1989 only 964 C2 & C4 use a gearbox mounted speedo sender, much the same as a 3.2 Carrera. From 1990 onwards this was deleted by using the ABS sensor from the front wheel - the ABS signal is converted to the required speedo signal using a frequency change module which looks like a relay and is located in the main fuseboard. Unfortunately for 1989 owners the belhousing design of the gearbox also differs to the later cars because it used a 3.2/930 derived flywheel and clutch. You cannot convert this belhousing to the later design because the starter motor is also located approximately 2mm closer to the axis of the input shaft (ask me how I know.....). My recommendation for any owners of 1989 model cars contemplating this change is to fit a 1989 C2 gearbox to avoid all these issues, however finding one will probably be the hardest part of the conversion!
