Best handling....lightness vs. distribution vs....?

[PropellerHead]

Originally Posted by 911nut

In the "light vs. rigid" debate, I'll take rigid every time. Makes for a more predictable and better handling car. Since we are discussing street cars, ultimate 'light" is most likely not the best kind of car to have from a comfort and usability standpoint.

Ideally it would be both light and rigid (DUH!) but lightness wins in my book. Starting with an early chassis gives a 100-200lbs advantage out of the box. The better handling afforded by a more rigid chassis isn't worth much if the other car is 200lbs lighter (and all else the same)!

I'm biased as the owner of a non-sunroof early coupe but it is significantly lighter in full street trim (2150#) than a stripped 964 (even the heavily lightened versions are 2400#!). Do the same techniques to an early chassis and you'll have it at closer to 2000#.

In addition to the added rigidity of the 964 chassis you also have added mass due to crash worthiness. Safety adds weight.

If you're building a street car - lightness isn't as critical. You can afford a couple hundred lbs of dead weight. If you want the 'ultimate' street car, go lighter to start with and you can add creature comforts instead of stripping them all out. Think of it this way: you could take an early chassis, add a 3.6L, good stereo, A/C, lightweight carpet, door panels and sound insulation. Or, take a 964 and strip all that stuff out. In the end you may have the same power/weight ratio, balance, etc. but one is much more comfortable on the street. If the 964 is marginally faster - who cares, it is a street car and you can't exploit that very small difference on the street anyway. Oh, and the early car hotrod will always be worth more than the stripped 964 not to mention look much cooler.

[winders]

Originally Posted by 911nut

In the "light vs. rigid" debate, I'll take rigid every time. Makes for a more predictable and better handling car. Since we are discussing street cars, ultimate 'light" is most likely not the best kind of car to have from a comfort and usability standpoint.

Comfort and usability? We are talking about sports cars here, right? Comfort was not high on the list of things the OP wanted out of the car. Then again, the car I am talking about is not uncomfortable to drive for long distances.

In my experience, the extra rigidity of the 964, however much it is, does not offer enough handling improvements to overcome the extra weight.

Take a '73 RS clone with a 3.6L and a 964 RS America, both well setup. Which car is more fun to drive? Which would go faster at the local autocross? Which would be the best handling? Which would more enjoyable overall?

My answer is the '73 RS clone with the 3.6L. It would be a rocket ship compared to the RS America.

Maybe you would want a nice comfy car. Maybe a soft 964 C2 or C4 would suit your needs. I don't think that is what the OP was looking for.

Scott

[al lkosmal]

This is turning into a great thread, with lots of good info, advice and opinions, but it is a little short on actual examples......come on....show me what you have done to achieve the perfect balance. I'd like to see actual examples, including pix and specs of your "street rod". Include as much info as you want, describe your decision making process, handling/weight/suspension vs. comfort/driveability, and the results, subjective and otherwise. Where are the hot rodders??....show me your stuff. Show me good examples of the what and the why!

Regards,

Al

[Flieger]

A rigid chassis makes for better tunabilty of the suspension. It will respond more sensitively to changes. The rigid chassis removes an unknown-rate, undampened spring from the equation. It allows for more extreme biases of roll stiffness distribution. I would say that this tunability means better handling and a better real world lap time.

[island911]

"come on....show me what you have done to achieve the perfect balance."

the thing is, the perfect balance depends on the driver and the road being driven on. (for the 911s)

That is, on a perfectly smooth road, a very stiff suspension is great. As the road gets bumpier the suspension needs to become more compliant. -think go-kart vs rally car.

If you want the best, you will be looking to active suspension. And there again, the 'best hot-rodder' seem to be Porsche engineers. Although, the Porsche Active Stability Management (PASM) actively controls only the damping component -- w/ only slow acting change capability for the (air)springs. (maybe that's changed by now - dunno)

[winders]

Originally Posted by Flieger

A rigid chassis makes for better tunabilty of the suspension. It will respond more sensitively to changes. The rigid chassis removes an unknown-rate, undampened spring from the equation. It allows for more extreme biases of roll stiffness distribution. I would say that this tunability means better handling and a better real world lap time.

All other things being equal, you are right. But all other things, specifically weight, are not equal.

Scott

[Superman]

We have about as much consensus here as a room full of economists. It all depends on what you want, and what you are willing to sacrifice. Me? I just love a lightweight, tossable 911. Think of a go-cart coupe with license plates. Something done on a 964 platform would probably perform better overall......certainly have more power......and I suppose could be very light, but would be a bit more expensive than I would want to tackle.

Good luck in your decision-making. Fortunately (or perhaps unfortunately), the Porsche 911 is almost certainly the most widely hot-rodded car in automotive history. There is virtually nothing about these cars you cannot learn here, at this site, likely in minutes, and the various parts and options are nearly endless.

Having said that, I will make one more stab at selling my suggestion. Buy a decent but tired 1969-1989 911 (or 912 for that matter), take the whole darned thing apart, deal with engine/transmission/chassis issues, and reassemble using only the parts necessary to drive the thing down the street. Choose a known-balanced system of torsion/sway/shocks and freshen every suspension bushing. You'll really enjoy driving the outcome.

[Superman]

Or better yet. Buy someone's completed project.

[ghost1001]

Ok, you asked….I will comment on my process up to this point. My car will be street driven 90% of the time….it is not my daily driver it will be a fun 911 “hot-rod”. I was really after modern high-end sports car performance in a vintage 911 chassis, vintage looks, feel and fun….dialed up to 10+.

Here is my list of priorities for my project in descending order:

1) Speed/acceleration
2) Handling
3) Looks, feel, sound, etc.
4) Comfort

It seems to be widely accepted that weight is the first consideration to achieving a high performance 911. Power to weight is a big factor and played a major role in my decision to use a 1976 chassis. Also, the fringe benefits of lightness are that there is less mass to throw into turns or slow down when braking. That said a light car seemed to be necessary to achieve my goals.

I stripped the car to the bone and I am reluctantly adding back in “comfort”, light weight sound deadening will be used on floorboards, and the rear seat area. All metal body (except bumpers), real glass, stripped down heating system, no cage.
As to suspension and handling, I went back and forth and asked some of the best both on and off forum. All basically agree that the handling of the car is one of the most subjective systems. I think this is the main reason the debate rages on, weight vs. rigidity, TB vs. coil-over, etc. My feeling is that few have driven, let alone built, enough cars to really comment on what the “best” setup is, as this is also subjective to the driver. I have also found that budget will dictate MANY decisions about what we use on our cars.

I have found that the people that I respect have a”formula” based on your budget….the first question is ALWAYS how much do you want to spend. Next is to define your goals/use…..then a plan can be developed. In my case I have a 930 engine and trans to stuff into the 911 chassis as well.

My total suspension build including coil-over conversions and bracing is about $10k. This also includes some proprietary mods to the front struts. The shop that is building my car is primarily a race shop, so the coil-overs are his “formula” to create a very good handling car. The suspension will also be easy and relatively cheap to “tune” based on MY impressions once I have driven it a while. I have also been told that the coil-overs will help a great deal with keeping the car on the road, power to the ground, predictable handling, etc (in addition to proper wheel widths and tires) as we will be running about 400hp to the rear wheels.

I have not discussed weight distribution at length with my builder. He has commented that the battery placement on the stock cars is “not good” and he I don’t see many areas where this can be affected. He advises moving the battery be to an area behind the front wheels. One of the coolest mods I have seen for this is moving the oil tank to the smugglers box, this is not cheap and obviously requires re-plumbing the car.

So my simple answer to the question is weight first….then suspension components…then weight distribution……and then comfort

[boba]

Originally Posted by RWebb

the numbers I've been give from a couple of people who have weighed them are < 100 lbs.

that is for a bare tub - and IIRC 40 lbs. or so; maybe it was 80

Good catch Mr. Webb, after reading your post I went back to look at my notes and I was wrong, the DELTA was not for bare tubs as I had remembered. So as you suggested something in the 40-60 lbs. range sounds more like it.

[rfloz]

Originally Posted by al lkosmal

This is turning into a great thread, with lots of good info, advice and opinions, but it is a little short on actual examples......come on....show me what you have done to achieve the perfect balance. I'd like to see actual examples, including pix and specs of your "street rod". Include as much info as you want, describe your decision making process, handling/weight/suspension vs. comfort/driveability, and the results, subjective and otherwise. Where are the hot rodders??....show me your stuff. Show me good examples of the what and the why!

Regards,

Al

While your goal is laudable, almost all your criteria are subjective - handling, comfort, driveability, e.g., all vary with the eye of the beholder.

My <2500# (a/c, stereo, etc., etc., etc., delete) 911 w/ 22/29 torsion bars, 22/21 anti-sway bars and 245/315 17 R tires seems a near perfect driver to me. My wife is less enthusiastic. In fact, she calls it an oxcart and refuses to ride in it.

So, who's right?

You could, at a not insignificant cost, build a sub 2000# street legal 911. With moderate torsion bars and sways and 50-60 series tires, it would handle and ride reasonably well. Of course, it would have no HVAC and conversation would have to wait for rest stops. After you took your earplugs out. Works for me (except that cost part). Would it work for you?

My car, although street legal and street driven, is heavily biased toward auto-cross. I like to think it handles very well. Comfort, not so much. But, I don't mind.

So, what are you willing to give up? A/C? Stereo? Your hearing? Your kidneys?

Have you ridden in many hot-rodded 911s? If not, round some up in your area and try it. Ask the owners what they have done (and not done).

Good luck in your quest.

[winders]

Bob,

Excellent post! You make very good observations and points.

Scott

[Superman]

Originally Posted by rfloz

Have you ridden in many hot-rodded 911s? If not, round some up in your area and try it. Ask the owners what they have done (and not done).

Ergo my suggestion. Let's get together, drink beer until we can't stop giggling, then take our 911's out on some twisty roads and test their limits. Okay, I'm kidding about the beer part. Sort of. But seriously, you could certainly take my car for a spin, as a data point.

[RWebb]

Originally Posted by al lkosmal

This is turning into a great thread, with lots of good info, advice and opinions, but it is a little short on actual examples......come on....show me what you have done to achieve the perfect balance. I'd like to see actual examples, including pix and specs of your "street rod". Include as much info as you want, describe your decision making process, handling/weight/suspension vs. comfort/driveability, and the results, subjective and otherwise. Where are the hot rodders??....show me your stuff. Show me good examples of the what and the why!

Regards,

Al

I used to have some files posted that summarizes about 20 cars, including Jack Olson's.

as others have implied you need to be more specific about what you want.

BTW - Ghost - I don't think you will achieve modern levels of sports car performance or feel, even given your extensive work. The geometries are just not up to it. BUT, you will get a very fun and high level car. My goal was a light wt. high perf. car that was FUN to drive, and that I could feel the road in, with that old-timey religion of feel. My testing on a familar, known road, back to back with a Boxster S, and a stock suspensioned '75 911 (a bit more motorvated than stock) was described in the Yet Another Rgruppe Suspension link I posted.

[911st]

Don't be afraid of stock suspension. I rebuilt my 86 Carrera to stock specs with new shocks, lowered ride height, LSD diff, 7&9's, and 205/245 MPSC's.

Was faster than a lot of cars on the track and probably could not have been much faster on the back roads if it had a stiffer suspension.

I left the spare wheel, jack, tools, and cat at home which saved about 70lbs.

A stiffer suspension is more predictable in transition. However, if you have the tires and camber they can have very close to the same speed potential.

[Flieger]

Originally Posted by winders

All other things being equal, you are right. But all other things, specifically weight, are not equal.

Scott

Weight does not have to be equal. If the track is really tight and point and shoot is the fastest way round, then you should make the car oversteer even if it means carrying a small weight penalty for rigidity. Just carry a gallon less fuel. I think weight in the chassis is about the best definition of useful weight. If the driver is comfortable, he will reach a greater percentage of the car's capabilities. The better handling balance, just like weight distribution and moment of inertia, will result in a faster lap time and can overcome a moderate weight disadvantage.

[Flieger]

Originally Posted by rfloz

You could, at a not insignificant cost, build a sub 2000# street legal 911. With moderate torsion bars and sways and 50-60 series tires, it would handle and ride reasonably well. Of course, it would have no HVAC and conversation would have to wait for rest stops. After you took your earplugs out. Works for me (except that cost part).

That pretty much describes my car although I currently have no side windows or windscreen wipers. The car is not sub-2000 pounds but then again, I have a roll cage- which is good for rigidity so I am willing to put up with the mass. The Engineer in me would rather have it fully welded into the suspension pickup points, and seam-weld the chassis.

[winders]

Originally Posted by Flieger

Weight does not have to be equal. If the track is really tight and point and shoot is the fastest way round, then you should make the car oversteer even if it means carrying a small weight penalty for rigidity. Just carry a gallon less fuel. I think weight in the chassis is about the best definition of useful weight. If the driver is comfortable, he will reach a greater percentage of the car's capabilities. The better handling balance, just like weight distribution and moment of inertia, will result in a faster lap time and can overcome a moderate weight disadvantage.

But the C2 is not at a moderate weight disadvantage. Nor is the rigidity difference great enough in practice to make a significant enough difference to overcome the weight penalty.

The tighter the track, the more the extra weight hurts.......

Scott

[James Brown]

Randy, where are these files you talk about?

[RWebb]

um.. they're gone - I guess he got tired of hosting

one is a MS Word file with a table & footnotes - the table lays out some light wt. cars by P AG - 911R, RS, etc. & what they did to get there; also include Jim Calzia's car (in it's original purple form).

it has a list of magazine articles & etc. and some info on other noteworthy sports purpose builds (hot rod outlaw modded 911s)

the other file is my MS Excel sheet of the accurate wt. of various components, stock & otherwise, includes the table that Jim used to have posted or still does - it is in different sheets, so not sure if it can be posted in Google docs

anybody that wants to tell me an EASY & QUICK way to stick them up on comcast.net, fire away...