Weighed my SC today

[Howard Nelson]

FWIW, I am in the middle of corner balancing my '72T, which has been moderately lightened (race seat, no rear seats, no AC, etc.) for the track, and it weights 2250 lbs with a half-tank of fuel.

[Kurt B]

I would be cautious about that number. I weighed my car before, not much gas...very little. What is the weight of gaoline per gallon?
Anyway, it weighed 2540 according to the weigh station. After I removed the back seats, padding and bumpers it should have been 100 lbs lighter, but it weighed 2560 lbs.

So..something's wrong. the only difference is a tank of gas, from full to empty. That means that a full tank of gas would weigh like 120 lbs. does it?
So those scales are not accurate unless a full tank of gas can account for 120 lbs.

[Randy W]

One gallon of fuel is 7 pounds, so a 21 gallon tank full would weigh 147 pounds.

[Kurt B]

Okay, that explains it. Thanks Randy. Wow. that stuff is heavy.

[pjv911]

gasoline is 7.9 lbs per gallon to be exact.

[dd74]

What other things did you do to this car to make it so light - like exhaust system wise. I'm thinking of replacing my Bursch. What's your suggestion?

Thanks

[Kurt B]

You guys are right. After Randy posted that, i drove down to the Sunshine truck stop in wilmington and weighed the car. It had around .6 of a tank. It rang in at 2500 lbs.

That means, if I race on a quarter tank of gas, I'll be weighing at 2,463 lbs or so, which is just plain awesome. I estimate my HP at the flywheel to be around 225, so lbs per HP would be= 10.94.

This is fewer pounds per HP than the new 350Z, which rings in at 11.1 lbs per hp

[speeder]

So Kurt, Can we look forward to a "I spanked a new 350Z" thread soon?

[Adam]

For the 1976 911S, my owner's manual claims a weight of 1,120kgs. Remove the A/C (which mine no longer has) and you're looking at closer to 1,100kg. This equates to approx 2,420lbs.

I don't know how accurate that is, but the car drives like a go-kart. It's huge fun.

I don't even wanna think about how heavy the pork-ass Cabriolet is...

[sewell94]

The early 930 aren't that heavy, i weighed moroso and it was 2590Lbs, It is a 76 930 with power windows, power sunroof, AC (extra condensor), Turbo spoiler, 930S Air dam, 930S consule. Half tank of gas, FYI it ran 12.9 @106.

[Kurt B]

the cab top is no heavier than your coupe top from what I understand. the biggest problem with cabs is in the frame flex not in the weight.

However, if I need to, I can unbolt and remove the top in around 20 minutes. It's fairly straightforward. Yet another advantage of cabs. In fact, after that, it'll be coming in a lot lighter than a coupe or a targa.
The heaviest must be targas. I think the weight of all the glass is probably the problem for you guys. I don't have any glass back there, just the frame, which ideally, could be drilled and bored out and lightened a lot if I needed to without causing leaks.

[Bill Verburg]

The dmv weights are total fiction, mine also says 2400#, the landfill scales are not particularly reliable either, my local one gave me 2559#, the only really reliable ones are the $2000 electronic corner balance scales used at all PCA races and many reputable shops, 2687 with full tank, spare etc. The 3.6 sans ac is ~20lbs heavier than a 3.2, the Al. case trans is w/lsd is ~27# heavier than a mg case w/o

[JWest]

On fictional DMV weights - I once had a '78 Scirocco and the title said 3800 lbs!

[Randy W]

Noah, '73 RSL (Touring) and RS (Lightweights) did have partial undercoating in the splash areas under the fenders and other areas. I have seen three genuine RS Lightweights and they all had this. It is also documented on page 103 of the Carrera RS book.

P.S. After April 9, 1973 all '73 RS Touring and Lightweights built had series production undercoating, according to the Carrera RS book.

[Kurt B]

Bill, I respectfully disagree that the scales are not accurate. It weighed 2560 with a full tank of gas. After the post, I went down there, and by then, 2 days later it had just over half a tank and lost 60 lbs. Using Randy's estimate, 60 lbs is about what you'd expect to lose in losing close to half a tank.
Those numbers ring true to me. If you bring the weight down to near empty when I had it weighed a few months back in which it weighed 2540, you get a final weight of 2440 or so, which is exactly what I'd expect from having lost 100 lbs (which I did weigh the items as I took them off).
the Sunshine Truck stop scales are accurate to within some few pounds.

[Bill Verburg]

Kurt, 2 things, Don't confuse repeatability with accuracy and the response curves of scales are non linear. We have a lift to pull boats weighing up to 150 tons out of the water, but the accuracy of its strain gauge goes out the window at the extremes of its range. A friend is a state trooper in charge of truck weighing, the only scales that he can go to court with are the electronic load cell type as used in corner balancing, they need to be calibrated regularly and are only accuate(in a legal sense) over a range well above that for an auto, he told me that the weight for a car would be + or - a few % because of the non linearity. Perhaps the scales you used were calibrated and are accurate/repeatable in the range of you car weight. All I know is that on scales I believe I got weights well above those from the typical transfer station. My car is a euro version with f/g bumpers and only the slightly heavier 3.6 and al case/lsd dif. to add any extra weight. No air, no power anything, If so Iwould really like to know why mine is so heavy wrt yours.

[Kurt B]

I do know we can glean information as to the accuracy of the weighing device by noting that it accurately measured a 60 lb decrease in weight.

It could be luck--granted. I would have to repeat experiments by adding and removing (known) weight and measuring the change in the device.

I could do this easily, but it's hard at the place. I will make a trek up there again, this time with no gas, and if I see a weight pushing 2440 lbs, then I know the device is precise. It may not be accurate, but it is precise.

Accurate = the mean of all of its errors tends toward zero but its standard deviation can be anything.

Precise = the mean of all of its errors tend toward X, but the standard deviation is very small.

My weighing experiments so far indicate it is AT LEAST precise because it is properly grouping its measurement very near the known deltas in weight. Now it could still be inaccurate by being biased some X pounds (like 100 lbs heavy) while reading small changes in weight accurately, but I doubt it.

[Bill Verburg]

Kurt,I have no idea of the precision of your scale, I just would take anything but a certified, calibrated result with a grain of salt. for referecnce here are the factory data measured per DIN standards all #s in kg x2.2 for lb some of this data seems odd at times;

• 76/77 911 1120
• 76/77 Carrera 3.0 1120
• 76/77 930 1195
• 78-81 SC ROW 1160
• 78-79 SC/USA 1160
• 80/81 SC USA1250
• 78-81 930 ROW 1300
• 78-80 930 USA 1295
• 81 930 Can 1300
• 82/83 SC ROW 1160
• 82/83 SC USA 1250
• 82/83 930 ROW 1300
• 82/83 930 Can 1300
• 84-87 Carrera 1210
• 84-87 Turbo look 1260
• 84-87 930 1335
• 89-94 Carrera2 ROW 1380
• 89-94 Carrera2 USA 1375
• 964 Carrera RS base 1220
• 964 Carrera RS touring 1320
• 964 RS America 1340
• 89-94 Carrera4 ROW 1380
• 89-94 Carrera4 USA 1375
• 964 3.3 turbo ROW 1470
• 964 3.3turbo USA 1485
• 964 3.6turbo ROW 1810
• 964 3.6turbo USA 1785
• 993 Carrera 1370
• 993 Carrera4 1420
• 993 Carrera RS 1270

[Kurt B]

Well that puts mine at 2662 lbs. But my manual said like 2750? Keep in mind, we can factor up to 150 lbs for gasoline. And i believe the tests are done at sort of "half of everything" half a tank of gas, half load capacity...etc. Maybe they put in 3/4 of a tank for the manual but that other measurement is without any gas at all?

You know, I don't even know the gas capacity of my car at this point. I don't remember how many gallons it holds.