Power steering build, MR2 Electric Pump Options

[drive-ability]

I'm now working on a power steering system for my V8 car. I'm using a Golf P/S unit and a Toyota MR2 electric pump. There will be some pictures soon, I'm building the bracket to mount the power rack to the 914 cross member.
I'll doc the build up in this thread.. (IMG:style_emoticons/default/driving.gif)

[byndbad914]

1" longer is still a pretty good amount, which means that it might be hard to get the bump out of it, but I think it is more doable at 1" than, of course, 4" like I thought before (IMG:style_emoticons/default/smile.gif)

charlie - I don't know about a stock 914 but I think it is rather low - the rack sits just above the lower arm pivot point and pivots at the same width and lines up decently with the upper mount locations, but when I built my tube chassis car I relocated the rack up, etc and have measured my bump - I have 0.005" on the first 1" of compression and an additional 0.007" on the second 1", so 0.012" overall for the max compression I expect on a race car, which is essentially what one would call "zero bump".

So, back to drive's issue, if the rack were in stock location then I can guarantee the 1" difference per side in tie rod length would have a strong effect for creating bump steer, like 1/4" in the first 2" of motion I would hazard to guess, and a street car should expect 3" of compression travel at minimum so the bump could be significant. Just being a bit off can cause 1/8" per side.

However, the rack is relocated a bit, so I dunno what effect that would have - it might be even worse. I suspect that an aggressive rack relocation and/or tie rod offset might fix it over a small range of motion but it will never be a "zero" bump setup because within just a couple inches of motion the difference in pivot locations will never want to zero out over 3" of travel (or more). But if it were an 1/8" even on 2" of compression, it isn't optimal but on a street car it probably wouldn't be that noticeable for most people (I would notice it cuz I am used to recognizing it). On a racer with really sticky and wide front tires, it would be very noticeable.