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931 Top Speed...
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-nick  



Joined: 16 Nov 2002
Posts: 2700
Location: Cambridge, MA

PostPosted: Thu Sep 25, 2003 1:51 am    Post subject: Reply with quote

Hey CMXXXI-
Interesting specs on the RoW box. It is counter-intuitive. By these numbers the RoW box has more top end in all the gears except 5th, where it is geared lower than the US box's. Seems odd.

I think your gauges maybe fairly accurate. A 70mph mile run should be done in about 51.5sec. 75mph in a mile should be 48sec. You're reading between 70.5-72mph according to your numbers. Your timing accuracy could make up a second or so plus reading the speedo and tach accurately and any fluctuations from 3000rpm you might have over the mile trip could all easily make up the difference.

My speedo reads about 2-3mph fast across the entire face according to multiple "your speed is" roadside radars. It's not uncommon to be off by a small amount. My girlfriend's car reads about 2mph fast.

If anything your tires should make the speedo read a touch faster at 70mph (about half a mph).

-nick
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CMXXXI  



Joined: 05 Nov 2002
Posts: 1939
Location: Vicksburg, MS

PostPosted: Thu Sep 25, 2003 4:16 am    Post subject: Reply with quote

I suppose all this is "academic", huh?

But, I'll continue to do timed miles at various indicated speeds to give myself "peace of mind" about the gauges, and some time I'll get someone to "pace me" in another car for additional verification. As long as it's close enough to keep me from getting tickets I'll be satisfied.

With that said, I drove home last night doing 110mph (indicated) over a 5 mile stretch of interstate. It brought back memories of driving in Germany. It sure was nice to cruise at 4.5-5Krpm for long stretches without having to worry about law enforcement.
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'79 Eurospec 931
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Paul  



Joined: 02 Nov 2002
Posts: 9285
Location: Southeast Wisconsin

PostPosted: Thu Sep 25, 2003 10:39 am    Post subject: Reply with quote

Borrow someone's GPS, it will quickly tell you the story.
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numbbers  



Joined: 05 Nov 2002
Posts: 1910
Location: Highlands Ranch, Colorado

PostPosted: Fri Sep 26, 2003 12:23 pm    Post subject: Reply with quote

Yeah nick, the us models have the smaller gears 1-4 because we got the lower HP engine, and we got the higher fifth gear in order for Porsche to meet the CAFE requirement. Ain't big government fun.

I tried to top my '80 out once, but ran out of road. I don't know how fast it was, as I had the 85 MPH speedometer at the time. Since I installed the 170 MPH speedo, I have never had a clear enough road to ge over 90.

By the way, for all you guys that have the green lettered 85 speedo, I can convert a 150-170 MPH speedo to match your other guages. You need a speedo with white numbers, not the yellow 944 type, and I can dye the letters. I experimented for about a month before I got the dye just right.
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Khal  



Joined: 26 Sep 2003
Posts: 4859
Location: Hot and sunny interior BC, Canada

PostPosted: Fri Sep 26, 2003 5:34 pm    Post subject: Top Speed Reply with quote

I've got an '81 (Euro?) Australian-delivered 932 (I think that's the right designation for RHD?).

I've had it up to 230km/h (142 - 143mph), indicated on the speedo, at approx. 5500rpm. But I've heard the speedo's are unreliable. I think the owners manual quotes 225km/h (140mph) as the top speed.

Mine's producing about 25hp over standard, approx. 200hp.

Felt like it'd go a bit faster still but I had to back off. Scenery comes at you pretty quick at those speeds!
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Khal  



Joined: 26 Sep 2003
Posts: 4859
Location: Hot and sunny interior BC, Canada

PostPosted: Fri Sep 26, 2003 6:03 pm    Post subject: Top Speed (again) Reply with quote

[quote="Paul"]Borrow someone's GPS, it will quickly tell you the story.[/quote]

Actually, I'd forgotten. I did this when I fisrt bought the car about 2 years ago.

The speedo was reading 8km/h (~5mph) fast at 100km/h (~62mph). If it was that fast all the way through, then I'd have been doing about 222km/h which is near enough to the quoted top speed.
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J1NX3D  



Joined: 06 Feb 2003
Posts: 1332
Location: New Zealand

PostPosted: Mon Sep 29, 2003 7:57 am    Post subject: Reply with quote

im doing 100kph at 2800rpm does taht sound right? most cars ive driven are geared for 100kph/ 3000rpm except for a sti type r, that was 100kph/ 4000rpm!!
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Khal  



Joined: 26 Sep 2003
Posts: 4859
Location: Hot and sunny interior BC, Canada

PostPosted: Mon Sep 29, 2003 10:25 am    Post subject: Top Speed Reply with quote

JINX3D, actually sounds a bit high to me. I can't recall exactly what my engine's turning over at 100km/h but I thought it was just over 2000rpm; maybe 2200 - 2300rpm?

Not 100% sure. Will check it out next time I'm in it...
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Lizard  



Joined: 03 Nov 2002
Posts: 9379
Location: Abbotsford BC. Canada

PostPosted: Mon Sep 29, 2003 10:27 am    Post subject: Re: Top Speed Reply with quote

Khal wrote:
JINX3D, actually sounds a bit high to me. I can't recall exactly what my engine's turning over at 100km/h but I thought it was just over 2000rpm; maybe 2200 - 2300rpm?

Not 100% sure. Will check it out next time I'm in it...


you are correct, however you have a 81 931 which has an audi based tranny, and J1NX3D has a 1980 931 with a snailshell/dogleg tranny, his has shorter gear ratio
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J1NX3D  



Joined: 06 Feb 2003
Posts: 1332
Location: New Zealand

PostPosted: Mon Sep 29, 2003 12:19 pm    Post subject: Reply with quote

oops, forgot to mention that, and that its in 5th.

cheers guys
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Khal  



Joined: 26 Sep 2003
Posts: 4859
Location: Hot and sunny interior BC, Canada

PostPosted: Mon Sep 29, 2003 2:34 pm    Post subject: Top Speed Reply with quote

Thanks Lizard. Didn't know they were different. My gearbox has 1st on a dogleg, though. Very awkward. My least favourite feature of these cars. Don't know if that's what you meant by 'snailshell/dogleg tranny'?
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Lizard  



Joined: 03 Nov 2002
Posts: 9379
Location: Abbotsford BC. Canada

PostPosted: Mon Sep 29, 2003 3:20 pm    Post subject: Reply with quote

snailshell dogleg trannies have a shift pattern of

R.2.4
1.3.5

where as your model year should have

R.1.3.5
...2.4

do you follow me
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Khal  



Joined: 26 Sep 2003
Posts: 4859
Location: Hot and sunny interior BC, Canada

PostPosted: Mon Sep 29, 2003 3:45 pm    Post subject: Wrong Tranny? Reply with quote

Yeah mate, I follow. But my gearbox goes;

R.2.4
1.3.5

Bugger of a thing, too. Hard to drive in city traffic. Then again... it's fantastic on a mountain pass, when you don't need first!

But mine has been modified for racing previously. The gearbox may well have been changed.
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Lizard  



Joined: 03 Nov 2002
Posts: 9379
Location: Abbotsford BC. Canada

PostPosted: Mon Sep 29, 2003 5:50 pm    Post subject: Reply with quote

the gearbox has DEFINATLY been changed, however IIRC there are 3 versions of the G31 .01, .02 and .03 all all 3 have different gear ratios, although, i dont hink you should be running at 2800rpm in 5th gear, J1NX3D, it could mean that someone has swapped out to a shorter diff, although 1 of the 3 versions might have had a short diff like you have,
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924 turbo  



Joined: 02 Nov 2002
Posts: 1566
Location: Simi Valley, CA, USA

PostPosted: Mon Sep 29, 2003 11:52 pm    Post subject: Reply with quote

Lizard wrote:
the gearbox has DEFINATLY been changed, however IIRC there are 3 versions of the G31 .01, .02 and .03 all all 3 have different gear ratios, although, i dont hink you should be running at 2800rpm in 5th gear, J1NX3D, it could mean that someone has swapped out to a shorter diff, although 1 of the 3 versions might have had a short diff like you have,


Huh? The Euro/ROW 931 models used the snailshell throughout production.
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Jon Furst
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