So if the 40th anniversary is the only RWD Carrera that comes with LSD, then what do I have in my 2003 C2? I've looked everywhere and can't find the answer to this.

I don't know the technical terms but does that mean only one of the rear wheels has power? I find this hard to believe. My previous fun car a Honda S2000 had an LSD in it. So can anyone shed a little light on this for me?

 

It depends on whether you have PSM or not. If you don't then you have nothing, no LSD, and not active braking, etc, as I think PSM was still an option on MY03 cars.

Basically, LSD (at least Porsche's) is a clutch setup that will transfer power to the wheel with more traction (as opposed to the wheel with least traction, the way an open diff works). It is a mechanical solution, that works thru the diff.

PSM electronically monitors wheel slippage, etc, and adjusts either braking (via ABS) or accleration (via Egas). Totally different in that there is not transfer of power directly, but rather slows down the wheel the is slipping and adjusts the power at the same time.

Does that sorta kinda answer the question?

 

I have PSM, but from my understanding of your post, the mechanicals do not change with or without PSM.

I know what an LSD does and how it works, but I want to know how my Carrera works without one.

Does only one wheel spin/receive power? So the other three wheels are just rolling?

Do both rear wheels receive power? If so how does this work. If they split the power that would imply LSD and if they didn't split the power that would imply a solid axel which I don't think I have either.

If one was to take off agressively breaking traction in the rear would it leave two tire marks or one?

 

OK...so yes only one wheel will receive power, but will apply brake or gas to each wheel individually to keep the car on the intended path.
There are somethink like 12 sensors:
ABS sensors (which measure the speed of each wheel),
engine speed (RPM),
throttle position (via E-Gas),
gear selection,
lateral acceleration,
yaw,
steering wheel position.
This enables the PSM to detect oversteer and understeer. Oversteer is minimized by automatically applying the brake on the outer front wheel in a bend, slowing the rotation of the car; understeer is minimized by applying the brake on the inner rear wheel, speeding the car’s rotation.
If you lift off the throttle in a low traction situation (wet, snow, etc.) and the back of the car gets loose, it will increase the engine speed (blip the throttle) to keep the car in line. Also, if traction is low, it can use engine braking to slow the car. It calculates the amount of available traction by comparing wheel speeds at all four corners of the car.

So the long and the short of it, in your C2, with PSM on it won't let you leave marks. With PSM off, you are only leaving one mark. Pretty much a normal diff set-up, but all kinds of techie geek stuff to make sure that the car goes where you point it, by controlling throttle and the brakes at each wheel.

 

Ah...that's what I was looking for...

Ok, that said(by you) and understood(by me), why doesn't the 911 being all that it is and all that is costs have an LSD as standard or even optional equipment?

Are there pros and cons? I only see the pros, and I can't see how it would add that much cost, but it would provide more traction without PSM or without braking/egas interuption.

Again I don't have much knowledge in this aspect so go easy on me. Thanks

 

Jenner, I'm not sure what you mean by only one wheel getting power. Without LSD, only one wheel will get power iff one wheel has completely lost traction and the other one has not. For example, if you lift the inner wheel off the ground on a curve. In that case, PSM will brake that wheel, adding resistance to that half of the axle, and then the open diff will continue to split power.

If both wheels have similar traction (actually resistance) then the open diff will split power between both wheels. That's the normal situation. So drop the clutch and most of the time you will get two skid marks.

LSDs come in different designs with various tradeoffs. BMW has the one of the slickest LSDs on the M3. I don't know how the Porsche LSD compares.

It should be noted that BMW includes the slick LSD AND DSC. Not sure why Porsche doesn't.

 

Ok, now I'm totally confused...

So like I thought both wheels get power?

How does the open diff work? (going to howstuffworks.com to check it out now)

 

Ah...I just read up on it....so my car has an open diff.

Thanks for your help guys!

 

jenner,
Why doesn't Porsche still used LSD, which was avail in MY99, and i think is now avail on the 40th anniv....Dunno? Its sitting on their parts shelf...it should at least be an option... I think they can sell PSM for alot more than LSD...so maybe that's why...

 

So can you get LSD and PSM?

 

On the 40th Anniversary Edition you can:
http://www.suncoastporsche.com/news/index.html

"Aggressive sport suspension settings help to enhance the 40th Anniversary 911's handling. Combined with the standard electronic Porsche Stability Management (PSM) system, an additional mechanical rear-axle differential lock provides even better traction and optimum acceleration potential."