TESTED- Perrin Master Cylinder Brace - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

GSpeed · 08-19-2015, 05:51 PM

We had a spare analog input, a spare shock pot, a Perrin master cylinder brace, and some time to kill. Let's find out if it actually works!

First thing we did was mount a shock pot horizontally in line with the master cylinder:

Interestingly enough, we had marginal deflection. On the order of a few thousandths of an inch. Watching it, we noticed the master cylinder was actually deflecting upwards, not forward like you'd think. It rotates around a point on the firewall, roughly, so that the end is pushed upwards. So we got a little creative with some machining measurement fixtures, and wound up with this:

Despite the angle of the picture, the shock pot was perfectly vertical and in line with the front face of the master cylinder. Once we had that setup, we definitely recorded some deflection.

The tests were performed with the engine off (no vacuum assist). The brake pedal was pressed several times at varying pressure. Brake line pressure was monitored via OBD2 at a resolution of 1 bar (14.7 psi), and the master cylinder deflection was measured via analog channel at a resolution of 0.001" (4 inch linear potentiometer at 12 bit resolution).

You can see here, despite what may be a structurally inefficient position, it's absolutely effective, reducing master cylinder deflection by 57%. Could it be better? Maybe, but the returns would be minimal. You guys already know it improves feel, here's why.

Chazzzy · 08-20-2015, 09:49 AM

VERY Cool!! Thanks for the Info!

Rameus · 08-20-2015, 01:39 PM

Practically every thread by you guys provides real data or at least truly useful information.

Thanks for taking such a comprehensive approach to developing the platform, and above all, sharing the results with us on a regular basis.

If I had 10 posts to my name I'd just click thanks, but this probably gets my point across better anyway.

waltco · 08-20-2015, 06:12 PM

This is awesome! Thank you so much for sharing!

why? · 08-20-2015, 07:51 PM

that is total win.

aegisdrgn · 08-23-2015, 08:47 PM

The numbers don't lie! Thanks for making the test results available!

duke_FRS · 08-24-2015, 01:49 PM

This is why I love this community. Great information

JS + BRZ · 08-27-2015, 08:34 PM

Awesome stuff. Thank you so much.

timurrrr · 08-07-2020, 03:23 AM

Quote:

Originally Posted by GSpeed

Brake line pressure was monitored via OBD2 at a resolution of 1 bar (14.7 psi)

Sorry to necro this old thread, but do you happen to remember how to monitor brake pressure via OBD2?

7c8 · 08-07-2020, 07:17 PM

Quote:

Originally Posted by timurrrr

Sorry to necro this old thread, but do you happen to remember how to monitor brake pressure via OBD2?

This is only available over the CAN:
Address: 0x0d1
Length: 1 byte
Offset: 2 bytes

timurrrr · 08-07-2020, 08:09 PM

Quote:

Originally Posted by 7c8

This is only available over the CAN:
Address: 0x0d1
Length: 1 byte
Offset: 2 bytes

Got it, thanks! I was thinking you knew some trick to get it via OBD-II without CAN

7c8 · 08-08-2020, 12:27 PM

Quote:

Originally Posted by timurrrr

Got it, thanks! I was thinking you knew some trick to get it via OBD-II without CAN

Haha, unfortunately I haven't seen it available through OBD. Good luck!

08-19-2015, 05:51 PM	#1
GSpeed Join Date: Apr 2015 Drives: 2015 BRZ Location: Motorsport Ranch, TX Posts: 619 Thanks: 227 Thanked 1,181 Times in 362 Posts Mentioned: 30 Post(s) Tagged: 1 Thread(s)	TESTED- Perrin Master Cylinder Brace We had a spare analog input, a spare shock pot, a Perrin master cylinder brace, and some time to kill. Let's find out if it actually works! First thing we did was mount a shock pot horizontally in line with the master cylinder: Interestingly enough, we had marginal deflection. On the order of a few thousandths of an inch. Watching it, we noticed the master cylinder was actually deflecting upwards, not forward like you'd think. It rotates around a point on the firewall, roughly, so that the end is pushed upwards. So we got a little creative with some machining measurement fixtures, and wound up with this: Despite the angle of the picture, the shock pot was perfectly vertical and in line with the front face of the master cylinder. Once we had that setup, we definitely recorded some deflection. The tests were performed with the engine off (no vacuum assist). The brake pedal was pressed several times at varying pressure. Brake line pressure was monitored via OBD2 at a resolution of 1 bar (14.7 psi), and the master cylinder deflection was measured via analog channel at a resolution of 0.001" (4 inch linear potentiometer at 12 bit resolution). You can see here, despite what may be a structurally inefficient position, it's absolutely effective, reducing master cylinder deflection by 57%. Could it be better? Maybe, but the returns would be minimal. You guys already know it improves feel, here's why.

08-24-2015, 01:49 PM	#7
duke_FRS Member Join Date: Mar 2015 Drives: 2015 FRS Hot Lava 2014 CT200H Location: Miami, Florida Posts: 54 Thanks: 5 Thanked 19 Times in 12 Posts Mentioned: 2 Post(s) Tagged: 0 Thread(s)	This is why I love this community. Great information __________________ Open Flash Tablet Stage 1 93 \| Borla Cat-Back \| VOSSEN VFS1 \| Eibach Sportline

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08-20-2015, 09:49 AM	#2
Chazzzy Member Join Date: Apr 2015 Drives: VW GTI Location: 845; NY Posts: 14 Thanks: 73 Thanked 5 Times in 4 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	VERY Cool!! Thanks for the Info!

08-20-2015, 01:39 PM	#3
Rameus Member Join Date: Mar 2015 Drives: 2015 FR-S Location: Toronto Posts: 28 Thanks: 7 Thanked 15 Times in 9 Posts Mentioned: 3 Post(s) Tagged: 1 Thread(s)	Practically every thread by you guys provides real data or at least truly useful information. Thanks for taking such a comprehensive approach to developing the platform, and above all, sharing the results with us on a regular basis. If I had 10 posts to my name I'd just click thanks, but this probably gets my point across better anyway.

08-20-2015, 06:12 PM	#4
waltco Member Join Date: Jul 2015 Drives: 2013 Subaru BRZ Location: Raleigh, NC Posts: 13 Thanks: 12 Thanked 5 Times in 3 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	This is awesome! Thank you so much for sharing!

08-20-2015, 07:51 PM	#5
why? Only happy when it rains. Join Date: Feb 2013 Drives: series.blue Location: Harnett county NC Posts: 1,995 Thanks: 5,698 Thanked 1,263 Times in 749 Posts Mentioned: 25 Post(s) Tagged: 0 Thread(s)	that is total win.

08-23-2015, 08:47 PM	#6
aegisdrgn Senior Member Join Date: Dec 2013 Drives: Scion FR-S 10 Series #2263 Location: Los Angeles Posts: 471 Thanks: 208 Thanked 277 Times in 179 Posts Mentioned: 4 Post(s) Tagged: 2 Thread(s)	The numbers don't lie! Thanks for making the test results available!

08-27-2015, 08:34 PM	#8
JS + BRZ Banned Join Date: Dec 2013 Drives: 2010 MS3 Location: Los Angeles Posts: 1,820 Thanks: 1,180 Thanked 1,161 Times in 597 Posts Mentioned: 18 Post(s) Tagged: 0 Thread(s)	Awesome stuff. Thank you so much.

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