Darwantae951

Yes. Depending on the direction of travel, the force implied can be called either positive or negative acceleration.

333pg333

'Negative acceleration', now doesn't that sound like a contradiction of terms.
So in effect if I floor my car going in a straight line and am (e.g.) hard on boost 24psi in 4th gear @5000rpm and then just suddenly throw the car into neutral, am I still accelerating?

Chris White

Yes…but not the way you think!
Due to aero drag you are actually initially accelerating in the other direction.
Sorry – buts its never too early to screw with your brain via Physics….

Chris White

To borrow a term from a different area of Physics – acceleration is relative.

Mark944na86

In a Newtonian universe (i.e., ignoring relativistic effects), unless you are at rest or travelling in a straight line at constant velocity, you are accelerating. 'Deceleration' is just a convenient term for negative acceleration.

Throwing the car in neutral after hard acceleration would result in immediate deceleration as frictional forces start to slow the vehicle in the sudden absence of a forward driving force via your drivetrain.

I think the most natural way to think of it is that acceleration is due to the result of imbalance of forces; the net result of the imbalance can be calculated by F = ma. If all forces are balanced, there is no net acceration, e.g. a parachutist hitting terminal velocity when the force due to drag is equal in magnitude to the force of gravity. Before hitting terminal velocity, the forces are unbalanced, and the parachutist experiences acceleration. Once reaching terminal velocity, there is no further acceleration until the 'chute opens (or he hits the ground because he was thinking about physics rather than concentrating on what was really more important at the time.)

Chris White

Nothing is more important than Physics....its the Physics of the situation that killed him!

mikey_audiogeek

H&R RSS coilovers - pretty sure they're just Bilstein Escort without any valving changes.

Mike

mikey_audiogeek

Yeah, even I'm surprised. I've learned a few tricks over the years for taming semi-trailing arm suspension, especially on cars with a rearwards weight bias so either a) I've been wildly successful, or b) I've missed something.

b) is the default until I check everything out...

Techno Duck

I have been researching installing these without torsion bars. I talked with KW North America this morning and they advised me that going over 100lbs on the spring rate the shocks should be revalved. The guy on the phone sounded like he just rolled out of bed, so after further reading i found a thread on a PCA - Great Britain site where it was mentioned the highest spring rate you should put on the 944 Turbo / 968 V3's are aprox. 390lbs, which is right inline with what i was told this morning. (stock spring rate is 280lbs aprox). The info about the 390lb max was gotten from KW Europe (from a guy named Klause, so its gotta be true!). I was planning on going with a 500lb spring as DVC because when working out the effective wheel spring rate it is close to what is the wheel rate of the torsion bar + coil over. So if any of you guys are running these without torsion bars, what did you end up doing?

The other thing is the lower threaded spring perch on the KW's is a high density plastic. Any concerns running a 500lb spring with a plastic lower perch?

I am thinking i may just install the coil overs with torsion bars and see if i can get them dialed into my liking. The benefits of no torsion bars (easy ride height adjustment, spring rate changes..etc) are not a big deal to me.. as i do not plan on making any changes to that stuff once they are installed. My big concern is figuring out the 'preload' using torsion bars and rear coils.

KW N/A said it would be about $100 to revalve the rear coilovers with a 2 week turnaround. The other thing is swapping the springs out on the rear coils looks like a bitch.. looks like i will need to hold the shock shaft in a vise and hopefully be able to get the lower mount unthreaded. From the looks of it, its not going to be pretty.. i have a feeling a pipe wrench or big *** pair of chanel-locks will be necessary! .

Some eye candy..

Chris White

OK, either you are dealing with a technical ‘putz’ or there is something seriously wrong with the way KW is setting these up.

The shock should be valved for the total spring rate (torsion bar plus coil spring) since that is what it will be damping. If you delete the torsion bar and go with a coil spring that is the same spring rate as the old Tbar + coil spring then there should be no change to the shock…..

If KW is selling their set up with the shock valved for jus the ‘helper’ coil spring then they are way out of touch…

BTW – 390 is on the low side for an ‘average’ coil over set up. I was running 550 on my street car….390 would be OK but I would sure hate to have that as a max limit in case I wanted stiffer springs.

Changing the spring should not be hard – if they included tender springs that means the main springs are fully relaxed with the ride height adjusted out…

Techno Duck

The lower spring perch does not thread off completely as its blocked by the slightly offset lower mount.

The only way to get the coil springs off is to unthread the lower perch so the springs relax. This allows the top spring perch to slide down on the shock shaft. The upper bushing is threaded onto the shock shaft, so the shaft would have to be held in a vice while the upper bushing is unscrewed. I am betting that is torqued down fairly tight.. hence my apprehension about attempting to remove the top mount myself and likely voiding the warranty by damaging the shock shaft, even if the part i am clamping in the vice is the top inch or so covered by the upper perch / bump stop.

Mark944na86

Jon,

I wouldn't stress too much -- "dialing in" the t-bars shouldn't be that big of a deal, really. As long as your final ride height is within the 1" or so range given in the KW specs, and your perch collar is is positioned on the threads within the 1" or so range given in the KW specs, I think you'll be fine. That's how it is on my car, as I said earlier, the set-up is great!

Techno Duck

Mark, that is the plan right now. Just waiting on a few more parts to arrive on friday. ER spring plate bushings, a few more bushings from RE, the RE upper spring hats for the front struts and the Porsche locking nuts for the camber eccentric.

Chris White

So now I am intrigued – are the shocks valved for the total spring rate (Tbar + coil) or just the coil? If they are valved for the total spring rate what did they assume for a Tbar spring rate?

ehall

Dammit Man! Real questions are out of line here!