JMortensen

Roll center is not defined by the center of gravity. As shown in the diagram, it is a relationship between the strut top, the ball joint, the lower control arm pivot, and the center of the contact patch. The center of gravity has nothing to do with it. Many lowered Z cars have their roll centers underground. That doesn't mean the CG is underground. Look at the diagram again. If you think the CG moves as much as the IC, then we have reached an impasse that I can't talk you through. You are right about the weight transfer, but that isn't always the biggest priority. If you can't get any heat in the tires (at a cold autox in OR for example), perhaps getting heat in the tires would be a bigger priority in some cases. I'm starting to think that your posts aren't serious. Are you a troll? http://en.wikipedia.org/wiki/Internet_troll

Go back and look at the original uprights for that CSR Stohr. The originals are not some crazy FEA inspired design. They're pretty simple aluminum pieces shaped like a box more or less, but they're at least shaped to deal with stress in different planes. Could a flat plate work if it was thick enough? Yes. Is that a crappy way to design race parts? Yes. If you're going to all this hassle to design your own upright and connect it to your own control arm, why use the spindle pin? Why not use a double shear connection for a front and rear rod end that bolt up into the bottom of the upright? Why use a conventionally mounted caliper instead of a radial mount caliper? Why use an H arm at all? Really, if you're going that far you pretty much have carte blanche. Might as well use it.

Raising the car ALWAYS lowers grip? You're sure about that? You don't think that raising the roll center 1/4" or 1/2" might have a different effect if the car was unbalanced before you did it? You don't suppose that raising the roll center has any effect on the roll resistance of that end of the car? You don't suppose that increasing roll resistance on one end might change the balance? Is it impossible that raising both ends works the tires harder? None of the above is true??? I'm not even touching on the myriad other reasons why raising the car might make it handle better, probably the biggest one for Z car is because the car is driving around on the bumpstops before it was raised, but there are others, bumpsteer curve, camber curve, caster curve, etc. Check the diagram on p2 against your roll center ideas. Lowering the car CLEARLY lowers the roll center on strut suspension. So then what does raising the car do??? http://www.banningcohen.com/buick/handling/documents/making%20it%20stick%20-%20suspension%20tuning%20guide.pdf

Concourse people have a special kind of price tolerant retardation.

I'm sorry if this is insulting, but you do realize that the name L4 applies to 4 cylinder Datsun engines like the L16, L18, and L20B, right? L24, L28, and L28 are all 6 cylinders L6 engines. Just want to make sure we're on the same page there. So you would want to start with an E12-80 distributor from a NA 280ZX most likely. As far as your question goes, yes you can get spark from a 6 cyl E12-80 distributor on a turbo block. The issue you'll have is disabling the advance mechanisms, as I said before. That wouldn't be too hard to do. I'm also not sure if the stock ECU accounts for some degree of timing change, and if it needs to hook up to a turbo distributor to do so. That's something someone else could probably answer for you.

So you have a 4 cylinder distributor and you want to use it on a 6 cylinder. You'd need to change out the breaker plate, or on your E12-80 model you'd need the correct stator and reluctor for a 6 cylinder. After that you'd have issues because the turbo distributors don't have timing advance, and the E12-80 will have both mechanical and vacuum advance. You could lock all that down, but after all that trouble why not just find a turbo distributor???

Have a snap ring groove machined on the shaft after grinding to get it apart, or get some other CV shafts. Not sure what your PM meant or if it was intended for me, but that's what I'd do, and I'd lean towards the latter.

Try relying on the unibody and then improving the stiffness and see if you can tell a difference. When I added some strut tower bars I damn near drove off the road on the inside of a corner because the car reacted so much differently. Why did it react differently, because geometry was being lost previously. In particular, the strut tower bars help to keep your camber settings steady. The Z chassis is not very rigid out of the box. In fact, I'd say it's really flexy out of the box, a wet noodle compared to any modern sports car. This is also why you hear people like John saying "don't use more than a 300 lb spring without increasing chassis rigidity" because after a while things like sway bar changes and spring changes don't have the effect they should, because the chassis can't take the strain and it flexes too, lessening the impact of a change that should affect the handling.

Have you tried http://www.wolfcreekracing.com?

Just a guess: Nissan doesn't stop production and throw out all the leftover old parts on September 1. Look at the 70/71/72 stuff. Lots of those parts bleed from year to year.

Around the end of the thread I reposted a lot of the pics.

http://forums.hybridz.org/showthread.php?t=106974 I'm off to bed. If you want to see more of mine, search "2 year roll cage" and read the link above. I think I had a thread on stitch welding too. You might look at my project post. It's on the last page, as I think I was the second one to post one and then I've never updated it...

Here's my front strut tower bars. One connects to the cage as close as I could get it to the rocker, the other V's to the dash bar and then goes straight back to the rear strut towers via a bar right down the middle of the car a la Herb Adams in Chassis Engineering. This necessitates a right side net. I could have done an X from the strut towers to the A pillar bar at the dash bar nodes on either side. That probably would be a better solution, but I think that would make it a lot harder to get the engine in and out of the car. My other nit pick with what I did is that the tube to attach the strut tower to the sway bar mount is straight, but it has to hit a bracket off of the strut tower instead of hitting the tower itself. The bracket is pretty beefy, and this is not so much to brace the strut tower as it is to brace the frame rail, but still I think I like bjhines' solution a bit better:

Looks like a lot of careful thought and attention went into building that car. I see very few nits to pick. The bar from the strut tower down to the sway bar area would be better if it were straight, but he would have had to cut into the fenderwell to do it. A curved bar is less stiff. Also in the front I think the bar from the strut tower that presumably attaches to the dash bar node is in my opinion redundant. I looked at doing the same thing, but the upper frame rail is right there and attaches basically the same parts in the same plane. Not sure the load path is the best for the tube that goes from the strut tower to the TC rod/rocker arm bar. Those are all pretty small issues though. Interesting rear suspension solution. Looks like he has no front diff crossmember either. Diff changes must be a snap. Is this guy a member here? He should be...

You know... 600 lbs/corner and a 16.6666666g bump. There you go, 10,000 lbs per corner!!! It's like when you've got Roscoe P Coltrane on your tail and you see that dirt ramp. You just gotta take it!!! YEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEHAAAAAAAAAAAAAAAAAAAAAAAAAAW!!!

Haven't seen cold rolled square tube, that doesn't mean it doesn't exist though. Cold rolled sheet won't have the mill scale on it, so I'd go that way just to save yourself the hassle of grinding it off.

http://forums.hybridz.org/showthread.php?t=103886

Not really. Terry has pictures of raising the diff with the plate that he made, and extending the strut to lower the spindle pin though: http://www.fototime.com/ftweb/bin/ft.dll/pictures?userid={7DC317B0-8EDB-4B2E-A837-F708D07C9769}&inv=9C67398D46D99D9&userid={7DC317B0-8EDB-4B2E-A837-F708D07C9769}&AlbumId={A74939D0-8C30-4904-9655-FE71445052A7}&inv=9C67398D46D99D9&GroupId={4265E8B7-5F1C-435B-AF0D-52BFF208A1F1}&nt=a

Get past the bling and analyze the part. Think of the loads the upright takes, and then think to yourself "Is a flat plate the best shape to deal with these loads?" Compare to real race car uprights. See a difference? Single shear mounting of the strut to the upright? Connected with bolts no less (built in stress risers)? The one brace he does have in there is on the opposite side from where the strut connects? And then there are the arms he has connected to it, which are another case study in bad design. This is billet bling crap guys. Just for comparison's sake: http://www.luxonengineering.com/pdf/news_9-25-2008.pdf http://www.luxonengineering.com/pdf/asme_presentation.pdf

I went back to find this quote for you and couldn't find it. I think I had come to this conclusion on my own and had remembered it being stated more explicitly. On p.61 you get this: And on p.69: Put two and two together...

Because the Z is a product of the 70's with a low roofline. When you intrude on the meager amount of space that is there by adding a cage, there just isn't a way to get the bars far enough away from your head to avoid hitting them in an accident. Unless you drive your car with a helmet on the street, I'd suggest you don't install a cage. A roll bar you can get away with since the hoop is behind the driver's head.

Dammit, wrong book. I meant to say Competition Car Aerodynamics.

OK. I think that's where the problem is. You're right that these areas are venting, but not specifically to reduce high pressure, they generate low pressure. Have you seen the exhaust based PCV systems? Same thing there. They use the flow of the exhaust to create a vacuum in the crankcase. I don't know if any of those cars has a front diffuser. Have you read "Race Car Aerodynamics"? It has a pretty good bit on front diffusers. It says that the front diffuser works like the bottom side of a wing in ground effect, and the top side of the car forms the top of the wing, the pressure differential between the two gives your lift value. Likewise on the NASCAR it is also a pressure differential that gives downforce, only it is the pressure differential on either side of the hood and fenders, which is a much less efficient way to make downforce. I didn't mean to say that you SHOULDN'T look at the Bentley, only that the NASCAR stuff would likely be more useful.

Well now that I've actually looked at your link, maybe I can make more sense... I think the reason the exit is so far back there is to keep the flow connected, a sharper curve there would probably hurt the effectiveness of the diffuser. The reason for the triangular bit between the back of the wheel and the diffuser exit is to keep the flow reasonably attached so that you can use the low pressure from the high velocity air to enhance the front diffuser, not to separate the high pressure of the wheel well from the low pressure of the diffuser exit. There is low pressure in both areas, they're just using airflow along the side of the car and maximizing the low pressure in both. If you take a look at an older IMSA car or a Spec Racer Ford, they have no triangular wedge in between, just a wide open space from the rear of the tire back out to the full body width of the car. Spec racer Ford: http://upload.wikimedia.org/wikipedia/en/7/7c/SRF.jpg Here's one in between: http://www.conceptcarz.com/view/photo/191824,13482,0,0/1981-Porsche-935_Photo.aspx Pike's Peak Celica: http://www.carsbase.com/photo/photo_full.php?id=36966 I would guess that we would be better off looking at the NASCAR example and not the Bentley example, since NASCAR does a lot with a little and very crude aero (no tunnels or flat belly pans, etc) while Bentley does a lot with a lot and has a lot fewer design constraints. EDIT--Look at the huge vents on the Pike's Peak Tacoma (and the rear tunnels) DAMN!!! http://www.ultimatecarpage.com/pic.php?imagenum=4&carnum=3266

Good point Dave. I think the "low pressure around the wheelwells" ASSUMES that the car has been designed to have low pressure around the wheelwells. NASCAR does this, they have a front fender that extends past the tire, so creating a lip in front of the tire which creates a turbulent low pressure zone in the wheel well area and this constitutes a large part of the downforce that NASCAR's have. I had linked to a circle track article about this previously but I can't seem to find that old CT page anymore, but suffiice it to say that they talk about putting a concave shape in from the nose to the wheel opening for the purpose of getting more downforce by evacuating more air out from under the car. With the front of the tire exposed (eg spook) the tire itself generates quite a bit of lift, and I honestly don't know what happens in terms of pressure around the wheel well area, but I can't imagine it being a good thing.