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Superman's Avatar
 
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SC Top Speed

So....the transmission diagram/graph in my owner's manual suggests that in fifth gear at 6500 rpm, the car should be moving at about 150 mph. This is higher than the top speed figures I have seen. This suggests that the car simply does not have enough power to achieve that speed. However, my car feels as if it might....have enough power. So.....

What is the top speed of an SC?
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Old 11-10-2018, 12:16 PM
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European SC or African? Unladen?
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Old 11-10-2018, 12:37 PM
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If I remember, 139mph.

I was way over 130 speedo indicated on a long slight downhill on the Ohio Turnpike. Came back with GPS and it indicated it was 123mph. Ha! Speedo error must grow with speed.
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Old 11-10-2018, 12:49 PM
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African. Unladen.

If the top speed of my car is only 139, then either:

1) The transmission graph in the owner's manual is wrong (unlikely) or;
2) The engine does not make enough power to achieve 6500 rpm in fifth gear (possible)

Honestly, I think the engine may have enough power. Certainly, in fourth gear, the car accelerates from 100 mph fairly easily.
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Old 11-10-2018, 01:02 PM
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Only one way to find out...
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Old 11-10-2018, 01:09 PM
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My SC got up to 135mph. But it felt like it was raring to go faster. It had just got into the powerband. Felt quite good haha.
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Old 11-10-2018, 01:12 PM
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my sound 3.0 SC with overhauled K-Jet, fresh 915 and SSI, Permatune runs 150mph/240 kmh as per GPS no problem
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Old 11-10-2018, 01:16 PM
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Only one way to find out...
I got a dang speeding ticket three weeks ago. I will likely get a 'deferment' but this means I need to be a good boy through 2019. And besides, 150 mph is not a civil infraction.

I am thinking of checking out the speedway in Shelton but even then, the straight may not be long enough.

Quote:
Originally Posted by Flojo View Post
my sound 3.0 SC with overhauled K-Jet, fresh 915 and SSI, Permatune runs 150mph/240 kmh as per GPS no problem
That's what I thought.
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Old 11-10-2018, 01:22 PM
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I had mine up around 5500 rpm and it was about all it could do. Wish I knew how fast it was but only 85mph spedo. It felt very fast. We did 135 in my brothers gti on the same stretch and it felt nowhere near as fast. Cant imagine ill ever try that again it was sketchy
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Old 11-10-2018, 01:40 PM
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SC speed..........

I've had my SC up to 7,000 rpms in 4th gear which should be 140 or thereabouts. Of course, the engine is a 3.3SS with big port heads, cams, etc! There was more but I really wanted to keep my license!
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Old 11-10-2018, 01:45 PM
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Gearing

Quote:
Originally Posted by porsche930dude View Post
I had mine up around 5500 rpm and it was about all it could do. Wish I knew how fast it was but only 85mph spedo. It felt very fast. We did 135 in my brothers gti on the same stretch and it felt nowhere near as fast. Cant imagine ill ever try that again it was sketchy
If your car is geared like my SC, 4th gear is about 20mph per 1000 rpms and 5th is about 23-24mph per 1000 rpms.
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Old 11-10-2018, 01:48 PM
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all US Sc had the same top gear, .8214, and cwp, RoW '80-83 had a bit taller, .7857. So it depends on aero, tires and max rpm used. Neglecting aero, theoretical top for a US SC is 152mph w/ 245/45 x16 & 6800, 155mph w/ 215/60 x15 & 6800. 153mph w/ 225/50 x16 & 6800.

RoW '80-83 w/ 225/50 x16 & 6800 is 159

Now actual recorded stats are 140,141 for '78-79, 146,148 for '80-81 & 148 for a very fast '83RoW SC sport cab.

For comparison recorded tops for 3.2 Carrera are 149 to 158 clustering ~154
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Old 11-10-2018, 02:07 PM
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Quote:
Originally Posted by Superman View Post
I am thinking of checking out the speedway in Shelton but even then, the straight may not be long enough.
We reach a higher top speed on the front straight and through turn one at Pacific raceways than we do down the front strait at The Ridge in Shelton. The entrance to the straight at The Ridge is much slower, and the straight is shorter than at Pacific. In a relatively stock SC you probably won't even need to get it into fifth gear on the straight at The Ridge, so it's not a great place to verify top speed. At Pacific, in a relatively stock SC, you will probably grab fifth somewhere around the kink on the front straight, carry it around turn one, and get on the brakes for turn two before redlining fifth. My son's '79 with stock cams, Euro pistons, SSI's, and a single out Dansk sport will go somewhere around 125 through there before getting on the brakes for two. So, not quite top speed. Not quite long enough at either track.
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Old 11-10-2018, 02:34 PM
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According to the Car and Driver magazine review of the US-spec 911SC in the Aug 1980 issue: 130 mph.

Maximum speed in each gear:
1 - 37 mph
2 - 65 mph
3 - 94 mph
4 - 118 mph
5 - 130 mph

By comparison, in a C/D Feb '84 article, the 1984 US-spec 911 Carrera speed in each gear is given as:
1 - 37 mph
2 - 66 mph
3 - 93 mph
4 - 117 mph
5 - 149 mph

Last edited by dw1; 11-10-2018 at 04:14 PM..
Old 11-10-2018, 04:05 PM
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Quote:
Originally Posted by Jeff Higgins View Post
We reach a higher top speed on the front straight and through turn one at Pacific raceways than we do down the front strait at The Ridge in Shelton. The entrance to the straight at The Ridge is much slower, and the straight is shorter than at Pacific. In a relatively stock SC you probably won't even need to get it into fifth gear on the straight at The Ridge, so it's not a great place to verify top speed. At Pacific, in a relatively stock SC, you will probably grab fifth somewhere around the kink on the front straight, carry it around turn one, and get on the brakes for turn two before redlining fifth. My son's '79 with stock cams, Euro pistons, SSI's, and a single out Dansk sport will go somewhere around 125 through there before getting on the brakes for two. So, not quite top speed. Not quite long enough at either track.
Agree Pacific is not a long enough straight to hit top speed in a 911. My 3.2 used to hit 125 at the braking zone, well shy of top speed. That same 3.2 saw an indicated 140 somewhere in Wyoming a couple years later, but it took a good long while, even with my daughter nailed to the back bumper driving our much faster 944S2. I ran out of nerve before the car ran out of go.
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Old 11-10-2018, 05:21 PM
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Wow! That’s cool I guess I didn’t realize the top speed potential of a SC. I do recall, many years ago following my budies 964 in my 80 Targa from Seattle to PIR and hitting 125 on 1-5. Sketchy only begins to describe it.
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Old 11-10-2018, 06:50 PM
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In my 80SC i did 125-128mph pretty comfortably. I have the cat delete and removed the AC. Its all stock, except 160mph speedo from a carrera. It felt much faster then it actually was, i think another 10mph no problem
Old 11-10-2018, 07:08 PM
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Quote:
Originally Posted by Flojo View Post
my sound 3.0 SC with overhauled K-Jet, fresh 915 and SSI, Permatune runs 150mph/240 kmh as per GPS no problem
There you go all you CIS haters. It's possible, see? Thanks Flojo.
Old 11-10-2018, 07:08 PM
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Yep, mine's lightened a little, got the ROW 930/10 engine with cams and SSIs. The more it rev's the more the power comes on - even in top gear
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Old 11-10-2018, 07:53 PM
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The Red Rocket had a 915 with 345/35-15 rubber would run 145mph in 5th at redline. Did that with the 930 engine but also the 3.0L SC engine, just took a little longer to get there.
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Old 11-11-2018, 05:05 AM
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