tstkl Posted February 2, 2012 Share Posted February 2, 2012 Hey guys, I was wondering if I could get some input on which direction to take my car. I have an 88 chrysler conquest that I've done a motor swap in and I'm looking to race it eventually after I get it running. Its a long way away from being able to hit the track (roll cage, harness, seats, etc). I ripped the stock steering box steering system out of the car and will be fabbing up a custom rack and pinion set up. Even if this isn't legal to race in any class the factory steering was horrible so its getting a rack and pinion. My question is, the car will be around 2600 lbs, is front engine, rwd, has a wheel base of around 98", and will make in the range of 300 (short term) - 700 (long term) horse power. Everything is there to make the high hp I just want to build up my skills as a driver before turning up the boost etc. So heres the question. Can I get away with manual steering? I'd like to run the widest rubber I can obviously and this is mostly dictated by class, but with the weight/power this car is capable of I might end up in SU. Lets say for arguments sake, 275 R6 hoosiers go on the front, in the 25 inch diameter range. The reason I am considering manual is because the factory steering geometry would require a steering rack with inner joints approximately 20 inches apart. I've yet to find anything power steering smaller than 23 inches, and nothing smaller than 26 inches with the ratios/ turns lock to lock that I want. Ideally I'd like to make the electric power steering from an s2000 work on this car, but that is a 32 inch system which would cause a good deal of bump steer. Thanks for any input. Quote Link to comment Share on other sites More sharing options...
ghettoracer Posted February 2, 2012 Share Posted February 2, 2012 sounds like you will have plenty of hp to spare so i would say put in a PS rack. you will thank me later... it is much easier on the driver. manual rack with 275 R6 up front? you better have some huge arms for that... ps, what do you mean by s2000 is a 32" system? Quote Link to comment Share on other sites More sharing options...
tstkl Posted February 2, 2012 Author Share Posted February 2, 2012 In order for a system to maintain the same geometry as OEM, the tie rod end links should be the same length as the lower control arm (McPherson suspension) and the pivot point should be in the same plane. When changing rack the most important dimension becomes the distance from the inner pivot joints of one side to the other. The length of the arms are adjustable so they don't matter. That distance on the s2000 is 32". Because my car had a steering box it was extremely tiny at 20". I agree with needing PS I just don't know how to do it without a lot of bump steer Quote Link to comment Share on other sites More sharing options...
zchris Posted February 5, 2012 Share Posted February 5, 2012 Flaming River will narrow up to your spec any of there racks. And they have them in both manual and power versions. Easy button pushed. Chris Howard Quote Link to comment Share on other sites More sharing options...
tstkl Posted February 12, 2012 Author Share Posted February 12, 2012 I contacted them a while back and they only go as small as 23 inches. I think I'm going to get creative with the s2000 steering rack and the welder so I don't have to have power steering lines, fluid, pump, etc. Luckily for me the computer for the s2000's system runs off the same frequency signal for speed as my ecu so I can use that. Thanks for the suggestions any more ideas are welcome. Quote Link to comment Share on other sites More sharing options...
speedengineer Posted February 12, 2012 Share Posted February 12, 2012 The Acura RSX steering rack has the distance between the two inner tie rod ends about 2 inches apart. That's not a typo - the attachment point is in the center, rather than at each end of the rack. Also, you may want to consider measuring or modeling the bump steer on your car. Just because the factory made it a certain way does not mean the bump steer is desirable. Do this - get some toe plates, and measure the toe as the car sits on the ground. Then jack the front of the car up say two inches, and measure the toe again. From this you can calculate what the toe change is per inch of wheel travel. You may find that the oem bumpsteer is not what you want for a track car. Ideally, you usually want very small amounts of toe in from compression, say 1/16" per inch on each side. If it's not like this (likely is not) you may want to alter the length of the tie rods and also the height of the inner tie rod ends to achieve more optimal bumpsteer characteristics. Quote Link to comment Share on other sites More sharing options...
speedengineer Posted February 12, 2012 Share Posted February 12, 2012 Also, the EP3 civic has the same geometry rack as the RSX, except it is electric, not hydraulic. Might be a nice option. http://forums.clubrsx.com/showthread.php?t=606165 Quote Link to comment Share on other sites More sharing options...
tstkl Posted February 13, 2012 Author Share Posted February 13, 2012 yeah I've seen those too, I actually first noticed it on my buddy's honda insight, LOL. All those cars have double wishbone suspensions so ideally you'd want your steering rack to have the longest arms possible, I guess honda decided the geometry got too complicated having the two cross or anything, lol. The front suspension from the factory is mcphearson, so the length of the lower A arm is basically the "golden length" for my set up right now. Your right because of the front torque rod it could have a virtual length that is surprisingly different than the physical lower control arm, but I figured getting as close to the oem spec would be the best place to start. Thanks for the heads up tho on measuring. Do most systems tend to be linear? Your method would only work for suspension extension I feel. I guess I could lift up the back half of the car to get some compression and see how it effects toe but I don't think I could get a considerable distance of compression especially with some stiff springs. From the factory the steering arms stay very very close to the lower control arm though so I think the length I'm aiming for should be a good starting point. Quote Link to comment Share on other sites More sharing options...
speedengineer Posted February 13, 2012 Share Posted February 13, 2012 Naw, RSX and ep3 are MacPherson strut also. Regardless, there are many combinations of suspension geometry between different vehicles (MacPherson or otherwise) that there is no real golden length. FYI, the RSX geometry causes absolutely horrible toe-in bump steer. I highly recommend measuring your setup, you might be surprised what you find. In my experience they are fairly linear, particularly over the small range we are measuring them in. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.