Variable pressure (?) power steering pump?

Helped a buddy the other week replace the p/s pump on his wife's car (fwd Cavalier or something). The p/s pump had an electrical connector on it. I'm curious what it does. Does it allow the pressure to be modulated by the ECM? I'm curious about a custom system that would open a bypass in the pump to reduce the pump drag at WOT or near WOT, and also possibly help reduce the fluid temp at high RPMs. Can anyone enlighten me on these pumps?

Thanks.

That is an EVO valve. It regulates the bypass pressure based on vehicle speed and handwheel rate ( full boost for evasive manuvering). I have looked into making a controller for an EVO valve and it would be pretty easy for the vehicle speed but a little more difficult to package the steering wheel rate sensor.

My feeling is that it could be done with a 2 axis accelerometer.

BBShark said:

That is an EVO valve. It regulates the bypass pressure based on vehicle speed and handwheel rate ( full boost for evasive manuvering). I have looked into making a controller for an EVO valve and it would be pretty easy for the vehicle speed but a little more difficult to package the steering wheel rate sensor.

My feeling is that it could be done with a 2 axis accelerometer.

Click to expand...

:shocking: What does this bring to the table???:beer:

BBShark said:

That is an EVO valve. It regulates the bypass pressure based on vehicle speed and handwheel rate ( full boost for evasive manuvering). I have looked into making a controller for an EVO valve and it would be pretty easy for the vehicle speed but a little more difficult to package the steering wheel rate sensor.

My feeling is that it could be done with a 2 axis accelerometer.

Click to expand...

As we spoke here :
http://www.vettemod.com/forum/showthread.php?t=8693
The steering sensor problem remains.
Accelerometer might be a problem soo many vibration to screw the acceleration integration. A magnet on one wheel with an hal sensor would be more reliable.
....
That make me think about a post on hackaday where a guy was using a laser mouse to sense the speed of a robot by shining at the carpet below it.
You could sense the steering column, provided you can keep it out of the dust with a casing and give the sensor a nice uniformly surface to shine at.
It's dirt cheap, works out of the box and interfaces nicely by usb or serial.

denpo said:

BBShark said:

That is an EVO valve. It regulates the bypass pressure based on vehicle speed and handwheel rate ( full boost for evasive manuvering). I have looked into making a controller for an EVO valve and it would be pretty easy for the vehicle speed but a little more difficult to package the steering wheel rate sensor.

My feeling is that it could be done with a 2 axis accelerometer.

Click to expand...

As we spoke here :
http://www.vettemod.com/forum/showthread.php?t=8693
The steering sensor problem remains.
Accelerometer might be a problem soo many vibration to screw the acceleration integration. A magnet on one wheel with an hal sensor would be more reliable.
....
That make me think about a post on hackaday where a guy was using a laser mouse to sense the speed of a robot by shining at the carpet below it.
You could sense the steering column, provided you can keep it out of the dust with a casing and give the sensor a nice uniformly surface to shine at.
It's dirt cheap, works out of the box and interfaces nicely by usb or serial.

Click to expand...

The accelerometer actually works well. Transients (vibration) can easily be filtered out. Also hydraulics systems are inherently dampened.

I did this with a Wiimote and plotted the vectors. You can actually draw pictures in the air with it (that is what we were trying to do).

Could the VSS from a newer trans (ie: T56) be used for speed sense, and then an ABS or similar sensor & reluctor wheel (not sure if thats the right terminology or not) be mounted on the steering shaft or rag joint area?

The VSS could be used for speed sensing and the encoder for the steering wheel could be adapted. Ford makes a standalone module that could provide an output for the rate solenoid (on the pump). However, I think the accelerometer based control would be easier to do. Hell, it's already done. Take a look at products like the G-analyst

I'm curious about at what speed "threshold" that the pump assist isn't needed. (I assume it depends on the car weight, tire footprint, and the personality of the steering rack/box) My interest in this sort of project is just for track days, and it would be handy if the assist wasn't needed most of the time, both to free up a couple horsepower and keep the p/s fluid temperature down a bit. IIRC I have ABS wheel sensors in the front of my car (the front suspension is a '96), so it would be easy to build a F/V converter feeding an adjustable threshold comparator for when to disable or enable the assist.
A MAP sensor input might also be usable as this would indicate (depending on the selected comparator threshold) if the car was accelerating hard (indicating that the car was most likely in a straightaway) and the assist could be disabled. The MAP reading could also be used to override the speed input so that there is always assist under part throttle conditions (such as cornering).

There's several questions I don't have answers for yet.

1) What is the worst case horsepower drain to run the pump at full assist?
2) What is the horsepower drain to run the pump when the bypass is open (ie: is this project worth the time and effort)?
3) What kind of signal and amount of current does it take to drive the solenoid?
4) Can the solenoid be turned on 100%, or does it require some PWM control?
5) What GM cars came with this type pump (I need to retrofit a v-belt pulley to it for my application)?

There's a company out of Denmark called something like EZ steering. Not sure how much but they take stock steering columns and fit their electric motor/controller to add pwr steering to vintage cars. Nice thing is the motor goes on the column under the dash so you can remove the pump and all hoses associated. The also have a speed sensor that goes in the speedo cable so the system is variable assist. Not sure how much or if they have a C2/C3 option.

Scoured a junkyard yesterday looking for a pump that ideally has three traits:

1) Aluminum body
2) EVO valve
3) Shaft size allowing swap to vee-belt pulley

Pretty much struck out finding one meeting all three traits, so I might just focus on an EVO pump that I can somehow get a vee-belt pulley to fit. IIRC, the old pumps I have use a shaft size of about .660" while the serpentine pulley pumps look to be closer to .720. One upside, the two wire harness to the solenoids in the cars I looked at used very small wires, making me think the solenoid current was reasonably modest. That makes life easier when sourcing a switching transistor for the PWM circuitry.
When the weather cools down a bit more I'll take a trip to one of the other junkyards to see what they have out in the yard.

Mike I'm not sure but I think the bypass valve on the EVO pump will fit the pump yo have. If I recall you are using the smaller ~80's pump? You might want to look at Ford pumps which are aluminum and the EVO system they use is the same setup, a solenoid on the bypass valve. Both the GM and Ford are 10ohm coils. Here is some info I got a while back about the Ford system. Ford system is called VAPS

Steering Wheel Rotation Sensor
An optical encoder electronic steering sensor (photocell), mounted on the lower steering column, is used to establish the rate of the steering wheel rotation.

· When the steering wheel rotation rate reaches 30 rpm (15 rpm for air suspension model), the output current to the power steering control valve actuator begins to reduce, providing additional power steering assist.
· Once the steering wheel rotation rate reaches 60 rpm or greater, the output current to the power steering control valve actuator reaches zero and full power steering assist is provided.
· After the steering wheel rotation rate drops below 30 rpm, the output current returns to the amount of current regulated by the vehicle speed sensor input within one second.


Vehicle Speed Sensor
The vehicle speed sensor is located on the transmission and is used to establish vehicle speed

· The output current to the power steering control valve actuator is a function of vehicle speed and the steering wheel rotation rate.
· When vehicle speed is less than 16 km/h (10 mph), the power steering control valve actuator output current is less than 60 mA and full power steering assist is provided.
· As vehicle speed increases to 40 km/h (25 mph), the current increases linearly to 300 mA.
· As vehicle speed continues to increase up to 142 km/h (88 mph), the current increases linearly to 590 mA. The current then remains constant at 590 mA for vehicle speeds greater than 142 km/h (88 mph).
· Conversely, as vehicle speeds decrease, the current decreases at the linear rate.

I have some better information (somewhere) but this gives you an idea of the control scheme

Thanks for the additional info, Larry. This gives me a few more options. It will certainly save me time if I can just transplant a solenoid into the present pump I have on the car (I won't have to make new pump brackets or modify a pulley to fit). I'll take my VOM with me next time to double check the solenoids to try to weed out any obvious bad samples.

Thanks again.

69427 said:

Thanks for the additional info, Larry. This gives me a few more options. It will certainly save me time if I can just transplant a solenoid into the present pump I have on the car (I won't have to make new pump brackets or modify a pulley to fit). I'll take my VOM with me next time to double check the solenoids to try to weed out any obvious bad samples.

Thanks again.

Click to expand...

Well, I'm suspecting I've run into a bump in the road here. I looked at my pump as best I can (it's still bolted on the engine) and I only see the two fluid ports (pressure and return). It looks (to me) like the output port and the relief valve "stuff" share the same port. I don't see a separate port that a solenoid could be installed in. So, unless I'm missing something here, I may still have to get another pump, and then figure out how to put a v pulley on the different size shaft in the later (serpentine belt) pumps.

Mike, Here is a picture of a conventional bypass valve (top) and an EVO valve (bottom).

BBShark said:

Mike, Here is a picture of a conventional bypass valve (top) and an EVO valve (bottom).

Click to expand...

Thanks for the picture Larry. For whatever reason I was under the impression that the solenoid screwed into a separate/third port in the housing. It looks like, as you mentioned before, that the solenoid can just replace the old setup.
How do you clock the orientation of the electrical connector and the outlet fitting? I see a hex nut looking thing in the middle of the structure, but I'm unclear if both items are individually clockable.

Thanks again.

The outlet port housing (the thing with the blue plug), can swivel around and I think there are oring seals on the valve. The electrical connector also swivels around and is held on wit an e-ring. The electrical connector is also the coil housing so the coil rotates with the connector (around the core).

BBShark said:

The outlet port housing (the thing with the blue plug), can swivel around and I think there are oring seals on the valve. The electrical connector also swivels around and is held on wit an e-ring. The electrical connector is also the coil housing so the coil rotates with the connector (around the core).

Click to expand...

Thanks again Larry!

Power steering cooler question.

I need to put a cooler on the system over the winter, but some aspects don't make sense to me. The coolers all seem to be in the return line to the pump. Correct me if I'm wrong, but isn't most of the heat generated in the system due to the pressure/bypass in the pump? It seems to me that the fluid in the reservoir just keeps getting hotter as the engine (and therefore the pump) is at high RPMs in the straights, and then when you turn into the corner all this hot fluid is pumped into the rack. The hot fluid exiting the rack then goes through the cooler, gets cooled a touch, and then goes into the reservoir to be heated up again down the next straight. The low pressure location of the cooler only makes sense to me if there is a low volume quiescent flow through the system all the time, allowing the cooler to continually pull heat out of the fluid. It seems the best location for a cooler is in the line between the pump and the rack so that the fluid can be cooled before it gets to the rack (although the line pressure issue gums up the works).
So, help me understand things. My main concern here is protecting the rack from overheated fluid. The pump was uber cheap ($10) and easily replaceable, but the rack is a custom width unit that was a PITA to procure and not cheap.
I'd appreciate some input here to make sure I understand things before I waste a lot of time replumbing the lines.

Thanks!

My only comment is that ATF lines are on the return into the pan, and that engine oil coolers are on the same side, return.....and from what I remember about my '87 vette, the cooler was on the return line.....

I leave that to the guys that designed it....it maybe a cost/pressure/hose issue or maybe that in fact, given a certain volume of cooling capability, it really don't matter which end, long as the fluid is cooled enough.....


:thumbs: