JMortensen

http://www.theonion.com/video/today-now-interviews-the-5yearold-screenwriter-of,20188/

No.

I've pulled several cams on the same motor by pulling the cam towers, but I also pulled the spark plugs and drained the coolant. Now that you have a coolant leak past the headgasket, I think you're pretty well screwed. If you had done it the way I did and then retorqued the head, I think you would have been OK. I actually pulled the cam towers twice on the same gasket with no problems.

You would need to look up the spring length and bound length, figure out how much travel you'd have at the ride height you want and see if it would bind before it hit the bumpstop.

The main difference is that the 10" spring has more travel, this is important with lighter spring rates. When you go stiffer you can go shorter on the spring and not run out of travel. You can look at Eibach's website and see what the total travel of the spring is. Most people with coilovers lower their car to the point where coil binding an 8" 300 lb spring is not going to be an issue. You'll hit the bumpstop first. The smaller spring has the added benefit of not bending as much as it compresses, and it's lighter.

It's OK.

Same thing, just updated to allow brake and fuel line clearance.

Ordered my rack today. Ended up with part number HLM266CC-2325/2475 950-1/210. So this is an HL rack with monoballs, high load, 23.25" rack with 24.75" housing 950-1/210. The housing being 1.5" longer than the rack limits the travel by 1.5", so it will have 4.5" of stroke vs the stock 5". I had previous issues with the tires hitting the TC rods, and although the new TC rods are in a slightly different location, I figured it wouldn't hurt to cut the travel back. I used my Ackerman charts and this brings my max angle on the outside wheel from about 33 degrees to about 30 degrees, so I don't think it will have a very dramatic effect on turning radius. Also ordered a KRC pump. Will take pics when the rack is received.

Yes, the U-joints are a weak point. If you're doing an LS swap and drag racing or otherwise testing the strength of the shafts, you'll need to spend money for a CV conversion and maybe a stub axle conversion as well.

CV conversions are expensive. If you're using the Subaru diff, you would either need to a. use the Beta Motorsports stubs and the Wolf Creek style CV adapters, or b. Use the Subaru inner CV joint with a custom shaft to a outer 280ZXT or 300ZXT outer CV with a Modern Motorsports adapter. Either way you're buying expensive adapters. If you had the expertise you could have some machined, but if not I'm guessing you'd pay a machinist more than you would Beta Motorsports or Modern Motorsports. I would suggest that since you didn't feel it was necessary to upgrade to the R200, you just stick with the Beta Motorsports stubs and stock U-jointed halfshafts. Halfshafts aren't as cool, but there is probably not gong to be a noticeable difference between halfshafts and CV's. Wolf Creek talks about picking up hp on the dyno, but that was with 510s which have some REALLY bad u-joint angles when lowered. I don't think you'll see much if any hp benefit on a Z unless you've done something really wrong on the rear suspension.

Too much droop on the inside wouldn't make it have less traction because of weight transfer, but it would make it have less traction because the tire rolls over on the inside edge. It also makes the outside tire roll over on the outer edge. Body roll = bad is basically the idea. You can crank more neg camber in there, but you get to a point where you're hurting straight line accel traction and braking traction as well. Too much droop limiting basically means that if the surface isn't very flat the back end will skitter around on bumps. I haven't tried it, but I hear you can make the car very tail happy with too much droop limiting.

Strut suspension has a tendency to extend the inside suspension more than it otherwise would as the sprung mass slides up the canted strut, causing body roll. Body roll in a strut car is also camber loss for the outside tire. Some other suspensions like SLA don't respond to the angle of the spring and shock, so they aren't negatively affected in the same way. Struts are not the best suspension, and what we're really doing here is working around the limitations of the strut geometry. If the Z was designed for much stiffer springs, Nissan wouldn't have used so much droop in the suspension. So really what we're trying to do first and foremost is get rid of the extra droop that allows the body to roll excessively which is only there because we've upped the spring rate by a huge amount. That means setting the limiter to stop the suspension when the spring comes loose. There is a potential benefit to limiting the droop even further, but this is where you get to the fine tuning bit, and I would start with your limiters set as described above, and then reduce the front droop until you get the turn in you want. I would bet that you find that zero droop doesn't work that great, as it causes its own problems. I drove in a Toyota truck that had the front torsion bars cranked up to zero droop and it was very uncomfortable and the front end would lose contact with the ground a lot. It might be OK for a Formula Ford that drives only on smooth tracks, but not a good idea for a Z car that has to drive on bumpy autox courses or tracks. I wouldn't limit front droop on the front of a street car beyond the loose spring scenario.

I'm going to double post this because I saw it in another thread and think the info should be in both. Strut suspension has a tendency to extend the inside suspension more than it otherwise would as the sprung mass slides up the canted strut, causing body roll. Body roll in a strut car is also camber loss for the outside tire. Some other suspensions like SLA don't respond to the angle of the spring and shock, so they aren't negatively affected in the same way. Struts are not the best suspension, and what we're really doing here is working around the limitations of the strut geometry. If the Z was designed for much stiffer springs, Nissan wouldn't have used so much droop in the suspension. So really what we're trying to do first and foremost is get rid of the extra droop that allows the body to roll excessively which is only there because we've upped the spring rate by a huge amount. That means setting the limiter to stop the suspension when the spring comes loose. There is a potential benefit to limiting the droop even further, but this is where you get to the fine tuning bit, and I would start with your limiters set as described above, and then reduce the front droop until you get the turn in you want. I would bet that you find that zero droop doesn't work that great, as it causes its own problems. I drove in a Toyota truck that had the front torsion bars cranked up to zero droop and it was very uncomfortable and the front end would lose contact with the ground a lot. It might be OK for a Formula Ford that drives only on smooth tracks, but not a good idea for a Z car that has to drive on bumpy autox courses or tracks. I wouldn't limit front droop on the front of a street car beyond the loose spring scenario.

Stick your hand up under the tower and you will feel that there is a formed plate that is welded to the sheet metal underneath, which goes down ~1" on the sides. I'd guess it is .100 or so thick. I have mine bolted to that plate area. I think you're forgetting the damper's effect. If you jump a car with droop limiters, it isn't going to "snap" them tight because the damper will slow the movement of the suspension. So they're already going to hit it somewhat softly compared to a non-damped example. If you're setting the droop limiters so that the suspension tops out when the spring is loose on the perch, then it probably doesn't really matter if they're soft or not when they hit the limiter, but if you're trying to use them to actively limit roll, then you're introducing a small amount of extra squish at the end of the travel, and that muddies the tuning that you're doing. EDIT--What you're doing here is limiting the suspension movement and the roll of the chassis, but the tire will still be firmly in contact with the ground, so any additional shock will be at least partially dealt with by the tire as it acts like an air spring. Like most other things race suspension related, having extra compliance in there isn't going to benefit anything at all, and it's only going to make the transition from on the limiter to not slower. It adds abrupt stress to quadruple your spring rates, but I think you've done that compared to stock. It adds abrupt stress to run camber plates with monoballs, or poly bushings as compared to rubber, etc. Making things smooth is not necessarily the goal of racing suspension. The droop limiters on a 4x4 truck perform their task for an entirely different reason. They are there to prevent stress on the ball joints and in some cases maybe to prevent a driveshaft from disconnecting and falling apart.

If you mount the plate on top, then basically you have the surface area of the 4 nuts underneath holding it to the strut top. If you mount it on bottom, you have the surface area of the entire camber plate on the strut top. Some people have mounted them that way and it has been discussed in the past. For my car, I'd prefer to have them underneath just for the safety aspect.

The Gurney does deflect air upwards, but I think the more important effect is that this creates a vortex behind the Gurney. This vortex in turn sucks the airlflow tight against the low pressure side of a wing, where it is normally liable to separate. This reduces flow separation and allows for a more aggressive angle of attack. Now in the case of the whale tail, the argument seems to be that the whale tail acts like a Gurney which is trying to keep the flow attached to the bottom side of the car. The flow really can't be attached, because the back of the car isn't a smooth surface at all, but creating more low pressure on the bottom side could pull more air out from underneath. I think that this might be happening to some degree, but since the bottoms are not flat and the flow cannot stay attached due to the shape of the rear valance/bumper/whale tail, I think the advantage the whale tail has is more due to leverage. That's pure gut instinct though.

510's mount rear bars to the bottom of the semi-trailing arms all the time. You do occasionally see the end link that is bent because it has obviously run over something in the road, but I don't think it's too big a deal when that happens.

I used to race with Jack Hidley and he is a very knowledgeable and helpful guy. Check out his .avi's showing bumpsteer in action. http://forums.corral...296-post36.html

If you narrow the control arms you'll run into problems with either the stock halfshafts or CV shafts. Wheels or flares, or fix the understeer with front suspension geometry, springs, sway bars, etc.

How about different offset wheels? Agree though, there are many ways to skin that cat, and you don't need to go straight to narrowing the rear track to get it done.

How about some pictures?

The 280 strut tube is also longer, and the whole assy is heavier.

You need to take it out, pull the cover and see what is going on.

Not enough info there to make a determination. Take the diff out and check it out if you suspect that is the problem. I did have a diff lock solid on me once. Before I knew anything about diffs I paid a shop to replace all the bearings in mine (waste of money) and they forgot to torque the pinion nut. I drove it around for about 15 minutes and then went home and had my roommate jump in the car with me. We got about 3 houses down the street and it locked solid. Had to pick the back end of the car up with a jack and roll it back home. The pinion had walked out the ring gear into the LSD. No harm done other than a nice mark left on the carrier, but that happened at about 15 mph.

Speed = unknown. Spring rate = unknown. Spring compression = unknown. Result = useless. I did some simple calculations out of Tune to Win, and they make your testing method look even more dubious. Consider that longitudinal weight transfer is acceleration g(weight x cg height/wheelbase). So let's assume that you accelerated relatively slowly, like 0-60 in 10 seconds. That is roughly .3 g according to this caclulator: http://measurespeed....calculator.php. Make a guess at the weight with you in it at 2550, cg height at 21" and wheelbase at 91, and you get 176 lbs of weight transfer to the rear WITHOUT the whale tale. You didn't mention whether you measured the zip ties on the strut or had someone else do it for you while you sat in the car, but that would also skew the numbers by a pretty large margin. Factor in a crack in the pavement anywhere along your test run and the resulting suspension movement, and you really don't have anything useful left. I think what you were trying to do works reasonably well if you have data acquisition and you can monitor the compression of the strut over a period of time and at different speeds, but what you have there is just a maximum displacement measure, not anything useful to calculating downforce. I've been trying to consider the effectiveness of the whale tail vs wings, and I've come to the conclusion that the whale tail is VERY efficient at producing downforce when using the wind tunnel numbers when compared to the APR wing. What I can't say is where that downforce is coming from. I brought it up on another forum and didn't get a satisfactory answer, so then I emailed Simon McBeath again and he showed me the limitations of the wind tunnel: it is easy to see the effect of the tail, but impossible to know what caused it. Quoting doesn't seem to work on this for some reason so here is the email to McBeath: Hello again. I have another question for you, hoping you could help shed some more light on a different aspect of aerodynamics for me if you have the time. I've seen on some Porsche sites where they say that whale tails are only spoiling airflow over the top of the car, and that they cannot make any actual downforce. I've also seen wind tunnel test results on a Z where they were able to make a 253 lb change in rear pressure, with at least 176 lbs of that being “downforce†at 120 mph. Data here: http://forums.hybrid...nnel-test-data/ I was interested in the Coefficient of lift required to make such a change, and how one figures that on a spoiler vs a wing. I have not come across an answer so far, and I’ve been trying all my usual knowledgeable sources to no avail. I've got a rough area of the top side of the whale tail at 6.28 sq ft, and I've plugged that into a downforce calculator (for wings) in a couple different ways. To figure out effectiveness of the tail, I'm plugging the area and the lift desired into a calculator, and just adjusting the Cl until I get the number I want to see. If you figure from the test previous that the tail made 253 lbs downforce, that works out to a Cl of 1.1, which seems VERY impressive for a spoiler. If you figure that the downforce was only 176 and the rest came from spoiling the 76 lbs of lift in the test previous, then you get .76 for the Cl. There was an APR wing tested, I believe it was the 55" span with the 7.5 and 5.5 chord lengths. I don't think this wing is sold anymore, but it was the ubiquitous dual element ricer wing in the States for a couple years. Anyway from the base test before the wing was installed to using it with the highest downforce setting, the change in pressure was 110 lbs @ 120 mph. I've figured that out at about .6 Cl on my calculator. That seems about right by gut feel for a cheap wing that may not have been at the most advantageous angle of attack. There is another whale tail for the 280ZX which was homologated for IMSA racing back in the early 80s which is much smaller and Nissan claimed 370 lbs downforce at 100 mph. http://zhome.com/History/ZXR.htm That claim seems utterly outlandish, it's Cl would have to be in the 3.5 range to get the amount of downforce from my estimate of its size. It was the ZXR whale tail and its wacky numbers piqued my interest and got me wondering about the efficiency of the tail that had been put in the wind tunnel. So what I'm interested in knowing is which is the proper way to use these numbers, and whether I've done my figuring right. I realize that the whale tail might have a significant effect on the flow of air underneath the car as well, so it may be a combination of the spoiling of the airflow on top and some downforce production with speeding up airflow on the bottom, but the numbers look almost too good to be true even out of the wind tunnel tests. These were not flat bottom cars or anything, they were stock underneath, and Z's have lots of edges sticking out to catch air on the bottom, and the wind tunnel did not have a rolling road, just a stationary tunnel. In asking others about this, I’ve gotten a pretty uniform: “Speeding up airflow below the car is the source of the downforce.†I understand why that would seem to be the case, basically they’re assuming that the whale tail acts as a Gurney on a wing and that accelerates the air below the car, creating the downforce. In actual practice though, that seems very unlikely due to the rough underbody. Maybe I’m underestimating the effect of the tail though, I don’t know. My thought is that the whale tail is acting as a kind of parachute, and the leverage of the whale tail sticking out behind the car is what translates this into downforce. The only problem with my theory is that the coefficient of drag actually DROPS .05 from the test previous to the whale tail test. ... Thank you for your time, Jon Mortensen Response: Hi again Jon Time for a quick reply, which is to say that without the benefit of CFD it just isn't possible to figure what the direct contribution from a wing or spoiler is on a car because of all the interactions you mention. All that's possible to say is that all the things you mention will be happening. So there will be raised pressure on the deck ahead of a spoiler, leading to downforce, and reduced pressure behind the spoiler, leading to reduced base pressure in the wake, which in turn will lead to reduced pressure under the car. If you were to CFD a model with a whale tail you could assess the forces on the whale tail itself and those on the car body separately, which is about the only way I know of that allows the various contributions to be evaluated. In the wind tunnel, all you can do is measure the forces at the front and rear axles through the tyre contacts. So whatever 'delta -CL' you measure is related to the car as a whole. And a car's coefficients are calculated using frontal area, not plan area don't forget. Only wings are conventionally referenced to plan area. So this complicates any attempts at factoring out the effect of specific parts too! But like I say, without CFD you can only address the changes to the whole car's coefficients, which the wind tunnel alllows to be split as CLfront and CLrear. I'm ashamed to say we haven't done any rear spoiler evaluations in the wind tunnel for Racecar Engineering... So the only data I can point you at is the CFD study in CC Downforce and its succesor CC Aerodynamics, 2nd edition out now. Hope that helps... Cheers Simon So far my best guess is that it is the top side that produces the downforce, and just as a wing is more effective if you hang it off of the back of the car because it has more leverage there, so too the extended length of the spoiler is what gives it its power. Regardless, I really do think that it is a good option for efficient downforce, but many racing classes won't allow them (nor will they allow wings hanging off the back of the car to get the same increased leverage).