[Clipse3GT]

Alright, so in another step to pioneer our car platform. I was thinking about converting from a mechanical pwr steering system to a electric power steering system. It's not very common in most cars, however, a few cars do come with electric power steering (i.e. 2nd. Gen Toyota MR2). A lot of off-road/ rock crawler guys use electric opposed to mechanical.

Now there is an obvious advantage to using a electric pump over a mechanical, which is cutting down the parasite drag that the mechanical pump produces thus lower the hp./tq. The also advantage that I see is that the stock pump is sluggish if anyone hasn't noticed yet. Perhaps chaning to a electric pump would solved this issue a bit.

The pump itself runs off a 12V supply, however it draws alot of amps. About 70-80 Amps @ 12V while it turned full to either side, less while the wheel is straight or the car is moving since the wheels are in motion requiring less effort.

Thus knowing this we know we need a circuit breaker and a relay, both have to be heavy duty. The relay would have to be a heavy duty one made by Bosch (Single Pole, Single Throw) rated at 75 amps (Part # 0 332 002 156). The circuit breaker is a high current one made by Buss rated at 80 Amps, self-resetting breaker, (Part # 181080F). Now this is important in case of line spikes, which could reset the breaker so there is need to have a self-resetting one so it does not present a safety hazard at the track.

The pump has another 4 wires beside the pwr and ground that are PWN controllers, which I think I could use to control the pump via my Haltech E8 to relate the vehicle speed sensor to speed up or slow down the pump.

***NOTE***
It would be perfectly fine to run the pump at full speed, the PWN control is not a must.

Incase you are inclinded and want to know how the pump is controlled.

How To:
Toyota MR2 Power Steering System

Installing the Electro-Hydraulic Power Steering System



Plan:
2nd Gen Toyota MR2 PWR Steering Pump

Bosch Relay 75amp (Part # 0 332 002 156)

Buss HC Circuit Breaker (Part # 181080F)

Let's discuss the pro's and cons :wavey:

 

[Phil]

Yeah, you're crazy in all the right ways.

 

[Clipse3GT]

A little article I found on Honda-Tech

To me, power steering is a great help for autocrossing, particularly when running 9.5" slicks. With the electric pump, there are no problems with 'beating the pump' in tight turns or slaloms. It's just constant power steering at any speed. The other really nice feature is that I don't have to worry about throwing a belt at 8500rpm. I have found that the power steering has saved me quite a few times when I'm trying to catch a spin or something and before I physically couldn't move the steering quick enough, or the torque steer would rip the wheel out of my hands. Now, it just goes where I tell it to.

-Chris

 

[Twizted3g]

I really cant event think what a con to doing this would be, inless there is a problem with mounting the pump. Or if the pump is hard to find and or expensive. Even still it sounds like the pros would still out way those minor problems.

 

[Clipse3GT]

I really cant event think what a con to doing this would be, inless there is a problem with mounting the pump. Or if the pump is hard to find and or expensive. Even still it sounds like the pros would still out way those minor problems.

Well the con is the electrical strain and controlling the pump so its not at full speed. The pump ranges from $50-80bucks and another $20-50 for supplies. However, IIRC the stock amp is rated at 90amps, so the pump would draw alot of power constantly. This could be solved with running a more powerful alternator. Also there is a way to control the pump. I am sure the haltech could do it. To have sort of the pump run at two speeds, low and high. I am sure you could set even more mods with the haltech. So it would read the speed from VSS then relate that to pump and switch it to a lesser voltage at higher speeds. So the pump would be pushing less fluid. At lower speeds it would run at high.

It seems a project in itself, so I am still researching everything how to make it all work.

 

[tracer bullet]

The H-T article mentions controlling torque steer.

?????

Because it dampens it? Because it's easier to physically overpower it with the steering wheel? Something else?

I "get" quite a few things about steering as far as the geometry of it all goes, but the power steering and etc. is sort of new territory.

The idea seems kick ass. It works on other cars, why not ours?

If I had to ask a question it would simply be - what would Porshce or Ferrari use, and why would they use it? If they use electric, then I'm sold on this as a great idea for a swap. If they use hydraulic, then - what would be different between theirs and ours, and can we emulate it?

 

[Clipse3GT]

The H-T article mentions controlling torque steer.

?????

Because it dampens it? Because it's easier to physically overpower it with the steering wheel? Something else?

I "get" quite a few things about steering as far as the geometry of it all goes, but the power steering and etc. is sort of new territory.

The idea seems kick ass. It works on other cars, why not ours?

If I had to ask a question it would simply be - what would Porshce or Ferrari use, and why would they use it? If they use electric, then I'm sold on this as a great idea for a swap. If they use hydraulic, then - what would be different between theirs and ours, and can we emulate it?

Well the entire article is here:
Honda-Tech.com: Road Racing/Autocross: Electric Power Steering

The system itself is used in some Subaru's, Toyota, Honda Civic, Vauxhall, Renault, Citroen, Seat, VW. That's the use of Electric Pump.


Honda, Toyota, Ford, Mazda 3, Mercedez-Benz, and few other use electric pumps coupled with electric steering columns.

THe technology isnt really brand new or anything, but it does seem to work really work in autoX it seems from all the things I read and track use. As far as porsche and ferrari I have no idea if they use the system.

The problems I can to find out is the problem of controlling the pump speed, I'm sure could be done via switch to run 2-4 modes. Voltage variable. However to run it properly you have to run MR2 PWR steering ECU, which seems like too much work. My idea is to find out if the Haltech EMS can control the unit via PWM channels and control via Vehicle Speed Sensor to relate it to the voltage the pump operates at. Like Full speed up to 35mph, 2/3 speed up to 65mph, and 1/3 speed 85 and above. I need to contact haltech to find out if that's possible.

 

[Clipse3GT]

Here is some info.

From the MR2 Service Manual

1991 MR2 BGB Online - Mechanical - Steering

 

[autoxgalant72]

Gains in power will be minimal and not quite worth the effort.

In what way does the stock pump feel sluggish to you, that could potentially be another problem.

Cool idea even though I wouldnt take on the project its up to you. If you really got into it you could make the power assist progressive so that the furthur out in the steering travel you got it the more assist it gives you, leaving the center heavier to help keep jerky panic motions from the driver from hitting the ground as abruptly.

 

[Clipse3GT]

Well one of the largest resource hog to drive is the waterpump and the power steering pump. I run a full V1 Vortech foxbody cobra supercharger. So minimizing the parasitic drag on the system is the main reasoning behind this. THe point is that the Eclipse has generally sluggish steering compared to other cars, It's not a problem I have with my car. Most autox guys that run these cars will tell you the steering response is slow. One of the reasons is that the pump maybe causing this issue the other idea was that the power steering fluid gets too hot.

Now as for the system itself. The MR2 steering system is pretty complex in itself. It has multiple feedbacks to where it adjust the voltage that the pump runs at. The closer you are to center the lesser the voltage, the more you turn the higher the voltage and the more the pump flows and creates pressure. Now if you just hook this pump up to a 12v supply it will create this issue, the pump will run full speed no matter if you are turning or going straight, which could potentially be a bad thing at high speeds since it will create too much feedback. The MR2 system would regulate the pump in regards to the position of the steering wheel, engine rpm, vehicle speed, and probably some other variables.

In order to even achieve that there has to be a way to adjust the voltage of pump in stages. For example reduce the voltage with higher rpm, or reduce the voltage with higher vehicle speed. That question is how do you do this.

 

[zeeshan]

clipse3gt you're talking about an electro-hydraulic system -- those are very inefficient like you said electronically. those pumps also prematurely die and need replacing. your best bet is converting to a FULL electric steering rack like most modern cars do. those are efficient, and will outlast the electro-hydraulic pumps

 

[Clipse3GT]

clipse3gt you're talking about an electro-hydraulic system -- those are very inefficient like you said electronically. those pumps also prematurely die and need replacing. your best bet is converting to a FULL electric steering rack like most modern cars do. those are efficient, and will outlast the electro-hydraulic pumps

The question is finding one that will fit in there. I know Mazda 3's have them as well as a few other cars. But will those fit with engine location etc... That's the harder part.