BTW, where is the fuel cell located in the stock TT? As the amount of gas decreases, does the balance of the car stay relatively even? Or does it create a front/rear bias?

 

That's exactly right, thanks for the catch!

 

Chris - I think it is closer to the front...I remember my dad telling me that on his 993 Turbo S the nose is much more stable at high speeds and the car handles better with more fuel in it (the Turbo S had a bigger tank than the regular 993TT)

 

Ken

I had the car on four pad racing scales accurate to 0.025% (according to the manufacturer). The scales belong to my gear head neighbor who is also an engineer. We've weighed a lot of cars and we normally look at as many configurations as we can when checking the CG. We actually tried the rear seats up and down several times to make sure the readings were really different, and they were.

We checked a Boxster with the top up versus the top down, and it's CG also moved between the two positions.

 

There's no question in my mind that the car has a higher rear weight bias with less fuel in the tank.

I also think that unless you're a very "tuned in" driver, working near the limits of the car, you won't tell that much difference in balance full tank versus low tank

 

Thanks guys...this gives me some ideas for the corner balancing job tomorrow. I plan on going in with 1/2 tank and my weight.

 

Dock,
Is your car stock? Based upon your corrected weight distribution, the CG of the car is located at the reverse percentages from the rear and front wheels respectively. In other words, the CG is located .385L from the rear wheels and .615L from the front wheels where L is the wheelbase. Does anyone know the wheelbase?
I am trying to figure out where the CG is with respect to the driver's butt.

 

My Turbo is stock (except I did order it with the sunroof deleted) . I don't have the data on my car with me at the moment, but I do remember that on the Boxster the CG did not change with the addition of a driver; the seats are right on the CG in that car. I think that was the same result with the Turbo, although I'd have to check to make sure.

 

Ken

About your Turbo's power (in your signature)...

Did you mean 603 pound-feet of torque? Foot-pound is a unit of energy/work, not torque.

 

Isnt torque really a fomr of work though?? I thought it was the rotational force on the crank....Force x distance = work.....besides if ft and pound are ultiplied in that unit the order should not matter since multiplication is a distributive operation (I might be wrong on all this as it is late and I grew up with metric units not English so torque would be in N.m)

 

Torque and Moment are the same things. They both represent the vector multiplication of a force times its perpendicular distance to the point under consideration. It does not matter whether you say pound feet or foot pounds. They are synonymous. I have a thing about saying pound feet. It has to do with the conventions of different areas of study. In the wrenching community, when using a torque wrench, it is commonly referred to as foot pounds. In the engineering community, it is commonly referred to as pound feet. Even though I am an engineer, I grew up wrenching on bikes and cars and always knew it as foot pounds.

When one describes torque for an automobile, in this case, 603 foot pounds (or pound feet), I like to think of it as a 603 pound force applied in a tangential direction 1 foot away from the crankshaft center. It gives a certain gritty realism to the numbers. Of course you could also think of it as a 1206 pound force applied six inches from the crankshaft center or 301.5 pound force applied 2 feet from the crankshaft center.

Work is defined as force times displacement. It is a little different. It is too late to go into that.

 

Thanx KPV - You are right - I had the right idea but just remebered that the word I was looking for is moment since Work = Force x Distance moved in direction of force...

 

Torque is the tendency of a force to cause a rotation; it is the product of the force (pounds) and the distance (feet) from the center of rotation to the point where the force is applied; it's pounds of force times feet of distance. One pound foot is equal to approximately 1.355 818 newton meter (N·m). Algebraically, torque has the same units as work or energy, but it is a different physical concept. Scientists and engineers traditionally measure torque in pound feet (or newton meters) and work or energy in foot pounds (or joules).