fast951

100% agree. Learning how to brake with no ABS is a must, however having ABS has many advantages. The first time you ruin a $300-400 race tire by flat spotting it, you will opt to go with ABS.

fast951

No time frame, I have all the parts but not the time. Too many projects and products to complete first.

theedge

Cant use the ABS sensors with Links (or Vipecs, since they are a Link G4) for traction control. Link G4s expect a Hall sensor signal on a digital input for the wheel speed, whereas ABS sensors are VR sensors.

In theory you could use the ABS sensors, but you would need a converter circuit to change it to a digital signal. Easier just to mount a 1GT101 sensor to sense the back of the wheel studs, which is what im planning on doing.

Van

I think you'd need supporting evidence to say the 997 GT3 Cup doesn't have ABS... I don't think that's true.

Edit: I guess I spoke too soon: http://www.porsche.com/uk/motorsport...911gt3cup-997/

I'm unsure why it was dropped, though.

2nd edit: It's actually a dual master cylinder system with an adjustable balance bar - maybe those systems are not compatible with ABS: http://www.porsche.com/uk/motorsport...ogyandconcept/

APKhaos

Hey Patrick! Good to see you planning the new car already!

I retubbed my 89 into an 88 tub that did not have the ABS option. This turned out to be a fair bit of work:
- transplant all the brake hard lines into the new tub
- fab and weld an ABS pump bracket in the left fender space
- cut an access hole for the ABS harness to the pump
- transplant the ABS harness into the new tub
- ideally, transplant the entire dash harness into the new tub to get the ABS warning circuit [does not exist in the early dash module and harness]
- Obviously, transplant the front suspension and rear end to get the ABS speed sensors and correct ABS offset geometry

Its doable, but there are a few more elements that you might think at the start [shocker!].

333pg333

I haven't felt it noticeably on the track. Doesn't mean I'm not getting into it. Coming to a complete stop on our Auto X I have felt it but that's stopping to 0 mph. Maybe during braking at eg 120mph to 70mph you don't feel it? I am pretty sure I late brake enough to not be ***** footing but I can't be sure I guess.
See here at the end of the short straight where Sean keeps getting some tyre squeak under brakes.

http://www.youtube.com/watch?v=618XxIbX_4E

Whereas here I am on the same track with no squawk at all. Different day though. Colder.

http://www.youtube.com/watch?v=L-d4V0W2ByQ

Granted, there is a bit of a bump just as you are getting into the brakes here which makes it worse, but I don't get the same reaction. This is also a bumpier track than the one we'll be using mostly so maybe not as important.

333pg333

Tony, that's just what I needed to hear. Thanks. Sounds like it's not really a wise option. Think if I want our stock ABS then I'll have to buy a car already equipped with this, but it also sounds like there's a strong argument for a dual m/c - balance bar setup. Hmmm....???

samluke

I just did mine.

Similar to Apkaos, I ran ran an 89 TurboS for many years. Totalled the car and kept the ABS system. Re-tubbed into an 87 without ABS. Ran 1 race weekend without it, and ruined a bunch of good tires trying to drive it like my old car. I have a spare pump and computer if anyone needs one. The harness is failrly simple. I used the stock harness but you could easilily make your own.

I just put the ABS back on. Its not a hard job, just a little time consuming. Its well worth it compared to the cost and frustration of flatspotting tires. Maybe I just suck as a driver, nevertheless I won't go back to non ABS, there is no downside to having it. Make sure you put a re-set circuit on if/when you install it, if its for a track car. I used to have to key my car off during races to re-set, which takes your focus away from what you should be doing.

333pg333

Ok, Richard could you describe what you had to do and what you might do differently if you had to do it again.

Another thought would be to sell this '86 that I have and just buy a more recent model. So to clarify, only the '89 has the same wide track and with ABS?

Oddjob

Like Richard and Tony, I retrofitted ABS onto a non-ABS late offset tub. Is some work, but extremely worthwhile for a dedicated track car.


May be a few more difficulties with the 86 vs the 87 and later cars, since the 86 tub and wiring harness was never designed for the ABS option. I recall the ABS wiring harness has a plug connector into the main passenger harness, which would likely not be present on the pre ABS cars. Tony's idea of transplanting the entire passenger wiring harness might eliminate some wiring problems, if you cannot figure out what needs to be done from looking at a factory wiring diagram.

Duke

The later track came in -87, I think ABS was standard from -88.

Duke

I have to admit it's not really that noticeable with ABS on the track, so just for fun I once removed the fuse. I was in for a surprise So my guess is that it's doing more work than one might think.
I've tried to stay away from too much curb riding with the stock control arms. But now with new chrome moly arms I have to put a reset switch on the future improvements list.

333pg333

Ok that's interesting Duke. I don't recall getting 'into' the ABS on the track even if I'm a *****. Thing is I've had the pedal to the floor when experiencing the 'soft brake pedal' phenomenom yet still no 'thunk-thunk-judder'. Now as you've just alluded to, you didn't notice it until it was gone so that gives me confidence that I'm right. Speaking to people, we get different viewpoints. On face value it looks like there shouldn't be too many problems to convert to a later system such as the Boxter, but I've sent Tony an email to ask him his opinion. Should be ok from the weight and balance, but what if we lighten a car to say 2600lbs. Will that have an overriding effect on the Boxter ABS? Does the Boxter ABS sync in with the PASM? If so, what about pre PASM or can the units with PASM be disconnected and run without that feature? Can this be (no pun intended) Linked in with the Traction control? Is TC almost the opposite of ABS? What about just tossing the stock 80's ABS and putting in something, anything from something more recent? I'm not talking about the standalone Bosch ABS system that is on the Porsche Spyders but something inbetween. lol.

Olli Snellman

We did it mostly.

We installed a complete undercarriage parts from Pete's 951 with ABS (RIP) to a 1986 951 race car.
We did this mainly because owner of that 1986 wanted Pete's GT2/GT3 brakes and possibility to use newer ET wheels.
We decided it will take took long time to change also brake lines, install ABS pump/computer. We were also worried about the wiring loom differencies there might be. Change of these parts did not took long time, just few hours.

1986 951 leaving my place about a year ago



starting point



These came out



These went in





GT3 rears installed



On wheels again



1986 951 ready last spring

333pg333

Brian, that is what I thought we were going to use, and may still do so, but I was talking to someone who worked with Bosch and their ABS and he was saying in response to some questions that I asked him re my situation, well...

"I downloaded all the info from their website on your controller that I could find. It isn't very specific about how the traction control works. I'd guess they will send you better documentation with the kit.

Here's my best guess as to how it works. It takes a vehicle speed input. Presumably you would use one of the front wheel speed sensors. The controller should be able to map out engine speed with no tire slip versus the vehicle speed. Once that is done it will do traction control when it sees the engine speed (rear tire speed) exceed some slip threshold over the front...probably something like 10%. When that happens it will start dialing back ignition timing to reduce power. You can do it with throttle control, but I'm 99% sure you will be using a cable throttle and the ECU won't be modulating and electronic throttle. You could modulate boost, but cutting timing will drop boost pressure anyway.

If the controller is really smart you could use an accelerometer to feed in some data. When at high lateral acceleration (cornering hard) you would want to cut the slip target down to something like 3%. At 100% of the tires capability you can either go/stop or turn, but not both...

That said, you will not be able to modulate brake pressure. 1. The hydraulic unit in your car does not have the capability.
2. Even if it did, you would not be able to command a pressure at a wheel. There is no way to tell the brake controller what you want. If you could, it still wouldn't listen because it would be extremely dangerous to just accept a brake pressure command from an outside source. You can easily "turn" a car with brake pressure. If you sent the command to the wrong corner you might find yourself hitting a wall. This is the premise that electronic stability works under. It redirects the car by only using brake pressure, and is quite effective.
3. With just a vehicle speed input to your ECU, you wouldn't know what wheel you would want to do a pressure build on. You would need all 4 wheel speeds to know where to put the brake pressure."