# Donor Car Selection - Avoid Power Brakes and Power Steering?



## Cornelius (Sep 15, 2007)

Hi Mitch,
I'm far from an expert having done only one conversion (my red S-10), but perhaps I can get you started in the right direction...

1. On my S-10, I replaced the power steering with a manual gearbox ($125 new-rebuilt). Depending on the vehicle, this may not be possible if a manual steering gearbox is not available for that model. This is the easiest way to do it. If power steering is required or desired, then you have three options: The first is to run the power steering pump off the tail shaft of the main drive motor with a pulley and belt. Since you usually need power steering the most when stopped or at slow speeds, this may not work too well as the drive motor is also stopped or turning slowly. The next option is to use a second small motor, pulley and belt to drive the power steering pump. The third choice is to use an electric power steering pump. Any power steering will cause additional load on your batteries. If I recall, the pump sold by Canadian EV draws 12A. Hopefully someone who has done a conversion with power steering can provide some more insight on the subject.

2. Power brakes are pretty easy. You just need a vacuum pump, vacuum switch, check valve, and a reservoir. A 12V vacuum pump is about $200, a good vacuum switch is $60 to $125, check valve is $10, and the reservoir is simply some 2 - 4 inch diameter PVC pipe parts from a hardware store. Add a few $$$ for fittings and hose. The vacuum pump runs intermittently as needed (controlled by the vacuum switch), so power load is not a significant issue.

3. Good brakes are certainly important, especially with the added battery weight which can increase braking distance. As for the power steering decision, it is up to you. I find in driving my S-10 pickup truck that there are very few times I wish I still had the power steering, but that's just me. A fellow EV'er who also converted an S-10 and has power steering, preferred his after test driving mine. I don't think there is a right or wrong answer on this one.

I wish you well with your conversion. It is worth the time and effort.

Cornelius


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## Greenflight (Sep 13, 2007)

IMO, power brakes aren't much of a problem at all. Not to mention, it would be pretty hard to find a car that's not 30+ years old without power brakes. You can set up a good power brake system pretty cheap using a used vacuum pump and homemade reservoir. I got my system used for $125 total.

I don't use power steering, mainly because I just don't see the point in it. It just isn't that much easier to steer a car with power steering than one without, at least with cars in this size range. But it really all depends on personal preference. Both options are perfectly safe.

Good luck!


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## houseoffubar (Nov 18, 2007)

Be sure to check the Wiki, In the top right corner of this page. There is a post for both brake upgrade options, and power steering options, Eric


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## Pb Cruiser (Oct 29, 2007)

Just to chime in regarding power brakes, on Ebay I have seen 12vdc vacuum pumps that actuate the cruise control on Saabs and Volvos. My daughters '04 Dodge Stratus I believe has one. I was even the winning bidder back in May on one that would fit a Saab but I never heard from the seller nor did receive anything. Got my money back from Paypal but I really wanted the item. The cost was only 9.95. I plan to use such an item on my Geo; but I'll forgo power steering for now, at least on my first conversion. I plan to use the vacuum switch and the reservior as well.


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## MitchJi (Dec 14, 2007)

Hi,

Thanks Cornelius, Andrew, houseoffubar, and Pb Cruiser!

PB conclusions:
It is virtually impossible to find a modern vehicle without PB but it is not an important issue:
1. Driving the PB with an electric motor is easy and inexpensive.
2. Not a substantial energy drain (especially with regen).

PS Information followed by a question:
http://www.automotivedesignline.com/howto/165600237
"the hydraulic steering system in your car siphons off somewhere between one to three miles per gallon from your vehicle's performance and consumes more energy than your car's air conditioner? In fact, it's the third highest energy-loss mechanism in your car, following wind resistance and road friction."

http://en.wikipedia.org/wiki/Power_steering
Electric systems have a slight advantage in fuel efficiency (almost 1 MPG) because there is no hydraulic pump constantly running, whether assistance is required or not, and this is the main reason for their introduction.

Question:
Wikipedia does not mention an efficiency advantage with Electro-hydraulic power steering systems. On vehicles with a secondary electric motor installed to drive the stock power steering pump how much energy is used? Is it as efficient or close to a full electric system? Is there a constant parasitic loss?

Thanks Again!

Mitch


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## jcm55 (Jan 19, 2008)

I saw a P/S solution that I thought was pretty clever on a Toyota Tacoma pickup EV conversion. The owner had connected a 12v electric drill motor to the shaft of the stock power steering pump, and mounted a switch on the dash. That way he could manually activate the power steering only when he really needed it, like for parallel parking or backing out of a driveway. The rest of the time the motor/pump was off and consuming no energy.


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## Xanerrix (Sep 25, 2007)

What type of vacuum pump would work?
I know it needs 12V but is there a guide for sizing or somehting?
What would be the equivalent to the ICE vacuum?

Thank you
Andre


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## Alex Everett (Dec 26, 2007)

F.W.I.W. there are a multitude of models (one for example is the 80's model Ford Crown Victorias) that were factory equipped with a smog pump. This is a belt driven vacuum pump and availiable in nearly any junk yard for a pittence of money. Using one of these with a reserve tank and a one way check valve would easilly accomodate the needs of a brake booster. It can build vacuum while driving off a belt from drive motor, store in reserve tank for pedal application, and rebuild when you drive again.


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## xrotaryguy (Jul 26, 2007)

An obscure side-note on power brakes. Some vehicles (trucks) have hydraulically assisted brakes rather than vacuum assist. This type of brake booster uses the power steering pump to make hydraulic pressure for the brake assist unit. This type of system is not common. I generally only see it on GM full-size trucks and on some Cadillacs. I guess this type of brake assist could be adapted to other vehicles... particularly other GM vehicles.


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## Alex Everett (Dec 26, 2007)

Those are availiable on most any Brand of truck rated 350/3500 series and above, as well as most handicapped vans, Large Suburbans, and some Cab-Over Isuzu industruial road trucks. As mentioned in previous posts here, you need the P/S pump along with the booster from the donor vehicle. Hose mods will allow connection to your existing power steering gearbox/R&P.


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## veperformance (Aug 17, 2007)

You may also find racing parts adapted for you vehicule that will work quite well and eliminate the extra motors and associated power drain and as a bonus you save weight and also recuperate some space.


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