Wouldn't it be sufficient to make it so the MR2 pump is on full power at zero-10mph and then the have the power assist decline up to 60 mph? Then you get power steering at low speeds but none at high speeds when you don't need it?

[This message has been edited by mrseidler (edited 07-07-2007).]

A bump for Troyboy.

quote Originally posted by mrseidler: Wouldn't it be sufficient to make it so the MR2 pump is on full power at zero-10mph and then the have the power assist decline up to 60 mph? Then you get power steering at low speeds but none at high speeds when you don't need it?

That is exactly what I'm doing. The stock MR2 power steering electronics will work fine for controlling the pump speed inversely with the vehicle speed. I don't know how to emulate the MR2 steering position sensor. The MR2's steering position sensor helps lengthen the life of the electro-hydraulic PS pump by reducing its speed when the car is at low speed but needs little or no PS assist. For instance, when stopped at a traffic signal, there is no reason to have full power assist.

Tom

Ha! I hooked it up backwards. I didn't know which port on the rack was pressure in and which was out, so I took a guess, and I guessed wrong! It is kinda funny though, without turning the wheel, it sits perfectly still. Then, as soon as the wheel is turned even the slightest amount, the PS takes over, rips the wheel out of my hands and turns the OPPOSITE direction. HA!!! If you ever wondered what would happen if you connected PS up backwards at the steering rack, I now know.

Well......I thought I had a Corvette power rack.....?!!
Does anyone have any input on this one?
The rack came from wrecker/parts seller already off the car but tagged as a vette rack.
Here is the date stamp and the casting number of the rack. Note that it appears correct:



Problem is the rack is not centred on the front cossmenber as can be seen by the different distance from the end of the rack to the control arm mount holes on each side of the crossmember. Note that I took care to center the rack prior to doing this. The pen marks show how much past 2 turns the rack goes, but there were no bump stops mounted for this determination. Pen marks are full left, full right, and center.






Also, I measure the 88 Fiero rack to be 28 9/16" long measuring from the shoulder to shoulder of the ends ( not the ends of the threaded part) and the same measurement on my "apparent vette rack" with Rick's adaptors mounted is only 28 3/16" which is 3/8" shorter. I cannot move the rack any further to the right to accomodate the offset as the hydraulic line would interfere with the right side mount as seen here:



Oh...the odd color of the crossmember is because it is already blasted and etched for paint - I kinda got out of step here I guess!
Any ideas or do I just "got the wrong rack"??? I can't go back since the 88 mount is gone!

Edit: just a typo.
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Daviero - 88 N* GT

[This message has been edited by Daviero (edited 07-29-2007).]

Well, I just picked up a rebuilt rack from Napa for an 84 or 85 Corvette with the 2 turns ratio. It turns out to be the same rack as the 86 date stamped rack rack I got already from the yard! I will return it to recover my $310.00. So my dimensional saga continues...Help?
Also some info from rebuilder I got through Napa: 84/85 racks are the same dimensionally and extrenally as the 86/87 racks, but have differences internally. I did not get the inside difference information though. Thus Napa has different part numbers for the 84/85, 86/87 and 88 to 92 racks. I suspect the diferences may be something like orifice size, assist/effort ratio or flow matching to a different pump?
Still - any suggestions from anybody as to the dimensional problems outlined in my last post? Rick??

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Daviero - 88 N* GT

Hmmm. I probably wasn't as exact as you are being with your install. However, I had no trouble getting mine to center. I remember grinding on Rickady's mount a bit to get it level with the cross-member, but no problems centering it. Similarly to you, I put the rack in the center and installed it trying to get both sides even. I think it came out pretty close. Are you sure the steering shaft is aligned to where the center is on the car? It doesn't entirely matter where the center of the rack is for this install, because the steering wheel is not indexable (or not much, some say it is). Therefore, you have to have the corvette rack's input shaft in the same position as the steering wheel and column in the car for straight ahead.

I find this difficult to explain, but if you were to set it up perfectly centered, but it was 90degrees off from the steering wheel in the car, they would mess it all up at alignment, because they would move the tie-rods over till the steering wheel was point straight and so were the wheels. All I'm saying is to make sure the steering input shaft matches the steering intermediate shaft (for lack of a better name).

If I can be of any help, post, PM or email me.

Tom

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1988 Fiero GT
Cleveland Fiero Club

Just got back from a week long camping trip. Give me a minute to look over some of the questions and then I'll reply.

Thanks for the input guys, I appreciate it. Rick, you must like the mountains – you were vacationing there earlier in this thread too! Like you guys I finally settled to the realization that minor differences in the mount of the power rack would yield minor if any differences in the steering performance of the car. So I forged ahead. I mounted the rack using the bolts in the lower control arm ears as the side to side and vertical dimension reference points, and 2 mounting holes in the crossmember for the fore-aft reference. I got all to with ± .020” with whatever tolerance my vernier/trisquare/table arrangement allows. To center the travel on the rack I measured the travel at each end of the rack and equaled the dimensions. I also relocated the right side mount for the rack on the crossmember so I could use the right side rubber and strap without modifying them, and to provide clearance to the hydraulic tube.

Question: It appears that I will need a longer input shaft. I pulled a string side to side of the crossmember between 2 mounting holes and the dimension between the string and the end of the input shaft on the rack is about 5/8” longer for the vette rack. The Fiero rack has a slide, but is pinned with 2 plastic pins about 3/32” diameter. Is it prudent to break the pins and extend the slide? I could thru’ drill the hole again and re-pint it with plastic. The vette input shaft is longer, but about 5/8” too long.

Another question: My Fiero rack had only 1 plastic bump stop. The vette rack had 2 but are thicker and would rob travel. Would it be prudent to leave these out to achieve more rack travel (since the vette has less I think?) or should I hunt down another plastic Fiero bump stop to eliminate the hard surface contact? I suppose I could thin down 1 vette bump stop to match the Fiero one I have, or just use the 2 vette ones and be done with it? Am I thinking to hard on this?

Thanks, Dave.

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Daviero - 88 N* GT

quote Originally posted by Daviero: Question: It appears that I will need a longer input shaft. I pulled a string side to side of the crossmember between 2 mounting holes and the dimension between the string and the end of the input shaft on the rack is about 5/8” longer for the vette rack. The Fiero rack has a slide, but is pinned with 2 plastic pins about 3/32” diameter. Is it prudent to break the pins and extend the slide? I could thru’ drill the hole again and re-pint it with plastic. The vette input shaft is longer, but about 5/8” too long.

I had no problems using the stock input shaft. I would not drill out those pins. They are shear pins. In case of an accident, the plastic shears and the steering shaft collapses, preventing the steering column from making a Dave-Ka-Bob out of you. I know you could put plastic back in, but I recommend test fitting it in there as is. Mine worked just fine.

quote Originally posted by Daviero: Another question: My Fiero rack had only 1 plastic bump stop. The vette rack had 2 but are thicker and would rob travel. Would it be prudent to leave these out to achieve more rack travel (since the vette has less I think?) or should I hunt down another plastic Fiero bump stop to eliminate the hard surface contact? I suppose I could thin down 1 vette bump stop to match the Fiero one I have, or just use the 2 vette ones and be done with it? Am I thinking to hard on this?

I have several extra plastic bump stops around here if you need them. On mine, I put Fiero bump stops on the corvette rack. As far as travel goes, it is magnificent, I can turn much tighter than before. When cranked over to the stop, the inside rear tire is barely moving! However, I am concerned that I may be over-extending the rack. I have no proof either way, apart from the fact that in the corvette, GM didn't allow the rack to extend as far as I am using it. Therefore, I am trying not to ever reach the bump stops. You really won't need to...unless you are showing off!

Tom

Yes true, - a Dave-Ka-Bob would not be good. I will test fit and report back. In the case that the shaft needs to be longer though, if I extened it and even used a bit of silicone or similar to make it not rattle, then I would have even more anti - Dave-Ka-Bob compression space? Thanks for the offer for the end stops Tom. I'll see if I can find a Fiero one locally - failing that I'll let you know.

Dave

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Daviero - 88 N* GT

The test fit went well. The stock Fiero steering shaft fits perfect unmodified, just as Rick and Tom suggested it would. I did see however that my movement of the right side rack mount a little to the right to accomodate the hydraulic tubing will make it a little more difficult to make and install a boot extension though. All in all this is a good modification - Thanks again Rick!
Dave

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Daviero - 88 N* GT

Rick- I'm fitting the Corvette rack to the '88 crossmember and see for the first time the passenger side mounting point is round, not "D" shape:

1991 Corvette rack mount bushing:


1988 Fiero rack mount bushing:


This is the best view of yours I can find. It looks like a "D" shape bushing with a round center:


What did you use for a bushing?

quote Originally posted by sspeedstreet: Rick- I'm fitting the Corvette rack to the '88 crossmember and see for the first time the passenger side mounting point is round, not "D" shape: What did you use for a bushing?

As I recall, the "D" shaped bushing is for the mount that you are replacing. The other "tube" end of the rack has a round bushing that will work on the corvette rack, with minor trimming to make it thinner (less wide). The "D" shaped bushing you can leave on the Fiero rack, it is not needed. The corvette rack comes with its own round bushing that will work with Rickadys mount.

quote Originally posted by Daviero: Thanks for the input guys, I appreciate it. Rick, you must like the mountains – you were vacationing there earlier in this thread too! Another question: My Fiero rack had only 1 plastic bump stop. The vette rack had 2 but are thicker and would rob travel. Would it be prudent to leave these out to achieve more rack travel (since the vette has less I think?) or should I hunt down another plastic Fiero bump stop to eliminate the hard surface contact? I suppose I could thin down 1 vette bump stop to match the Fiero one I have, or just use the 2 vette ones and be done with it? Am I thinking to hard on this? Thanks, Dave.

Well we just got back from an 8 day stay in the mountains We love the Jeep on off road trails that are so far away from the ordinary. We stay in a pop up trailer.
The last time I replied to this thread, we were home for a day and a half to get ready for another trip.


GM makes many different sizes of "bump stops" that clip over the inner tie rod ends. Just be aware that the rack may not have the clearance for the extra travel of the piston between the fluid in/out holes if you use thinner bump stops. In other words, if you use thin bump stops for extra wheel travel the piston will travel further and possibly interfere with the inlet holes? IF the rack has the clearance for longer travel, then it IS worth using thin bump stops. But the need for lock to lock steering is rare for me. If you use after market wheels, they could limit your steering more than the rack. The 88 is sensitive to wide wheels and different off sets.

Thanks, Rick. I tried to get that bushing off the Fiero rack and was afraid I'd tear it trying to get it off. Since my last post I bought two of the straps the Corvette uses.



This way the stock Corvette bushing can be used. I'll post some pictures of how I'm going to mount them when they get here.

All is almost done except the plumbing.....
Which port is pressure - port # 1 or port # 2?



Thanks, Dave.

quote Originally posted by Daviero: All is almost done except the plumbing..... Which port is pressure - port # 1 or port # 2? Thanks, Dave.

Crap, I cannot tell from the picture. On mine, it had two different sized openings. I am 100% positive that the LARGER port is the pressure side. I originally hooked it up in reverse thinking that the smaller size should be higher pressure; I was wrong resulting in very funky steering response. I hope I didn't damage anything. If you need me to, I can take a look at mine, but it is raining pretty heavily today so I'd rather not.
Hope this helps,
Tom

Tom, please have a look if you don't mind. I have not pulled the port plugs to check the port size, but if they are different sizes all the more reason to get it right - I want to have crimped end hoses made up to connect to the steel lines that run up to the front next to the gas tank. If they are different sizes I'd of thought the low pressure side would be larger?
Thanks, Dave.

I discovered at my local hydraulic hose supply that GM PS racks (and pumps) use metric O-ring sealed fittings. If you're not using original Corvette lines you need an adapter. I used steel ones from here:

http://www.jdaent.com/deskt...abID=5546&pCatID=816

The 16 and 18mm sizes.

I don't know which port is pressure and which is return either, so I'm also waiting for an answer.

[This message has been edited by sspeedstreet (edited 08-20-2007).]

quote Originally posted by sspeedstreet: I discovered at my local hydraulic hose supply that GM PS racks (and pumps) use metric O-ring sealed fittings. If you're not using original Corvette lines you need an adapter. I used steel ones from here: http://www.jdaent.com/deskt...abID=5546&pCatID=816 The 16 and 18mm sizes. I don't know which port is pressure and which is return either, so I'm also waiting for an answer.

As I said above, the LARGER port is the pressure side. I had at first assumed that as the fluid lost pressure, it would need a larger cross sectional area to flow through. This is apparently not the case.

I know this 100% for sure because I hooked it up backwards. If you like, I can tell you exactly what happens when the power steering system is hooked up backwards. At rest (not turning the steering wheel) all appears to be fine. As soon as the steering wheel is moved even the slightest in one direction, the pump rips the wheel out of your hands and sends it spinning all the way to the bump stop in the opposite direction. Trust me, I think I might have cause some damage to the internals because I did this at least twice before I figured it out.

And yes, they are metric power steering fittings. I got JIC adapters from www.a1racing.com.

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1988 Fiero GT
Cleveland Fiero Club

For custom hydraulic fittings like this, I silver solder the GM o-ring fitting to a standard crimp fitting and get the local hydraulic shop tp crimp it. A little fooling around, yes, but much cheaper, and also less bulk. As far as pressure capacity goes, I noticed that even my stainless steel brake lines I got from the Fiero Store have some silver soldered fittings.
As far as the ports, I guess I'll try the large one on the pressure.......
Thanks, Dave.

Not knowing much about steering racks (other then standard citation rack sucks compared to x-11's), but wonder if the corvette rack would be better than my 85 x-11 rack and would it fit?

For the pump lines I used GM lines that fit the pump best. I looked for lines that did not cause interference with the engine or compartment and ran them were I wanted them to go as if they were just factory Fiero power steering lines. Then I cut off the metal ends on the rack side about half way between the flare and the crimp. I welded the "remnant" to the front end of hydraulic rated metal hydro pipe that I custom bent under the car. I did this for each line. The fittings will only go on the pump and the rack one way, so do one at a time and you cant mix them up.
The rack end of the hard line dose not need a flexible hose, so it can be hard lined all the way to the rack. But the rear (engine end) dose need to flex with the engine. So the stock GM line that fits your application best will have some rubber hose and a metal end crimped on each end of it. The end you cut the flare off of will need to be welded or some other way of "disconnect" like a furl to connect the factory metal hose to the custom hydro pipe. The engine may need to come out some day so I would not weld the ends together at the rear. So basically what I did was take a set of stock GM power steering lines and bolted one end to the pump and "stretched" the other end of the lines to reach the rack.


REMEMBER, THE POWER STEERING LINE PRESSURE CAN BE AS HIGH AS 2000 PSI. Don't underestimate it. Don't cheap out. DO THE LINES RIGHT.


Does this make sense? If not I will try to explain it again.

The Citation X11 rack is a rear steer rack, it won't work

I used 3/8 steel brake line for my piping under the car, and welded JIC fittings to each end to connect flex lines to the pump and the rack. I hope brake line is strong enough?
I found that a pressure line from a 90 Intrepid fits the rack and is about 2'-0" long - long enough to reach the front of the tunnel where the hard line ends. Ugh - a Dodge part though!!

Question: I removed the front tub after I removed the front crossmember. I have the front crossmember back in the car now with the new rack but can't seem to get the tub in with the crossmember there. Does the crossmember have to be lowered a bit to get the tub in or do you have to twist the tub a certain way like a chinese puzzle??
Thanks, Dave

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Daviero - 88 N* GT

quote Originally posted by Daviero: Question: I removed the front tub after I removed the front crossmember. I have the front crossmember back in the car now with the new rack but can't seem to get the tub in with the crossmember there. Does the crossmember have to be lowered a bit to get the tub in or do you have to twist the tub a certain way like a chinese puzzle?? Thanks, Dave

The first few times I did it took a while, and I even thought I would have to lower the X member. But I just worked it in. That tub will bend. And two of the tubs I put in had the WCF front battery tray just to make it harder to fit in.

Bump for a good upgrade.

JC

Bump

Regarding the PS pump speed: Is the pump you are using the MR2 pump? I'm unaware of how it works but I would think that a standard engine-mounted pump would be valved to regulate pressure at higher rotation speed. Either it is this or the rack is valved to adjust for the increased pressure from the pump's faster rotation.

I would think that you would not want to completely drop the fluid pressure at higher speed as the take-up from zero may introduce lag in your steering response.

Of course, this is only my speculation. I am not an engineer.

------------------
Kendall (Icelander) Whitlatch
'85 Fiero 2M4 - 5spd Isuzu
'67 LeMans/GTO clone 6.5 litre TH400
All the rest aren't Pontiacs, so what does it matter?

quote Originally posted by Icelander: Regarding the PS pump speed: Is the pump you are using the MR2 pump? I'm unaware of how it works but I would think that a standard engine-mounted pump would be valved to regulate pressure at higher rotation speed. Either it is this or the rack is valved to adjust for the increased pressure from the pump's faster rotation. I would think that you would not want to completely drop the fluid pressure at higher speed as the take-up from zero may introduce lag in your steering response. Of course, this is only my speculation. I am not an engineer.

I don't mean to hijack Rickady's thread, I beleive he is using the standard engine mounted pumps. I think he does the power steering conversion along with or after an engine swap; thus, using an engine mounted pump (from the swapped engine) is relatively easy.

I, on the other hand, wanted to wait until I do an engine swap, but my 88 rack was worn so I had to put in the PS with the old 2.8. I searched on here for a way to mount a PS pump on the 2.8 and even spoke to Rodney Dickman about the mounting of the PS in the Meras, but I could not come up with anything simple enough to match my limited fabrication skills and tools. Therefore, I opted for the MR2 electric power steering pump.

You are quite right, there is the potential for lag, or delay in the assist, but I have it wired as best as I can. The engineers who designed the MR2 system thought of all this as well, and they did the best they could to combat all these problems. They solved most of the issues. After all, if they hadn't, it wouldn't have been an option in the MR2. There is a timer in the electronics so that if the computer doesn't get a signal from the VSS for 45-60 seconds (I never timed it but really long lights will trip it) the pump will completely turn off. This is bad at really long lights, but very nice when you want to just turn the radio on, or while working on the car. While at speed, I don't think it turns all the way off. You really can't notice anyway, because above about 40 mph it takes very little force to steer the car. I installed the PS for the ratio, and for parking lots, not for the highway. It is all about trade-offs.

Since I live in Ohio and don't want any salt on my baby, I haven't driven it in several months now. When I put her away I needed to deal with a few remaining issues: 1. I need a new rack from Autozone, the one they gave me is loose. 2. The pump makes an excessive amount of noise. I need to see if the flow is restricted at the rack (see #1), PS fluid cooler, connections, or reservoir. 3. I need to tidy up the mess of wires I left in the front. I was so happy it worked and I got to drive the car in the fall before putting it away I left the mess. When I get her back out this spring I'll start a thread documenting what I did and see if I can solve the problems I have encountered. I've already had a few people email me with questions so there are a few others already tackling this and I'm sure I wasn't the first anyway.

Edit to add #3 and correct grammar

[This message has been edited by TG oreiF 8891 (edited 01-16-2008).]

I am doing a 4.9 Cady conversion in the Vette rack GT. The pump is a 3800 series II with a remote reservoir. Custom brackets that mount it in the 2.8 V6 alt location. I started a thread a while back but don't think I will keep it going.

I don't mind at all if people contribute to the tread. Someone will always figure out a better way of doing things, and that will help us all if it is posted.

quote Originally posted by Rickady88GT: What is an x-11 rack? What do you mean by "better"? What do you want power steering to do for you? The Corvette racks come in two ratios. One is very fast and will make the Fiero turn like a Go Cart. The other ratio is more for street driving in a daily driver. BUT the slower ratio rack is much faster than the stock Fiero rack and will reduce your steering wheel lock to lock turning from about 3.5 to about 2.25 or 2.0 depending on the rack you get.

x-11 refers to the chevy citation x-11, but its a rear steer rack, it wouldnt work for this app anyways

Bump because knowledge is POWER!!!