JMortensen

Found the article by Zapletal. It is well worth the read. The figures discussed in the article are all the way at the end, so I suggest printing the 23 pages so that you can reference them as you read it. Going to pick up some graph paper and a compass tonight and see just what effect moving my rack back had. http://forums.hybrid...846#entry914846

I don't know that you can make a statement like "it's just for feel" very accurately with this chart as your backup. To me it's a bit like saying: "Some racers run softer springs in front to reduce understeer, others use a stiffer rear bar. So which approach is "right" and which is "wrong" between the two? IMO, neither, it's gotta be more of a feel thing than any meaningful difference in performance potential." There is undoubtedly more than one way to skin a cat. I think there is a distinct difference between running toe out or Ackerman as there is with the softer spring vs ARB example. Maybe not as pronounced as that, and as I said before I think that most people can run some toe out and call it a day. On the other hand, you yourself seem to suggest that static toe settings matter from a drag perspective, and I think the advantage Ackerman has over toe out is that it minimizes the static toe setting, then becomes more active the tighter the turns get. Probably the most useful thing one can take away from your chart is that in this limited sample 6 of 7 of these performance cars use Ackerman to some measurable degree or another. It seems doubtful that they would do so if it tended towards understeer. Why does the Vette not use it is the next logical question. I don't have an answer for that other than maybe they decide to use another method to skin the cat, but I think it is interesting to look at the top speeds of the cars in question. The Vette is the only one without a speed limiter and should do 190, the Lexus has a limited speed of 170 and has the next lowest amount of Ackerman. The rest of the cars are limited to 155 or lower. This also is not "proof" of anything in and of itself, but it does conveniently fit with the idea that for more stability (understeer is more stable) and turns with larger radii like the ones you might encounter at very high speeds, less Ackerman makes sense.

You NEVER had that problem with the BBC version? Watch the Ford Raptor vs Halo parachutist guy and then watch the BBC version vs Red Devil guy, and compare 8:12 to 14:32. The whole thing is basically a carbon copy, right down to end of the race. It really is the same show, but the Brits do it in a little more polished fashion. The fact that it is contrived as all hell doesnt bother me that much. It's entertainment, not a documentary. TGBBC TGUSA http://www.youtube.com/watch?v=q3eNDcWpL60 I am happy to hear about the new Carolla show, but I just hope that Farah d-bag doesn't ruin it for me.

For 99% of the people, I agree; just run the static toe out, and it accomplishes basically the same thing. For the super anal though. I think there is an argument for Ackerman in there. In my case, having cut and hacked just about every other part of the car, modding for Ackerman wasn't that big a deal.

Just remembered this other thread, because I recalled that Richard had cut and welded the steer knuckles on his previous car. Two people who have modded for Ackerman posted. Guess what they both thought? http://forums.hybridz.org/index.php/topic/39229-ackermann-article/page__p__317252__hl__%2B260det+%2Backerman__fromsearch__1#entry317252

Pay attention! Actually I didn't address the toe in on rebound, but I think the key there is to minimize bumpsteer as much as possible. If you do that then the effect is pretty negligible. At least it was on my car after slotting the crossmember and adjusting it out that way.

Why not just try toe out in the front? I used to have a reference line on the inner tie rod and two on the outer so I could run toe in on the street and toe out at the track. I'd drive to the track and make the change from one mark to the other, only takes a minute, and then when I was done I'd put it back to toe in for street use so I didn't chew up the front tires. The only downside was I had the wheel slightly off center in both toe settings, but it wasn't so far off that it was bothersome to me. EDIT--Also, I don't think you'd get even close to 100% Ackerman with just modding the steer knuckles to get them closer to the rotor. You'd need the line drawn through the tie rod and ball joint to intersect at the rear axle line, which I don't think is possible on the Z. I don't think you can get 100% by moving the rack back either. I think with moving the rack I'll get something closer to 100% than the steer knuckle mod alone, but I'm doubtful that both together would actually get 100%. Caster or other suspension settings that help front end grip are also relevant, but that's a subject for another thread and it's been talked about quite a bit. Let's keep this one isolated on toe setting.

I don't think you're going to get such a nicely refined test, because any test would require quite a bit of work between runs. Probably the least labor intensive would be to have two sets of steer knuckles, and swap between runs. You wouldn't want to use longer steer knuckles to test because that would slow the steering and that would change the feel to the point where it might hide the effect of the Ackerman, so it would have to be the cut and welded or the bent knuckles. The proof to me is the ubiquitous toe out recommendation (which I have tried and found works in back to back runs) and is a rough simulation of the effect of adding Ackermann. If toe out works, Ackerman should work, because the effect is basically the same in toeing out the inside wheel. Ackermann has an advantage in that the tighter the course the more toe out you would need, and with the Ackerman just turning the wheel farther gets you more toe change. I don't think you'll find a more tested opinion than Keith Thomas's when it comes to Z cars. Here is what he has to say on the subject of toe out: http://www.improvedtouring.com/forums/showthread.php?t=16613

Really? If that were the case, I wouldn't have continued arguing the point. Let me remind you what you started out saying: Maybe your position has changed since we started. If you'd like to limit it to "in a long sweeper the outside tire should be turned in more than the inside tire" than I think we can agree and end the argument. Right. I was talking about steering wheel turns to tire angle change. The rack ratio is 1.8125 inches per turn. That means nothing with regards to the angularity of the wheel in and of itself.

So for an imaginary track with no sharp turns or mostly sweepers, not considering turn in or other handling effects, and using the tire constraints from the graph you posted, you would like to posit that toe in would generate more grip. All right then, I concede this point to you. Let's try to put this back in the real world again, shall we? I wish I knew the real steering ratio of the Z car in terms of steering wheel degrees to tire degrees. I really don't know what the ratio is in a Z, but I'd guess that most cars are in the 15 to one range. Here are various in car camera clips from various Z's at various tracks. I watched them and only noted how many times the wheel crossed 90 degrees in a lap by watching the spokes or the driver's hands (rudimentary, but it's what I have to work with). If you had a 90 degree turn at the steering wheel, that's going to be 6 degrees at the tire with the assumed 15:1 ratio. 100% Ackerman gives 6 degrees on the inside and 5 on the outside. The outside is the important one, so if my assumption of 15:1 is right in all of these cases the car would have more than a degree difference in the tires if it were running 100% Ackerman. Again, using a 225/50/15 tire, that's .206" of toe out (note how John Coffey somewhat coincidentally suggests .125 to .1875 toe out in his alignment sticky). This is a very significant amount of toe that is definitely going to affect handling. I wish I could have caught exactly what the steering wheel angle was, because of course the toe changes more radically as the wheel turns farther, but I think this makes the point. On a road course, the turns really are tight enough for Ackerman to make a difference, and I believe that's why so many Z racers run toe out on road courses. Datsun 240Z at Laguna Seca has the wheel turning past 90 6 times in a lap: Datsun 240Z at Streets of Willow - 5 times: Datsun 240Z at Firebird Track West - 9 times: Datsun 240Z at some track in Phoenix - 10 times: Datsun 240Z at VIR - 4 times: Datsun 240Z at Heartland Park Topeka - 8 times: Datsun 240Z at an autox - 18 times (counted 19 but discounted one because I think it was a counter steer, hard to watch and count at the same time):

Assuming that you started with the tire that produced the chart that you posted, I'm with you right up to the last sentence here. If you were racing on a super speedway, I'd be with you all the way, because the turns are so large that a slip angle that would produce the lateral acceleration desired on the inside wheel might very well require toe in. In reality though, Z racing doesn't usually involve really long steady state cornering, at least at the tracks that I've been to, and certainly not at autocrosses. For that kind of racing, the slip angle still has to be found relative to the individual wheel's intended path, and that path is going to require a lot more toe out on the inside wheel for a lot of those turns. Running a lot of toe out is a stop gap measure for those that don't or can't make the Ackerman changes required. It would also be possible, assuming that one could get a lot of Ackerman in a Z (I don't think my rack modification got me 100% Ackerman) that one could then run toe in, so that on those long sweepers you might get a result closer to what the tire needs for optimal traction, but when you get to the hairpin the inside tire turns a lot sharper as it needs to do. If you use the chart from the Smithee's website then I think Ackerman or toe out would still be a better way to go, assuming the drag increase didn't slow the car more than the lateral accel improved it (something relevant to both the pro and anti-Ackerman cases). John, Ackerman can be added by moving the steering rack back towards the crossmember, or by lengthening the steer knuckles, or by cutting and welding or bending the steer knuckles out towards the rotors. Toe out is free, Ackerman is hard to do, that's why most every Z racer runs static toe out.

Sachs makes good stuff. Centerforce is crap IMO. You'll find other opinions on that, but you've got mine. I would suggest an ACT pressure plate with either their kevlar disk or a stock disk. I don't think you need a puck disk for that kind of power if you can get the stiffer pressure plate.

OK, but look at Dan's dyno plot. In L series terms, that is a pretty big cam. Even so, from 2700-6500 he's got over 150 ft/lb of torque. If you can't keep it in that range, yeah, you need gears or transmission swap. It's a good point to make and you're right to make it, but I just thought some perspective would be helpful. The L6 is inherently torquey. Go for the hp. My $.02.

I think it is answer A, but that is specifically what the previous page he linked to says shouldn't happen. I don't think B is likely if the top nut is tight, because that would hold the shock shaft to the monoball tightly.

That thing at the top is a swivel. I know that much. I still don't see how it would be possible to turn the wheel without the monoball moving, unless the bottom half of the strut turned and the top half didn't. I know it's blazing hot out there, but I'd appreciate if you would turn the wheel and see if the shock shaft moved with it. Maybe also take a marker and put a dot on the monoball itself and see if it moves. FWIW, I also turned mine today (with the top nut loose), and I watched the shock shaft turn in the monoball.

Solid axle works better for rock crawling because it articulates and it's easy to get a strong solid front axle. Independent suspension goes more or less straight up and down and if you have 8 inches of travel, that's what you have, the axle can't twist under the chassis. Solid axles can droop and the axle can twist really far away from the chassis and so they can keep tires on the ground in places where no conventional IFS setup can (there are some freaky weird IFS setups that can do amazing things...) Regular IFS articulation, watch how easily one wheel comes off the ground around 1:05: Solid axle: Insane independent suspension:

I think that answer doesn't make sense. Just thinking about it logically I'd like to see how the monoball does not rotate with steering effort. Once you tighten down the nut on top of the strut, it forces the strut to hold tightly to the monoball. If you turn the wheel, when the strut housing turns at the bottom, there is no way that the monoball at the top can resist turning unless the shock shaft turns, which is what the site you linked to says they are trying to prevent with their design. If you isolate the vertical load from the monoball then presumably the monoball will spin more freely and that will ease up the steering effort. I don't think there is a way to put a monoball over the shock shaft to allow for angularity changes and not have it also turn with the strut. You'd have to have some disconnect in there, or have the monoball itself mounted inside a bearing so that the outer race of the monoball could rotate in its housing while also allowing the strut angle to change, which is something I've never seen before. Even then it might move radially if the twisting force was high enough for some odd reason.

How are you guys sealing the cover to the floor in the rear? I was thinking of getting some of that VW fender weatherstrip, or some thin foam weatherstrip and putting it around the edge of the hole so that the cover seals up. Looking to minimize exhaust fumes as much as prevent the gas from getting in around a leaky cover.

Richard, you're contradicting yourself. The first one says that the vertical load should not be carried by the monoball. The second one has a bearing to allow for steering to be handled separately, but the vertical load still goes into the monoball. The idea behind the thrust bearing in the Ground Control, EMI and other plates is to put the vertical load on the needle bearing and isolate the monoball so that all that it has to do is handle the angularity change. It has the side benefit of handling the steering as well. FWIW, I had the old style GC plates in my car for 40K miles and although grit did indeed get in there, they still worked pretty smoothly when I took them off and I sold them to another member here who is probably running them right now. I think the more important issue than the steering load is the vertical loading, which when put into a 5/8" monoball is asking a bit much of the bearing, but a high quality 3/4" ball should hold up OK. The spring angularity issue comes from trying to use a needle bearing to take the vertical load. The new GC plates allow both the needle bearing to take the vert load and for the top hat to stay inline with the spring. The EMI, old GC and probably some other plates hold the top hat rigid so it doesn't change angularity with the strut, and this is where you get the side load on the spring.

The modification you would need to run the Bilsteins is nothing more than installing a spacer to fit under the strut cartridge. IMO Bilstein>Tokico, and I certainly think that is true of the Illuminas, but you're right that you wouldn't need the spacer with the Illuminas.

Bilsteins have an internal bumpstop, so nothing needed there. If you replace them all because of the damage, I wouldn't revalve the struts if it's a street car. Just get that part number and install them as is. I am not a fan of the poly camber plates from MSA. Poly is very stiff, so the risk is that the same thing that happened to the current struts would happen with the poly in there. It just doesn't give enough. With a monoball in there the strut can swing back and forth with virtually no resistance. That's what you want. I don't think you "need" the thrust bearing either. It is a good idea when you use a 5/8" monoball, but if you used a 3/4" monoball in the top, I think you could get away without it. The problem with the thrust bearing is that in order for it to work you have to put a weird side load on the spring, unless you use the new Ground Control camber plates. By putting the load right on the monoball you alleviate that side loading of the spring, but I don't know anyone that makes a 3/4" monoball camber plate for a Z.

With a lot of duration you are pushing the charge out the exhaust at low rpm, but it works better at higher rpm; it's a trade off. With a small cam, you are keeping it in the cylinder at low rpm, but it doesn't work very well at higher rpm. If you read online you'll find people that say that you need torque, and people that say you need hp. For my money with an L6, having run both, I'll take the hp. If you go for torque, there just isn't much hp to be had. If you're talking about a V8, it's a different story, but even there it's not a clear decision. Basically you have my previous post right, but I'll rephrase for clarity: If you want to go down to the local gas station and fill up, don't get too zippy on the compression ratio. If you don't mind paying for race gas then go for the compression. If you gave me a choice of the same motor built with 9.5:1 compression that was known to run on pump gas with the timing optimized or the same motor built with 11:1 compression where I knew I had to at least mix race gas to make it run with the timing optimized, I'd go for the lower compression motor. E85 might be a solution, I don't know I haven't used it. I think if you used high octane gasoline you'd get more power than E85 just because it has more energy per gallon, but E85 might be a way to build an 11:1 motor and not detonate the crap out of it trying to get the timing to where it makes the most hp. How that compares to the 9.5:1 motor, I really don't know, but I would suspect that E85 makes a bigger difference on a forced induction motor than it does on an NA engine. Heavier pp was referring to the ACT pressure plate. The point there was that I had a combo that everyone says would be absolutely horrible on the street: big(ger) cam, 44 triples, heavy clutch, big exhaust, and it really was easy to drive in traffic. I never dynoed my engine so I don't have any numbers to give you for comparison. I always thought the money that I could spend at the dyno would be better spent on some new suspension mod.

Mark is right, my bad. I didn't click on the photos to make sure there was a monoball in there, I just assumed it was there. After clicking, I don't see one at all. That would be a real problem. Might take those aluminum pieces off and see what is under there. If the stock strut tower is all hacked up, you might be looking at a set of camber plates to fix it.

I've run scattershields that I made myself. Basically I cut and bent a piece of 1/8" plate to fit the area of the trans tunnel where it hits the floor pan. Then I cut another and bent it over the first and welded the two together, and bolted them in the car on the driver's and passenger's sides. I don't have any pictures. I can tell you that they aren't pretty, but I'd rather have ugly shields and my feet than not run them. I mostly did this because I had 3 separate machinists look at my Arizona Z Car flywheel and ask if I had a scattershield. Another option is a trans blanket. I don't know if they're rated for an exploding flywheel, but they're certainly better than nothing and a lot easier to install than a scattershield.

Looks like a 5/8" monoball in the top, You might need a bushing in there to center the strut in the monoball. If you're going to replace all 4, you can buy the Bilsteins mentioned in the strut thread here: http://forums.hybridz.org/index.php/topic/50944-the-strut-thread-koni-illumina-tokico-carrera-bilstein-ground-control/ and then you can buy the bushings to center the strut from Ground Control. With those current Bilsteins you will probably need a spacer underneath the strut. I used some 1.5 x .090 tube, which you can get from www.online-metals.com