Variable pressure (?) power steering pump?

[BBShark]

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

[69427]

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]

Originally Posted by 69427

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.

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.

[BBShark]

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

[69427]

Originally Posted by BBShark

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

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.

[BBShark]

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).

[69427]

Originally Posted by BBShark

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).

Thanks again Larry!

[69427]

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!

[mrvette]

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.....