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Well I'm the dumbest man alive. The whole point of me thinking about rear steer racks was because the radiator I plan on using (Scirrocco drag style) was going to have the lower inlet/outlet right in front of the steering rack. However I failed to think that if I just lifted the steering arm pickup point then I could lift the rack and get it in a proper position to be out of the way of the radiator hose. So now I'm back to looking at using my old 02 WRX steering rack and shortening it. Right now I'm in the process of figure out proper rack length, eliminating bump steer as much as possible and trying to get close to Miata like Pro-Ackermann angle by adjusting rack length, tie-rod length and steering arm pickup location on the spindle. (Will use Wilwood Mustang II 2" drop spindles with bolt on steering arms so I can have steering arms made to fit)



Here's a link to a good set of pictures and a bit of info on setting up your racks and eliminating bump steer.
https://www.motortrend.com/how-to/ctrp- ... explained/

The image I posted below shows how you can have longer or shorter rack depending on where the outer tie rod ball joint center is. So if you have a good idea where your inner ball joints are located on your inner tie rods you can sorta figure out if your OEM steering rack will work or not with adjusting your steering arm location to be more outboard if possible.

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My build -> viewtopic.php?t=15585

The radiator NEVER should affect the location of the steering rack!

The rack determines it's own location to reduce bump steer.

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Honey anyone?

While I agree, I'm also trying to make less physical work for myself and build the major components of the car in solidworks to keep from having these interference issues while building in real life. Either way I've fixed the issues I had with the rack and radiator locations. I've raise the rack itself in the chassis as well as redesigning the steering arm on the spindle (2 piece design) to allow for the rack to be raised without affecting bumpsteer badly. I also redesigned the steering geometry a bit so I don't have to cut the rack down as much as previously thought.

While doing all this I also found I was having interference between the upper balljoint and the spindle. So a went ahead and redesigned the mounting points of the upper control arm and steering (again). I'll still have to make actual physical design changes rather than just the changed location. But at least this way I won't have to redesign half the front suspension again. The last picture I highlighted the steering rack (dumbed down design before I actually model it properly) as well as the inlet for the radiator.

If you look closely on the first, second and third images you can see dimensions in millimeters. The ones in the chassis are for measuring the tie rod end from the KPI angle as well as the distance from the inner tie rod ball to the imaginary line between the upper and lower control arm pickup points. I tried to get those two dimensions as close as possible to keep bumpsteer from being affected too much. Between that and adjusting the location vertically of the steering rack and the outer tie rod I was able to get a bump steer range from full bounce to full jounce of 0.10 degrees outward. I'm planning on making the rack mount slightly lower than it needs to be so I can add in some spacers so I have a little adjustment either way. Where I currently have it I don't think 0.10 degrees would even be noticeable.

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My build -> viewtopic.php?t=15585

So this morning I went out to the garage to check how many turns lock to lock the 02 wrx rack I have is. Looks like it is 3.5 turns, whereas everywhere online I saw 3 turns for the wrx of that gen and 3.2 for the rs. So basically they must have physically make the steering arm on the spindle hit the control arm at some point to limit travel. The wrx of that gen is also a 16.5:1 ratio steering. I decided to check my model and do a bit of math and out of the 140mm total of travel the rack has, dividing that by 3.5 turns, I get 40mm of travel per turn. In my solidworks model I moved the steering 40mm from center and got 19.29 degrees of angle on the inside wheel. Dividing 360 by 19.29 degrees I get a steering ratio of 18.66:1 which is slightly worse than a stock 02 wrx.

Today I think I'll try to work out the steering geometry to get close to 12.5:1 (28.8 degrees per turn) or 13:1 (27.69 degrees per turn) ratio steering as that would be exactly what I'd like to have in the car. Then I will design in stops on the control arms to limit travel down to 2.5 turns.

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My build -> viewtopic.php?t=15585

the intercooler should be in front and radiator behind?

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Honey anyone?

I'll be running a water to air intercooler. The Intercooler core is just in front of the engine (has big black hoses going to it in the pictures) the heat exchanger for the intercooler is in the very front with the radiator directly behind it.

frozenboost.com is where I'll be getting the setup. I'll eventually step up to much larger hoses and a bump to suite.

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My build -> viewtopic.php?t=15585

Redesigned the steering geometry slightly to finish up the basic design of it. Total inner wheel turn in angle is 39.86 degrees, outer tire turn in angle is 31.49 degrees for an ackermann amount of +.837 degrees. I also ended up adjusting the steering arm and ended up at 12.75:1 steering ratio. I'll be running a Toyota/Subaru Steering column with electric power steering as well so that should be perfectly fine as far as a steering ratio.

I also bought a K772 balljoint to tear apart and get dimensions from so I can get proper dimensions since I can't find an accurate drawing for these anywhere. OEM K772 balljoints have a total misalignment angle of 64 degrees by the way.

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My build -> viewtopic.php?t=15585