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Could you get the ride height data for each front wheel from the OBE II interface and use that to track wheel position?

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Yes, I was Jims_97_ETC before I changed cars.

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3 minutes ago, Cadillac Jim said:

Could you get the ride height data for each front wheel from the OBE II interface and use that to track wheel position?

My car is the ESC with non-electronic suspension. I went that route so that I could build it old school. I'll have to make measurements using a tape measure.


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You don't need the OBD II system if you read the sensors directly.  The ride height sensors are, within the sensor, just a source of voltage proportional to sensor arm angle.  It's possible that there are more electronics in the sensors, and they vary from year to year, but if you interface with the sensor directly, you can have data recording or even cockpit monitoring of wheel height on each wheel with signal directly from the wheel height sensors.

You can install the ride height sensors of your choice or even make your own.  If the sensors are a problem for racing, you can remove them after testing.

This is a concept of a wheel height sensor.  Complexity added in later models will include a gear reduction between the sensor lever and the voltage divider shaft, and, for a later model that uses full modules at the wheel height sensors, digital electronics to digitize the voltage output and put it on a Class 2 bus.  You will like the early model, perhaps with the gear reduction (a little plastic planetary producing about 4:1 is about right).  You will need to calibrate your guages from 0-5 volts to inches or cm of wheel height.

Notional_Wheel_Position_Sensor.png


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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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It is a good idea and it looks doable, but I'm really not interested in spending the time to build or troubleshoot the system for this car... I mean, sure as a scientific minded individual, the prospect of geeking out the car has crossed my mind many times. However, if the final cut of the springs result in fender lips that sit at (or just below) the top of the tire tread, we're good. 

The Grand Prix struts are also non-electronic. So if I was going to add the ride height sensors, it would be a "from scratch" build.

Now if I was using air bags instead of springs, it would be cool to even program pre-set heights and control them from the driver seat.

Rough road

Smooth road

High speed

Smooth track

Car show low


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

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One thing I didn't mention before. The Thunderbird springs have about 0.10" wider inside diameter than the springs intended for the Cadillac upper mounts. To keep them tight and centered on the perch, I used their isolators in addition to the isolators supplied with the mounts. This made them a press fit and it also increases the vibration absorption.

I used the springs' lower isolators in place of the Grand Prix strut lower isolators on the bottom and they fit well with the contour of the strut base. There is just a slight spring overhang on the inboard side of the perch, but the spring is fully supprted and the fit is good and safe.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

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The Cadillac uses 16MM bolts to mount the struts to the spindle. And it uses slotted lower holes to make camber adjustments. The Grand Prix struts use 14MM bolts and do not have a slotted hole. I bought a 16MM drill bit to open the GP holes, but instead of slotting the lower hole, I chose to first try camber adjustment bolts on the upper hole.

0917171854a-1.jpg

The camber adjustment bolts are 14MM with an egg-shaped cam for positioning the spindle. By marking the bolt head and spindle, I can dial in some camber for the track and return it to the original setting for the street.


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The ride height sensors don't have anything to do with the shocks, electrically.  They are little boxes that bolt to the chassis and have arms that stick out, then links from the ends of the arms to a suspension arm.  All Cadillacs that have rear-end leveling have them on the rear.  The ones that connect to the PZM have three-wire connectors (hot on start and run, ground, signal).

But, I see your point, and also that you have moved on.

Adding a bolt with a cam on it for quick adjustment of camber for road vs. track is a really great idea.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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26 minutes ago, Cadillac Jim said:

The ride height sensors don't have anything to do with the shocks, electrically.  They are little boxes that bolt to the chassis and have arms that stick out, then links from the ends of the arms to a suspension arm.  All Cadillacs that have rear-end leveling have them on the rear.  The ones that connect to the PZM have three-wire connectors (hot on start and run, ground, signal).

 

Oh, yeah. I remember seeing those on the ETC models. My lowe A-Arms have unused tabs for them and I bet that all necessary bolt holes are in place too.

It might not be such a pain to add on. Worth another look when I get the car farther along.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

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My thinking is that if you do geek out the car just a bit, like you do when you use auto tuning software, having a record of ride height for each wheel could be very valuable in selecting shock damping, evaluating tires, etc.  Very little software can tell when all the tires aren't in the same plane and thus flag wheel hop, for example, and whenever any wheel hits its limit of travel you need to know that the suspension dynamics have gone back to the stone age for that wheel.  I can think of ways that a real-time display from that data could be more valuable in an autocross race than any other dashboard readout.

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-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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A very good point, Jim. Very good. The readout would have car show value as well. 

It may even be possible to incorporate accelerometer data to get lateral acceleration values along with using the ride height sensors to gauge the car's tilt and determine what amount of outboard tilt provides the right balance between loading the outboard front tire for traction in a turn vs. level ride for stability and suspension geometry.

Front suspension roll, rear suspension roll and the combination of both could be tuned for the best overall result or for the slow sharp turns of solo 2 races where reaching speeds above 50 MPH is rare as opposed to the faster sweeping turns of pro solo where 80 MPH or more might be experienced.

I could even replace the manually adjustable supports on the rear wing for actuators and have a variable rear end down force capability.

Come to think of it, I would like to explore these possibilities as a phase 2 upgrade.

For now, I will focus on finishing up this phase 1 build and then work on some engine and paint and body issues. As it is, due to time and money limitations, this car has not been driven regularly in a year and a half, and now leaks oil too badly to be driven again without attention to the engine. It has been up on jackstands for 3 months for this front end build, and my suspension build in current form started about 4 years ago.

I need to finish baking the cake then work on the icing.

BTW: I was playfully using the "geek out" term.


Click here to visit the main directory for my subforum about my 2002 Eldorado build for autocross racing:

http://caddyinfo.ipbhost.com/index.php?showforum=96

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Engine oil leaks?  That bothers me because sitting unused should not cause things to open up.  Where is the oil coming from?

Wheel height sensors can always be added later because it's all totally separate and the mounting is easily accessible.  It's the kind of thing you would use in road tuning and trial laps, and you don't need it in the way when you're doing design and construction.  I got the idea when you mentioned wheel travel limits and measuring wheel height with the strut bellows/boot off, then having to put the bellows/boot back on for the road.


CTS-V_Dashboard.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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