Gilhart 54

I'm in the process of turning a street 996TT into a World Challenge GT race car.

The question I have is if I simply pull the PSM/ABS fuse from the fuse box what will the result be. Will the car go into any type of "limp mode" or will the car drive normal and just be without PSM and ABS.

I'd do it myself however the car is just getting the roll cage finished and won't be back for another week or so.

Thanks in advance for your help.

Rick Gilhart

Greg Fishman

Not sure. You do know there is another 996TT that did race in the Speed Challenge didn't you? Maybe look him up.

Who is building your car? What weight does the SCCA require you to run at?

Gilhart 54

Thanks Greg,

I've got his number but haven't got a hold of him yet.

Fabcar is building the car.

2900 w/o ABS, add 100 lbs. for ABS

Rick

Gilhart 54

More info:
I've found three different fuses pertaing to PSM.

1. In the fuse box row B 9th fuse labelled ABS/ASR/PSM

2. Row E fuse 9 labelled PSM

3. Row E fuse 10 labelled PSM

Has anyone tried this on the track yet?

Thanks,
Rick

Gilhart 54

Guys,

I know this has been an on-going topic for some time and I appreciate everyone's latest input.

I am aware of Motec but was looking for a simple solution.

I'll talk to a few of the people you suggested and get back to everyone with an answer.

Thanks again,

Rick Gilhart

Gilhart 54

Okay here's what I have.

I've pulled the three fuses mentioned above. I've taken the car for a 15-20 minute ride, pushed hard on the brakes to lock up tires(it's wet out), put the car in a couple of on the gas 180's and am able to still get full boost and rev to 6500rpm.

The question I have is, what is limp mode and when will it decide it's time for it to come on? Will it say limp mode on the display, will it throw a check engine light, or will it just slow you down to under a certain rpm?

Any help would be appreciated.

Thanks,
Rick

mpaton

Rick,

I don't know if this helps, but my 996 is sufficiently lowered and the ramp out of the Porsche dealer sufficiently steep that I have to exit at an angle. One time I did this, I was coming down the ramp at about 10MPH, saw a car coming, an dput on the brakes to slow to about 5mph. One of the front wheels was in the air and stopped, and the dashboard display went

BEEEP! PSM Inoperative, Drive to dealer
BEEEP! ABS inoperative, Drive to dealer.

Apart from that, it didn't seem to be in limp mode. I drove a block away, stopped power cycled the ignition, and found that didn't reset it.

So I had to drive back to the dealer, and by the time they told me what had probably happened, it had reset itself.


Michael

Gilhart 54

Michael,

Thanks for your input. I've been able to duplicate what your saying but have still been able to retain what I believe is full power.

Quote from my other post:

"Thanks for the input. I'll go a step further and recommend everyone keep all their systems active 100% of the time. ABS and PSM are great systems and can save your a$$ more times than not. You can still run very fast times with the PSM in the standby mode(lurking mode) and the ABS is great for late braking.

The car(my car) is going to be used 100% on the track and no where else. I've converted my braking system over to a dual master-cylinder setup with the ability to now adjust brake bias. With that being said after taking out the above mentioned fuses I'm still getting .8 bar of boost and rapid acceleration. To me, this doesn't seem like any type of limp mode. "

Thanks,
Rick

Z-man

Rick;
While I understand not wanting PSM on the track, I do not understand why you wouldn't want ABS, unless its in the rules that you cannot run with it.

IMHO, the 'safety net' of ABS far outweighs the 100lb weight disadvantage. Now I just do DE's, but there are plenty of bumpy braking zones where ABS can come in play. (Watkins Glen and Pocono come to mind)

-Z.

ColorChange

I think Rick's problem with the ABS is that it is tuned for street driving and street tires. If this is true (I think it is but have not tested it with my DAS), his braking will be significantly impaired buy the sub optimal ABS system. Since we cannot retune our ABS systems so that they work like a racing ABS systems, he is choosing to eliminate it. His approach makes sense to me.

Greg Fishman

Also a 100lbs is a significant difference at that level of competition.

Bob Rouleau

FWIW, the PSM switch turns off active stability management and traction control. When you turn it off, it stays off. Yaw control cannot be turned off by the switch. Yaw control is the part that dislikes trail braking and it will intervene especially with sticky tires. Yaw control is the reason people seem to think that PSM turns back on when you brake hard. On the latest models, it does not turn back on but yaw control is always there. CC I bet you felt it when you trail braked. It gets your attention by banging the brake pedal hard upwards - not the vibration of ABS but a hard shot to the foot. I can see why you'd want to disable PSM and Yaw Control but I'd leave ABS on unless driving on track where the braking zone is very bumpy.

Rgds,

Gilhart 54

Guys,

The purpose for me getting rid of the Stock ABS system is because:

1. It seems to be linked to the PSM and or Yaw sensors, which interfere with trail braking.

2. I believe a dual master cylinder provides greater brake tuning including bias control.

3. I can keep 100 lbs. weight penalty off by doing so. (World Challenge GT)

The weight of my car will be in the 2900 lbs.+ range and many things have changed with the car compared to a normal street car. I'll be tracking the car at VIR in a couple of weeks and will share any feedback from that event in a follow-up post.

If I choose to go back to ABS it will be the racing ABS from a Cup car.

One other thing to consider is that the RSR has a dual master cylinder with NO ABS while the Cup car has ABS.

Thanks for the input,
Rick

Greg Fishman

Rick,
What was your reason for not going with a Cup Car instead? I am sure you could make the TT competitive but not sure that it would be a more cost effective choice. Not criticizing, just asking.
Thanks

Gilhart 54

No problem Greg, I had purchased my brand new TT in '02 and was in the process of enjoying my new car when with only 500 miles on the odometer I was hit by a drunk driver. It was a clear, still lit, Weds. night at 8:30 p.m. The guy and 3 buddy's were next to me on a 35mph road when they turned into me and that's where the damage occurred, front right. The driver was twice the legal limit, it was his girlfriend's car but fortunately she had insurance...

The car sustained about 20K cosmetic damage, right fender front bumper, radiator, and front right suspension/wheel damage. Airbags deployed etc, etc.

The shop took 6 months to acquire parts, paint car and re-assemble. Parts weren't available because of supply problem.

In that 6 month time I decided to go out and buy another new TT, this time an x-50 version and planned on selling my wrecked car when it was fixed.

In sitting 6 months at their shop(reputable shop) the car collected over-spray from other cars that would not come off without swirling the paint.

Long story short, nobody wanted to buy a slightly wrecked car. I say slightly because the tub was 100% straight and only the front fender and bumper were replaced however the paint no longer looked perfect.

I deemed it race car time and here I am converting my once beloved street car into a flat out GT racer. Hey, I just realized we wouldn't be having this conversation unless I was hit by that knucklehead, I'd be racing a Cup car.

Rick