JMortensen

CFD > building teeny models for every change you want to make.

This will explain the NASCAR thing: http://www.circletrack.com/techarticles/ctrp_0707_stock_car_aero_downforce/viewall.html Tony's stovepipe thing was just a theoretical, although I'm sure land speed cars have probably done it for real too. He was literally talking about taking a tube and connecting it from the engine compartment to the back of the car; cutting a hole in the firewall and in the back of the car, and connecting them. Since there is a low pressure wake behind the car, this would suck air out of the engine compartment (and reduce the wake behind the car - useful for LSR). Yes, there is a low pressure area behind the tire on the Z, this was clearly shown by the first wind tunnel test. Cutting holes below the inspection covers and venting to the fenderwells would help. They did this in the last windtunnel too, and they put fender vents on the outside to help get the air out on the blue car and tested covering the vents vs leaving them open. Again, the vents and the holes were pretty small. If you have a caged front end, you should be able to cut much bigger holes, and putting them further forward (in front of the strut) might help a bit too. Airdam 2" off the ground by itself reduces drag and lift, but you're not going to get real downforce until you close up the grill and do some of the other things in addition. If you look at those NASCARs though, they DO make real downforce and they are not very complicated, they just have very low ground clearance, have a rad duct, and exhaust the underhood air out through the fenders. It would be interesting to see what Dan's car (74_5.0L_Z) would do in the tunnel, since he has no fenderwells and the rad ducting. I'd bet his car would be among the best of the ones on this site. Just needs a splitter and big ass wing to complete it.

I don't think you can get around the fact that there will be low pressure on top of the hood. Your spoiler idea will create LOWER pressure on the hood, by spoiling the airflow. That's what a spoiler does, it makes high pressure in front of it and a low pressure wake behind it. You'd be creating low(er) pressure than would otherwise exist and allowing it to act on the hood's top surface. This is why you see the Gurney in front of a hood vent. It produces lower pressure and helps to suck the air out of the vent. With no vent, it's just going to be sucking on the hood. What we're after is a better pressure differential. If we can get lower pressure under the hood than on top, then we have downforce. Blocking off airflow and ducting air to the rad are no brainers. Rad exhaust duct is also a fairly easy one to do, and you see this on lots of ALMS cars, and we have a couple people here who have gone that route (74_5.0L_Z and blueovalz). Controlling the airflow through the radiator and into the engine is most of the battle. Above and beyond that we can try to lessen the pressure under the hood in any number of ways. We can do this by venting the hood, and letting the flow on top suck the pressure out from underneath. We could remove the fenderwells and shape the fenders to exhaust the underhood air out the front fenders like NASCAR does. Tony D just mentioned a stovepipe in one of the other aero threads. Put a tube right through the middle of the car and terminate it right where the license plate is. There is a nice low pressure wake right there, that would suck air out of the engine compartment to fill that low pressure area and probably reduce drag as well. Your idea of fans might work, but I wouldn't put them (or vents) on the inspection covers and call it a day. Venting the inspection covers isn't a bad idea, but the covers are too small to get the job done. If you're going to do a sucker car, do a SUCKER CAR!!! Thinking Chapparal 2J, gas powered fan motors, etc...

This issue of hoods lifting was mentioned right after the wind tunnel test as well. I don't believe that the hoods lift ONLY because there is high pressure under the hood. There is also low pressure on top of the hood. The old experiment to show Bernoulli's principle applies: hold a piece of paper by the bottom corners and let it fold away from you. Blow over the top of it and the end of the paper will pull up towards your airstream, with no extra pressure forced under it. In the case of a Z, there is both low pressure on the top side and high pressure underneath, so to say that it lifts because there is air packed underneath misses a big portion of what is going on.

You're suggesting installing a spoiler on the leading edge of the hood? Seems like a drag and lift creation device. The area behind a spoiler is a low pressure turbulent wake. Put one on the leading edge of the hood and you're creating low(er) pressure on the hood than would have been there without it. The Gurney on the leading edge of a vent reduces the pressure behind it and helps pull air out of the vent. If there is no hole behind the lip, you're just making the situation worse.

Search "chassis stiffening" and read up for a while. Short answer is no, that's not a good idea without a cage to attach to, at least in my opinion. There are ways to do a triangulated strut tower bar to the firewall that would work reasonably well, and there are many pics of how to do it here. John Coffey (johnc) has posted pictures of his setup quite a few times and John Hines (bjhines) has an even better setup for a triangulated STB.

Look at adding clutches. There is a thread in the FAQ section. You'll need them with a V8 swap.

I'm a bit hesitant to suggest it but Kevko Racing makes custom depth pans, and you can get it with a trapdoor setup too. I ordered and got mine just fine and so did 74_5.0L_Z, but I sent someone else there and he had some hassles before it was finally made right, caveat emptor.

Kydex is a plastic that you can heat up and bend. Popular with gun guys who make holsters out of it. I don't know that it's necessarily the best material to use for this, but I know Mike likes it and uses it all over his car and it would be easy to form.

Your formula and the DG spreadsheet are not coming up with the same result when I try them. I don't want to derail Keith's thread, but if you don't mind I'd like to continue in PMs.

Here's another idea, since the first ones went over so well. Some Miata guys are running a vertical piece of plastic bent around the front end with a hole cut for the rad duct. This super simple idea removes all of the hassles with the shape of the valance and the turn signals etc where they (don't) cover the front wheels. It also would give a chance to try different heights for the rad duct, which I think would change the pressure on a splitter. Higher the hole for the rad, more pressure on splitter. The Miata guys did some CFD and found this to be advantageous as compared to the stock front end plus airdam. It would also give Mike Kelly a chance to play with some more Kydex. Pic here: http://949racing.com/enduro/Team949_5wins_1024.jpg

I'd love to see that spreadsheet. Would you upload it here, or email to me at mortensenjone at gmail dot com?

If you jump on the back bumper would it bounce like in the video? You have a relatively consistent amount of weight transfer happening here. You're not jumping on the gas and off the gas to make it bounce, and it doesn't seem to be related to wheel hop based on what I saw. So if you put a load on the back, and the problem really is underdamping, it should be repeatable. Another solution you could try to improve the bounce would be a better bump stop. Most people with Z's run the poly Energy Suspension bumpstops which are very hard and bouncy. Better bumpstops are much softer and less progressive in their effective spring rate. As to the Far North Racing site, I am a devotee and have quoted it here probably 20+ times, but his calculator for shock valving doesn't work correctly, or if it does, they espouse what in my view is extremely underdamped shocks. I tried to use it to come up with ideal damping rates for my Miata and it was just grossly wrong.

Seems to me like an Accusump is the best cheap solution. Instead of trapping maybe a cup or two of oil around the pickup tube, and Accusump can hold 3 qts of oil and have it feed in automatically any time the pressure drops. Adding a pan with an Accusump gives less likelihood that the Accusump will run dry and the oil will still slosh away from the pickup, which is possible. Dry sump is the best, but a lot more expensive. I had the AZC pan on my L6 and thought it was a very good pan. Mine had a leaky pipe plug drain on it, but I understand the newer ones use a flanged drain plug with a better seal to solve that minor problem.

That guy Tim from TIP used to hang around here a bit, and obviously knows his stuff. With Illuminas that's a lot of knowledge you can't use though. IMO in more practical terms what you need is stiffer springs, probably stiff enough that the Illuminas won't work for them. Looks like you're hitting the bumpstops repeatedly. Since your options are so limited, try the Illuminas on all 5 settings and do videos and check time slips to see if that improves things. I suspect springs are probably the right answer. Illuminas have "cross-talk" where the rebound setting affects the bump, but I doubt you're going to get enough bump damping to keep it off the stops. You may get enough rebound to where it doesn't bounce back up as high, but I'd guess that it will still be smacking the stops similarly. There are all kinds of different theories on damping too, so beware that this is a rabbit hole that is deep and wide, if you decide to jump in. The best setting for autox is likely to be completely different than the best drag racing setting, so your choices are either to get really good adjustable shocks or to run some sort of compromise.

Chequered Flag uses MM's supplier. It sounds like the companion flange fits the 39 spline chromoly stub axles. It may be that Ross never had those parts made for the 27 spline axles. If they were made, Joe @ Chequered Flag could get them for you. If not, one (good) solution would be to upgrade to the chromo stubs.

A real cell is expensive and heavy. I like the regular ones, I think they're cheaper than the spare tire well style and you can cut the floor and mount them lower so as not to negatively affect your cg.

Ground control makes coilovers that work with their camber plates. Other peoples' coilovers won't work with their new style plates, as they need a rounded washer thingy that sits on top of the hat. EDIT--I think if you buy their plain old coilovers those also won't work with their camber plates. You would need to ask them to be sure, but their newer plates require the dished washer thing.

I've got Toyo R1R's on my Miata. They work GREAT in the rain, but you can overheat the tires when it is sunny. See you're in BC, so they might be an option for you if you're autoxing. Any tire is going to wear the outside shoulder off in pretty short order with stock suspension, so it would be a good idea to work on adding neg camber and pos caster to make the tires last longer.

Pick up motor with cherry picker. Use impact to remove flywheel bolts. Put back on cherry picker. If you don't have air you can rent an electric impact from your local tool supply.

You referring to Mike's cowl induction style vents? They'll pull air out if they're in clean airflow, but not as well as a regular louver style vent would do. With the typical 280 vent position I think you're likely to get air out of them. Guys with cowl induction hoods were getting yarn alternating in and out of the hole, and these are mounted a couple inches forward and more to the side from that.

How far back did you run your undertray? Lots of racing classes limit it to the axle centerline.

Cockerstar makes a good suggestion. Run the struts on 1 or 2 and it will drive pretty comfortably on the street. I had that setup for years, and it was overpowered by sticky tires on the track but worked great on the street.

280 is slower. http://forums.hybridz.org/topic/99017-240z-rack-into-280z/ As to the Ackerman issue, I moved my rack rearward to try and increase it. Had an argument on the value of Ackerman with Leon here and ended up diagramming it out, and found that my work to move the stock rack back had resulted in something like 1 degree more Ackerman at full lock. I found that the Z has a little Ackerman but not very much, and it wasn't worth it to try and keep it during the process of mounting my ps rack. I ended up moving the rack inline with the tie rods, and I'm going to run a bigger static toe out setting in front instead. I imagine you'll need to move the TC rods to the rear to go front steer, or figure out an A arm setup.

I agree with Todd. By the sounds of it they're pretty dialed. One thing I wanted to try was different emulsion tubes. The Mikunis don't have all the different options like the Webers do, and pretty much every runs the OA, but there are the OBs and the 8s to try. IIRC the 8s were supposed to be a "street" setup so I was thinking of trying them on the hunch that they might do better on the transition. Never got to it though.