Z-man

Well, one of the biggest reasons not to use the tranny to slow down is the simple fact that brake pads are cheaper and easier to replace than a transmission is. If you're overcooking the brakes, then your brake technique isn't right.

Back in the early days of racing, drivers would downshift to slow the car down - but that was because they were lucky if their brakes lasted through the first two turns! Braking technology has advanced so far since then, that it is no longer necessary to use the transmission to slow you down. 99% of Porsches have 4-wheel disk brakes - they are more than adequate to slow the car down.

Do a quick search in the DE/Racing forum for the term "Heel - toe - downshift." That is the proper technique for getting into a lower gear on the track. If done correctly, a heel-toe downshift will have no notable effect on the decellerating attitude of the car. In a nutshell, the technique allows the driver to get into a lower gear during braking without having the motor add to any of the slowing down of the car. This is accomplished by blipping the throttle with the side of your foot while you're still on the brakes, as the driver selects a lower gear. With the rev's higher, when the clutch lets out, the car won't jerk or slow down any more than what the brakes are doing. If a passenger in a car is blindfolded and can't hear the motor, this passenger won't be able to tell when the downshift occurred with a good clean heel-toe downshift.

Using two things to slow the car down (brakes and downshifting) make it more difficult to be consistent in the braking zone. Using one system (the brakes) will allow the driver to be more consistent - and consistency is the key to driving around the track fast.

I've said it here before, but I'll say it again - Do not use a downshift to slow the car down. Despite the cool feeling of the motor revving high, and the feeling of g-forces, it is NOT the right thing to do. In the long run, it will cost the driver more, and it isn't the proper technique to slow the car down.

-Z-man.

jbrill

it's not that i dont heel toe to slow down. Its just the fact that it isnt right and somethign is vibrating in the csr. Im not talking about technique here, its the simple fact that something is vibration badly in the car and i want to fix it.

hpservertech

back to the question at hand....

with the car cooled down and the ebake set, can you get behind the car and shake your muffler or pipes? Might have to lift the back end and start shaking possible causes such as the exhaust or sway bar.

jbrill

yea tried shaking it it wiggles like it should, i only get the vibration when downshifting to 2nd ...probably because the mottor, TT and trans all move when it torques up from the downshift...
Since this is the case it doesnt do anythign bad when wiggled at a stop

Dmitry S.

I had the same problem when I installed a Centerforce clutch in my old S2.

Check and make sure that all your mounts are in good shape. Mine were all fine. To echo everybody else, it is most likely not a problem with the car, just something that you have to keep in mind when driving.

Catfood

I dont ever rev match and i always slow the car with the tranny, of course I am on my third transmission!!!

jbrill

it is for sure a problem with the car because after it installed the new exhaust it did this, never before

tifosiman

Sounds like you better take it to a mechanic then if you don't like our e-diagnosis.

Report back with your findings to close the loop.

Andial951

I think you are right about this. I recently posted a new thread on this same issue and then I realized after driving the car the other day that the shudder had stopped. So I tried to think about what was done to the car recently and I remembered that last time I had it in the shop the mechanic was complaining that my exhaust was not secured very well and said he had tightened everything up. So I think that was it.

Jay W

By saying the exhaust is swinging around I was making the point that the exhaust is moving more than it probably should, shaking the car with it. I did get under there and weld back up a broken hanger and until it re-broke because I am a crappy welder and I was welding rusty metal 1 inch from my face mask, the vibration was reduced significantly.

jbrill

where abouts was yours broken ?

Jay W

Its the exhaust hanger right at the connection between the catalytic converter pipe and the rear muffler section. I am going to refabricate a mount this spring so my entire exhaust doesnt pull down. You may also want to check the mount at the front of the catalytic converter, I found mine to be loose there as well.

V2Rocket

You know it's pretty easy to downshift to slow the car if you just let out the clutch gently. Don't drop it like you seem to be doing, but just slowly lift your foot up and the wheels will spin up the engine. The compression of the engine (foot off throttle, no fuel being used) will be what is slowing the car down.

As for the exhaust, make sure everything that is boltable is tight, and make sure that the cat heat shield (if there is one on the S2) isnt banging the cat. If it's not either of those, check the rubber "donuts" that hang the pipes from the torque tube. Age causes them to harden and bounce around, which is probably the cause of your vibration. It certainly is on my car :P

Z-man

Cue Apocolypse Now flick:
I love the smell of a burning clutch plate in the morning...


-Z

Mongo

Have you checked your transmission mount? Could be a good start. Loose or worn transmission mount can also cause this. Although I haven't really heard of one being an issue on a 944 lately, SOMETIMES it can happen.