"underdrive" power steering pump? - Fuel Economy, Hypermiling, EcoModding News and Forum

gascort · 07-03-2008, 05:52 PM

I know, I can buy an underdrive crank pulley for about $130 for my car that will underdrive all my accessories. I'm not interested in shelling out that kind of dough for a mod that might give me 3-4 mpg on the highway.

I know some off road guys, (4x4 with big, near-flat tires) overdrive their power steering pump by altering the high pressure bypass valve in the pump. They want more help in maneuvering giant tires on steep boulders.

I was curious if anyone knew of someone altering it in the other direction; to reduce the amount of assist. I'd be fine with about 25-50% of the assist I currently get. It would also reduce wheel turn with bump starting during a slight turn. (bump starting during a big turn or a slight turn at high speed is dangerous because of the sudden steering response!)

gascort · 07-03-2008, 05:55 PM

HowStuffWorks "How Car Steering Works"

wagonman76 · 07-03-2008, 07:57 PM

I wonder if they make an electric power steering pump. Then somehow make it so it only runs below a certain road speed. Some cars have speed sensitive power steering anyway, since you only really need it going very slow.

reformed · 07-03-2008, 08:02 PM

They do make electric power steering pumps. A lot of hardcore autocross racers have them.

You have a fairly light car, you might be able to eliminate the P/S all together. If you run a tube from the "out" to the "in" on your rack and put a breather on the bypass tube, you can get pretty good steering with a power rack and no pump, this only works well on light cars. On my civic I have something similar done, and its actually barely noticeable. Its only a little tough when you're going really slow, but hardly anything that I would complain about.

elhigh · 07-03-2008, 08:06 PM

The Escort could possibly be retrofitted with a manual rack. That would permit you to forego power steering entirely. That'd eliminate weight, engine drag, and one more component to break.

Formula413 · 07-03-2008, 08:10 PM

Underdrive pulleys are a popular performance mod. However, many people have found that they need to add an overdrive pulley for the alternator when adding an UD pulley so it will keep the battery charged at idle. How much you would gain is hard to say.

As for the power steering delete, I don't know if I would want to try that. I have tried to EOC in my Escort, and even at about 40 mph the steering felt very heavy, probably too heavy for an emergency avoidance maneuver. I know this car is available without PS, but I believe a manual steering equipped car would have a much lower steering ratio (i.e. more turns lock to lock for less effort).

FWIW, you can also get an electric water pump for some cars, another common performance mod.

reformed · 07-03-2008, 08:25 PM

Quote:

Originally Posted by Formula413

As for the power steering delete, I don't know if I would want to try that. I have tried to EOC in my Escort, and even at about 40 mph the steering felt very heavy, probably too heavy for an emergency avoidance maneuver. I know this car is available without PS, but I believe a manual steering equipped car would have a much lower steering ratio (i.e. more turns lock to lock for less effort).

100% correct on that. That is why you put the bypass tube in and the breather, it actually lets the P/S rack operate with more ease then it would normally with the pump off. Granted, a manual rack would be best, but on my car, these was so little difference that swapping out the racks was hardly worth the time and money. I guess it all boils down to how confident you are with doing mods and how comfortable you are with driving your car like that.

gascort · 07-03-2008, 10:29 PM

I've been wishy-washy between the two - replacement with an Escort Pony manual rack or just looping the lines together on mine. I called every junkyard in the area this morning and noone has a Pony - they're kind of rare.
I can get a remanufactured one for $350 - over 75% of the cost of the car!
I do ok with the steering in EOC and I've been told it's easier if you bypass.

I won't do an electric one - another thing that's very expensive.

I just thought I might be able to keep some PS for convenience when the car's running and have it be closer to what it's like in EOC - that way I get used to the increased effort and if I do have to avoid something while coasting up to a red light (highly unlikely), I'm ready for what it'll take.
I think next fall (when my official FE testing begins) I'll route the lines together and see how much FE gain I get, if it's worth it, etc.
Thanks for all the input, guys!!!
Matt

Formula413 · 07-04-2008, 12:10 AM

So do you EOC in your Escort? I tried it once in mine (even though I am told it shouldn't be done with an automatic). The brakes were scary, I had almost no stopping power.

johnmyster · 08-19-2008, 09:36 PM

From past experience - a PS rack steers much easier if you can get most of the fluid out of it. This is pretty easy to do. Simply diconnect the hoses, put them into a bucket and go lock to lock several times. Then do your "bypass hose" trick to keep dirt out of the system. If you can get most of the fluid out of the cylinders, you won't have to push it back and forth in manual mode.

The best way to find a PS underdrive pulley would be a tour of the junkyard. You'll find that most Ford vehicles use the same PS pump. Taurus, Explorer, Thunderbird, F series, etc. If you can snag yourself a pump with a pulley that is 20 to 50% larger, you'll be set.

Lowering the bypass pressure will lower the pressure seen by the pump. Mechanically, the more efficient route is to slow it down so that it makes less pressure in the first place, rather than spilling it off.