Where to put a brake pressure sensor?
Hi,
I want to add a brake pressure sensor to my datalogger. Now is the time to do it, in between seasons and with the car up on stands. Since the RX-8's ABS has control over front to rear braking force, where should I put that thing? Thanks, Nick |
What data are you wanting? How hard you are pushing on the brake pedal, how hard the braking system as a whole is working, something else?
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I put it in the line from MC to front brake input at ABS controller. If you have a DSC controller I can hook you up with the entire setup.
AC |
Originally Posted by NotAPreppie
(Post 4879720)
What data are you wanting? How hard you are pushing on the brake pedal, how hard the braking system as a whole is working, something else?
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Originally Posted by Adax
(Post 4879741)
I put it in the line from MC to front brake input at ABS controller. If you have a DSC controller I can hook you up with the entire setup.
AC |
Originally Posted by Mr. Pockets
(Post 4879772)
This was what I thought I’d just do. But I’d be real interested to see specifically how you did yours. |
Originally Posted by Adax
(Post 4879873)
I'll take a pic tonight
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Oh that's very interesting. Is that flexible line a single part you bought?
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Originally Posted by Mr. Pockets
(Post 4879970)
Oh that's very interesting. Is that flexible line a single part you bought?
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Originally Posted by Adax
(Post 4880006)
Yes, you want it? Switched to a non DSC ABS unit which it does not work with.
Why did you seitch ABS units, and did the ECU care? |
Originally Posted by Mr. Pockets
(Post 4880022)
I totally do. I’ll send you a PM. Why did you seitch ABS units, and did the ECU care? |
Do you have any CAN dumps from your car? I'm playing with CAN on mine... but the car doesnt run yet and I don't have any CAN from a running car
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I'd love to have a better understanding of the CAN and an ability to interpret a CAN dump. PM me and I can send you something if you walk me through it.
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Originally Posted by Adax
(Post 4880135)
I'd love to have a better understanding of the CAN and an ability to interpret a CAN dump. PM me and I can send you something if you walk me through it.
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I may still have a CAN log somewhere...the vendor for my datalogger used it to find throttle, rpm and wheel speed. |
does S2 cars have brake pressure or bake switch signal through CAN? I have AIM DL 2 and been trying to get brake signal but none of the protocol i tried worked.
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Originally Posted by trackjunkie
(Post 4880434)
does S2 cars have brake pressure or bake switch signal through CAN? I have AIM DL 2 and been trying to get brake signal but none of the protocol i tried worked.
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Originally Posted by Adax
(Post 4880468)
All DSC cars have a brake line pressure sensor but I don't know if it is accessible via CAN. You'd probably have to convert it to some usable units which would require your own sensor for calibration but I'm just guessing.
According to OBD Fusion with the $10 Mazda add-on pack, the ABS/TC module is on "Network B" (with the Restraint Control Module) and there is a PID for Master Cylinder Pressure. The unit options given are kPa, inHg, and psi. OBD Fusion only lets you connect two one of the two networks at a time. Apparently, the RX-8 has two CAN networks; ISO 9141 and ISO 11898 (MS/HS CAN). I guess both are made available via the plug but my hardware/software combo can only address one at a time. FWIW, network A includes EPS, instrument cluster, ECU, remote keyleses entry and TPMS modules. |
Well, shit. If we could find the PID and decode it, then None of us would need a pressure sensor. :) I’ll try to find a CAN log. My car is not currently running. I wonder if I could dump one out anyway, with just the ignition on... |
The catch being that you'd have to be monitoring both CAN networks simultaneously if you wanted both ECU data and ABS/DSC data at the same time. Theoretically, if your data logger doesn't support interfacing with more than one CAN bus at the same time, you could bridge the two with an Arduino and a pair of CAN shields. Just have the Arduino poll the brake pressure PID periodically via one shield and store the data. Then have it respond to polling requests for that data via the other shield.
But yah, finding the PID should be as easy as connecting your CAN logger and ELM327 to the ABS/DSC network and logging the desired PID from both devices. Then just cross reference the data to get the module ID and PID. |
Originally Posted by Adax
(Post 4880468)
All DSC cars have a brake line pressure sensor but I don't know if it is accessible via CAN. You'd probably have to convert it to some usable units which would require your own sensor for calibration but I'm just guessing.
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Originally Posted by trackjunkie
(Post 4880508)
well that's good to know. now just have to keep bugging AIM to get it working with the DL. they have several protocol for rx8. one works with AFR and water temp but the RPM is jacked up. the other one rpm works fine but AFR and water temp doesnt work.
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That's kind of odd since the ABS/TC module is on a different CAN bus from the ECU.
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Originally Posted by NotAPreppie
(Post 4880488)
The catch being that you'd have to be monitoring both CAN networks simultaneously if you wanted both ECU data and ABS/DSC data at the same time.
Granted, it hasn’t event been able to read CAN and OBDII without messing with the car. So I think going the simpler route of an analog pressure sensor is the way to go. |
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