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post #1 of 6 (permalink) Old 03-31-2017, 11:56 AM Thread Starter
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Discussion on manually adjusting EVO Solenoid sensitivity

Let's start a new thread here to discuss how to manually adjust the EVO Solenoid to raise/lower the level of assist.
As some of you may know, unplugging the controller from the EVO Solenoid actuator on the PS pump will make it default to "full assist" mode.

I'm personally polling my team to see if they would prefer to lower the level of assist or leave it alone. I'm on the fence here as I think my specific lemons car suspension is stiff enough now that lowering it might give us better sensitivity at speed (might be a hair too light).

GROG6 Started this conversation in my Race 7 recap thread and provided a ton of good info
Results/Experiences from our 7th! 24 hours of Lemons race with a tbird

EVO Module Pictures from XR7-4.6
move along people, nothing to see here



EVTM Diagrams from Rayo
move along people, nothing to see here



Pinout of connector going into the EVO control module from XR7-4.6
move along people, nothing to see here


Two leading solutions:
1) Add shims to the EVO Solenoid to lower pressure
2) Create a box to send the right signal

My thoughts
#1 will require a bit of trial and error here (I don't know how thick a shim to use and since my tbird isnt' street legal, I cannot contribute here).
Bills Hot Rod Company


Therefore, I will focus on #2:

* I see from the block diagram that the VSS is a PWM signal. For some of you, emulating/replacing the VSS signal might be good enough but the law of unintended consequences may come into play here as the EVTM ALSO mentions that this signal is used for determining the upshift schedule. WHile this is a "dont care" for anyone with a manual transmission, I don't have this EVO wiring on my car anymore so I cannot just mod the VSS signal for my personal needs.

My suggestion if you went this route is to look at a cheapie arduino. You can rig up a potentiometer as a dial and it the arduino can generate a 5V PWM signal without any fuss (0-100% duty cycle). I'll help with the code if you need it.
https://www.arduino.cc/en/Tutorial/PWM

* It seems like the signal going to the EVO solenoid may actually be a PWM signal. This seems wierd to me but I guess it makes sense if you consider that solenoids really only are ON or OFF so if you are trying to adjust flow of fluid and the solenoid is blocking the way, adjusting between ON/OFF makes the most sense.

The best way to confirm this would be to have someone put a multimeter on the Y/LG to LB voltage differential at the plug where it goes into the EVO solenoid while the car is running (but not driving). it could also be the opposite of what I'm suggesting below but I wouldn't know without being able to put a voltmeter on a car with a currently working EVO system (some voltmeters can also measure duty cycle BTW so you can put to rest what kind of signal this is and how high it ranges).
https://www.amazon.com/Multimeter-Au...dp/B015OFMUYO/

Gunn's thoughts:
- Right now, the signal is 0% duty cycle so it's at FULL ASSIST with the connector unplugged.
- If the signal is 100% duty cycle (which could be 5V or 12V -- I really don't know), it should be MIN ASSIST. I don't see how this would wear out the solenoid since it will just be pushed out all the time (vs going in/out according to the PWM pulses)


NOTE:
You can easily output/control a 12V PWM signal from an Arduino without much effort.
Arduino for Beginners: Controlling a 12V DC motor/fan with an Arduino

There's also a $34 12V tolerant Arduino you can buy off the shelf but that board is probably significant overkill for this simple project (unless you have other plans like using the Arduino to read OBD2 codes/signals and make decisions (library still in early development though so I don't expect you'll get far in the near future).
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post #2 of 6 (permalink) Old 03-31-2017, 04:48 PM
No, Mr. Lemmywinks, No!!!

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I plan to do some experiments this weekend; I have a solenoid, and a PWM driver that has variable frequency and duty cycle, and if get good results, I'm not above testing this on Lazarus.

A parking/driving switch would be good enough for me; others might want fine control. Actually, pass thru and manual would be better.

I understand why we have a cooler on our Steering; our steering uses almost NO flow, and tight pressure control.

Remember, you only adjust down, and that has to go somewhere.

I can measure motion of the solenoid, but not under pressure, so it will be a tough measurement.


Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
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post #3 of 6 (permalink) Old 03-31-2017, 09:01 PM
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Minor correcton - the VSS is a pulse stream, 8000 pulses per mile when calibrated properly.

One possibility would be to take the signal, and divide it by, say, 8 or 16; that would make it see the speed as being 1/8 to 1/16 the actual speed (i.e., at 64 MPH it would see 8 or 4 MPH). Or even /2 or /4 (again, at 64, you'd see 32 or 16 MPH effective).

But it's not PWM; it's just a frequency dependent pulse train.

It's also capped at 12V; so if you want to do anything, a frequency generator that puts out 5 to 12V at the frequency you want (figure 8,000 pulses per mile * miles per hour / 3600 to get it back to Hz) and you can dial in the speed it SEES that easily.

(THOSE are dirt cheap on places like Banggood and DX ... I've got one I use to play with speedos for the Cougar now, as I'm working out how to do a few things. This is nice in that you can also recalibrate the needle on the bench, no driving needed - take the frequency, multiply by 3600, divide by 8000, and that's the MPH it should indicate. Or to put it another way, 120Hz = 54 MPH; 240 =108, 60 = 27. You can probably plot any other speeds and frequencies you need.)

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post #4 of 6 (permalink) Old 04-01-2017, 12:33 PM
No, Mr. Lemmywinks, No!!!

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An arduino box is probably the way to go, and almost any of the PWM driver plugins would work.

That can't be much more than ~5A, looking at the size of the traces on the board.

Here's the analysis I did of the circuit; if anyone can read me the numbers off the transistors, that would be helpful.

Quote:
That said, I looked at those; it is indeed a PWM control circuit; the main drive power is supplied by the larger, to-126 package transistor beside the connector.

I can't find anything on that chip; I'll call someone tomorrow, and find out what it is.
Moto got bought by ON Semi, I buy stuff from them, so I should be able to find out something.

Those are tiny resistors and transistors, linked with tiny traces, so there's not much current in that circuit.

There are multiple lines from the chip into the circuit, so it monitors for failures; all the sensors go into the chip thru buffer circuits.
I'm going to make some measurements today, and see what it takes to move the solenoid around, and how hot it gets.

I have power supplies, and a variable PWM, so I should get some good results.

I wish I'd saved the poloroid scope camera from the trash heap; There's film available again now, lol.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
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Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.

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post #5 of 6 (permalink) Old 04-01-2017, 12:51 PM
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Just throwing this in here.
Attached Images
File Type: jpg IMG_0776.JPG (20.3 KB, 10 views)

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post #6 of 6 (permalink) Old 04-01-2017, 01:44 PM
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One more thing would be to take a portable DSO into the car, do some driving while scoping the VSS and the PWM output, and see what you get.

Ditto for the steering wheel sensor and the PWM output over an identical pass.

Enough channels and storage, monitor both.

But a quick synopsis - if you don't want it to soften up any (i.e., more assist) during hard turning (i.e., when cranking lock to lock; I don't think that's a concern in Lemons racing) then a simple frequency/PWM converter, either an Arduino-alike (shucks, the stand alone microcontroller and proper buffering would do the job!) or even a brute force discrete solution (say a freq/voltage converter, and a voltage-controlled PWM output, along with buffers) would do the job fine. (The Arduino or microcontroller solution adds the possibility of monitoring something like, say, the switch XR7-4.6 showed, or even tweaking on the track; even possibly different profiles so Muscles Armstrong gets a firmer steering feel than Wally Wimpster ... )

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