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 Post subject: Power Steering in a Midi
PostPosted: August 20, 2015, 3:29 am 
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Joined: January 30, 2010, 7:01 pm
Posts: 27
Hi Guys , maybe some has more experience with this than me, I am building a Countach replica, its taken more years than I can remember and there's still not a lot to see.
I currently have a Lexus 1uz v8 attached to an Audi 016 in the rear, its also possible that may change to a m70 bmw v12, as I have a donor I'm working on in the driveway.
Is it possible to run some hard lines from the existing hydraulic pump on the 1uz or BMW up to the rack, and if so what size lines would be good,the rack sits just in front of your feet and the pump right behind my shoulder ,so I figure the lines will have to be about 2.5 mtrs each way.
I have followed a lot your builds for years and have searched for hours, but cant find any info on it, or if it's even possible, I currently have a runabout an MGF and that has really good electric steering, but after careful measurement I don't even have room for that at the bottom of the steering column. I am using a Toyota SC400 for most of the donor parts, and so are using the tilt column from that
Do you think the length of the lines will cause me any issues, I have run out of ideas so any help much appreciated.
Best Regards
Graeme


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PostPosted: August 20, 2015, 9:22 am 
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First off, is it even needed? With not much weight on the front tires, it won't be hard to steer. However, since you're asking I assume it's wanted. You'll be fine. See what size lines are used now for the pump and have some made up that are one or two sizes larger. A great place is your local Parker dealer, which supports industrial hydraulic systems.

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PostPosted: August 20, 2015, 9:52 am 
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Location: worcester county, Massachsetts
does a real Countach have power steering? if not, then I wouldn't bother on a replica.

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PostPosted: August 20, 2015, 2:29 pm 
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Joined: July 6, 2009, 11:50 pm
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When I added power steering to my old fiero I think I just used the orginal size lines 5/16 high pressure and 3/8 return if I recall correctly. I was using a camaro steering rack and cadillac pump and it worked perfectly. It couldn't hurt to go up a size if you're concerned about it though.


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PostPosted: August 20, 2015, 7:11 pm 
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Thanks guys for your thoughts, I did get to move a car identical to mine years ago at the original suppliers workshop, it had a very smooth concrete floor, and the car was fitted with 225 rubber on the front, and with a steering wheel of 340mm it was almost imposable to turn the wheel without going to the gym first it was seriously heavy, maybe its the fact it has a space frame chassis estimated to weigh about 475 lbs, and I also suspect it may have been running at least 5deg caster so that may not of helped. Once it was driving it was fine, but stopped it was a mission to even turn it a little, it would not be fun trying to reverse, by sitting on the sill , aka Balboni style.


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PostPosted: August 20, 2015, 11:29 pm 
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Joined: May 17, 2008, 10:55 pm
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Location: canada
Countach wrote:
Thanks guys for your thoughts, I did get to move a car identical to mine years ago at the original suppliers workshop, it had a very smooth concrete floor, and the car was fitted with 225 rubber on the front, and with a steering wheel of 340mm it was almost imposable to turn the wheel without going to the gym first it was seriously heavy, maybe its the fact it has a space frame chassis estimated to weigh about 475 lbs, and I also suspect it may have been running at least 5deg caster so that may not of helped. Once it was driving it was fine, but stopped it was a mission to even turn it a little, it would not be fun trying to reverse, by sitting on the sill , aka Balboni style.


I suspect it was running several inches scrub radius, too.

Anyway, you don't need a power assist set up based on one blatantly mis-engineered car.
Also 5 deg caster is just over half what it should be. Check your SAI, plan on 75-100% of your SAI(KPI) number as caster.


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PostPosted: August 23, 2015, 6:17 am 
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hi Iadr, yep never thought about the scrub it may have had, the supplier used to build Countachs to sell and to race, the whole chassis suspension was professionally designed but its hard to say if it was correct, I was thinking of a figure around 5 deg because the OEM diablo runs 6 deg with a 7.5 kpi and I was trying to follow that design as a general guide.


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PostPosted: August 23, 2015, 6:44 am 
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Joined: August 19, 2014, 5:17 pm
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Location: England
I have built mid engined cars and despite the supposed weight bias to the rear they can still be very heavy on the steering when slow moving or parking. Power steering on this will be a good idea as long as you can retain some feel , there is a tendency for power steering to take some of this away. There certainly wont be any issues with running the power steering lines from the engine to the rack, but it may pay to leave options open on the pulley size of the pump, you may need to play with pump speed to get it right. BMW/mini do an electric driven hydraulic unit that is progressive, benefits would be very short pipe runs with less mechanical complications.


Citroen do a neat one as well http://www.ebay.co.uk/itm/Citroen-C4-1- ... 2a56333be2



Bob

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PostPosted: August 23, 2015, 7:07 am 
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hi Bob thanks for the info, I have looked hard at an electric pump but they are not cheap and then you have all the electronic stuff to sort, I am an electronics tech but a simple std pump will be easier, the donor is a SC400 and they have a progressive steering setup that's got a small computer to handle all that, and the plan was to just graft entire SC400 loom into the car, only issue is moving the engine ecu etc to the rear.That way everything should work straight off ie headlights, tail lights, tilt steering etc should all just go, and no fiddling with all the other wiring but I am a long way off from there at present.


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PostPosted: August 23, 2015, 10:01 am 
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Joined: August 28, 2010, 7:53 am
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A friend autocrosses a Fiero. originally it had a SLOW manual rack. He installed a corvette rack with an MR2 electric PS pump. works great. He initially used GM PS fluid but it seemed to boil/air lock (he would lose assist in slaloms). He switched to the fluid toyota recommended for the pump, which solved the problem. I think he spent about $1000, including used rack, pump, new hoses and machined adapters to adapt the corvette rack and tierods to the Fiero spindles.


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PostPosted: August 23, 2015, 12:30 pm 
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I think trading electric wires for hydraulic lines could be a good move. removing an accessary from the engine might help with fitment. On the other hand maybe you would have trouble re-routing the fan belts etc.

This may not really be a help, but I'd like to clarify about the steering geometry. Scrub radius is the offset of the steering axis to the center of the contact patch. Having more scrub radius will reduce the steering effort for parking. It's one reason cars used to have more scrub, before all cars had power steering. When you have no scrub radius and the car is still, turning the car's steering wheel causes you to scrub one side of the tire forward and the other side backwards. If you have 2 or 3 inches of scrub, the tire does not scrub as much when you turn the wheel, it rotates in a circle around the steering axis.

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PostPosted: September 7, 2015, 2:37 pm 
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Joined: February 20, 2015, 12:04 pm
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Location: Cotswolds - UK
robbovius wrote:
does a real Countach have power steering? if not, then I wouldn't bother on a replica.

No, a real Countach doesn't have power steering as standard, but ironically a lot of owners fit it, because it's a real brute to manhandle, otherwise.

Electric power steering is the usual solution to retrofit on the real thing, so that it can be switched off if desired and isn't as disruptive to the cars' originality as a hydraulic system would be.

The OP appears to be bang on the right track. ;)


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PostPosted: September 7, 2015, 4:08 pm 
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I had a Pantera for a couple of years, and it was a workout to parallel park. I think they wanted to keep the steering quick, and figured the valet would be in good shape.


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