Modern Motorsports Ltd Posted September 20, 2000 Share Posted September 20, 2000 Just got hit out of the blue from seeing another totally unrelated hybrid. My hoodclearance/oilpan clearance issue bugs me. On my 280ZX as I've mentioned my 'rear-steer' rack and shorter Xmember to firewall (-3") makes for quite a different install. What if I reversed my Xmember for front steer thus increasing rear room quite a bit with no steering rack/mounts in place (and possibly offset gain in Xmember centreline as well)?? New 'dragstrut' mounts (what are those called?) would have to be added to the new 'front' of the Xmember and steering link's somehow moved fwd/customized?? Figured someone may have thought of this or understand more of what's involved than I and be able to comment. I'm so busy doing school it's easy to type a q' and do some 'net surfing but hard to break time away into the garage for some 'real' study breaks. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 20, 2000 Author Share Posted September 20, 2000 OK, got some measurements here: for engine height comparison: I have 5" from ground to bottom of my rails at the front of my car (figure they must be within 1/2" or b/t Z/ZX -14-3/8" from ground to ~ centre of crank bolt my crossmember has 2.5" rearward offset of the centreline of motor mount to centreline of xmember built in, overall 4-1/8" from centreline of xmember to rearward edge of Xmember (excluding steering mounts etc) front edge of mount receeds at least 2" (ie. only 1/2" max fwd of centreline) so going reverse w/ Xmember in quick look would gain (all relative to xmember frame mount centreline) 4-1/8" minus 1/2", 3-5/8" which is a helluva alot and would clear most any pan etc....hmm, certainly justifies further investigation.... Quote Link to comment Share on other sites More sharing options...
Guest Jason Posted September 20, 2000 Share Posted September 20, 2000 Good idea! It might require the steering geometry be redesigned though. I'm not sure how much time the Datsun engineers spent on steering, but most cars are designed such that the toe-in increases as the wheels turn, so the inner wheel has a sharper turning radius than the outer wheel. This keeps the wheels from scrubbing in tight turns. Moving the steering rack can have a signifigant impact on this toe-in gain (or whatever the proper name is). On the bright side, if you re-engineered the steering geometry, you could probably do a better job of it. I think there's some software available that would simplify most of the math involved (a few angles calculated by trig). I'd like to do this one day when I make a new crossmember that would also cut down on weight. But I need to convert the car before I get too ambitious. -Jason Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 20, 2000 Share Posted September 20, 2000 Jason's first paragraph is talking about Ackerman steering. The other thing to consider is bumpsteer. If you can bolt the steering knuckles on the struts so that they are turned around 180 degrees, and remount the rack at the same distance from the imaginary line connecting the ball joints, but in front instead of behind that line, the only variable you'd need to worry about would be the height of th e rack, which will govern the amount and type of bumpsteer. Making that adjustable once you get it close for welding on new brackets for the rack would be a great way to go. I think the above method would keep the Ackerman steering the same. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 20, 2000 Author Share Posted September 20, 2000 quote: Originally posted by pparaska: The other thing to consider is bumpsteer. If you can bolt the steering knuckles on the struts so that they are turned around 180 degrees, and remount the rack at the same distance from the imaginary line connecting the ball joints, but in front instead of behind that line, the only variable you'd need to worry about would be the height of th e rack, which will govern the amount and type of bumpsteer. Making that adjustable once you get it close for welding on new brackets for the rack would be a great way to go. Well from memory the steering knuckles have a slight inward arc to them but if my pass. side one was reversed AND taken to drivers side the inward arc would be maintained. I have no idea where the control arm centreline relates to centreline of Xmember yet (ie. if wheel/control arm is centred about Xmember then ~steering rack spacing would be maintained) but visually from above would have to guess it's offset rearward ~2". If I did change to a front steer rack I wonder if the ZX rack is preferred as so many like a Must. II or mazda rack? Any others have engine height comparisons? Quote Link to comment Share on other sites More sharing options...
Guest Jason Posted September 20, 2000 Share Posted September 20, 2000 quote: Originally posted by pparaska: If you can bolt the steering knuckles on the struts so that they are turned around 180 degrees... I think you'd also have to reverse the direction of the rack to make this work. Maybe you could spin the rack 180 about the shaft and mount it upside down to reverse it. Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 20, 2000 Share Posted September 20, 2000 Duh, I didn't think about that. You're right! Maybe a right hand drive 280ZX rack flipped over? Hmm. Seems a 280Z rack might be something to look into, since it's a front steer rack and plentiful. You'd have to compare the inner tie rod ball to inner tie rod ball distance on both to see if it would work. Custom might be in order here! Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 20, 2000 Author Share Posted September 20, 2000 quote: Originally posted by pparaska: Duh, I didn't think about that. You're right! Maybe a right hand drive 280ZX rack flipped over? Hmm. Seems a 280Z rack might be something to look into, since it's a front steer rack and plentiful. You'd have to compare the inner tie rod ball to inner tie rod ball distance on both to see if it would work. Custom might be in order here! On that note, why not just take the 280Z crossmember.....seems playing with frame mounts is easier than rack geometry.Doooh! And then I'd be v. similar to 'normal' Z engine bay/JTR configuration and could most likely take my steering 'rod' outside my drivers side headers! Rather than inside with custom header pulled away from block. Hmm, their's a v. good custom susp. shop 1.5 hrs away that I wish was closer by......I was about to measure up for headers etc but if I do need to severely modify Xmember setup to lower my engine (and the engine has to be lowered a fair bit for improved breathing!, this is a must) then the header mod should be integrated with it. Damn, been sucking in exhaust fumes with poor header/head match and wanted this done yesterday:-((( Ross (feel free to bid up my r200 4.11 on ebay:-) C I'll have to put the car up in the air and have a v. good/hard look to see how much more drop can be gained via more oilpan mods before I get so involved in Xmember but enjoying pondering it.....I'm pretty sure 1.5" is the max gain I"ll be able to lower my motor which isn't much extra but with an airdoor/EFI it could open up that area as well...$5k from Ed Mcmahon could solve this methinks:-) Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 20, 2000 Author Share Posted September 20, 2000 Replying to my own posts as we go here:-) Anyone know how different a 280Z front strut brake mounts etc are compared to a 280ZX strut? (I'd want to carry over my custom 13" setup). How's about transplanting a 280Z front endcompletely?! I know bearings are the same so could bolt my current 5 bolt setup etc on their....hmmmmmm, how am I supposed study now (in a comp. lab at school) Reinstall my swaybar etc....that system is already engineered etc, wonder how similar mounting/pickup points are. Quote Link to comment Share on other sites More sharing options...
jeromio Posted September 21, 2000 Share Posted September 21, 2000 Zxs are rear steer? Didn't know that. As for ackerman/steering geometry - if anyone is going to attemtp any kind of chassis wierdness, I strongly recommend buying a Lego Technics set - a good one, like the latest Car Chassis one. It's a good way to get a feel for how things like ackerman, suspension geometry, bumpsteer - all that stuff - fits together. You can vary the basic elements - steering arm length, for instance, rack placement, control points, and then see how it affects the behavior of the wheels in relation to the chassis and in relation to each other. For instance, simply flipping the steering knuckles 180 and transposing the rack placement (back of crossmember to front or vice-versa) will result in anti-ackerman steering (wide inside wheel, tight outside). Not a good idea. It's cheap (less than $100), it's definately fun, and it will help a great deal to figure out your options before you mess with your actual car. Think of it as a real time, 3 space, tactile modelling tool......(or at least tell that to your wife when she sees the Toys'R Us bill). Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted September 22, 2000 Author Share Posted September 22, 2000 PSS I'm going to THE dudes for suspension this Sat. am hopefully to have him look at what would be involved to convert my car to front steer and improve bump steer. Custom suspension/total design is their business and he has the goods to take your suspension right thru travel in his shop and read out it's characteristic changes with travel etc. He was fully intune with all requirements and is a roadracer himself so would have a fine approach. If I understood correctly he said Ackerman is only an affect if your steering knuckle is offset in on my rear setup. If it's parallel with car geometry then they can flip 180, otherwise they have to do their customizing. He'd use a 280z rack and just tack up mounts and test out till it's in the dead right spot and then fully weld among other parts:-) Makes me feel it's better spent than EFI mod right now (assuming all height clearance can't be gained by fully tweaking oilpan, we'll check that first). EFI still in full planning though:-) Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 23, 2000 Share Posted September 23, 2000 jeromio, I love the Lego idea! I haven't played with legos in umm, like 25 years! Quote Link to comment Share on other sites More sharing options...
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