2008 Polo GTI 9N3 brakes and brake master Cylinder upgrade - ESP question

[pologtiforfun]

Hi All,

Firstly hi to everyone and thanks for your help in advance.

I was looking at brake upgrades, which have been discussed on this forum from my searches. currently looking at the audi TT or S3 ones, possibly r32. With the view to do brakes and suspension first takng into account further power enhancements to come

I was wondering who has upgraded their brake master cylinder to say to a 22 mm or 24,31 mm one ? seeing the forum posts the current one will work, but was just seeing if what others had done or used to match the upgraded brake packages, ( I've also seen the porsche brakes upgrades etc )

and which version have people used ? it also got me thinking and i'm not sure at all hence my post and question.

In regards to the ESP on the 2008 polo gti, is it an earlier version and slightly dumbed down so to speak. By this I mean the brake master cylinder from what i can see only has 2 brake line ports and no micro switch etc attached. Hence possibly a non esp brake master cylinder could be used ? as most seem to have 3 or 4 ports, so with only 2 lines they become redundant and need to be blocked off. and these are easier to find which match to the brake servo as far as bolt patterns. ( happy to be corrected if i am wrong )

Is the ESP function on the polo run from the ABS pump unit ( and possibly combined with an ecu to cut power to the engine/wheels ) this controls the traction control and wheel spin via ABS etc. so hence no need for the micro switches on master brake cylinder ?

I am totally all for using the right master cylinder for the purpose especially in regards to the brakes as stopping is a key safety function.....no use having all the power in the world if you cant stop and steer the car. So not looking to do anything dangerous with the upgrade etc.....just looking to understand more before progressing

thanks for your help and responses, sorry if this has already been answered elsewhere on this forum.

cheers
clay

[sambb]

sorry I run standard brakes but with ok pads and ducts so cant really help you with rotor/disc info.
I have an 08' currently and I just checked the master cylinder and it has two ports. There are other towers cast into the body that could have alternate/extra fittings conceivably taped into them on later models? but only two ports on mine. My other car was an 06'. Its master cylinder is under the house but i'll check it out next time I'm under there.
As far as I know and can feel, all the models have ESP. There are no non -ESP ones to my knowledge. My 06 and 08' behave the same way with the ESP. Its possible that the degree of intervention and /or the threshold at which they kick in is defferent (software) but its definitely there. I know because when you pull the 5 amp ESP fuse the car is very different at the limit. The n dash ESP switch does nothing to ESP - it remains active no matter what. What it does do is turn the traction control on and off. Traction control consists of a throttle cut and below 40km'h it brake modulates too. My car is being tuned at present and one of the things I've asked for is modifying the system so that when the dash 'ESP off' button is in the default 'on' setting ie button not lit that it will run the brake modulation but I want the throttle cut to be erased. When the ESP off button is pressed/illuminated then I will have neither throttle cut or brake modulation. I want to do away with the throttle cut which is horrendous I think.
Yep the ESP is ecu operated. whether that's from the main ECU or a separate dedicated CAN linked ESP ECU I don't know. I'll ask the tuner because I'm unsure myself. All I know is that to negate it you can pull the 5 amp fuse or you can unplug the brake pedal sensor (you can reach it from where you sit) but be warned it stops the brake lights from working. In both cases you have to use vcds to clear esp errors afterwards. I asked the engine tuner/mapper if he could modify the ABS thresholds but he wasn't sure about that. I know that in some of the newer cars eg a guy in a skoda ocatvia vrs was telling me he could change ABS thresholds with VCDS! but not us unfortunately. That has to be done in code from what I can gather but don't quote me on that. I desperately want that changed. On the weekend I was on the track and the stupid abs was hammering away under my foot for a third gear left hander after braking down a hill and I was nowhere near the brake limit so I'd love to address that - maybe not permanently but at least in a track file that I could flash in.
Also what you find re master cylinders and boosters i'll be interested in. I think the Polo is way over boosted and has way too much pedal travel with the stock brakes and have been thinking about playing around there for a while. hope you get into it.
sam

[pologtiforfun]

Thanks Sam,

I think thats confirmed my thinking in regards to the ESP.....ecu and ABS operated on the polo 2008 gti hence the brake and power cut. What also seems to highlight this the mk4 golfs which had esp since about 2002.....i pulled off a brake master cylinder and it was the same setup ie only 2 ports. (again happy to be corrected)

My logic is, which your tuner maybe able to confirm......the car has sensors which feed the information to the ESP which then utilises the ABS unit to control the master brake cylinder resulting in the brake modulation....and the ecu cuts the power to the engine controlling the power and wheel spin accordingly.

Other higher end cars ie Audi TT, S3 that have the 4 ports with 2 ports have the electronic switches / solenoids / sensors....which would be a more sophisticated version of ESP.....which would make sense as more dollars invested in the car all around.

Obviously looking and researching as its a hard way to learn if the brakes dont work...due to the brake master cylinder.

i do know of the 23.81mm BMC which are 2 ports like the one on my car, and will fit. guess i'll have to do the trial and error method.

Will have a set of Audi TT brakes shortly, along with a rebuild kit for the calipers......i am thinking a great time to swap over the BMC as doing the brakes need to bleed the brake fluid so may as well hit both at the same time.

[pologtiforfun]

Thanks Sam,

I think thats confirmed my thinking in regards to the ESP.....ecu and ABS operated on the polo 2008 gti hence the brake and power cut. What also seems to highlight this the mk4 golfs which had esp since about 2002.....i pulled off a brake master cylinder and it was the same setup ie only 2 ports. (again happy to be corrected)

My logic is, which your tuner maybe able to confirm......the car has sensors which feed the information to the ESP which then utilises the ABS unit to control the master brake cylinder resulting in the brake modulation....and the ecu cuts the power to the engine controlling the power and wheel spin accordingly.

Other higher end cars ie Audi TT, S3 that have the 4 ports with 2 ports have the electronic switches / solenoids / sensors....which would be a more sophisticated version of ESP.....which would make sense as more dollars invested in the car all around.

Obviously looking and researching as its a hard way to learn if the brakes dont work...due to the brake master cylinder.

i do know of the 23.81mm BMC which are 2 ports like the one on my car, and will fit. guess i'll have to do the trial and error method. ( This matches the audi tt BMC which the brakes are off. )

Will have a set of Audi TT brakes shortly, along with a rebuild kit for the calipers......i am thinking a great time to swap over the BMC as doing the brakes need to bleed the brake fluid so may as well hit both at the same time.

[sambb]

Yep with regards to traction control it uses the same wheel speed sensors as the ESP and ABS and if it detects wheel speed differential it'll apply brakes and cut throttle. This traction control side of things must be part of the ESP ecu if there is such a thing - surely? The ESP obviously also uses these same wheel speed sensors to apply select braking in case of a slide. If you understeer it'll grab the inside rear which acts like a lasoo and drags the nose of the car back into line. Oversteer I think it grabs the outside front. With an inside rear in the air (a symptom of lots of rear roll stiffness if you are set up for the track) it sometimes chucks a complete wobbly and tries to kill you which I don't think the bosch engineers intended.
The ABS system must be separate. Probably for failsafe reasons. Eg if I pull the ESP fuse or the brake sensor switch plug, I have tested it doing a simulated crash stop and the ABS still works! I t could be that it becomes less clever but the ABS definitely stays active if the ESP computer/routines **** themselves, that I can confirm atleast on 06/08 cars. That I find interesting because it suggests that it is able to read inputs (wheel speed sensors) and activate outputs (brakes) independent of the ESP system, even though they share the same hardware.
Don't be too certain that the TT/S3 system is better because its newer more sophstiacted. Maybe for your missus if she swerves to miss a beetle in the wet but not for performance driving. We have a lat/long G sensor under the drivers seat, but the later models have yaw sensing as part of it too. Ive read/heard/spoken to cluey people trying to nut out strange handling traits in those cars that turn out to be the yaw aspect eg on track you want the car to rotate, back thru a corner but the yaw sensor will see this and go into ESP overdrive. Our simpler system doesn't seem to react to that type of thing unless you really start to slide.
Also our car is very rear light. 66:33 or something like that which only gets more extreme when you pull out tool kits/rear seats/ spare wheels/fuel at the track. Pretty sure an R32 or TT would have more rear bias (to the weight distribution )than us, so don't go nuts on the rears and unnecessarily add weight, braking power that you just wont be able to utilise and more piston volume etc that may upset the pedal when it may not be needed.

[pologtiforfun]

yeah interesting.....i wonder if the esp uses different wiring and software.....but same hardware hence another layer of safety on top the ABS system.....and hence a fail safe if esp fails ABS still works......very clever and german way to think.

I upgraded a mates suspension on his 08 polo gti......brakes felt very spongy and like wasnt going to stop/work....then a few mm more brakes worked......very unsettling at first....after upgrade brakes felt heaps better and more trusting if that makes sense.

i was actually talking about the audi tt and S3 prior to 2006....maybe more sensors ie yaw control etc not sure...need to do a bit more research on that one

my aim is to not have a long braking pedal when i upgrade the brakes.....good point ie the weight distribution will have a good think about that one....guessing a general rule of thumb if using brakes off a different vehicle use the BMC from that vehicle. assuming similar weight etc

[pologtiforfun]

just found 2006 audi tt fwd weight distribution....62/38

[sambb]

yeah the yaw is in later ones than the 8L I think. Who knows the airbags might use that sensor too so not something I'd touch. Yeah ours is very front heavy and I think spinning bigger rotors and suspending bigger calipers at the back is going to just make the rear end lethargic and sap you of straight line poke but that's just me.
Like I said i'll be watching because if a BMC/booster combo surfaces that can give a firmer shorter pedal with some actual feel, I'll be all over it.

[pologtiforfun]

thanks Sam for your input and help.....i'll keep you posted on the trial and error of the BMC/booster.

And also keep reading your build thread

[sambb]

just got word that the ABS controller is separate to the ECU and is a module on the pump itself. Apparently it is separately fused to the other ECU's but takes its inputs via the main ECU. Traction control (ESP off button) is done in the main engine ECU which is why the tuner is going to make an attempt to kill the traction control throttle cut.

[pologtiforfun]

Thanks Sam,

Thats exactly the info i was after.....and it makes sense that the BMC only needs 2 ports as the module on the ABS unit controls it from there. Let me know how you go with the traction control kill as that would be handy to know about as later down the track i am sure the car will be seeing some track time.

[sambb]

If it works it'll be a great feature. It'll help launching it from a standing start and probably also dull wheel spin coming out of tight corners within reason if you have n open diff. As it is, I have a wavetrac torsen front diff. Not as badly as a quaife torsen, they will still spin up an unloaded wheel and it can be hard for the diff action to bring it back. Its my hope that thebrake modulation will help by loading that spinning wheel so that the torque sensing in the diff can re lock it. Might work. huld be getting the tune to try it out in the next couple of days. I'll let you know how it goes.

[pologtiforfun]

Sam, how'd the tune go ? as i am curious to see.

I rebuilt the front calipers on the weekend, i thought while they are off may as well put new seals and pistons in........the old pistons where actually fine. But better safe than sorry. Will do the rears in the next couple of weeks, as i have a bit of time before the new BMC arrives. As looking to do upgrade both front and rear brakes as well as upgrade the BMC at the same time.

From reading on these forums seems the bleeding the brakes can be tricky or easy but needs to be done in a certain way....so will see how that goes. Any words of advice more than happy and open to any tips on the best way to do this.

[sambb]

The tunes revision with the throttle cut delete hasnt arrived yet. Its being worked on as we speak.

The usual brake bleed technique is the furthest caliper to the closest but for some reason which still confuses me apparently you are meant to do the fronts first. Maybe that's the best way to avoid air in that ABS manifold - not sure. I've done plenty of bleeds on the Polo but not a complete flush. I had the rear beam off my car for days and the fluid had drained all the way up and I was worried about air in the ABS distributor. I wasnt exactly sure what that meant so I bled it as good as I could with my 6 yo on the pedal and went down to the pro's.
If you do it with 2 people it'll be easy or some guys on here have used the pressure packs that screw directly onto the master cylinder which would speed things up. I'd probably just confirm the fronts first thing.

[TDIfan]

Brake bleeding procedure
Volkswagen Workshop Manuals > Polo Mk4 > Brake systems > Brakes, hydraulics, regulator, servo > Bleed the brake system


Sam the ABS pump on non-GTi 9N3s don't have ESP function, might be another way to go if you have no luck with your tuner. Swap the pump and ask the tuner to delete fault code completely in the software, done. But you won't get brake modulation on the standard pump though.