Racing and Drive by wire

Trouble

Veteran Member
Joined
Feb 20, 2000
Location
Deep in a Holler
TDI
Golf
I've got two gripes about my 2000 Golf when I'm running it in a competition event.

1: The annoying lack of LFB. Hit the brake and you have to wait for the power to come back on.

So for the RallyX, I used rubber bands around the brake light switch to leave it in the normally closed position. For those who haven't looked under the dash, VW installed a normally closed sprung switch on your brake pedal. Depress the brake, the plunger extends, and your lights come on. And it disables full engine power. Try it while sitting at a light out of gear, and it will usually limit your max rpm to ~1500.

So anybody got a fix for this other than disabling the switch? I accidently drove 15 miles before realizing I hadn't hooked back up the brake lights.

2: ABS. More precisely the lack of a rear proportioning valve. Ask this question on the forum: How do you disable the ABS? Pull the fuse..
Doesn't quite give the proper response. Pulling the fuse disables the dynamic rear proportioning circuits. VW did away with the style mechanical proportioning valve that was on older VW's. Instead there is an inherent high rear brake bias. When you push the brakes, if the ABS fuse is disconnected, the rear will lock WAY before the front.

In normal operation the ABS system is used to prevent the rear wheels from locking while braking. While braking the rear tires are at threshhold braking long before the front tires. This does not allow maximum braking without the ABS fully functioning.

I've been searching for a rear brake inline pressure reducer stateside but haven't had any luck.

Any thoughts on either topic?

-Justin Wimpey
 

Ted_Grozier

Veteran Member
Joined
Aug 25, 2000
Location
Hanover, New Hampshire USA
TDI
2002 Golf GL 4-dr
For LFB I don't think anyone has a solid solution yet but you could wire a switch with a resistor to ground. A lighted switch so you wouldn't inadvertantly leave it on.

As for the brakes, what's wrong with the stock ABS? Why is that not good for competition?

Regards,

Ted
 

Jon Hamilton

Veteran Member
Joined
Nov 18, 2001
Location
Marysville, OH
Trouble,

A good ABS fix is to disconnect one of the front sensors, you will get a ABS light. This disables the ABS but does not disable the Dynamic rear prop. This worked well at our first rally. We are still working on the LFB problem. I found a post on here that in theory will work(wiring fix) I will see if I can find you the link. We have not had a chance to test it as we are busy working on the suspension and brakes right now...stay tuned. Our next event is March 15-17 in Chat. TN. The competition is getting stiffer as we now have 2 Toyota Celica GTS to beat along with the Focus ZX3, Neon ACR, NB, and a rumored Toyota Matrix! I think we will need to upgrade to the 11mm pump and big injectors after this race...one thing at a time!

Jon Hamilton
RallyVW Racing
www.rallyvw.com
#72 2000 Golf TDI
 

RedT

Veteran Member
Joined
Nov 2, 2001
Location
Portugal
Hi guys!

I just got a magazine with a test drive of a Golf TDI 150 running in the national championship. The cars that run in it are N+ level. For the diesels you can change very little to the engine apart from the ECU software (this car pulls only 200hp and 400Nm). The curious is that thay have the same problems you talked about: high rear braking bias and they cannot brake with the left foot. About the brakes, the guys who prepared the car said that the problems is probably due to the lack off EBV when the ABS is disabled. And they have another problem: sometimes the brake pedal goes down to the floor under braking.
Even with all this problems and with suspension set-up far from developed this car has won races against Honda Integra-R and BMW 320 (gas).
 

Trouble

Veteran Member
Joined
Feb 20, 2000
Location
Deep in a Holler
TDI
Golf
I'm going to go do a little practicing tonight.. (sometimes it just doesn't get any better than living next to the GWNF)

So far I've tried the disabling the brakelight switch, but not in combination with pulling the ABS fuse. I'm going to try Jon's disconnect the front sensor trick too.
I'll hopefully report things tommorrow.. (or be in the woods near sugar grove, WV)

Ted,
ABS is made to work well under only one set of conditions:
In a straight line, on a surface with resonable traction (i.e. dry paved road). Any time you throw most ABS systems (including VW's) a situation where the wheels are traveling a widely differing speeds such as:
sharp turns
sliding
spinning the front wheels
etc.
It (the abs computer) doesn't know how to properly brake each individual wheel, to maintain the drivers desired course of action. You can't jab the brakes and initiate a predictable slide with ABS.

Just for grins, pull the ABS fuse and drive around a gravel lot at less than 15mph. Take a slight turn and jab the brakes. Notice how the car will nicely rotate around. Now put the fuse, and repeat.

With the older VW's you could adjust the rear proportioning valve to get this behavior and still be able to maintain excellent threshhold braking on pavement in a straight line.

Sorry for the long reply.
-Justin Wimpey
 

Trouble

Veteran Member
Joined
Feb 20, 2000
Location
Deep in a Holler
TDI
Golf
Scouting the gravel roads were fun. We made about a 100 mile loop out of a few forest service roads. North out of Harrisonburg, West on 259, west on rt. 820, west on rt. 826. South on unknown WV road to Fort Seybert, WV. South east on FS 151. East on Rt. 33 back to Harrisonburg.

Did the whole loop in just over 2 hours. Not bad for the dark.

Couple of notes:
If your going to try to disconnect the front ABS sender units, do so at home, with the wheel(s) off. In the dark in the middle of West By God, on a wet and muddy road is not the most fun place to try and pull apart stubborn connectors.

The TDI with 205/60R15 snow tires and Bilstien HD shocks has a decent amount of ground clearance. Surprised to NOT bottom on a few rock strewn creek crossings (taken very slowly).

The ABS sender disconnect works nicely. No rear end stepping out in a massive way. Things are nicely under control while braking hard. Stopping distances on dirt are greatly decreased (possibly less than half).

If your ever in the neighborhood and WANT to ride on some smooth(ish) gravel roads, let me know..

-JW
 
Top