Thinking of the weight and balance thing for a street car.

I still think it is best to reduce weight until the cost per pound or one's vision of comfort starts reaching a point of diminishing returns.

However, if after most of the weight has been removed, if one can move some things to achieve closer to a 50/50 side to side distribution it might be worth looking at.

I would not go so far as to put ballast back in the car to do this.

The gain from doing this is better braking at the limit.

It is not much fun having the right front tire brake loose at the limit or when cold. This might also be useful in the twisties.

If this can not be achieved one might consider playing with the corner balance toward a more equal front tire weights. If the variance is not to significant.

Remember, weight jacking one side to achieve front wheel balance may make for a bit different handling side to side.

In most cases the rear braking is set to a lower threashold than the front on a 911 so the rear tires do not seem to lock as often inless braking into a turn. If the car has a LSD this also reduces rear lock up potental.

Not sure if there is much of a way to do this. Porsche already put the oil tank on the right side. One might move the battery as far to the right as possible. Might be able to offset the driver seat if one is going with a narrow shell style seat. If keeping tools, jack, and or spare, move them as far right as possable. Of course the driver could look at losing weight.

Worrying about front to rear distribution is probably not worth the effort on a street car except for a few that just feel better knowing they have moved there motor forward an inch or so or relocated the oil tank to the front.

I would still just tune the suspension for the weight of the car and for where the front to rear weight distribution on ends up with.

Just a thought.

911 - Weight + balance + handling = 914 Do the math.

Back in the day when I thought I could drive autocross well, I looked into how to make my car faster(fastest?) It went something like power, weight, tires, weight, suspension, weight, mo power, chassis stiffness...oops, mo weight ,weight, weight, weight, wait! 1725lbs should be good.:confused:

I finally got someone good to drive the thing....problem over.

Right! A well set up 914 will run circles around a 911 in the handling department. Too bad they discontinued that in '76. It would have been fun to watch that morph into the 918 spyder over the years.

Here is a great example :-)

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I agree with 911st that I would try to get better weight distribution if I can move things around easily, but would not ballast the car to achieve that (unless for a class weight regulation).

I believe the story was that the 914 above had qualified near the front but got moved to the back for some infringment or maybe he missed qualifying after being fast in practive or something.

I know it rained during qualifying so the start order was skewed a bit. Nice to see what a well set up 914-6 can do to the well set up 911s though. It makes we want to finish my 914-6 project.

Yeah, but what would a well set-up 944 do! :eek:

Well, there were several of those in the race as well :D You aren't one of the holier-than-thou 911 folks are you? As an owner of both a 911 and 914-6 I definitely appreciate the capabilities that a 914 brings to the table and it is one of the best handling platforms Porsche ever produced.

Not as good... Yes, balance is nice, but still too much weight in front and doesn't have the same polar moment. Mid engine will always be the best design and the 914 hit the magic numbers in regards to balance, wheel base, track, and CG. I'm surprised more people don't "get it".

one of the best posts yet on this thread

Like you BulletBob I've owned both the 911 & 914. For several years after committing to the 914 there was something missing....the feeling that the car was a "piece" as the 911 gives.
The car was fairly quick but not confidence inspiring ...... quirky.

Then I added down tubes from the cage to the suspension towers......AH HA!
There it is....the front & back are connected......all the TM&E I put into the suspension actually gives a payback by doing it's designed work rather than being dampened out/distorted by chassis flex. It now did the same thing every time.
Sure, it still does a vicious snap spin when you get it wrong....but that is a small price to pay.

Since the original question was about street cars, a couple more thoughts/answers about my car:

-Most of the original undercoating remains, and I resprayed the areas where undercoating was removed. I was absolutely flabbergasted when I started dismantling the car that I could find no rust, and no sign of rust repair. This car has obviously been pampered. I purchased it from an insurance auction after it suffered a minor engine fire. Perfect candidate to yank out the whimpy 2.4 the factory installed.

-Why the stock steel rear bodywork? It's what I had. Whatever parts I had on hand got screwed together. I have an "S" style front bumper in fiberglass that I have yet to prep, paint and install. While it will look better than the original with the 73.5-only rubber blocks, I do like the protection they offer over plastic for minor parking lot bumps..

-I used 23/31 torsion bars with autocrossing in mind, but would not want them any softer, even on the street. I love the quick turn-in and responsiveness. The roads near me are not in bad condition. If I drove the car in pot-hole land, I may think differently.

-However-

-The car is NOT a daily driver. It has no radio, no A/C, no cup holders. I really like the race seats, but would switch to a little wider sport seat for daily use. I've got a pair of Sparcos sitting in storage, but will keep the OMP seats currently in the car to insure adequate headroom when wearing a helmet.

-Finally, the 3.2. While I went with that because "It's what I had", I like the idea that the car has gobs more power and torque, yet has the same reliability as any stock 1984-89 Carrera. The Motronic box is under the driver's seat, just like any other car powered by a 3.2. Just put gas in it and go. Starts every time. At some point I may want a Steve Wong chip for it, but I'm very pleased with it just as is. A stock 3.2 pushing a 2200 pound car through a 7:31 ring & pinion is a hard combination to beat.

For a daily driver, a few more creature comforts may be nice for long drives, and an 8:31 tranny would offer better mileage and less rpm noise at freeway speeds. But I'm keeping mine the way it is. Couldn't be happier.

Should I bring up the F word?......yes, I will go there...Ferrari. The view that mid engined is the best in handling isn't always supported in GT2 racing is it? Porsche has beat Ferrari many many times.

On a purely theoretical level, it is true that mid engine is the best, but racing has so many variables that the advantage of mid engine can be overcome. Handling involves 3 basic things: Stopping, accelerating, and turning. Those 3 basics things are actually very complex subjects of course and this doesn't even include the driver or race strategies.

The thing a 914 has over a 911 is less weight, which is key. So, it's not so much that the 914 is mid engined as it is that it's much lighter, right?

Back to the OP, a light early 911, say 2000 lbs with a 3.6 making 325 HP and a 6 spd G50 with close gears....that would be very quick. Weight to power of 6.15. That's pretty close to super car stats...

Did anyone tell teh other drivers it was a race? That is AWESOME!!!!!

Really? There was a well setup 914 that raced in the PRC GTL class in 2010 that was well setup and well driven. It was comparable to the fastest 911 (964) in the class.

The class has weight with driver limit of 2350 lbs. The 964 was not running any ballast and I believe weighed more than the class limit. I would guess the 914 was running ballast and weighed in at the class limit.

The PRC GTL class limits engine size to 3.6L or less. Engine management and EFI are free. The intake manifold must be from a 1984 – 1995 911, and must be stock from the exit of the throttle body to the intake of the cylinder head. Headers are limited to a max O.D. of 1 5/8". Other than requiring MacPherson struts at the front and Factory trailing arms at the rear, the suspension is free. The class has spec tires as well.

If the 914 were a vastly superior handling car, this class would show it. It didn't work out that way.

Scott

Even under these circumstance there is no way to know if this is an apples to apples comparison, unless you have very intimate knowledge of both cars. For all anybody knows one could be cheating, or one not built to the limit; or somebody have a bad day and/or somebody having a good day. I've raced my targa for many years, always at the front of the pack, and won many races, and my car is not exactly built to the limit. In fact, because I have always has a lessor budget than most, I have has a lessor car than most. Does that mean a targa is a better race car than a coupe because I can beat better built coupes?

Bottom line: There is a reason all the fastest race cars in the world are mid-engine.

My original post suggesting the 914 was because I was thinking that if the OP really wanted to get the balance right he should make his car mid-engine (its been done). Then I thought the 914 is basically just that: a mid engine 911, using many of the same parts and specs as a 911. So why not just start out with a 914?

Here is a question for JP Stein... How many 911s of any year or model beat you in autocrossing?

FYI: I have in fact taken FTD in a autocross in a stock 1.7l 914 on stock size 15 yr old street tires. There were many 911s in attendance.

So, lets get back to Al's questions for a STREET car. Race car debates will last forever. Al, are you set on a 911 or will a 914 /6 do?

You will never get an apples apple comparison when comparing and apple to an orange. But a spec class with spec weight, tire, and engine limits is as close as you are going to get when comparing a 911 type to a 914.

This is a established race class and each car is well developed and the drivers are of similar skill. A 964 with a G50 is certainly not the ideal 911-based car for the class. You can get the weight to the class limit but it is real close so there is minimal ballast to adjust weight distribution and cg. The advantage goes to the 914 here. It clearly can be made much lighter than the class weight limit so it is likely that a lot of ballast is run and put where it is most advantageous to weight distribution and cg. The 964 is not a cheater car. There aren't many rules and both cars have similar power.

Neither car is developed to the nth degree.

My performance observations are based on a year long series run on 4 different tracks.

Just because the 914 is mid-engined does not mean it will run circles around a 911-based car. Clearly the optimum choice is a mid-engine design. But there is a lot more to handling than engine location.

Scott

You just said the word "race car". However, we are not talking about race cars, we are talking about production cars. Except in extreme racing, the advantage of mid engine can be overcome by performing better in the thousands of other variables or keys to winning races. This has been proven by Porsche's 911 winning against the Ferrari F360/430s for several years now.

I like the 914 suggestion, though.

Agreed.

I also agree, BUT the 914 has a lower CG, better weight distribution, and lower polar moment of inertia, so as a platform it has more potential. With the weight in the rear the 911 will out accelerate and out brake a 914 and it has better aero characteristics so it will most likely have a higher top speed. So my guess is the 911 will have more speed on the straights with later braking but the 914 will carry more speed through the corners.

That's because Ferrari's suck! Everybody knows that.

Actually, I think the 914 has a lower drag than the 911.

. Better weight distribution and lower CG means it should also stop better.

When you slam on the brakes most of the load is transferred to the front tires. In a car with a 50/50 weight distribution you might end up with 70% of the braking done by the front tires and 30% by the rear tires. Since the 911's weight is biased to the rear initially, once the load is transferred you might have 60% braking by the front tires and 40% by the rear tires. With the tires loaded more evenly during braking there will be more stopping power. It all depends on the CG height and it would be interesting to crunch some numbers and see the actual results.

It is hard to argue against the advantages of a mid v rear motored car.

However, in the case of Porsche there has been a lot more development done by the factory and privateers on the 911. This gives it a big advantage over anyone wanting to build a race car.

If you are trying to build a class leading 914 you are a bit more on your own and will probably end up adapting a 911 drive train to do it.

Both cars make a great platform.

For a street rod it probably comes down more to personal taste and desire for comfort.

It would probably cost more to build a 3.6 914 with power steering, working AC, and ABS than to just source a good used C2. However, it would be fun.

Yes it would be interesting and the data is probably already out there. Just compare original road tests from the '69 911 T to the ;69 914/6. Same tires, brakes, motor, so it should be a good test.

The axis for polar moment of inertia goes through the mass center, so on a 911 the mass center is further back than on a 914. This means that the 911 wants to rotate about the rear wheel more than a 914, which would want to rotate around the middle.

The way I see it, this means that the 911 should go deep into a turn, trail braking, slow down and take a late turn-in, where it can use the quicker angular acceleration of the front wheels about the rear to point the front end towards the apex and then "shoot" towards it, using the rear weight to gain traction, stop the angular acceleration, and get down the track fast in a straight line.

The 914, conversely, should carry speed on a wider arc through the turn, with the wider arc shifting the pivot point out and forward from the rear inside tire.

This seems to be backed up by the driving styles adopted by 911 and 914 drivers.

I would conjecture that weight, power, and tires being equal, a 911 might have an advantage on autocross courses where there are long-ish straights with tight hairpins, and the 914 would be better at Willow Springs, for example.

The big thing is that having weight within the wheelbase means there is no "leverage" of weight off of the front wheels. The weight contributes to traction on both front and rear ends.

Actually, 911s don't trail brake well. They tend to want to swap ends. The way to do is is set the car up with understeer, turn in early and push the car through the corner. This does not work for auto-x where you need some oversteer so you can rotate the car.

Well, we have to go back a few years, but there is this guy named Doug Skinner.SmileWavy Also a few years back, I guy from NoCal. in a GT2.

Here in the last couple years, none. There is a fella named Dave Newman back in PA that has the quickest AX 911 that I know of....it would be a good tussle.

There are a few guys in Miatas that do the deed on us, heavier & less power.:D
Hopefully that will end with the new powertrain.

Only when its dry...

LOL, I'm a Porsche man, but those crappy Ferrari engines make a beautiful siren sound. If anyone decides to junk their POS Ferrari, please let me know. i will take it off your hands for free. :D

Interesting thread about weight distribution, and power. Even though my 73 RS spec is well set up for a streeter - oversized T-bars, lowered, bump steer, turbo tie rods, Quaife, etc, I have always been intregued how much better it might be in a 914. As a result, I am building a reasonably priced car, 71 914 with a newly rebuilt massaged 3.0 with Webers and sport exhaust. I find the 911 fairly refined, where as the 914 feels rather crude. The 914 and 911 should be approximately the same weight with almost exactly the same rubber - except the 914 has a complete Elephant Street-Track suspension. The teener also gets the nod with an additional 15 hp - with more low down torque. It will be very interesting to do the compare when it is ready at the end of Jan. From all I have researched for the past year, the 914 should be winner with that sweet flat six song even closer, but we shall see.

Al, make it as light as possible ( of course ;) ) , get to a comfortable target weight. THEN start messing around with suspension.

ps. you can always adjust suspension for weight distribution so don't be afraid to ditch weight in the front, where it's easy.

pps. just picked up a set of 951 spare-type rims for the '67 - another 20 lbs gone :D . now I have 1900 lbs in my sights.

For clarity, one cannot actually move weight around with the suspension: all one can do is to ensure equal weights both laterally and diagonally with a proper cornerweighting.

Changing the weight distribution requires moving, relocating, or lightening various components of the car.

Want to make a big difference in a 911? Move the engine & transmission forward by one to two inches. Not a simple job, but it can really help compensate for an overly light front end (which really aggravates understeer as well as cross-wind behavior).

I probably should have said you can adjust/set-up your supension to compensate as much as is possible for weight distribution.

Steve,

This can be hard to do without causing problems with axle life. It's bad enough at typical street ride heights. Lower the car for racing and it gets really bad.

What do you use for axles on your race cars? Stock? Aftermarket?

Scott

Rick,
Good luck with the 914. Post some progress pix.

Don,
My next project will definitely be lighter than the one I just completed (71E), but I still expect that I will make weight compromises to filter out road/tire noise. I'm really not after the lightest street rod, although that is a good thing in many ways........I'm focusing in on power and balance, with overall weight reduction as a side benefit of achieving a great handling, balanced 911. I'm not sure that I expressed that correctly, but the absolutely lightest weight is not my highest priority, but hopefully will be the result of the weight distribution/balance/handling focus. Also, my goal is to improve the power/weight ratio considerably as well.

Steve,
Moving the engine forward sounds like big bang for the buck to me, but may be a bit much for my street rod. However, I will crawl under my 71 today and stare at the mounts for a while. hmmmmm.

PS: Although I am getting sidetracked by absolutely great SC's and 964's....I am primarily focused on a long wheelbase longhood.

Happy New Year,

Al