List of series & classes where a 996 C2 can race ??
05-28-2012 | 12:29 PM
#31
Race Car
Joined: Apr 2008
Posts: 3,549
Likes: 2
From: Texas
I'm not expert on the 996 C2 yet but I'm studying what I can find and developing my own engineering "notebook". After a few years of modifying and tracking the car, I'm starting to "get it" ...
I'll add a few notes to JR's excellent post.
>> I don't think anything's more important than weight.
Always true, isn't it. Weight reduction thread.
>> Don't over-spring the car as the shocks like to travel. I use Clubsports with 500/700 springs and cup helpers.
I came to a similar conclusion (at least for the shocks I run). I'm running 570/855# because my car is still driven to the local track and I don't want to put triples on it yet until its a pure race car. Currently using Bilsteins from an H&R Cup kit. They are from H&R's "race" kit and were valved for pretty high rates to start with. Seems to be a good basis for my initial "race" setups.
>> Do use GT3 lower control arms and spherical bushings everywhere possible.
I've swapped out the rubber in the upper mounts, LCA "pucks" and toe links. Where do you think is the next most effective location to go with sphericals? Inner pickups on the rear LCA is what I'm thinking given the extreme lateral loads that a big 315 race tire can generate. I see many change the "dog bones" yet early cup cars left these rubber (albeit most likely a high durometer rubber).
>> Use the GT3 sway bars.
Ditto. I tried H&R bars. A: too heavy B: too stiff (might be ok for AX)
I run mine near full hard up front and at full soft in rear. The thought is to try to hold the rear down with front roll stiffness ( I have no LSD yet!) and let the rear bite with softer setting. Seems balanced and I do get oversteer when I need it or when I screw up LOL !
>> I run -3.5f/-3.0 rear with Yoko slicks.
Wow, I'm not running that much camber. Perhaps I'm not going fast enough yet
(remember... I still drive this to the track) but I've found that -2.0 front and rear are working. My 2:14 at Watkins Glen last week isn't bad so I don't think I'm that far off. Tire wear looked good and even across the tread.
Once I take the plunge and prep it for race only work then I expect it will allow completely different alignment specs. as I wont have the street compromises to worry about.
I've been using Hankook z214 & Goodyear RS DOT slicks. The Goodyears are fantastic! Check them out. (cheaper than Hoosiers)
Since other than the nut behind the wheel, the round & black stuff makes the biggest difference. I spent a lot of time looking at my options.
Seems like the stickiest DOT tires for these cars are Hoosier, Hankook & Goodyear with Kumho right in there. Nitto, Toyo, Yoko all make a decent "race" tire but while their constructions are good, seems their compounds are more suited to the DE guys looking for some longevity.
I settled on:
9x18 Front et44 w/ GY RS P245/35ZR18
OD Tread Section Weight
25.0 9.9" 9.2" 21.3lbs
12x18 Rear et64 w/ GY RS P315/30ZR18
OD Tread Section Weight
25.7 12.4" 11.8" 26.8 lbs
And yes... 12" fit.
I think I could easily get a 9.5" wheel up front with a 255 or 265 tire on it... but I wonder about the aero and/or weight affects.
I tried to keep the diameters in the 25" - 25.5" range so that the ABS doesn't freak out. I really dislike the ABS on these early cars and I often pull the fuse. Especially at a bumpy track.
>> Set ride height as low as possible in front(probably 95mm off Porsche measuring points) and 20mm higher in rear. Rake is really that important in these cars.
Are you doing this for aero reasons, anti-dive or ??
>> X51 headers to straight pipes,
Any idea where in the torque curve the 63.5mm pipes help vs the 54mm ?
Which reminds me... do C2 guys usually change the R&P on these cars?
>> FVD's enlarged TB for cable, and a stock air box. I got around 272rwhp with that setup on 91 octane.
Nice 3.4 rwhp #! Do you have verified gains from that TB ?
>> The trannies are a POS.
LOL, I'm on my 3rd !
>> Use a stronger trans mount, cup cables, cup shifter or the 997 GT3 shifter with solid bushings. Most importantly install a oil cooler. I run a Tilton pump to a cooler/radiator behind one of the side water radiators up front. Use a well known trans oil without any friction modifyers. Change it occasionally. I use Synolec 9920 and swear by it for Gertrag boxes. Its been 2 years and 35+ races without any tranny issues.
Thx for that advice on the cooling.
On the cup cables, how are you guys converting from the spherical ends on the cup cables to the plastic fittings on the GT3 street car shifter?
>> Most importantly, use a LSD preferably Guard's GT unit set 50/80. Nothing impacts handling in these cars more than a good working diff.
My plate type diff has been sitting here patiently until I have the time to buy a new box and install it.
I've been on the fence about ramp angles. But without any good (non-GT3) data I guess I'm just going to have to install it and deal with changes later.
When I make that move, what will I expect to need for suspension setup changes? I'm very familiar with LSD diffs but curious about anything unique to the 911 that might not be obvious.
>> Lastly use the cup car wing (or replica) with the taller Crawford GA uprights. Use the GT3 front bumper cover with a cup lip for better downforce.
What angle of attack do you run?
>> Testing setups is a blast in these cars. Just when you think you've got it down perfect a little shock or bar adjustment and you find even more speed. Fun cars to play with, enjoy the journey...
That's why I "play the game"
More Questions:
- Do you use a stock clutch with the single mass flywheels?
- Who is the "guru" shop to go to for DME programming a non-FBW throttle car to accept a later 3.6L ?
- Do you find that you need to alter brake bias or go beyond the GT3 cooling ducts on the cars when raced? I've had seriously bad heat soak issues on short track that don't give time for the brakes to cool.
-
I'll add a few notes to JR's excellent post.
>> I don't think anything's more important than weight.
Always true, isn't it. Weight reduction thread.
>> Don't over-spring the car as the shocks like to travel. I use Clubsports with 500/700 springs and cup helpers.
I came to a similar conclusion (at least for the shocks I run). I'm running 570/855# because my car is still driven to the local track and I don't want to put triples on it yet until its a pure race car. Currently using Bilsteins from an H&R Cup kit. They are from H&R's "race" kit and were valved for pretty high rates to start with. Seems to be a good basis for my initial "race" setups.
>> Do use GT3 lower control arms and spherical bushings everywhere possible.
I've swapped out the rubber in the upper mounts, LCA "pucks" and toe links. Where do you think is the next most effective location to go with sphericals? Inner pickups on the rear LCA is what I'm thinking given the extreme lateral loads that a big 315 race tire can generate. I see many change the "dog bones" yet early cup cars left these rubber (albeit most likely a high durometer rubber).
>> Use the GT3 sway bars.
Ditto. I tried H&R bars. A: too heavy B: too stiff (might be ok for AX)
I run mine near full hard up front and at full soft in rear. The thought is to try to hold the rear down with front roll stiffness ( I have no LSD yet!) and let the rear bite with softer setting. Seems balanced and I do get oversteer when I need it or when I screw up LOL !
>> I run -3.5f/-3.0 rear with Yoko slicks.
Wow, I'm not running that much camber. Perhaps I'm not going fast enough yet
(remember... I still drive this to the track) but I've found that -2.0 front and rear are working. My 2:14 at Watkins Glen last week isn't bad so I don't think I'm that far off. Tire wear looked good and even across the tread. Once I take the plunge and prep it for race only work then I expect it will allow completely different alignment specs. as I wont have the street compromises to worry about.
I've been using Hankook z214 & Goodyear RS DOT slicks. The Goodyears are fantastic! Check them out. (cheaper than Hoosiers)
Since other than the nut behind the wheel, the round & black stuff makes the biggest difference. I spent a lot of time looking at my options.
Seems like the stickiest DOT tires for these cars are Hoosier, Hankook & Goodyear with Kumho right in there. Nitto, Toyo, Yoko all make a decent "race" tire but while their constructions are good, seems their compounds are more suited to the DE guys looking for some longevity.
I settled on:
9x18 Front et44 w/ GY RS P245/35ZR18
OD Tread Section Weight
25.0 9.9" 9.2" 21.3lbs
12x18 Rear et64 w/ GY RS P315/30ZR18
OD Tread Section Weight
25.7 12.4" 11.8" 26.8 lbs
And yes... 12" fit.
I think I could easily get a 9.5" wheel up front with a 255 or 265 tire on it... but I wonder about the aero and/or weight affects.
I tried to keep the diameters in the 25" - 25.5" range so that the ABS doesn't freak out. I really dislike the ABS on these early cars and I often pull the fuse. Especially at a bumpy track.
>> Set ride height as low as possible in front(probably 95mm off Porsche measuring points) and 20mm higher in rear. Rake is really that important in these cars.
Are you doing this for aero reasons, anti-dive or ??
>> X51 headers to straight pipes,
Any idea where in the torque curve the 63.5mm pipes help vs the 54mm ?
Which reminds me... do C2 guys usually change the R&P on these cars?
>> FVD's enlarged TB for cable, and a stock air box. I got around 272rwhp with that setup on 91 octane.
Nice 3.4 rwhp #! Do you have verified gains from that TB ?
>> The trannies are a POS.
LOL, I'm on my 3rd !
>> Use a stronger trans mount, cup cables, cup shifter or the 997 GT3 shifter with solid bushings. Most importantly install a oil cooler. I run a Tilton pump to a cooler/radiator behind one of the side water radiators up front. Use a well known trans oil without any friction modifyers. Change it occasionally. I use Synolec 9920 and swear by it for Gertrag boxes. Its been 2 years and 35+ races without any tranny issues.
Thx for that advice on the cooling.
On the cup cables, how are you guys converting from the spherical ends on the cup cables to the plastic fittings on the GT3 street car shifter?
>> Most importantly, use a LSD preferably Guard's GT unit set 50/80. Nothing impacts handling in these cars more than a good working diff.
My plate type diff has been sitting here patiently until I have the time to buy a new box and install it.
I've been on the fence about ramp angles. But without any good (non-GT3) data I guess I'm just going to have to install it and deal with changes later.
When I make that move, what will I expect to need for suspension setup changes? I'm very familiar with LSD diffs but curious about anything unique to the 911 that might not be obvious.
>> Lastly use the cup car wing (or replica) with the taller Crawford GA uprights. Use the GT3 front bumper cover with a cup lip for better downforce.
What angle of attack do you run?
>> Testing setups is a blast in these cars. Just when you think you've got it down perfect a little shock or bar adjustment and you find even more speed. Fun cars to play with, enjoy the journey...
That's why I "play the game"
More Questions:
- Do you use a stock clutch with the single mass flywheels?
- Who is the "guru" shop to go to for DME programming a non-FBW throttle car to accept a later 3.6L ?
- Do you find that you need to alter brake bias or go beyond the GT3 cooling ducts on the cars when raced? I've had seriously bad heat soak issues on short track that don't give time for the brakes to cool.
-
Rake for aero or anti-dive ? BOTH !
X51 headers work, they help where you want them when racing, all along the tq curve.
The larger TB's help provided you have the other additional bolt on's to help, I use something even larger than JR, but JR and I don't run exactly the same motors and bolt ons either.
Wing Angle of Attact ? Track dependent but additional grip usually wins over loss of top end speed.
Clutch ? I use non-sprung disc, with one of two types of PP, one is a modified Sachs. The mods are for the prevention of the drive straps braking.
Flywheel ? Yes, single mass lightwt aluminum. No additional balancing.
ECU ? I have been thru 3 different guys and multiple generations of programming, but you won't have a motor like mine so it's a mute point. I now do mostly my own with some additional outside help for breaking into the ECU.
Brakes, I've been thru a few updates here as well. Grand Am package works well, we ran that at first which worked great until we started going faster, now we run a variation of GT3 Cup car set up with some additional tweaks, and it will stop !
Brake cooling ? Yes, get some air to those brakes and it will help quite a bit. Also use the right pads, different pads work in different heat ranges, that is key!
05-28-2012 | 04:43 PM
#32
Rennlist Member
Joined: Jul 2009
Posts: 5,902
Likes: 23
From: MA
rod did come out and they declined the core.
a path that really is a one i like is to bite a bullet and get a 996 cup car but this way you go into real expensive motor rebuilds. it kinda should last longer, but, if you can build a whole top level gts3 bmw e46 racer for a price of a single 996 cup car engine refresh - it makes you think to what degree do you like this sport.
05-28-2012 | 04:50 PM
#33
Race Car
Joined: Oct 2010
Posts: 4,580
Likes: 927
From: San Martin, CA
I could build and race a Spec Pinata or Spec E30 for a fraction of the cost it took me to build and takes to race my air-cooled 911. But, I have emotional ties to air-cooled 911 cars and that is what I want to race. I don't think I would race if has to race an old BMW or a chick's car.
Scott
05-28-2012 | 05:09 PM
#34
Rennlist Member
Joined: Jul 2009
Posts: 5,902
Likes: 23
From: MA
very true. i like driving and i like competition. i do not have an emotional attachment to any equipment i use...
i know for a fact that i would have a big issue with my wife to discuss $50K out of family savings to do an engine rebuild. that would suck.
as of what to race - i would love to own a 500hp/3k lbs car but not sure if i have a budget for such a platform. 996 car or 997 car still hovers around 320hp/3K lbs ratio, E46 car is not too far.
so all in all you choose GTS3 or GTS4 NASA class. most current top GTS3 cars are E36 or detuned E46 BMW. top GTS4 cars are mostly various porsches. so in the end it is all just about money. i owned M3 car and now are on 997 car. they are very different but i would not say it is an end of the world to race in a E46 car or E36 car. and I know $20K can get me into E36 and $40K will build a top GTS3 racer.
in my 997 DE car i already have close to $30K dumped and to build a racer out of it will take probably at least $15K more, if not $20K considering i will keep same mediocre JRZ RS shocks. so i am still thinking.
i know for a fact that i would have a big issue with my wife to discuss $50K out of family savings to do an engine rebuild. that would suck.
as of what to race - i would love to own a 500hp/3k lbs car but not sure if i have a budget for such a platform. 996 car or 997 car still hovers around 320hp/3K lbs ratio, E46 car is not too far.
so all in all you choose GTS3 or GTS4 NASA class. most current top GTS3 cars are E36 or detuned E46 BMW. top GTS4 cars are mostly various porsches. so in the end it is all just about money. i owned M3 car and now are on 997 car. they are very different but i would not say it is an end of the world to race in a E46 car or E36 car. and I know $20K can get me into E36 and $40K will build a top GTS3 racer.
in my 997 DE car i already have close to $30K dumped and to build a racer out of it will take probably at least $15K more, if not $20K considering i will keep same mediocre JRZ RS shocks. so i am still thinking.
05-28-2012 | 05:35 PM
#35
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Joined: Jul 2009
Posts: 5,902
Likes: 23
From: MA
what i want to do is to work out front fenders to fit 10" wide rims there. that is an only major issue left now on my car as 275 rubber does not fit 9" wide rim well enough in my opinion. 10" wide rim would help a lot to make sidewalls work better but to make it fit will take some major work.
05-28-2012 | 07:43 PM
#36
Race Car
Joined: Apr 2008
Posts: 3,549
Likes: 2
From: Texas
i have 997 car so my rear axle fits 335 tire ona 12" rim just fine all the way low, most issues are with front axle. i have it right now at an inch and 1/8th from the top of front tire to an edge of front fender. when i had it at 1/2 inch it handled worse so i got it to mechanic and he set it to what he suggested was an optimum ride height without bump steer arms and with current uprights. i do not know enough yet to alter this stuff as when i tried it on my own it sucked.
what i want to do is to work out front fenders to fit 10" wide rims there. that is an only major issue left now on my car as 275 rubber does not fit 9" wide rim well enough in my opinion. 10" wide rim would help a lot to make sidewalls work better but to make it fit will take some major work.
what i want to do is to work out front fenders to fit 10" wide rims there. that is an only major issue left now on my car as 275 rubber does not fit 9" wide rim well enough in my opinion. 10" wide rim would help a lot to make sidewalls work better but to make it fit will take some major work.
On your 997 you shouldn't have any problem getting a 10" with 275 up front, if all done correctly. I have a 996 and a 986 with 275's up front now, they fit.
I have a little more experience with these cars than probably the average Rennlister here. I know what works and what doesn't. My information isn't a guess or what I heard someone else say or write on the internet, it's from actual winning race cars that I have built.
05-29-2012 | 12:11 PM
#37
Thread Starter
Pro
Joined: Mar 2007
Posts: 641
Likes: 71
From: fahre auf dem Pittsbürgring
>> swapped out the rubber in the upper mounts, LCA "pucks" and toe links.
Where do you think is the next most effective location to go with sphericals?
On the cup cables, how are you guys converting from the spherical ends on the cup cables to the plastic fittings on the GT3 street car shifter?
I forget, what was the "Grand-Am" brake pkg allowed? Girodisk?
What have you learned about f/r balance on these cars when raced? Do the rears need more bias? Or is the balance correct when using the same friction compound on both ends?
Where do you think is the next most effective location to go with sphericals?
On the cup cables, how are you guys converting from the spherical ends on the cup cables to the plastic fittings on the GT3 street car shifter?
I forget, what was the "Grand-Am" brake pkg allowed? Girodisk?
What have you learned about f/r balance on these cars when raced? Do the rears need more bias? Or is the balance correct when using the same friction compound on both ends?
05-29-2012 | 12:26 PM
#38
Race Car
Joined: Apr 2008
Posts: 3,549
Likes: 2
From: Texas
>> swapped out the rubber in the upper mounts, LCA "pucks" and toe links.
Where do you think is the next most effective location to go with sphericals?
On the cup cables, how are you guys converting from the spherical ends on the cup cables to the plastic fittings on the GT3 street car shifter?
I forget, what was the "Grand-Am" brake pkg allowed? Girodisk?
What have you learned about f/r balance on these cars when raced? Do the rears need more bias? Or is the balance correct when using the same friction compound on both ends?
Where do you think is the next most effective location to go with sphericals?
On the cup cables, how are you guys converting from the spherical ends on the cup cables to the plastic fittings on the GT3 street car shifter?
I forget, what was the "Grand-Am" brake pkg allowed? Girodisk?
What have you learned about f/r balance on these cars when raced? Do the rears need more bias? Or is the balance correct when using the same friction compound on both ends?
I don't use cup car cables, plastic ends still work fine for me as long as replaced every couple years.
Grand Am brake package was a 30% increase in rotor size, I believe Girodisc has an offering although I use AP,PFC, or Alcon rotors before using Giro, they are offered in all.
Brake balance........ this is a little harder, results vary depending on tire size and type used,driver style, race tracks raced, pads used, proper brake cooling. You also have to be careful of the dreaded "black ice" condition, it does exist !
05-29-2012 | 01:10 PM
#39
Rennlist Member
Joined: Jul 2009
Posts: 5,902
Likes: 23
From: MA
On your 997 you shouldn't have any problem getting a 10" with 275 up front, if all done correctly. I have a 996 and a 986 with 275's up front now, they fit.
I have a little more experience with these cars than probably the average Rennlister here. I know what works and what doesn't. My information isn't a guess or what I heard someone else say or write on the internet, it's from actual winning race cars that I have built.
I have a little more experience with these cars than probably the average Rennlister here. I know what works and what doesn't. My information isn't a guess or what I heard someone else say or write on the internet, it's from actual winning race cars that I have built.
speaking of a 10" rim - what would you expect an offset for it to be on 997 car? current 9" i have fits there pretty tight with 275 nt01.
05-30-2012 | 12:47 PM
#40
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Pro
Joined: Mar 2007
Posts: 641
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From: fahre auf dem Pittsbürgring
44-45mm is the right ballpark for the NB cars ... recalling that one brand's 245 is not a 245 at all etc... you also have the "thin" 5-7mm spacer option to tweak things... if it's not perfect.
05-30-2012 | 12:49 PM
#41
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Pro
Joined: Mar 2007
Posts: 641
Likes: 71
From: fahre auf dem Pittsbürgring
Question about PCA H/I stock etc. I believe the PCA rules state wheels must be sized as delivered on base non-optioned 996. Yet I see guys running 9x18 fronts and 11x18 rears. What's the skinny there?
05-30-2012 | 01:23 PM
#42
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Joined: May 2007
Posts: 1,623
Likes: 4
From: Virginia Beach VA
PCA
OR Prepared I (1999-2001) and Prepared J (2002-2004)
Question about PCA H/I stock etc. I believe the PCA rules state wheels must be sized as delivered on base non-optioned 996. Yet I see guys running 9x18 fronts and 11x18 rears. What's the skinny there?
In Stock H we all run 8.5 or 9.0 fronts and 11 rear. The GT3 wheels fit the narrow body so I am not aware wheel size has ever been an issue.
Last edited by bella1; 05-30-2012 at 01:54 PM.
07-11-2012 | 12:41 AM
#44
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Joined: Feb 2012
Posts: 87
Likes: 0
From: Morehead, KY
For a '99 C2 (assuming GT3 LCA's & PSS10's or equivalent coilovers with moderate lowering) what offsets work for 9" & 9.5" fronts and 12" rears? - I have 245's on 8.5" GT3-spec wheels (offset=40) and had to roll fenders, so what's the trick to fit 275's up front? (i don't think I need that much up front with stock HP but just curious)
07-11-2012 | 12:58 AM
#45
Race Car
Joined: Apr 2008
Posts: 3,549
Likes: 2
From: Texas
For a '99 C2 (assuming GT3 LCA's & PSS10's or equivalent coilovers with moderate lowering) what offsets work for 9" & 9.5" fronts and 12" rears? - I have 245's on 8.5" GT3-spec wheels (offset=40) and had to roll fenders, so what's the trick to fit 275's up front? (i don't think I need that much up front with stock HP but just curious)