TonyG

I'm going to install ABS on my 86 LS1 951. It's already got the late offset suspension. So installing the ABS sensors is trivial.

I really dislike the 951 ABS system. It's been a long time since I've owned a 968, but I seem to remember it feeling like the 951 ABS. The later Porsches (late Boxters, 996's, Cup Cars, etc...) have a much faster acting (engaging/disengaging), less pronounced feeling ABS, that seems to let you brake much harder when engaged over that of the 951 system.

That said....

1. What is the difference between the 951 ABS and the 968 ABS if any?

2. Given the weight distribution of the Boxter S, and the fact that the late models have a 5 channel ABS (one channel to each wheel vs the 951 system that uses a 4 channel system... one channel to each front wheel and one channel to both back wheels) and that it requires no external "brain", do you think it would work on a 951 assuming one were to properly plumb and wire it?


Thanks for any input.

TonyG

anders44

Im in a similar dilmma, a bosch motorsportsystem is 5-6k euro, so a bit steep, in theory a boxster system should work from what I found out. its not tied into the ecu, and manual TB etc.

I made a thread about it on a racing forum, also talked to one of the engineers who made the bosch system saying its all very tricky stuff :|

TonyG

I was thinking the late boxter setup would work pretty good, but it's a lot of work to get it in there and I'd hate to do it and find out otherwise.


TonyG

Darwantae951

Is the ABS hydraulic unit dimensionally the same size as a 951 unit? Are you going to mount it in the factory location?

anders44

I don't think tony, or me is very concerned about whats where from factory :>

marky522

If you want to use the late Boxster setup I think you would have issues, as it gets signals from the other control units like PAS, Rear CU etc. And it is coded to the vehicle so would it work without the DME? I dont know... I am pretty sure it would set faults. I think an early boxster ABS setup without PSM might be able to be done. Anything i can help with just let me know, I have access to the PIWIS and all factory documentation.

Mark

Ski

I have a question: The PCA class cars that I've looked at or in at their instruments, that have ABS, they have an ABS button, usually next to the FIRE button. Does the ABS take a moment to reset if it activates, in street trim - you dont' need this at the track; is that what the button is for, a reset? If that's so, wouldn't it make more sense to put that on a coil wire with a button on the steering wheel? Just curious, as our track car is just a dedicated DE car, 87 but no ABS.

anders44

button is most likely to de-activate it all together

Olli Snellman

I scanned all the information i found from early Boxter OBD-manual concerning the ABS system:









Looks like the speed signal(from rear left wheel) is the only information delivered to DME, just like it was with 968 ABS. Haven't checked Boxter ABS system in live, but what i found out from the OBD manual, looks like ABS pump has all the electrics built in, so not external ABS "computer" like 951 had.
I checked out also 993 & 996 OBD manuals, and it seemed to be identical with Boxter what comes ABS wiring to DME.

Some pics of Boxter ABS/brakes system

Weston Dillard

Boxster ABS was one of the winter projects I was hoping to get to. The Motorsport setup would be the bomb because it's calibrated for racing, but as Anders points out, it's big money. The Boxster setup can be had for <$300. Let's figure this out!

Ski: The 944 ABS gets easily confused. If you slide across a rumble strip or drop a wheel, it goes into fault mode. A lot of us run a switch to reset it on the fly when that happens. It's just a power interrupt.

West

anders44

mm, I have a boxster, but I suspect I wont use it as a parts car

but the ABS is very good on that car. as with all my cars, I dragged it to the track after 2 days of ownership.

adrial

What does the wheel speed sensor read on the 944? on the boxster?

Since the rear of the 944 is only single channel, maybe it uses the speed sensor in the trans? Which would mean fabbing a speed sensor pickup for the rear to use the boxster system.

Interesting project...

TonyG

Are you sure about this? The ABS is "getting signals from" or is it sending "signals to" the PAS, ECU, etc... big difference.

The late model is a 5 channel vs the early 4 channel system (also a big difference).

I was told, not from anyone on this forum, that ABS could probably be stand-alone. But my source wasn't 100% sure.

Anybody?

TonyG

APKhaos

Tony,
The 951 ABS is stand-alone. I runs on a separate harness, which includes the ABS relay that plugs up in the fuse box independent of anythign else. It picks up controller power from the fuse box via a separate line, and main power from a heavy gauge line that joins that mass of cables on the battery positive terminal.

Retrofitting 951 ABS into a non-ABS car is a bit of a bear. It takes a set of ABS brake lines, running the harness, and some metal mods to create [or graft on [better]] the pump bracket. I transplanted the ABS from my totalled tub to a pristine 88 tub last winter.

TonyG

I've had 951's with ABS. The issue is that I don't like the 951 ABS. I want a better ABS, which is why I'm considering transplanting the late 986 ABS.

Fabricating the brake lines and the wiring is not a big deal. It's just that I don't want to start a project without knowing more information about the requirements of the late 986 ABS.

TonyG