Super-fast ratio Corvette power steering rack in '88 Fiero
Moderators: The Dark Side of Will, Series8217
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- Peer Mediator
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Re: Super-fast ratio ZR1 power steering rack in '88
Depowering a power rack is a common mod to Mjatas.
- Series8217
- 1988 Fiero Track Car
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Re: Super-fast ratio ZR1 power steering rack in '88
Speaking of Miatas, has anyone looked into running a Miata rack in a Fiero? They're front-steer..
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- Peer Mediator
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Re: Super-fast ratio ZR1 power steering rack in '88
Hadn't yet, but I'll check it out... a friend is putting a 1st Gen Mjata together with a bored/stroked 1.8 (2.0) in the next couple of weeks.
- Series8217
- 1988 Fiero Track Car
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Re: Super-fast ratio ZR1 power steering rack in '88
Got everything pretty much bolted together now except coolant pipes and the steering column. I pulled the column so I could remove the dust guard and check clearance. Rick had to grind a bit of the firewall to get the steering shaft to fit on his car, because the pinion angle of the Corvette rack is different than the Fiero rack and it moves the shaft over a bit.
Tomorrow I plan to finish fitting the column, and then Thursday I'll put the rest together and align it. I got some Longacre toe plates, so between those and some string I should be able to get it pretty close.
Tomorrow I plan to finish fitting the column, and then Thursday I'll put the rest together and align it. I got some Longacre toe plates, so between those and some string I should be able to get it pretty close.
- Series8217
- 1988 Fiero Track Car
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Re: Super-fast ratio ZR1 power steering rack in '88
For reference, the AC Delco part number for the passenger side steering rack boot is 45A7055.
It's available from Amazon:
http://www.amazon.com/gp/product/B000C9 ... 05_s00_i00
On the driver's side, I used the Fiero boot or the Corvette rack boot; whichever one stretched longer. I think it was the Fiero one. IIRC the Fiero one is rubber, but the Corvette one is plastic.
It's available from Amazon:
http://www.amazon.com/gp/product/B000C9 ... 05_s00_i00
On the driver's side, I used the Fiero boot or the Corvette rack boot; whichever one stretched longer. I think it was the Fiero one. IIRC the Fiero one is rubber, but the Corvette one is plastic.
- Series8217
- 1988 Fiero Track Car
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Re: Super-fast ratio ZR1 power steering rack in '88
The steering wheel is not centered... it's about 120* off. This was not expected based on others' experiences shared in the thread on Old Europe. They said the stock shaft worked as-is. It's possible that my rack is slightly different. I didn't check super accurately if the rack was centered; I just followed Rick's dimensions and eyeballed it to see if it was in the ballpark. I'll have to double-check tomorrow.
The steering shaft hole in the firewall needs to be clearanced a few mm like on Rick's car.
The driver's side tie rod hits the swaybar when approaching full lock while the car is in the air (full droop). I don't recall this being an issue on the stock 88 front suspension, but maybe it was.
I'm going to clearance the steering shaft hole and then put the car on the ground tomorrow with wheels on it so I can set the toe to 0 and confirm if I actually have a problem with rack fitment and left side travel.
The steering shaft hole in the firewall needs to be clearanced a few mm like on Rick's car.
The driver's side tie rod hits the swaybar when approaching full lock while the car is in the air (full droop). I don't recall this being an issue on the stock 88 front suspension, but maybe it was.
I'm going to clearance the steering shaft hole and then put the car on the ground tomorrow with wheels on it so I can set the toe to 0 and confirm if I actually have a problem with rack fitment and left side travel.
- Series8217
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Re: Super-fast ratio ZR1 power steering rack in '88
I have a 6-bolt Sparco wheel, I was able to recenter my steering wheel by clocking it 120* to the left. This gets me pretty damn close to center.
I remeasured and it looks like my rack ended up 3/16" too far to the passenger side. It may just be down to chassis manufacturing tolerances. One tie rod is going to end up being 3/16" longer than the other in order to center the steering wheel. I don't think that's significant enough to cause any noticeable problems, so I'll go ahead and center the wheel.
I remeasured and it looks like my rack ended up 3/16" too far to the passenger side. It may just be down to chassis manufacturing tolerances. One tie rod is going to end up being 3/16" longer than the other in order to center the steering wheel. I don't think that's significant enough to cause any noticeable problems, so I'll go ahead and center the wheel.
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- Series8217
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Re: Super-fast ratio ZR1 power steering rack in '88
That front suspension looks like it's been through hell. I bet the rack is all rusted out inside, and there aren't going to be parts available.
- Series8217
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Re: Super-fast ratio ZR1 power steering rack in '88
Drove the car around the block and on the highway today. I'm running the rack dry (full of air) with the fluid ports capped of with AN fitting caps on the port adapters. My caster is at the mechanical maximum for an 88 suspension with stock geometry. I haven't fully clearanced the steering column firewall hole yet so the steering shaft still rubs. I have a small steering wheel (and inch or two smaller diameter than stock) so this increases steering effort.
Effort is OK when moving but not ideal -- its pretty hard. Highway effort and response is good in a straight line. Tire force feedback is strong.
Effort with the ports looped may be better. I may experiment with that after I finishing clearancing the column (which should help a lot).
I'll probably hook up the fluid lines but the car is driveable as it is.
Effort is OK when moving but not ideal -- its pretty hard. Highway effort and response is good in a straight line. Tire force feedback is strong.
Effort with the ports looped may be better. I may experiment with that after I finishing clearancing the column (which should help a lot).
I'll probably hook up the fluid lines but the car is driveable as it is.
- Series8217
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Re: Super-fast ratio ZR1 power steering rack in '88
I forgot that reclocking the steering wheel means that all of turn signal cancel geometry is going to be messed up. One direction is now hard to set and the other doesn't cancel.
If I disassemble the column can I reclock these components?
Otherwise I guess I will have to pull the rack pinion and rotate it. Actually, that makes me wonder if the rebuilder just clocked it wrong during reassembly.
If I disassemble the column can I reclock these components?
Otherwise I guess I will have to pull the rack pinion and rotate it. Actually, that makes me wonder if the rebuilder just clocked it wrong during reassembly.
- Series8217
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Re: Super-fast ratio ZR1 power steering rack in '88
Reclocking the pinion looks really easy: http://www.vetteweb.com/tech/vemp_1106_ ... index.html
I think I'll just do that.
I think I'll just do that.
- VF1SkullAngel
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Re: Super-fast ratio ZR1 power steering rack in '88
I wouldn't mind doing this to my 86. I'm starting to think the steering rack is going and I might as well get something worth the while.
Sometimes you only need six cylinders to get the job done.
- Series8217
- 1988 Fiero Track Car
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Re: Super-fast ratio ZR1 power steering rack in '88
The F-body power steering rack conversion is well developed for the 84-87 suspension. As far as I know, there are no 84-87 cars running around with the 'vette rack yet; only 88s. The front suspension (and crossmember) is completely different.
- Series8217
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Re: Super-fast ratio ZR1 power steering rack in '88
I hooked up the pump and lines...
I ruined the car. I can't take it on the freeway like this. The W-body pump that goes with the 3.4 DOHC is NOT matched to this rack. It's so overboosted it's hilarious to drive. 2 turns lock-to-lock also makes it frightening as well.
I'll need to restrict flow somehow, or adjust the pressure bypass valve in the pump.
Also, how do I fill the system so the fluid doesn't just foam up like it has done now?
I ruined the car. I can't take it on the freeway like this. The W-body pump that goes with the 3.4 DOHC is NOT matched to this rack. It's so overboosted it's hilarious to drive. 2 turns lock-to-lock also makes it frightening as well.
I'll need to restrict flow somehow, or adjust the pressure bypass valve in the pump.
Also, how do I fill the system so the fluid doesn't just foam up like it has done now?
- Series8217
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Re: Super-fast ratio ZR1 power steering rack in '88
Foam seems to be going away now. It was just all the initial air getting stirred up. The pump has quieted down. No leaks yet! I'll take full pics of the system once I have all the bugs worked out.
The twitchiness seems to be alignment-related. It's more twitchy when turning slightly to the right than to the left. Still too much assist for my taste though.
The twitchiness seems to be alignment-related. It's more twitchy when turning slightly to the right than to the left. Still too much assist for my taste though.
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Re: Super-fast ratio ZR1 power steering rack in '88
The assist is in the spool valve, not the pump. I think all GM systems use the same pressure. This is one of the gotchas of a GM/BMW swap, as the BMW steering gear wants a higher pressure than the GM pump delivers.
Anyway, there *should* be someone in the Corvette and/or muscle car community who can recalibrate the spool valve. This requires machining a new spring rod.
The C4 Corvette--especially the ZR1--has something like twice the weight over the front end as the Fiero, as well as different steering and suspension geometry--most notably caster... some tuning will be necessary.
Have you measured the bump steer yet?
Anyway, there *should* be someone in the Corvette and/or muscle car community who can recalibrate the spool valve. This requires machining a new spring rod.
The C4 Corvette--especially the ZR1--has something like twice the weight over the front end as the Fiero, as well as different steering and suspension geometry--most notably caster... some tuning will be necessary.
Have you measured the bump steer yet?
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Re: Super-fast ratio ZR1 power steering rack in '88
You can check the pump output in pressure and flow on AllData or the GM factory manual for the LQ1 and the Corvette, even if the assist is controlled at the spool valve, if youre flow and pressure are reasonably in the range of the rack, lowering the relief spring force in the pump will help lower the assist. The gain remains the same, except the input force is lowered, so the output is lowered. Just dont outflow the rack's capacity, since it will blow out the seals. It looks like the Corvette and early luminas had the same style pump bodies. Im fairly certain that the corvettes had pressure compensated pumps as well. Swapping to a corvette pump may be a solution, mostly likely not though, given the size of corvette tires and the weight of the iron or 32v engines.
Edit: found these interesting articles, but useless for you at this point:
http://www.corvettefever.com/howto/16638/
http://www.vetteweb.com/tech/vemp_1106_ ... ewall.html
Edit: found these interesting articles, but useless for you at this point:
http://www.corvettefever.com/howto/16638/
http://www.vetteweb.com/tech/vemp_1106_ ... ewall.html
Last edited by FieroWanaBe1 on Tue Sep 11, 2012 3:41 am, edited 1 time in total.
car.
- Series8217
- 1988 Fiero Track Car
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Re: Super-fast ratio ZR1 power steering rack in '88
I found a place out in the valley that can modify the spool valve to change the assist: http://lee-powersteering.com/
I'm going to go through my alignment settings more thoroughly to see how that affects the twitchiness.
I'm going to go through my alignment settings more thoroughly to see how that affects the twitchiness.
No, but I don't see why it would have changed. With the adapters on, the rack is the same length as the stock 88 rack.The Dark Side of Will wrote:Have you measured the bump steer yet?
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- Peer Mediator
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Re: Super-fast ratio ZR1 power steering rack in '88
Mounts are different, though. If they are out (mostly up or down) just a little bit compared to stock, then you'll get bump steer.