SC or Carrera for SCCA class STR?
05-18-2012, 03:12 PM
#16
Rennlist Member
Charlie,
If the engine is in good shape, an SC or Carrera is much more reliable and cheaper to keep running than a Boxster, IMHO... all parts are available new or used, and reasonably priced, anyone can work on them, unlike my GT3 cup...
But the Boxster handles a lot better.
Good luck!
If the engine is in good shape, an SC or Carrera is much more reliable and cheaper to keep running than a Boxster, IMHO... all parts are available new or used, and reasonably priced, anyone can work on them, unlike my GT3 cup...
But the Boxster handles a lot better.
Good luck!
07-17-2012, 01:45 PM
#17
Just a quick bump on this for a hypothetical build, how would you do it? An SC / Carrera weighs less than an S2000, is narrow, and has a huge torque advantage. Old strut / trailing arm suspension hurts, and no room for huge front tires also hurts. Is the steering ratio quick enough? I'm one of those people that gets a kick out of being the anti-sheep, so this really appeals to me. I've never driven any 911, are they really that akin to trying to throw a dart backwards when they are at the limit?
Here's some uneducated wild guessing, please correct all my mistakes:
Weight / power:
swap for 25lb seats to fit rules (how much are OEM seats weight wise?)
Exhaust - looks like a lot of weight to save post - cat.
Headers - How would it work with the heat exchangers to fit the rules?
There's chips / tunes for Carreras, but nothing for an SC. Any hidden power?
Tire / Suspension:
You'll have to go 17" wheels to get the favorable tire sizes.
Larger torsion bars, lowered.
Through - body style front bar is a no go, so the biggest OEM style bar?
Adjustable rear bar, season to taste
Shocks - you'll need something adjustable, what's out there?
What am I missing?
Here's some uneducated wild guessing, please correct all my mistakes:
Weight / power:
swap for 25lb seats to fit rules (how much are OEM seats weight wise?)
Exhaust - looks like a lot of weight to save post - cat.
Headers - How would it work with the heat exchangers to fit the rules?
There's chips / tunes for Carreras, but nothing for an SC. Any hidden power?
Tire / Suspension:
You'll have to go 17" wheels to get the favorable tire sizes.
Larger torsion bars, lowered.
Through - body style front bar is a no go, so the biggest OEM style bar?
Adjustable rear bar, season to taste
Shocks - you'll need something adjustable, what's out there?
What am I missing?
07-17-2012, 04:27 PM
#18
Rennlist Member
> Is the steering ratio quick enough?
yes, no problem
>>driven any 911, are they really that akin to trying to throw a dart backwards when they are at the limit?
No, they actually plow a lot, especially when accelerating.
>>Exhaust - looks like a lot of weight to save post - cat.
Headers - How would it work with the heat exchangers to fit the rules?
There are SSI brand headers with heat exchangers available, I have not studied the rules but those are light and great for torque and make quite a bit more power than stock too.
>> There's chips / tunes for Carreras, but nothing for an SC. Any hidden power?
No real hidden power, just get the cams set right and the engine tuned right.
>>Tire / Suspension:
Shocks - you'll need something adjustable, what's out there?
I never liked Konis, they last maybe a year in a 911 if you are lucky. Elephant racing makes adjustable Bilsteins.
Good luck!
yes, no problem
>>driven any 911, are they really that akin to trying to throw a dart backwards when they are at the limit?
No, they actually plow a lot, especially when accelerating.
>>Exhaust - looks like a lot of weight to save post - cat.
Headers - How would it work with the heat exchangers to fit the rules?
There are SSI brand headers with heat exchangers available, I have not studied the rules but those are light and great for torque and make quite a bit more power than stock too.
>> There's chips / tunes for Carreras, but nothing for an SC. Any hidden power?
No real hidden power, just get the cams set right and the engine tuned right.
>>Tire / Suspension:
Shocks - you'll need something adjustable, what's out there?
I never liked Konis, they last maybe a year in a 911 if you are lucky. Elephant racing makes adjustable Bilsteins.
Good luck!
07-19-2012, 03:38 PM
#19
Addict
Rennlist Member
Rennlist Member
Anyone knows a source for the gearing chart from the 78-83 SC, 84-86 Carrera and 87-88 Carrera?
Was A/C optional or mandatory in U.S.?
Was sunroof mandatory or optional?
Did the SC or Carrera come with cats?
Any idea of weight difference between the G50 and 915?
Finally (and most importantly), is there a source that lists (Porsche marketing, window sticker, Porsche official literature) the changes made with option M637 for MY88 and 89?
I have driven a well setup SC, and I love the car, I've been wanting one for so long, and this STR thingy makes it very appealing (and affordable). An old 911 in a sea of ugly jap cabrios is too cool.
Was A/C optional or mandatory in U.S.?
Was sunroof mandatory or optional?
Did the SC or Carrera come with cats?
Any idea of weight difference between the G50 and 915?
Finally (and most importantly), is there a source that lists (Porsche marketing, window sticker, Porsche official literature) the changes made with option M637 for MY88 and 89?
I have driven a well setup SC, and I love the car, I've been wanting one for so long, and this STR thingy makes it very appealing (and affordable). An old 911 in a sea of ugly jap cabrios is too cool.
07-20-2012, 09:20 PM
#21
http://www.gboxweb.com/915specs.html might help on the 915 gearing.
iirc, yes, you could order an SC or a Carrera without AC or Sunroof for US markets. As you likely have noticed, 95+% came with such items and it seems by the Carrera, all dealers were spec'ing that way because they new they could be sold easier and at higher prices.
Weight:
iirc, yes, you could order an SC or a Carrera without AC or Sunroof for US markets. As you likely have noticed, 95+% came with such items and it seems by the Carrera, all dealers were spec'ing that way because they new they could be sold easier and at higher prices.
Weight:
From another post in response to a discussion about weight/performance between 915s & G 50s...
Originally Posted by Peter Zimmermann
Let's look at this a little closer. The weight of a filled 915 RoW version 915/67 with cooler is approximately 60 kg (132 lbs). The cooler weighs almost nothing (I can testify to this because I've cleaned a number of them), so let's call the USA 915/68 at 130 lbs. The weight of a filled RoW G 50 version 950/00 is 66 kg (146 lbs), which is virtually identical to the USA version 950/01. So we have a weight difference between the two transmissions of 16 pounds.
The 915 flywheel weighs 12 lbs, and so does the G 50 flywheel, so that's even.
The stock 915 clutch weighs 18 lbs, the G 50 clutch weighs 29 lbs. So, in total, the G 50 package is approximately 27 lbs heavier, which was offset (in 1986) by an increase in rear torsion bar size from 24.1mm to 25mm.
Something else comes into play here that contributes to the 915 car "feeling quicker" to some drivers. Back in the day of Hemi-Cudas, 427 Vettes, etc., the ticket to really quick quarter mile times was having a "short", 4.11 rear end (final drive) ratio, or an even shorter 4.56 ratio. Of course, the big compromise with a short ratio was having to run at much higher revs at freeway speeds. Cars with a taller, aka longer, 3.00, or 3.30 rear end (ring & pinion ratio) just wouldn't come out of the hole as quick, and the race was usually over in 2nd gear.
In 1974, 911s were fitted with a 7:31 ring & pinion, which is a final drive ratio of 4.43 (remember, the bigger the number the shorter the ratio). Later SCs and early Carreras w/915s had an 8:31 (3.88) final drive ratio, BUT, G 50s are fitted with a 9:31 (3.44) final drive ratio. Yes, the factory fitted all new, "shorter" ratios to 1st-5th to try and make up for it, but, while striving for better mileage and reliability, couldn't overcome that "longer" ring and pinion, which can make, combined with the extra pounds, a G 50 car feel more sluggish than a 915 car. A lightweight clutch will help the G 50 car, but on a road course there should be very little difference between the two because the rpm drop between second and third, between third and fourth, and between fourth and fifth, is very similar when comparing a 915 to a G 50. Yes, the 915, in some situations, will "feel" quicker, but can it generate quicker lap times on a road racing course? I doubt it.
Originally Posted by Peter Zimmermann
Let's look at this a little closer. The weight of a filled 915 RoW version 915/67 with cooler is approximately 60 kg (132 lbs). The cooler weighs almost nothing (I can testify to this because I've cleaned a number of them), so let's call the USA 915/68 at 130 lbs. The weight of a filled RoW G 50 version 950/00 is 66 kg (146 lbs), which is virtually identical to the USA version 950/01. So we have a weight difference between the two transmissions of 16 pounds.
The 915 flywheel weighs 12 lbs, and so does the G 50 flywheel, so that's even.
The stock 915 clutch weighs 18 lbs, the G 50 clutch weighs 29 lbs. So, in total, the G 50 package is approximately 27 lbs heavier, which was offset (in 1986) by an increase in rear torsion bar size from 24.1mm to 25mm.
Something else comes into play here that contributes to the 915 car "feeling quicker" to some drivers. Back in the day of Hemi-Cudas, 427 Vettes, etc., the ticket to really quick quarter mile times was having a "short", 4.11 rear end (final drive) ratio, or an even shorter 4.56 ratio. Of course, the big compromise with a short ratio was having to run at much higher revs at freeway speeds. Cars with a taller, aka longer, 3.00, or 3.30 rear end (ring & pinion ratio) just wouldn't come out of the hole as quick, and the race was usually over in 2nd gear.
In 1974, 911s were fitted with a 7:31 ring & pinion, which is a final drive ratio of 4.43 (remember, the bigger the number the shorter the ratio). Later SCs and early Carreras w/915s had an 8:31 (3.88) final drive ratio, BUT, G 50s are fitted with a 9:31 (3.44) final drive ratio. Yes, the factory fitted all new, "shorter" ratios to 1st-5th to try and make up for it, but, while striving for better mileage and reliability, couldn't overcome that "longer" ring and pinion, which can make, combined with the extra pounds, a G 50 car feel more sluggish than a 915 car. A lightweight clutch will help the G 50 car, but on a road course there should be very little difference between the two because the rpm drop between second and third, between third and fourth, and between fourth and fifth, is very similar when comparing a 915 to a G 50. Yes, the 915, in some situations, will "feel" quicker, but can it generate quicker lap times on a road racing course? I doubt it.
07-27-2012, 03:16 AM
#22
Instructor
Anyone knows a source for the gearing chart from the 78-83 SC, 84-86 Carrera and 87-88 Carrera?
Was A/C optional or mandatory in U.S.?
Was sunroof mandatory or optional?
Did the SC or Carrera come with cats?
Any idea of weight difference between the G50 and 915?
Finally (and most importantly), is there a source that lists (Porsche marketing, window sticker, Porsche official literature) the changes made with option M637 for MY88 and 89?
I have driven a well setup SC, and I love the car, I've been wanting one for so long, and this STR thingy makes it very appealing (and affordable). An old 911 in a sea of ugly jap cabrios is too cool.
Was A/C optional or mandatory in U.S.?
Was sunroof mandatory or optional?
Did the SC or Carrera come with cats?
Any idea of weight difference between the G50 and 915?
Finally (and most importantly), is there a source that lists (Porsche marketing, window sticker, Porsche official literature) the changes made with option M637 for MY88 and 89?
I have driven a well setup SC, and I love the car, I've been wanting one for so long, and this STR thingy makes it very appealing (and affordable). An old 911 in a sea of ugly jap cabrios is too cool.
Jrho has a threead in this forum that answers most of your questions. I can tell you that you'll never get the same power out of an SC with ST legal mods. And the weight difference is minimal if any. You want a 915 tranny 3.2.
07-27-2012, 12:17 PM
#23
Addict
Rennlist Member
Rennlist Member
KJ,
I think the ticket is to build a MY88 MY89 Carrera ClubSport clone out of a 88-89 car (Option Code M637), using the update/backdate allowance inherited from the stock classes.
It doesn't make sense to shop for a $75k-$85k 89 Carrera CS and ruin a collectible car, but building a clone starting with the 88-89 U.S. version is a lot cheaper and not a Porsche sin.
This would produce the lightest configuration. The car fits 17x8 and 17x9 custom wheels with 235/255 RS3, and being 2WD it can use any LSD (it works great with a OSGiken/Guard, not so well with open diff or Torsen).
The important part is to get official Porsche documentation on option M637, and the expense of opening the engine to replace the valves, as the M637 came with different valves. There might be a difference in other engine areas (unknown until official docs are found).
2002M3Drew has a 911SC that currently is STR legal, except the oil coolers. This car was 2 secs slower on Hoosiers than my SM2 996 GT3 on Hoosiers. On street tires, the gap closes, so the Carrera CS clone looks promising in STR (and looks cool in any garage).
I think the ticket is to build a MY88 MY89 Carrera ClubSport clone out of a 88-89 car (Option Code M637), using the update/backdate allowance inherited from the stock classes.
It doesn't make sense to shop for a $75k-$85k 89 Carrera CS and ruin a collectible car, but building a clone starting with the 88-89 U.S. version is a lot cheaper and not a Porsche sin.
This would produce the lightest configuration. The car fits 17x8 and 17x9 custom wheels with 235/255 RS3, and being 2WD it can use any LSD (it works great with a OSGiken/Guard, not so well with open diff or Torsen).
The important part is to get official Porsche documentation on option M637, and the expense of opening the engine to replace the valves, as the M637 came with different valves. There might be a difference in other engine areas (unknown until official docs are found).
2002M3Drew has a 911SC that currently is STR legal, except the oil coolers. This car was 2 secs slower on Hoosiers than my SM2 996 GT3 on Hoosiers. On street tires, the gap closes, so the Carrera CS clone looks promising in STR (and looks cool in any garage).
