tube80z

Unless you change the rear control arms to a different design you can't change the angle of the rear struts without putting the suspension in a bind. Ideally you'd install everything to make sure you don't have a bind and then tack in the plates. Cary

So commander cheap is finally parting with that

How much of a change can you get in your magic number by changing chassis rake?

There's also the cross weight change that happens because of caster. Put a car on scales and turn pads and you can really see it all working. Cary

It's probably just semantics then. I'm thinking weight transfer based on wheel base and Cg height. I guess going to a lot lower spring rate will cause the front to rise and the rear to squat but the overall Cg height isn't going to change that much is it? This is more what I was thinking and I call this load transfer. So I'd agree stiffer springs will increase the load transfer. And I'd agree softer springs will slow it down. But at the rates mentioned I have a hard time believing there will be any advantage based on the suspension moving a lot more and having camber change that works against you. My thought would be that this would be better controlled using shocks since what it appears we're looking for is based on suspension movement. Maybe softer rear compression and less front rebound. My own experience shows a slight gain in performance when running 450 pound rear springs that when my car was running 175s. But these were not using drag tires (FA rears). It seems like there are some people on this forum that are going really fast with the independent rear. And if I recall correctly one of those cars was using bumpstops to limit the rear compression. That will increase the rear spring rate fairly quickly. So I think the rear tires can handle a lot more than we give them credit for.

Weight transfer has nothing to do with the springs. I'm not following how that's going to work. I'm not a drag racer so maybe I'm missing something. Cary

I've seen pictures of a number of the Dodge Vipers that had vortex generators on the underside of their splitters. These were in front of the tunnels that fed into the wheel wells.

Having run similar arms on the back of a V8 powered car with wide slicks (FA) we've found that the toe-link rod ends need to be very high quality. The slot gap (speedway, jegs, summit QA-1 parts) wore out in about 6 events. These were the 5/8 best quality with kevlar liners. These parts have been switched to Aurora 3-piece rod ends in a higher spec. I'll report back how these do once we have more mileage. But for anyone looking to use this in competition (or possible extreme street use) please keep in mind the rod end requirements. Another option would be to convert to 3/4 rod ends to gain bearing surface area.

I used 200 pounds for pre-load and then went in 100 pound increments. I had envisioned going up to 1000 to 1200 pounds. I got chicken well before that. I did most of my measuring at about 600 pounds of load (800 actual). That 600 pounds is applied at the same level as the tire contact patch. Things moved much more than I would have thought. I could see changes at 300 pounds (500 total load) between the two struts. The suspension and wheel need to be constrained when doing this or the car will simply raise up as you pull the wheels together. Cary

So the stupid question. If you hadn't done this would you believe a combo like you have would work as well as it does? I still have people to this day that tell me droop limiters will not work and all I'll do is pull tires off the ground. Cary

I have been using a slightly different theory for setup based on some of what Ortiz has said. It doesn't try and set the diagonals equal but instead aims to mimic the asymmetry that's already their. Dennis Grant has a calculator that implements this principle if you want to take a look. It yields 682.94 640.06 687.06 643.94 I used to try and set diagonals equal but changed to this after reading Ortiz. The seems a little easier to drive but more importantly is kinder to tires. Cary

Now you're talking about a real race engine. The RX8 engine in the GT class isn't going to be the same engine as you'd get in a normal RX8. The Brumos Porsche Crawford runs similar RPM levels. Sure those last for a race at 9K all day and get tore down and inspected/rebuilt for the next race. That's not the same as saying I have a buddy with a stock turbo RX-7 and it can run 9K all day. It would be far more reasonable to say that your buddy has an engine with hardened stationary gears, upgraded apex seals, etc. And unless he has seriously upgraded the cooling system he'll have a hard time pushing the engine that hard for long. And yes Mazda has had a lot of racing success with rotaries. But on any one day I'd put my money on a chevy as being the dominant engine. Just think about NASCAR, all the feeder series, drag racing, etc. It's not that I have anything against rotaries but the hype surrounding them is ridiculous. It would be cool to see a three-rotor powered Z for sure. But there would be a lot of problems to solve. The 20B used to be used in a few SCCA EM cars. But noise restrictions have forced most of those guys to swap over to different engines. So if you're really looking for one you may find a few out there already setup. Years ago I was very excited to put a rotary into a 510. After a lot of research I found out that the beer keg engine needed a lot of exhaust, a huge radiator, and a lot of oil cooling. Unfortunately it's never as simple as it seems. We agree that rotaries are cool. But my experience has been that when pushed they aren't as reliable as most people think and add a turbo and it only goes downhill. There seem to be a lot of TSBs on the new RX8 to back that up.

Sorry to burst your bubble but I've never seen one of these rotaries that runs at 9K all day long. I've been around a number of the turbo cars and they don't seem to last too long before needing rebuilds. Most of the rotaries I've seen don't rev much more than the piston engines. We had a number of the FD cars where I race and they are fast. But they don't seem to deal with abuse for long before they are wounded. And how much do you think a Z weighs.

I think they are designed to keep slosh down when cornering. By far the biggest problem we had was fuel slosh from breaking getting into the carb and keeping the engine going. This required a bridge of the vents (some tubing with a hold in the air cleaner. I'm told this is a common thing to do. I a newbie to 4-barrel carbs. We ran a speed demon (both mechanical and vacuum) that had the standard choke stack and the sportsman that has none. The sportsman had annular boosters and this made a huge difference to low end power. All suffered the brake surge until we put the vent bridge on. The sportsman is a lot easier to do this too. None of the carbs seemed to suffer from cornering related issues, which we were worried about (generating 1.3 to 1.4 Gs) Cary

The carbed car I drive pulls from 1500 or so and may not have as much torque as EFI but it still goes like hell. From 2500 on up I'd bet there's little difference.

Myron, The arms look good. I think you'll be very happy with the results. You'll be amazed at how easy they go on. Cary

We're looking to do the same thing. I don't see any issues with this. Cary

No these both were unmodified. Maybe the gusset will do the trick.

I meant the just the threaded upper section leaving the majority of the 280 tube in place. The compliance testing bit is about what happens when you pull or push the struts together. In the motec seminar I took a few years back Claude showed us slides of a contraption that measured forces on wheel pairs. The idea was to push and pull across the axle and then the wheel base. You measure toe and camber changes based on this and can create force/deflection curves. I used my harbor freight porta power and a pull ram with a gauge. Not as high tech but it was enough to see that the 240 strut tubes deflected quite a bit. My guess is sticky tires on them can cause them to lose about half a degree of camber. The 280 tubes were less then a third of that. And simulated braking loads showed the TC boxes to move a lot on my car. A simple brace really made the car feel more stable. Anyway, that's the basic idea. The motec guys used a fancy load cell and hooked it all up to a computer to generate curves. The strut tube deflection was interesting for me to see. I'd guess similar results could be seen from different wheels with regards to camber loss. Something most of us don't think or worry about.

Can't you simply cut the top of the 240 and use the 280 bottom? If you ever do any compliance testing you will rethink the idea of using the smaller 240 diameter tubes. Cary

I'm about the last person you want to talk to for carb advice. I found the 750 from researching a few books and magazine articles and those had dyno curves showing annular versus dog leg boosters. We've ran three carbs, all demons. 750 vacuum secondaries (not so hot), 650 mechanical secondaries (dog legs) much better, and the 750 sportsman with road race floats (the best). You don't want vacuum secondaries for performance apps. A custom carb may be even better but when you have enough power to burn the rear tires off it gets to be sorta moot. Cary

Go over to ebay and search for the GMPP manifold by part number. Wegner is selling some for $259 and had 24 the last time I checked. This is what I have. I can't say if this will be better or worse. I'm putting this on an LS1 with a HOT cam. There's a guy on ebay that's doing LS cams for $100 from time to time. Dave built his motor more for mid-range power rather than top end. I can't recall his cam but he reads these threads and hopefully will chime in. It's supposed to stop at 65/6600 hundred but it will pull to 7200 if you're not careful. The single plane may be easier to drive because it won't have such a large amount of torque down low. It pulls from about 1800 on up with the performer manifold. His LS2 has the 26x reluctor but you're right they normally need the 6012. On the carbs we've found that you want the annular boosters. They do a much better job at atomizing the fuel down low and you get a lot more low end this way. We've tried a 650 demon DP and it seemed strong but the 750 annular feels like we have a nitrous button. In a car setup to turn with a poor launch he did a 12 flat at 120 in the quarter.

Yes, it has this effect on me. It's also the first car I've ever seen to shake it's tires.

Viperredls1 has a similar car. LS2 with edelbrock performer RPM manifold, MSD 6010 (better than the distributor option), cam, LS6 heads, and a 750 sportsman demon. It's making the power levels you're looking for. I can tell you that even with 14 inches of rubber in the back this car is able to spin the tires at will in second and for a good part of third. It's a handful to try and use that much power at an autox. It's a time machine. All the 40 and 50 year old guys that drive it suddenly act like they're 16 again and just snagged dad's keys Cary

I see that you have AZ racing brakes, which I believe are wilwood superlites up front. You need to clean the pistons on these periodically or the brake dust can cause them to hang up. Also check the pads for taper wear. One trick we use to get longer pad life is to flip the pads up/down/in/out after a few events. You have a number of options if you don't find a caster issue. Swap tires, then swap pads side to side. Those are all easy. My guess is one of these would solve the issue before you need to look into anything more sinister. Cary