A few questions- 964 RS VS 911 3.6 Conversion

[herman maire]

I have a few questions on a striped 964 RS VS 911 3.6 conversion, I would really like to hear some feed back on this.

I should mention that I am also building SLOWLY, VERY SLOWLY a 72 RSR with a 993 3.6 with a BIG single turbo ect.. ect... Target 5-600 HP.



Questions-

1- Is a STRIPED 964 REALLY that much heavier? ( 964 would have fiberglass hood, doors, engine lid ect.. as would the 911 3.6 conversion.)

2-steering feel- 964 manual steering rack VS 911 ?

3- chasis feel ? Does the 964 loose much?

4- 964 suspension design VS torsion bar

Any other input apreciated.

[pu911]

A well set up 964 is an awesome car. I have a 92 Carrera Cup can and a 3.5 L 73 RSR clone, both are awesome.
Phil

[herman maire]

Originally Posted by pu911

A well set up 964 is an awesome car. I have a 92 Carrera Cup can and a 3.5 L 73 RSR clone, both are awesome.
Phil

Thank you Phil for the reply.

Do you notice much between them? Does anything stand out, heavier G50 transmission, 964 not as edgy as old chassis ect..

Thanks again

[shamrockcustoms]

that is a gourgous looking 964..would love to see more pics of that one...

[Rory Mckenna]

I think that car and many others are on AP auto's website.

[RWebb]

1. No. Available data (hit search) indicate that the 964 unit body, tho FAR stiffer, is ONLY about 40 lbs. heavier than a 911 unit body.

[pu911]

Well I have raced both a 911 and a 964 and I find the 964 much easier to drive fast, better brakes, better gearbox better suspension. As far is weight goes my 964 is much heavier than my old 911 race car, about 500 lbs but still it really works on the track. Hard for me to really pin down the difference but it just a much more comfortable car to drive hard.
Phil

[mjshira]

I have both. The 964 is a heavy car when compared to an early car. Even after I've taken the sound deadner out and the heavy factory seats, etc. it is still something I notice. I have a manual steering rack, JIC full susp. and RS America sways. The car handles great, but I still love my 993 powered early car. I guess the best way to think of it is one is more raw than the other.

[DW SD]

That is a killer car! Are you considering purchase? The additional chassis stiffness will probably be important for you with a 600 HP monster motor. My lightweight 71 (2200 lbs) w/ hopped up '95 993 (275 RWHP) is already scary and that has 1/2 the horsepower. I'm just learning to drive it.

Doug

[RWebb]

James - there must be some things you haven't removed from the 964 - do you have an accurate wt. for the car?

Maybe there are some elec. motors, blower assemblies or hidden sound deadener?

Of course, the stock motor & powertrain is a lot heavier.

The wt.s I quoted are from completely stripped shells, undergoing heat bakes or dipping.

[mjshira]

Originally Posted by RWebb

James - there must be some things you haven't removed from the 964 - do you have an accurate wt. for the car?

Maybe there are some elec. motors, blower assemblies or hidden sound deadener?

Of course, the stock motor & powertrain is a lot heavier.

The wt.s I quoted are from completely stripped shells, undergoing heat bakes or dipping.

I have not wt'd the car but I've removed sound deadner, I have BBS wheels, I have recaro seats without power, etc RS carpet, removed sunroof motor, rear wiper motor. As for the wt of the engine, I have headers, so maybe I saved some there?

here are a couple pics, one of my 964, one of my r gruppe hot rod RS cab






I never set out to restore two 911's in three years and my new marriage won't support a third

[Bill Verburg]

Originally Posted by herman maire

I have a few questions on a striped 964 RS VS 911 3.6 conversion, I would really like to hear some feed back on this.

I should mention that I am also building SLOWLY, VERY SLOWLY a 72 RSR with a 993 3.6 with a BIG single turbo ect.. ect... Target 5-600 HP.

Questions-

1- Is a STRIPED 964 REALLY that much heavier? ( 964 would have fiberglass hood, doors, engine lid ect.. as would the 911 3.6 conversion.)
A 2.7RS l/w w/ 200hp mg block & trans will come in @~2000# race wt. A 964RS comparably setup @ ~ 2600#

2-steering feel- 964 manual steering rack VS 911 ?
the biggest difference in feel comes from the large scrub radius used in the older cars, put a 993 front suspension and wheels on a 964 and you can get some of that live feel back. Also there are ultra quick ratio racks which you won't want to use on a street car.

3- chasis feel ? Does the 964 loose much?
the old cars have such terrible camber and toe patterns that the name of the cgame is ultra stiff suspension to limit any such change. As a reult these cars may nbe fine on ultra smooth surfaces but get knocked around terribly when the pavement gets rough. I know several 2.7RS racers that won't do LRP any longer because of this.

4- 964 suspension design VS torsion bar
The 964 has very favorable compliance/camber and toe patterns, it will soak up the bumps rather than get knocked around by them.

[jakermc]

Originally Posted by Bill Verburg

Questions-

1- Is a STRIPED 964 REALLY that much heavier? ( 964 would have fiberglass hood, doors, engine lid ect.. as would the 911 3.6 conversion.)
A 2.7RS l/w w/ 200hp mg block & trans will come in @~2000# race wt. A 964RS comparably setup @ ~ 2600#

.[/COLOR]

If they are both stripped and set up for racing, where does the extra 600 lbs come from?

[RWebb]

Al vs. Mg block; induction; big-honkin' dual drive distr.; heavier trans... probably the CV's are even larger.

[Bill Verburg]

Originally Posted by jakermc

If they are both stripped and set up for racing, where does the extra 600 lbs come from?

The official PCA #S are

2575# for 964 Cup as raced in GTC1
2266# for 2.7 l/w as raced in PCA D

both include driver an equipment.

the l/w usually needs to add ballast to make wt, the Cup not.

differences
15" vs 18" wheels tires
282x20 vs 322x32 front brake rotors
mg 915/06 vs al g50/10
10 pin wiring harness vs 60 pin
2.7L mg block vs 3.6L al block along w/ all the internal and external components
non assisted brakes vs ABS/power assisted brakes
early chassis vs ~25% stiffer late chassis

[jakermc]

Great summary, thank you.

What has always been interesting to me is the trade-off between weight and the improved performance associated with the change adding the weight. Many of the items listed seem to be worth their weight penalty but that will ultimately vary between different set-ups and the driver's ability/style. For example, sometimes bigger brakes will reduce lap times and in other cases it goes the other way.

[petevb]

Originally Posted by Bill Verburg

3- chasis feel ? Does the 964 loose much?
the old cars have such terrible camber and toe patterns that the name of the cgame is ultra stiff suspension to limit any such change. As a reult these cars may nbe fine on ultra smooth surfaces but get knocked around terribly when the pavement gets rough. I know several 2.7RS racers that won't do LRP any longer because of this.

Quite right; I believe part of the reason the early cars with ultra-stiff suspension don't work over bumps is that their chassis are wet noodles compared to the 964- depending on how "early" a chassis you're talking I've heard numbers more like 2x more torsional flex rather than just ~25%. So you can't just add stuff suspension alone to neutralize the poor camber curves. If you do the resulting chassis flex is excessive, creating that "knocked around" feel because the chassis flex is undamped, meaning the tires won't stay on the road over bumps. A modern cup car/ rsr might have stiffer suspension, but it feels relatively planted over the same bumps because the suspension rather than chassis is what's flexing.

The camber change problem of early cars is compounded by modern radial tires (especially wide ones), as the stiffer sidewalls need to be held flat to the road to work consistently. Thus early cars often work best with softer suspensions (necessary because of chassis flex) and bias ply slicks and/ or narrower, taller tires (less sensitive to camber changes). This combination has a particular "feel" compared to modern cars, and this along with the light weight of the early cars is what makes them distinctive.

Closing the gap to the later cars requires a number of changes- stiffening the chassis significantly, changing suspension/ pickup points, and usually still choosing wheels/ tires less sensitive to camber changes, ideally while keeping the weight low. Not easy to get right, especially while adding power, brakes, wider wheels, etc.

[RWebb]

yes - Bill, can you fill in more info re the 25% value for chassis stiffness?

Is that a 964 vs. a late (say '87) 911? It's been suggested that the later 911s are already stiffer than the early (long nose) cars...

Is that for torsional rigidity (corner to corner)?

[Bill Verburg]

Originally Posted by RWebb

yes - Bill, can you fill in more info re the 25% value for chassis stiffness?

Is that a 964 vs. a late (say '87) 911? It's been suggested that the later 911s are already stiffer than the early (long nose) cars...

Is that for torsional rigidity (corner to corner)?

There were relatively minor increases in chassis torsional stiffness from '64 to '89 but it was minor compared to the changes on the 964 and up, advances in FEA and pressing techniques allowed more geometric stiffness from increased depth in the pressings and use of HS steel in selected chassis areas.

996 is even stiffer and 997 even more so. The computers and understanding of how to put different metals together to get enhanced strength w/o huge gains in weight just keeps getting better end better..

[Bill Verburg]

Originally Posted by Noah

The *real* reason for the weight difference is things like electrical components, the G50 gearbox, complicated HVAC systems, lots of electrical brains, wiring harnesses, and componentry, massive amounts of sound deadening, power steering, air bags, etc.

The Cup cars have a very simplified HVAC, more akin to a '73 than. The only brains left are ABS and DME(and hopefully the drivers), zero sound deadening in either, no seam sealing in either, fully welded seams though, no p/s in either (though the 964Cup has a variable ratio manual rack), no air bags, Cup wiring harness is ~13# lighter than in a 964 street