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Initial Observations on the Performance of Neuspeed BBK in Track-Day Environment

emichel6888

Go Kart Champion
Location
TX
As an update, if anyone cares, the MC is crossing the border into my grubby hands soon lol.
I hope everyone had a lovely holiday.

I hate to steal your thunder on this one, but it was taking too long and a friend had sent me a MC out of a wrecked 2019 Golf R he had no use for, and owed me a couple of favors so... It does appear that my theory was incorrect; see below, clearly the GOLF R MC is not a stepped QTMC.
MC1.jpg

MC piston1.jpg


One thing I would be curious about, I have seen were you (and others) have mentioned the MC piston diameter is supposed to be 23.8 mm for the Golf R however, when I measured this one it is actually 25.4 or 1”. I would assume yours should be the same but would be interested to know since yours is out of a different year/model.
MC piston2.jpg


As I said there must be another explanation, so I did a little more research and came across this interesting paper titled “Brake Pedal Feeling: Target Setting Techniques” you can download the PDF FOC at this link: Brake Pedal Feeling: Target Setting Techniques

After learning that we do not have a QTMC and seeing this paper; it is now obvious to me why these modifications cause the brake pedal to be higher and lot firmer with much better feel. It all has to do with the servo brake booster, I knew it provided pressure assist, but had no idea just how much!

This study tested a wide range of vehicles, on page 51 it provides an example of typical pressure curves for these systems. I had no idea the pedal force to brake system pressure ratio was so extreme! Understanding this now makes sense of what I have observed with these modifications.

2020-12-27 17_25_45-Brake booster servo characteristics.jpg

From the curves shown above, we can see why the pedal drops and feels soft when the engine is started and the servo brake booster comes online. With a typical standing pedal force (approx. 20 daN or 50 lbs) with the engine off the brake system pressure is <100PSI, once the engine starts the booster ramps the pressure up to around 1000PSI. At that pressure the brake components (lines, calipers…) start to deflect causing the pedal to drop causing even higher pressure and even more deflection, hence the soft dropping pedal that seems to sink further as you press even harder trying to find that hard stopping point.

The graph shows booster assist curve as a function of pedal force however, pedal force equates to the input rod position, which is what dictates the amount of assist the booster provides. By changing the piston take up point the pedal/input rod stops short due to the pressure increasing much sooner with reduced take up. This drastically changes the booster assist curve relative to pedal force.

booster diagram.jpg


With the Macan/Q5 calipers increased piston retraction the same pedal force causes the pedal to go lower causing the booster assist curve to be even more aggressive. This is why the initial engagement point is lower, and with more assist makes for an even lower pedal with even softer feel. So lubing the seals or just adding the RPV’s gets the system very close to the stock caliper piston take up, and that provides pedal height and feel similar to the stock calipers.

However, by doing both (RPV & lube), that significantly reduces displacement take up. This means for a given pedal force the input rod is further back significantly reducing the amount of booster assist. This is why when the engine is started the pedal does not drop and feel soft as it does with near stock take up. Clearly the booster is providing some assist otherwise it would be very difficult to stop the car, but it is not bad at all. It just has considerably less assist compared to stock, so it does not cause any noticeable deflection in the brake system when you start the car. This is why the pedal does not seem to change when I start the car and provides a much firmer higher pedal with significantly improved feel throughout the curve.

You do have to use a lot more pedal force to get the same amount of breaking power however, for my preference it feels just about perfect, in fact I would lower it a bit more if I could. I do not like a low soft grabby overly boosted brake system that is difficult to modulate. These mods fix that, and now I understand how and why. Like I said for track use...

The blue curve represents Macan caliper with increased take up and the green represents reduced take up with lube & RPV added. Obviously I did not take actual measurements so this is for rough concept purposes only.

2020-12-26 13_42_09-Brake booster servo characteristics.jpg

I imagine the StopTech ST40 with its smaller pistons has the same effect, perhaps even more so. So there you go, I hope this makes sense?
 
Last edited:

burgerkong

Go Kart Champion
Location
Ontario, Canadeh
Hmmm, I've got two GTI/R master cylinders at my house, were part of my plan to upgrade when I put 17z's on my Golf. I could get some pictures of them I guess, haha.

One of them is an earlier part number, maybe up to 2017...
5Q1614019 NREP

The other is the current part number, just got delivered this week, ordered 6+ weeks ago but apparently shipped to the dealer from Germany...
5QM614019 F

Hey, is it possible to stick a pair of calipers and measure the diameter of both M/C pistons like how I did below? I took apart my M/C (probably from a GTI, who knows) and it measures right at 23.81mm. Interestingly, the 5Q1614019xREP (regardless of revision code) fits basically all MQB vehicles across VW and Audi (and the rest of VAG), specifically the R and RS3. The 5QM614019F P/N however only shows compatibility with VW Atlas, Cross Sport, Tiguan and GTI's, from 2018 up, not to mention being many times cheaper.


20210106_011518.jpg


20210106_011527.jpg


20210106_011640.jpg


20210106_011838.jpg


20210106_011853.jpg
 

GTIfan99

Autocross Champion
Location
FL
Sounds like the MC in the later R has a larger diameter.

Hmmmmmmm.

Is the same MC listed for both PP and non-PP GTI?
 

burgerkong

Go Kart Champion
Location
Ontario, Canadeh
Sounds like the MC in the later R has a larger diameter.

Hmmmmmmm.

Is the same MC listed for both PP and non-PP GTI?

Yep. The 5Q1614019xREP which I have is meant for both R/GTI (all years) and RS3. The 5QM614019F is an unknown quantity at this time...I don't think VAG would opt to change something that significant (piston diameter) thru different revision codes, it'll warrant a whole new P/N. Time for more measurements.
 

GTIfan99

Autocross Champion
Location
FL
I hope everyone had a lovely holiday.

I hate to steal your thunder on this one, but it was taking too long and a friend had sent me a MC out of a wrecked 2019 Golf R he had no use for, and owed me a couple of favors so... It does appear that my theory was incorrect; see below, clearly the GOLF R MC is not a stepped QTMC.
View attachment 197553
View attachment 197554

One thing I would be curious about, I have seen were you (and others) have mentioned the MC piston diameter is supposed to be 23.8 mm for the Golf R however, when I measured this one it is actually 25.4 or 1”. I would assume yours should be the same but would be interested to know since yours is out of a different year/model.
View attachment 197555

As I said there must be another explanation, so I did a little more research and came across this interesting paper titled “Brake Pedal Feeling: Target Setting Techniques” you can download the PDF FOC at this link: Brake Pedal Feeling: Target Setting Techniques

After learning that we do not have a QTMC and seeing this paper; it is now obvious to me why these modifications cause the brake pedal to be higher and lot firmer with much better feel. It all has to do with the servo brake booster, I knew it provided pressure assist, but had no idea just how much!

This study tested a wide range of vehicles, on page 51 it provides an example of typical pressure curves for these systems. I had no idea the pedal force to brake system pressure ratio was so extreme! Understanding this now makes sense of what I have observed with these modifications.

View attachment 197557
From the curves shown above, we can see why the pedal drops and feels soft when the engine is started and the servo brake booster comes online. With a typical standing pedal force (approx. 20 daN or 50 lbs) with the engine off the brake system pressure is <100PSI, once the engine starts the booster ramps the pressure up to around 1000PSI. At that pressure the brake components (lines, calipers…) start to deflect causing the pedal to drop causing even higher pressure and even more deflection, hence the soft dropping pedal that seems to sink further as you press even harder trying to find that hard stopping point.

The graph shows booster assist curve as a function of pedal force however, pedal force equates to the input rod position, which is what dictates the amount of assist the booster provides. By changing the piston take up point the pedal/input rod stops short due to the pressure increasing much sooner with reduced take up. This drastically changes the booster assist curve relative to pedal force.

View attachment 197559

With the Macan/Q5 calipers increased piston retraction the same pedal force causes the pedal to go lower causing the booster assist curve to be even more aggressive. This is why the initial engagement point is lower, and with more assist makes for an even lower pedal with even softer feel. So lubing the seals or just adding the RPV’s gets the system very close to the stock caliper piston take up, and that provides pedal height and feel similar to the stock calipers.

However, by doing both (RPV & lube), that significantly reduces displacement take up. This means for a given pedal force the input rod is further back significantly reducing the amount of booster assist. This is why when the engine is started the pedal does not drop and feel soft as it does with near stock take up. Clearly the booster is providing some assist otherwise it would be very difficult to stop the car, but it is not bad at all. It just has considerably less assist compared to stock, so it does not cause any noticeable deflection in the brake system when you start the car. This is why the pedal does not seem to change when I start the car and provides a much firmer higher pedal with significantly improved feel throughout the curve.

You do have to use a lot more pedal force to get the same amount of breaking power however, for my preference it feels just about perfect, in fact I would lower it a bit more if I could. I do not like a low soft grabby overly boosted brake system that is difficult to modulate. These mods fix that, and now I understand how and why. Like I said for track use...

The blue curve represents Macan caliper with increased take up and the green represents reduced take up with lube & RPV added. Obviously I did not take actual measurements so this is for rough concept purposes only.

View attachment 197560
I imagine the StopTech ST40 with its smaller pistons has the same effect, perhaps even more so. So there you go, I hope this makes sense?

Is it possible your calipers are out of calibration?
 

jmason

Go Kart Newbie
Location
Frederick, MD
... Interestingly, the 5Q1614019xREP (regardless of revision code) fits basically all MQB vehicles across VW and Audi (and the rest of VAG), specifically the R and RS3...
From my research, I found that the REP part MAY [my emphasis] fit the RS3. I could not find a p/n specifically for the RS3.

The erWin manual calls out both diameters for Golf vehicles. I couldn’t find which applied to Golfs or GTIs
 

jmason

Go Kart Newbie
Location
Frederick, MD
Following-up on emichel6888 post of Dec 27 (very interesting BTW), I took a couple of quick measurements using VCDS to measure brake pressure. I don't know where the tap for the measurement is, although I suspect it is from the ABS module.

I have to say that my measurements are inconclusive, but here they are. In each case, I pressed the brake pedal as hard as I could to get a maximum pressure reading. All pressure measurements are in Bar. With the engine running, the Hydraulic Brake Booster adaption was set to 8. I don't have the security code to change it.

Engine off: 116 (According to emichel6888 charts, this is way off. I think it is correct. I've measured 75 bar when performing a MC leak test, and that wasn't pushing the pedal as hard as I could. If I had a better grasp of basic hydraulics, I should be able to do a sanity check. Alas, I don't.)
Engine at idle, Hydraulic Brake Assist Not Activated, Brake Boost at 1: 129
Engine at idle, Hydraulic Brake Assist Not Activated, Brake Boost at 8: 135
Engine at idle, Hydraulic Brake Assist Activated, Brake Boost at 8: 130

I didn't repeat the measurements, so there could be some sample-to-sample variation not captured here. The measurements didn't vary as much as I thought, around 5% with the engine running. I don't know if a 5% difference is noticeable in practice. Also, with the engine running, I was able to push the pedal to the floor. As the pedal travel increased, there as a slight increase in pressure (<5 bar).

Doh! I just realized that I didn't perform a test I meant to do, namely, pumping the pedal and remeasuring the pressure. Maybe next time.
 

burgerkong

Go Kart Champion
Location
Ontario, Canadeh
From my research, I found that the REP part MAY [my emphasis] fit the RS3. I could not find a p/n specifically for the RS3.

The erWin manual calls out both diameters for Golf vehicles. I couldn’t find which applied to Golfs or GTIs

E-ACCA gave me 8V1611021B for the 2019 RS3 which was superseded by the REP P/N's:

1609975431876.png


1609975469775.png


1609975393066.png


1609975502353.png
 

Mini7

Autocross Newbie
Location
Charlotte, NC
Car(s)
2017 GTi Sport PP
Following-up on emichel6888 post of Dec 27 (very interesting BTW), I took a couple of quick measurements using VCDS to measure brake pressure. I don't know where the tap for the measurement is, although I suspect it is from the ABS module.

I have to say that my measurements are inconclusive, but here they are. In each case, I pressed the brake pedal as hard as I could to get a maximum pressure reading. All pressure measurements are in Bar. With the engine running, the Hydraulic Brake Booster adaption was set to 8. I don't have the security code to change it.

Engine off: 116 (According to emichel6888 charts, this is way off. I think it is correct. I've measured 75 bar when performing a MC leak test, and that wasn't pushing the pedal as hard as I could. If I had a better grasp of basic hydraulics, I should be able to do a sanity check. Alas, I don't.)
Engine at idle, Hydraulic Brake Assist Not Activated, Brake Boost at 1: 129
Engine at idle, Hydraulic Brake Assist Not Activated, Brake Boost at 8: 135
Engine at idle, Hydraulic Brake Assist Activated, Brake Boost at 8: 130

I didn't repeat the measurements, so there could be some sample-to-sample variation not captured here. The measurements didn't vary as much as I thought, around 5% with the engine running. I don't know if a 5% difference is noticeable in practice. Also, with the engine running, I was able to push the pedal to the floor. As the pedal travel increased, there as a slight increase in pressure (<5 bar).

Doh! I just realized that I didn't perform a test I meant to do, namely, pumping the pedal and remeasuring the pressure. Maybe next time.
Try Security Code 11966 for Hydraulic Brake Booster
 

jmason

Go Kart Newbie
Location
Frederick, MD
I tried that code. It didn’t work.
 

emichel6888

Go Kart Champion
Location
TX
Following-up on emichel6888 post of Dec 27 (very interesting BTW), I took a couple of quick measurements using VCDS to measure brake pressure. I don't know where the tap for the measurement is, although I suspect it is from the ABS module.

I have to say that my measurements are inconclusive, but here they are. In each case, I pressed the brake pedal as hard as I could to get a maximum pressure reading. All pressure measurements are in Bar. With the engine running, the Hydraulic Brake Booster adaption was set to 8. I don't have the security code to change it.

Engine off: 116 (According to emichel6888 charts, this is way off. I think it is correct. I've measured 75 bar when performing a MC leak test, and that wasn't pushing the pedal as hard as I could. If I had a better grasp of basic hydraulics, I should be able to do a sanity check. Alas, I don't.)
Engine at idle, Hydraulic Brake Assist Not Activated, Brake Boost at 1: 129
Engine at idle, Hydraulic Brake Assist Not Activated, Brake Boost at 8: 135
Engine at idle, Hydraulic Brake Assist Activated, Brake Boost at 8: 130

I didn't repeat the measurements, so there could be some sample-to-sample variation not captured here. The measurements didn't vary as much as I thought, around 5% with the engine running. I don't know if a 5% difference is noticeable in practice. Also, with the engine running, I was able to push the pedal to the floor. As the pedal travel increased, there as a slight increase in pressure (<5 bar).

Doh! I just realized that I didn't perform a test I meant to do, namely, pumping the pedal and remeasuring the pressure. Maybe next time.

The graph was referencing pedal force from 22-112 lbs, perhaps pressing as hard as you can is not a good frame of reference. Under typical use pedal pressure is maybe 30-100 lbs, an average man pressing with full force can easily exceed 300-400 lbs. From what I have read the mechanical advantage from the pedal linkage and the MC/caliper piston ratio alone typically provides a force multiplier of 4-6. So if you were pressing as hard as you could, 116 Bar (1682 PSI) sounds about right.
However under actual use (with a functional booster) the brakes would lock up long before you get anywhere close to that much pedal force.
If you look at the graph the booster is really designed to provide assist in the 10-90 lbs of pedal force range. So to do representative testing you want to measure in that range, to do it properly you would need to rig something up like what was done in the paper I referenced, and then stay within the operable range of the system.

That is interesting though, I did not consider looking at the pressure sensor built into the system. I will have to see if I can find it with my OBD11 and see what kind of numbers I see with using my average pedal pressure ranges. While it won't be very precise it could give some idea of the difference in assist. What you want to do is pretend you are sitting at a stop light and try to replicate the typical pedal pressure you would use, and then again under hard braking, and then see what pressure the system see's with the engine on and off. Again, not very accurate but unless you are willing invest in some sort of rig to precisely apply pedal pressure...
 

emichel6888

Go Kart Champion
Location
TX
Is it possible your calipers are out of calibration?
I had the same thought when I measured it, but no it is accurate alright (see pic below). Now I am wondering if the one in my 2017 is 23.8 or 25.4? From what I can tell 2015-2019 all appear use the same part numbers so... However, that is also true for other cars (like the GTI w PP), and yet clearly we have two different sizes. All the different part numbers are very confusing, I really don't feel like removing it just to check. I am hoping someone else on here can provide more information. If it is the smaller one and they changed it at some point that would be great, because I will certainly install this one. But I don't want to remove the one in there now just to discover it is the same thing.
Piston size pic.jpg
 

Mini7

Autocross Newbie
Location
Charlotte, NC
Car(s)
2017 GTi Sport PP

GTIfan99

Autocross Champion
Location
FL

emichel6888

Go Kart Champion
Location
TX
Tentative plan is to have my MC replaced early-mid January. After that I'd be happy to gut the one they don't use. But assuming the one you just picked up arrives first, please tear that one apart and post what you find before I rip into a perfectly good new one, haha.
Would you be kind enough to take some measurements of the two MC's you have and let us know the piston size? There is no need to take them apart, if you would just use a caliper on the exposed piston. It appears that all of the MK7 GTI, Golf R, A3, S3, RS3,... use the same MC, and the one I have out of a 2019 Golf R has a 25.4 mm piston, which should be true for all since they all seem to reference the same MC part number, but there is also 23.8 mm version used in some applications, so it seems we can't be entirely sure until a few other folks take some measurements.

I am curious about it and was hoping someone would have figured it out by now but... I even tried contacting some of the eBay vendors selling these MC's online to see if they would check the size for me, unfortunately they all couldn't be bothered.
 
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