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ABS on C4

Konstantin

New member
Hi guys

as anyone had experience on deleting the ABS on a C4, I am thinking maybe have a switch and have it off during track days ,or will it upset the 4 wheel drive system ??

thanks for your comments

Konstantin C4 92
 
Hi Konstantin

You can do this, there's even a porsche motorsport switch available from dealers.

One lad on Rennlist has done this on his C2 but I bottled out doing it on my C4 as I think it will knock the 4wd system off and leave it constantly on the 69/31 split.

I'll dig the link to the thread on rennlist out when I'm at work tomorrow and post up.

Rob
 
Hi Rob would love to know more, if it is easy via a switch so revertable and not affecting the wheel drive system I may consider trying, I did a seach on Rennlist but did not find anything for C4s

Konstantin C4
 
Not sure why you would want to though. ABS is worth 1-2 seconds a lap around somewhere like Oulton Park in a 964 (if you're a pro). So not sure what you gain by turning it off.

Ian.
 
I agree with Ian that there's no reason that it should spoil your enjoyment. Also, if you run with track tyres like Toyo R888s you are highly unlikely to get it to cut in on a dry track (too much grip to get the tyres to lock up).
 
I can vouch for the fact that the ABS on a C4 can be disabled without having any effect on the PDAS - 'coz my car has been that way for years. It's currently in at RPM to see if they can get the ABS working and, if successful, I'll find out why it didn't work and you can do that to your car!!!

I do tend to agree with the others though, that I can't really see any performance advantage to NOT having ABS working. Quite the reverse I would have thought in that it can only help to improve the braking performance.

Regards

Dave
 
You could always replace the ABS/PDAS ecu with a faulty one....mine went bust last year and the only noticeable difference was the ABS didnt work....Replaced it with a proper one off eBay and now full 4wd and ABS is restored.

I still have the old one knocking around in the garage thought i could get it fixed and flog it but no-one seems able to at the moment...
 
Perhaps for driver enjoyment, as you dont chase lap times on trackdays, being in control of the car may be more important to you? I for one, am still getting used to ABS (albeit not on track yet), and find it very frustrating. Also I sincerley hope that even with 888s you can still lock the wheels, the brakes must good enough for that!

Sounds like a bit of hassle for a car with ABS, but can see why you would want to do it. The alternative is a less agressive map for the ABS ECU, didnt the cup cars and NGTs run with a different map to the standard C2/4? could this be retro fitted to a C2/C4?
 
ORIGINAL: h_____

Perhaps for driver enjoyment, as you dont chase lap times on trackdays, being in control of the car may be more important to you? I for one, am still getting used to ABS (albeit not on track yet), and find it very frustrating. Also I sincerley hope that even with 888s you can still lock the wheels, the brakes must good enough for that!

You probably could lock up a C2/C4 on track tyres (in the dry) if you really stamped on them but that for me would mean I'm going into the corner too hot. I'm glad to say that I've yet to experience that phenomenom. Remember our standard brakes are smaller than an RS so we can press a bit harder when looking for the threshold.
 
Hi Guys,
thanks for the replys, I would like to fit a switch so I can have it on/off, I run 888s but on a bumpy track or road track the abs may fight the driver and extend braking distance, I suppose definitly on when it is raining.
thank you Rob I will read this now.
Dave please let me know,thanks
regards

Konstantin C4
 
ORIGINAL: Steve Brookes


You probably could lock up a C2/C4 on track tyres (in the dry) if you really stamped on them but that for me would mean I'm going into the corner too hot. I'm glad to say that I've yet to experience that phenomenom. Remember our standard brakes are smaller than an RS so we can press a bit harder when looking for the threshold.

Very true, I guess that's the bit I havent worked out, on a dry smooth track, do you threshold brake, or do you use the ABS? I confess to having not driven my car in anger yet, so dont know.
 
ORIGINAL: h_____

ORIGINAL: Steve Brookes


You probably could lock up a C2/C4 on track tyres (in the dry) if you really stamped on them but that for me would mean I'm going into the corner too hot. I'm glad to say that I've yet to experience that phenomenom. Remember our standard brakes are smaller than an RS so we can press a bit harder when looking for the threshold.

Very true, I guess that's the bit I havent worked out, on a dry smooth track, do you threshold brake, or do you use the ABS? I confess to having not driven my car in anger yet, so dont know.

Hi h_____ , like most of us I'm learning all the time but have been trying my best to use threshold braking from the start. Having seen one of Andy Walsh's car limits videos and how threshold can stop the car quicker than ABS..I was quickly sold on the technique. Personally I find the pedal feedback from my C2 is so good I can feel when the ABS is about to act and hold it there. Also, I've had a couple of instructors/race drivers drive the car on track, far quicker than me, neither of who got into the ABS in the braking zone.
 
Interesting, thanks. So I'll avoid using it is the general view. Interestingly, I've asked a mate who races in the carerra cup, and he says the cup cars dont have it anyway! Didnt know that. but that he wouldnt use the abs in a race car such equipped anyway.
 
Hmm - I would not disable it. The abs is pretty good and you can squeal the tyres before it cuts in - any more you you would likely lock a wheel. I could always feel as the abs started to cut-in and could hold brake pressure there - when the abs is full on it does lose feel of what the brakes are doing. Some tuners did make special versions of the CU that sampled the sensors much faster and gave more control but they cost a lot 3X. More important for a track C4 is to trail brake and keep the abs holding off the awd engagement. If the awd is in control the car will understeer more. Anyway good luck.
 
Hello Alex,

this is what my fear was, so the ABS is related to the AWD, so when on the brakes very late the AWD is not acting ?! so does that mean it stays 31/69 ? maybe big front tyres are a must I run 225/265 , I was going to put 235/265 wich is a perfect OD for C4, what about disconecting AWD as well then ?

Konstantin C4
 
Konstantin

The awd takes it signal from the abs sensors (iirc) so if it sees a difference in wheel speed it does its thing (which is far beyond me) but I think it transfers power to the opposite wheel or diff which the speed differs on.

The only time I see the awd activate on track is when I'm exiting a corner, presumably because if I didn't have the awd I'd spin a wheel resulting in loads of tyre smoke and poss. oversteer.

Bigger fronts on a C4 help with the understeer they inherintly have as does a bigger rear arb. Proper geo made the world of difference to my cars performance on track as well.

For abs, you can get the controller reprogramed so it's a bit less aggressive but I struggled to find anyone to do it. I very rarely hit the abs unless the tyres are cold or warming up, or the tracks wet or damp in which case it helps. Without it you'd lockup and head for the gravel.

Try to find the threshold, as Steve said, they usually slow down quicker.

Having both systems working does make trail braking easy in the C4 as you very rarely make a mistake where you'd fall off.

For info, I run 225's up front.

Rob
 
Just to add a little to this subject I confirmed today, as best I can, that the non-functional ABS on my car is solely down to the out of spec accelerometers. As well as taking information from the wheel speed sensors as Rob rightly suggested, the C4 ABS uses the two accelerometers to determine the attitude of the car, i.e. accelerating, braking, yawing etc. This is competely different to how it's done with the C2, RS and Turbo, none of which have either accelerometer fitted. Although the RS and Turbo have the high pressure braking system they use a completely different ABS ECU - without the PDAS function - and, I'm guessing, solely rely on the wheel speed sensors to activate the ABS.

Regards

Dave
 
Yes the awd is still connected but it does not try to keep the car straight if you tail brake. So you still have the front wheels driving but it is in a better balance. You will never corner as fast as a C2 (unless wet) but you will be much closer in time, esp if you time the power back on to pull and push you. As it is a 911 the rear weight is still there to rotate the car.

I would try this first and if it does not work for by all means disable the abs if you can - I am not sure you can really do that as the awd is always connected so you can't stop the effect all together.

Make sue the geometry is set up for this also and the larger tyres will help also.
 

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