Porsche upgrade front not as expected + ABS problem

[audis293]

Now that the car is back on the road I feel that the brakes is not much better than stock brakes after the upgrade. I know it is difficult to explain, but how much improvement can I expect going to the Porsche calippers? Reading on the forum I expect a rather BIG improvement but this is not the case. Not sure which caliper it is, but I think it is GT 2 calippers. They have 140 mm cc bolt holes to carrier and are 4 pot monoblocks. I am also using the pads that came off the Porsche the calipers came from.

Some facts:
-The pedal is quite hard, almost like there is little brake assistance from hydraulic system. I can lock the wheels during hard braking if I want to, but I really have to step hard on the pedal.How can I find out if I have brake assistance?
-Brake pads are used (good thickness) but comes from the porsche the calippers came off.
-I get the (!) brake symbol with alarm for a few seconds during startups when the car has rested overnight. It then disappears.
-Stainless brake lines
-Brake reservoir and PAS reservoir is full.

In addition the ABS light has been on since the brake upgrade indicating ABS is switched off. I recently adjusted the rear left ABS sensor closer to "ABS ring" as this was to far from the ring. The ABS light then switched itself off indicating ABS should now be working, apart from a couple of times where I have seen it during driving, but when I stop and start the engine it dissapears again. The problem I got then is that the ABS seems to activate itself during slow brake downs (I get no alarms or lights when this happens)and it only activates from about 25 km/h down to zero/stop during slow braking. I can feel and hear the quick pulsing in the pedal when this happens.

Do I have 2 completely different problems or could the lack of brake effect be related to the ABS problem?
Could the porsche brake pads be off some kind that works better when they are hot, ie track pads of some sort?
Could the ABS problem be that the sensor I resently adjusted are still not correct distance to "ABS ring"

It should also be mentioned that at all vacum lines has been modified to fit a different inlet manifold, but I do not think the S2 brakes are vacum assisted?

Lots of question here but hope someone can guide me in the right direction here.

Johan

[avants2turbo]

have you tested the brake pressure accumulator (bomb) i dont see why this upgrade should affect the abs as the abs system has nothing to do with disk, pad, caliper. If you have fitted braided brake lines the pedal will feel harder (less flex in brake lines)
The big difference you should feel is after using them hard for a while, they wont fade like the standard ones

[audis293]

Thanks for the reply.
My limited knowledge about the S2`s brake systems tells me that the ABS issue should not be related to the "weak" brakes as you mention, but I am running out of ideas so just wanted to check if there is something I am missing here.
The bomb has not been tested. I assume it is not in "great" condition since I have the (!) light and alarm in the morning, but the light goes away after a few seconds so I think under normal driving conditions it works as it should. Is it the bomb who gives the brake assistance during normal driving? After reading a few threads I think the bomb is just for emergency if you loose all hydraulic pressure and it should give you a few pumps on the brake before it dies competely??

I had a PAS pump failure a few years back where I lost all pressure and bomb drained completely during driving. THAT was a scary thing in high speed I must say. The pedal is hard now, but not as hard and useless as if you loose all pressure like I have experienced earlier.

So if I understand you correctly the brake "effect" does not increase dramatically by upgrading to porsche calippers, but the fading will not be as mutch of an issue during track days? I must mention I have not tried on a track yet. Nor have I pushed the limit off track ether after the upgrade.
I forgot to mention I have 323 mm discs so I thought from reading a few threads this should give a notisably better brake effect vs stock discs.

Is it the PAS pump who gives the brake assistance via hydraulic pressure somehow? I am not sure how the brake assistanse system works, but I am speculating if the pump gives to low hydraulic pressure. I do have power steering though, so not sure if that can be the case ether.

Any ideas on the ABS problem? Could it be the same sensor I adjusted is still a bit off and gives the issue with activating ABS from 25 km/h down to zero, but it is clese enough to the ring to keep the ABS light off? I did not have this problem when ABS was not working due to the sensor was wrongly adjusted.

[4WheelDrifter]

The ABS problem sounds like a sensor problem, either the gap is wrong, or the sensor and/or teeth are dirty.

AFAIK the brake pressure accumulator also has a valve that regulates pressure, so that is worth checking.

[audis293]

The ABS problem sounds like a sensor problem, either the gap is wrong, or the sensor and/or teeth are dirty.

AFAIK the brake pressure accumulator also has a valve that regulates pressure, so that is worth checking.

I`ll do a VAG COM test on the sensors and see what it comes up with. The teeths was cleaned on all 4 courners when I upgraded brakes and suspensions so dirt is probably not the case, but I`ll keep it in mind.

This valve on accumulator, how do I check it and what is its purpose apart from regulating pressure? (what is it regulating pressure for)

[4WheelDrifter]

Tests on s2central. HTH

[dest]

When I first fitted mine I was doubting that they were much better, then I got them warmed up properly and it made a big difference!!
What pads are they? Did you use braided hoses/RS2 lines?

[audis293]

Tests on s2central. HTH

ahhh yes the good old S2 central. Will read through and see if I can make sense of it all.Thanks.

[audis293]

When I first fitted mine I was doubting that they were much better, then I got them warmed up properly and it made a big difference!!
What pads are they? Did you use braided hoses/RS2 lines?

I havent warmed them up properly yet (never been on a track yet and dont want to test this on puplic roads) so I do not know if that is where the big difference is, but it could very well be that is the case and that the pads I am using are more usable for track and becomes better when they are warm. I do not know the brand of the pads as they followed the calipers when I bought them but they are from the porsche the calipers came from. They looked almost like new so I took the chance and used them.
The brake lines are braided stainless.

Maybe I dont have a brake problem as my expectations was to have a big improvement in stopping power just by changing calipers and discs, but the real benefit from this upgrade is when you use them actively like on a track??
I think maybe some of my expectations comes from diffeent forums where you read about brake upgrades and it says that there was a big difference in stopping power and comments like "hanging in the seat belt harness" when braking. The part I maybe havent clued in on is that this could be on tracks and not in normal conditions?

[BRY]

What are the part numbers on the calipers that you have fitted?

[johne]

I guess @Bry is asking for the part number to see if you've got rear calipers fitted and their piston sizes.

The other thing to consider is that you've fitted old pads to new discs and they'll take a while to bed in to each other. From what you've said you've not used them much yet. I suggest you need more miles out on the road.

John

[Le S2 Audi]

I havent warmed them up properly yet (never been on a track yet and dont want to test this on puplic roads) so I do not know if that is where the big difference is, but it could very well be that is the case and that the pads I am using are more usable for track and becomes better when they are warm. I do not know the brand of the pads as they followed the calipers when I bought them but they are from the porsche the calipers came from. They looked almost like new so I took the chance and used them.
The brake lines are braided stainless.

Maybe I dont have a brake problem as my expectations was to have a big improvement in stopping power just by changing calipers and discs, but the real benefit from this upgrade is when you use them actively like on a track??
I think maybe some of my expectations comes from diffeent forums where you read about brake upgrades and it says that there was a big difference in stopping power and comments like "hanging in the seat belt harness" when braking. The part I maybe havent clued in on is that this could be on tracks and not in normal conditions?

I too have been dissapointed with my 996 upgrade... BUT I think you have to remember just how bad the orginal ones are whe the car is driven "HARD" & how much brake fade you get.... I have not had the chance to drive it for a long time or hard yet...

I think WE maybe expecting too much from the upgrade too quickly... And time will show the improvments...

[S2central.net]

ABS problem could be faulty sensor or damaged/dirty teeth on the outer CV joints. If your ABS does NOT have the cancel switch, then VAGCOM can pull fault codes and help pinpoint the fault.

Servo assistance on S2 is 100% hydraulic.

Sounds to me like pads aren't bedded in... or maybe the pads are the type for race use which need some warming up before they 'feel' nice and stop well. Road cars really need pads that give good rsults from cold.

[CP951]

Or maybe you adjusted the abs sensors too close to the rings. Pull back a little and see what happens. The sensors can get too far in if you push them all the way down the collar.

[CP951]

Thinking back I once had the same pulsating pedal problem like what you had. The ring was so close it was scraping on the sensor and the abs system on that wheel was activating spontaneously, which caused the hard pulsating pedal. The car was also pulling towards one side. I added a washer and the problem went away.