Enlightenment

[RWebb]

There have been many threads on making a classic 911 lighter in weight, but how light do you think a 911 could be feasibly made?

[petevb]

Originally Posted by RWebb

There have been many threads on making a classic 911 lighter in weight, but how light do you think a 911 could be feasibly made?

Set some ground rules- what do we need to keep?

[porschenut]

You mean, without replacing sheet metal with fiberglass?

If anything goes, I've seen race cars with a lot of fiberglass and lexan at 1,800 lbs.

[petevb]

Originally Posted by porschenut

You mean, without replacing sheet metal with fiberglass?

If anything goes, I've seen race cars with a lot of fiberglass and lexan at 1,800 lbs.

I think that's just scratching the surface. This german build-
http://www.auto-patutschnick.de/neuaufbau092004.htm
ended up at 1771 lbs with a near empty tank. That's with a heavy 6 speed, 964 based motor, GT3 brakes, big wheels and tires, a cage, etc. Just doing the math with a magnesium motor and trans, no cage and small brakes I get to ~1500 lbs. Take off the aero bits, simplify the oiling/ cooling, cut away more of the tub... I think you're under 1400. Might be a bit of a flexi-flier, though...

[old man neri]

Make a chassis and body replica out of carbon fibre?

[petevb]

Originally Posted by old man neri

Make a chassis and body replica out of carbon fibre?

I like that...

I feel like you need to keep a porsche flat 6 in the rear, the roofline and body shape and windows. You can obviously chop off the whole top and make it lighter, but I'm not sure it's a 911 in my mind then. I don't know that you need to keep any of the shell, though... A carbon chassis would need to be worth 100 lbs I'd think.

What's the lightest practical motor and gearbox? 901 and a carbed 2.0L I'm thinking, when cooling and other bits are accounted for?

[RWebb]

Originally Posted by petevb

Set some ground rules- what do we need to keep?

No making up new materials -- no use of unobtanium.

If it is so expensive that no one can make it or afford it once made, then say so -- or just skip it.

I suggest working from the rear of the car forward.

I bet it can be a lot less than 1,800 - some are already.

[RWebb]

Originally Posted by old man neri

Make a chassis and body replica out of carbon fibre?

how much would that weigh?

At least as much -- or about as much -- as the CF parts of a C-GT or modern Fcar, right?

So how much do they weigh?

I do have some wt.s for Al unitbodies on production or exp. cars somewhere.... will trey to post if I find it.

[vreference]

Carbon fiber chassis? At some point you don't really have a 911 anymore and shouldn't be bound to the platform's compromises. Certainly don't need the rear seats; go ahead and make it a mid engine. make the windshield a bit less barn door like while you're at it. Porsche already made that car, yes? The Carrera GT

[RWebb]

Ok, here is some info for Al unit bodies - perhaps a 911 made with an Al unit body would still be a 911, not a C-GT...


a stock 911 unit body weighs 640 lbs according to Autometrics Motorsports (ready for for acid dipping; no fenders incl.)

1990 NSX Al unit body wt. = 460 lb. (incl. doors hood & decklid) -- so, this means it is certainly possible to save significant wt. by doing something expensive.

stock (steel & Al) 928 body = 567 lb.; Al 928 body wt. = 333 lb.
- this datum is helpful b/c we can take the ratio and estimate how much wt. would be saved by making a 911 unit body in Al.
The answer is that the unit body would weigh 376 lbs. !!
i.e an Al unit would save 264 lbs.

if you could do it.

[911pcars]

Randy,
Your ground rules: "No making up new materials -- no use of unobtanium."

I would place an aluminum or carbon fiber chassis in the unobtanium group. IMHO, a 911 replica uni-body in aluminum would be even less rigid than the already less-rigid 911 platform without added engineering. And is anyone prepared to design much less fabricate and autoclave a CF chassis? Don't think so.

Actually, Jim Calzia's often-referenced 911 race car is pretty close to the minimum weight. Story from Excellence in 2000.
http://www.early911sregistry.org/jCalzia.html

"....Actually, the 1830 lbs is an estimate; the car weighs 1730 lbs with transmission oil but without engine oil and gasoline........"

Of more importance is the weight data Jim accumulated during his build. Link to charts in the above page.

Sherwood

[RWebb]

Sherwood - Fiberforge will make small run CF parts

I don't see why Al would be less stiff than sheet metal.

Some data for you:
1, 735 lbs. - Larousse Tour d’France car (a lightened S-T)
1,890 lbs. - Grant G’s Carbon Copy
1,830 lbs. (wet) - Jim Calzia’s purple car (now an RSR replica IIRC)


What is your idea to get a wt. lower than 1800 lbs.?

[YTNUKLR]

"kanna" has a car is something like 1830# wet, a 70s-80s car with 3.2 S.S. and fiberglass 993 body work

67 911R 1810

72 S-T Factory quote 860kg= 1892, full steel fenders, etc.


ideas:
-TINY battery
-CF fenders w/ integrated head light covers
-braided oil lines instead of brass
-delete dust covers on shocks/struts
-carbon fiber doorskins, no inside covers, w/ aluminum door hinges
-plastic windows
-carbon fiber rear quarters w/ DZus fasteners
-partial chromoly rollcage (if you are driving a car this light you need a cage because you are hauling a$$)
-911S alloy front brakes all-around (I have made adapters for the 911S brakes on the rear)
-drilled brake rotors, preferably worn down!
-aluminum trailing arms [hard to do on a SWB]
-CF or glass tail light housings, or 911R light housings
-delete turn signals
-remove spare tire
-plastic gas tank
-no tools
-some tube-frame stuff and drill a bunch of holes all over the unibody sheetmetal
-replace rear seat and parcel shelf area w/ aluminum sheet (if cage is present and bars tie into structural members)
-Integrate seat mounts into center tunnel and side frame, allowing you to replace floor panel with bonded CF
-carbon fiber roof
-no dash
-only tach and oil pressure gauges
-no switches, dials, ventilation
-magnesium case engine w/ '77 Magnesium 4-rib (like 911SC) oil pump
-2.0L 911T crankshaft w/ a set of 92mm RSR Pistons cylinders...2.6L Shorty, as light as they come, probably 46mm weber carburetors (bored out, less material), mag manifolds
-Mag 901 gearbox, open differential (LSD is heavy...that said, i'd make sure i had an LSD)
-alu pressure plate
-RSR flywheel
-Mahle 15x5.5" Magnesium Gas Burner Wheels
-no undercoating, no bondo, thin paint
-no windshield wipers, motors, or arms
-drilled floor boards
-(1) 911R Fiberglass racing shell, 4pt. harness
-Momo steering wheel
-no front/rear lid hinges, rubber tie downs instead
-no grillz
-drill the hell out of the rear engine cradle, RSR drilled engine mount bar
-no stinkin' badges

I think this could get down to 1600 . Obviously a highly impractical car, but might mop up in vintage racing...I'm thinking SWB...This is essentially a 911R with
-all plastic windows (10#), NO glass
-No wipers...remember Monza, needed wipers (8#)
-fewer gauges (4#)
-no passenger seat (15#)
-drilled holes in stuff (?)
-CF roof and floors (65#? and the roof will lower the CG)
-magnesium case and transmission, 2.0 crank (no counterweights), mag oil pump and open diff, aluminum cylinders (55# easily over the 911R solid aluminum engine, transmission and iron-aluminum cylinders)
-magnesium wheels (15#)
-CF rear quarter panels (20#)

This could add up to about 200 # off a 911R. Power to weight about 1625 to be safe, with 240 hp (easily)=6.8

[911pcars]

Originally Posted by RWebb

Sherwood - Fiberforge will make small run CF parts

I don't see why Al would be less stiff than sheet metal.

Some data for you:
1, 735 lbs. - Larousse Tour d’France car (a lightened S-T)
1,890 lbs. - Grant G’s Carbon Copy
1,830 lbs. (wet) - Jim Calzia’s purple car (now an RSR replica IIRC)


What is your idea to get a wt. lower than 1800 lbs.?

Will Fiberforge manufacture a small run of 911 chassis? A CF chassis was discussed, no small feat.

As built in the late 60's, the 911 chassis is fairly flexible. If built to the same form as the factory chassis, aluminum would need added reinforcement to reduce metal fatigue as well as to increase the rigidity.

Has Scott's (Ytnuklr's) fantasy car already built and successfully raced? What's the typical weight of the current crop of vintage 911s?

Sherwood

[petevb]

I can shed some light on a couple of these weights from my car:

-TINY battery

Found one that's 5 lbs, lithium ion.

-carbon fiber rear quarters w/ DZus fasteners

Bonded= 3 lbs each.

-partial chromoly rollcage

This is really heavy. An extensive cage can run 80 lbs easy. Lots of early street cars do without...

-CF or glass tail light housings, or 911R light housings

LED lights behind the stock cover (no housing) is perhaps the lightest. Weigh next to nothing. For a race car you might not have any other lights or wiring.

-replace rear seat and parcel shelf area w/ aluminum sheet (if cage is present and bars tie into structural members)

You can bond the aluminum in as a stressed panel to maintain the structure.

-carbon fiber roof

Only 8 lb difference vs early steel non-sunroof. Not sure about the floors.

Other ideas:
935 front A arms
Coilover rears, cut out the torsion tube carrier (although then you probably would need that cage)
If it's a race car, carbon/ carbon brakes instead of steel.

Aluminum is not stiffer than steel, pound for pound. So an aluminum body would be more flexible unless you changed the geometry.
Same goes for chromoly vs mild steel in the cage.

A tube frame would probably be the easiest- replace all the structure, then fill in the gaps with bonded CF or aluminum panels. Not pretty, though.
How many panels do they stamp replacement sheetmetal for, and could you stick thin aluminum into those presses instead?

[RWebb]

I think we should stick to things with major potential. Drilled floorboards is pretty far down the list of things to do.

And, it would be useful to give some estimate of how much could be saved and how that estimate was arrived at.

Also, Al made unit bodies are much stiffer than steel ones, while being lighter -- that is a big reason they were and are used. That does NOT mean that anyone less than a major manf. could make one...

Brakes:
Here is one quote that has potential:
-911S alloy front brakes all-around (I have made adapters for the 911S brakes on the rear)
-drilled brake rotors, preferably worn down!

The real weight is in the rotors. The 911S Al calipers weigh 5 lbs. each (Calzia data). People tell me the front Carrera Caliper weighs 8 to 9.5 lbs. (w/o pads, pins, retainer spring or fluid).
The Wilwood Superlite 6 Front caliper is about 5.2 lbs.

So, you could save about 8 lbs total for the front.

The drilled Front 930 Rotors weigh ~ 15 lbs. While it is 9 to 10 lbs for Wilwood's Ultralight Curved 32 Fin Rotor. If suitable that can take 10 to 12 lb.s off the front of the car.

So, using available parts might give a savings in front of 20 lbs. It would be less in the rear.

The real savings would be a ceramic PCCB type system that fit an early car.

[petevb]

Originally Posted by RWebb

I think we should stick to things with major potential.
Also, Al made unit bodies are much stiffer than steel ones, while being lighter -- that is a big reason they were and are used. That does NOT mean that anyone less than a major manf. could make one...

The only reason they are stiffer is because they use different geometry, ie larger box sections or large cross section extrusions. If you stuck with the same geometry you'd loose stiffness. An aluminum roll cage might be the move- that's a much stiffer geometry...

Originally Posted by RWebb

The real savings would be a ceramic PCCB type system that fit an early car.

Not really, unless you do smaller rotors and calipers than the normal PCCB. The PCCB system on my '69 is only fractionally lighter than my old 930 system, and it forces the use of 17" wheels. Of course it's a ton more brake- 350 mm diameter rotors and 6 piston calipers and you're still a couple pounds ahead, but in absolute terms it's not the lightest system.
An early S system would be a lighter package unless someone starts making 300mm or smaller diameter PCCB disks.

[Flieger]

Talk to Chuck:



Chuck Moreland at Elephant Racing

[petevb]

Originally Posted by Flieger

Talk to Chuck:

Chuck Moreland at Elephant Racing

Yea, he's been testing that from what I hear. More of a carbon system than Ceramic from what I understand. Any word on how it's been working out so far?

[snbush67]

Probably the best way to lighten the car is to remove the engine and the transmission. You would simply have to rely on gravity and a good tail wind. Another benefit could be to remove the floor boards so it could be propelled by foot.