JimB

Did you hear it once or on every lap? In a straight line or at turn in? When you applied the brakes or later? Did the car handle properly? For sure from the front? Was someone riding in your trunk?

Like Loren, my first guess would be sway bar but there's a lot of stuff under stress going into a corner under heavy braking.

Thanks Izzy,

I hope it's the fluid. Being an old farm boy from North Dakota I'd love to have a little John Deere oil in my car.

Jim

Hey guys,

I did a search but didn't get far. Sorry if this has been covered.

Last night I went to put the top up on my 2002 996 cab and nothing happened. When I hit the button the cab top warning light on the dash would flicker but that's it. No noise, no movement. I did all the normal stuff like turning the key on and off, engaging and disengaging the hand brake, opening and closing the engine cover, etc.

Any ideas?

Jim

As I mentioned on Rennlist, I'd bet my grandmother that it's the cam timing switching. Try this. First accelerate slowly and see if it's worse. If it studders and gains rpms slowly and then catches. Second see if it varies or if it always happens at the same rpm.

As my pal Billy struggles to share his misery with us I thought I would revisit the portion of this thread from last year that dealt with how many 996 are being raced/tracked. As of a couple hours ago there were 16 stock C class cars entered in the inaugural Daytona PCA club race. 9 of them are 996s. A new record. :cheers:

I'm going to go out on a limb and pick a 996 to win. I've actually got one in mind...

Jim

What year is your car? If you have a 3.6L I would bet its a problem with the variable valve lift. I had the exact symptoms when we swaped a 3.6L into a 99 and the valves were not switching properly.

Ed,

You haven't been around for awhile. What have you and your car been up to? I thought you were going to club race it.

JIm

I loved watching the Porsches kick butt at MO but I think the death of P1 might be a little premature. First, Audi didn't have the R10 at the race. They are off preparing for Le Manns. Second, Mid-Ohio is a track that doesn't reward HP. Just look at the results of the PCA club race a couple weeks ago. The stock class enduro was won by a B car but it was followed closely by an E car that started in 50th. Next was an F car and then a C. You won't see results like that at many tracks.

I wish the Porsches were going to Le Manns. Maybe next year.

Jim

This is a very incomplete article. It covers about 5% of what people should know about what causes understeer and oversteer.

FWIW, I prefer a racecar with a little "lift-off" oversteer for rotating the car in the first half of the corner and neutral to a little understeer under power for getting out of the corner quickly without burning up your tires.

You should be safe. I've heard that Hoosiers will be close and slicks will be a problem. I think this is only for a short time right? The club race is coming up in a month or so. It would be a disaster if e all had to switch tires.

Jim

Your car feels like it's floating because it is. The lift created by air passing under and over your car is causing lift. Remember studying how a wing works? The way to fix it is to reduce the amount of air passing under the car. You can do this by lowering the car or adding a splitter of some type or both.

Either way you are right that you should not be driving that fast on the street. There are plenty of opportunities to track your car where the only person you are likely to kill is yourself.

Jim

A couple of years ago I found out the answer to your question first hand. Before a race two of us added oil to my 3.6L 996. About 3 laps into a 90 minute enduro I turned into a 100 mph mosquito fogger. Oddly it happened within 100 feet of where I had totaled my car in the same race a year earlier. Assuming I had blown the engine I pulled to the side and watched cars fly through the kink at Road America from the wall for the remaining 1 hour and 20 minutes of the race. When we got the car home we fired it up, cleared out the oil and it's been winning races ever since.

Jim

Thanks for the info guys. Phil I know what you are saying but it's certainly not beyond Porsche to add a brace or a weld here or there to stiffen things up. I have an 02 cab so I'll do a little hands on research one of these days and post the results.

Thanks,

Jim

That looks pretty hard to duplicate. Got anything easier? Just kidding. Thanks for the info. I'll look it over tonight.

Jim

Hi guys,

Does anyone know what exactly was done to stiffen the 996 chassis throughout it's life? I race my 1999 tub as a 2004 so any changes that were made during that time I could apply. Actually, I'm required to apply. I know thay made them stiffer but I don't know how they did it.

Thanks,

Jim

Also check your rear tie rod. These are a weak point in the suspension and a bad one will cause your back end to move around like you described although it usually happens when you take your foot off the gas. Worth checking though.

Just what I needed. Thanks. Jim

I'm looking for old orderguides. Specifically 2004 but I might need others as well. I'm sure the local dealer has them but it would be much easier if they were on-line somewhere. Any ideas?

Jim

Thanks!

Thanks Loren,

One of the things I was looking for was the slight drop in both hp and torque when my cam timing shifts. The curves on the one you sent me were so smooth I suspect it might be a marketing chart that mimics a dyno chart rather than the real thing. Who knows.

Thanks again.

Jim

I'm sure I knew the answer to this at some point but I don't remember. Did gear ratios change during the life of the 996? Does anyone have the ratio data?

Thanks,

Jim

I'm looking for torque and HP curves for a stock X51 or even a normal 3.6. I don't care about differences in dynos because I'm really just interested in the relationship of torque the hp and what happens when the cams shift. Has anyone done a dyno run that would be willing to share?

Loren, Do have access to factory curves by any chance?

Thanks,

Jim

Bill,

A couple of observations. Take them for what they're worth.

Great braking means a lot of systems (tires, brakes, pads, suspension, your foot) have to work well together. Your car isn't quite optimal. Assuming you have 205/255x17 tires, they are considerably smaller than you would like them to be. The stock suspension is pretty compliant meaning your nose is dipping and your rear is lifting much more than you would like under heavy braking. Your brakes are heavily biased to the front and, it sounds like you are really jumping on the brakes.

Here are a few ideas (some of which others have already suggested).

1) 18 inch wheels with 225, 235 or 245 tires will help. Both because of the wider footprint and the stiffer sidewall.

2) a stiffer suspension (both compression and rebound) will help.

3) using a higher friction pad in back than in front will really help with the forward bias. I use Pagid Orange on front and Black on back.

4) when braking, think in terms of slowing as fast as you can within the limits of the car. Just jumping on the brakes distorts the tires and upsets the suspension. Think about first setting the suspension and shifting the weight and then adding heavy braking. It takes a little practice but will work much better.

Hope this helps,

Jim

The blue tool I borrowed did not work. I'll post the p/n later just in case there is a different one. Looking at the B&M, it would have to be a very different tool to work.

I'm picking up a blue tool this afternoon. They come in the factory SS kits so I'm just going to borrow one for a couple of days. I'll let you know if it works on a B&M.

Jim