RB30-ZED

Thought this might be of interest . Its a comparison of my RB30DE 240's 1/4 mile run with a Lexus SC400 V8 and a Skyline GTS-T(RB25DET). Both the Zed and the skyline lifted off the throttle just before the end of the 1/4, but its still a good comparison. Steven1/4 mile jpg

Move in to fill a low pressure area ( how did it get there?):classic: or was it that it was accelerating down the hatch to fill a increasing area that the low pressure formed in the first place ?:classic: Steven

Thanks beandip, now that you've mentioned it I think ive seen a scan of that page on the net somewhere. Did it have a drawing of the Zed over a grid ? Steven

Sounds interesting infomation, but what is SCG ? Id go with the brake ducts, as they look better, but if you dont need them block them of from behind to stop air getting under the car. Steven

But if the air accelerated up over the front to the roof, then it has to move back down just as fast, you see its not going any faster, but its still going just as fast as it did on the way up, and more importantly, its moving faster than the air under the car. Its the imbalance of air speed under and over that courses lift, ether up or down. Did that make any sense. But I do agree that your best to stop it getting under in the first place. When I get time im going to hook a spring loaded resister to the rear suspension and take readings at different speeds with the louver on and off, to work out the suspension hight due to lift. Steven

No Richard im not 100% sure, but I believe it does. As you say air pressure drops with the increasing speed of the air, and true as it rises over the front of the car its speed goes up and its pressure goes down , but as it is dragged back down the slopping rear of the Zed it is also accelerating in speed back to were it started, so yes, I think it does. Here is a quote from the ZCCW Newsletter Source: James Lux "The smooth top of the Z, gently falling to the tail, encourages high velocity air to remain attached to the roof surface and that attachment produces lift on the aft section of the body. The figure that comes to mind is 120 pounds of lift on the rear of the car, but I don't recall now at what speed that figure is reached, though I believe it was either 60 or 100 mph. Lift on the aft body relieves load on the springs and the aft body lifts slightly. The MacPherson strut rear suspension acts like the front suspension when the body is raised: camber becomes slightly more positive and toe-in changes slightly compared to the body's static setting. The mismatch of lift between front and rear at speed on the 240 is a major reason why the Z is known as an understeering car at low speeds and an oversteering car at high speeds. Oversteer and understeer characteristics are formed by more than suspension type and settings. An optional rear spoiler was available for the 240 almost from the beginning, though relatively few 240's possessed one. Changing the aft body lift characteristics of the 240 involves either creating downforce, as with the original rear spoiler, or "spoiling" the lift before it begins." A very interesting topic. Steven

Thats very true but from what ive read its a chioce between smooth air flow, which unfortunatly will cause lift as it races down the rear section of the 240's body or breaking up the air flow coursing drag but stopping lift. Lift scares me more than drag. Steven

No, I haven't seen them, but they sound easy to make. Im now considering refitting my old rear window louver to break up the air flow over the rear of the hatch to stop the air flow attaching and coursing lift. Any one noticed a difference with a rear window louver on or off? Steven

Wow, now ive heard every thing! Frank you said "think about it" in your reply,,,, did you? Yes removing the Vacuum booster from a zed will increase the effort required by the driver, by about 2 times for a 240z and about 2 and a half to three times for a 280XZ, but the ONLY components to be effected by the greater force would be the brake pedal assembly and the fire wall, oh and your leg. NO change to the master cylinder hoses or any other hydraulic component. If it took "X' amount of brake fluid pressure applied to the brakes to stop a car in "X" distance from "X" speed with a booster , then it will take EXACTLY the same amount of brake fluid pressure to stop it with out a booster. Only the driver will notice the difference in the application pressure needed to generate that pressure. The first thing I did when I rebuilt my 240 was to remove the booster and replace it with two master cylinders and a Tilton brake balance bar, with a small change in the pedal ratio by moving the push rod about 3/8th's of an inch closer the pedal pivot. With out the booster it is a little bit harder on the pedal, but you only notice it at slower speeds. But the brake pedal feel is vasty improved, with excellent brake feel and modulation. This makes the much easier to control braking in to corners, as there is much better feel and as you can make very small changes to your pedal pressure with out the booster doubling it or tripling it. I wouldn't make this modification to a family car, but for a performance car its a good way to go. Steven

Have you guy's read this article. http://zccw.org/Tech/Body/09-97EarlyZAerodynamics.html It is very interesting, especially the first part on air flow around the radiator area. And one more worth a look.http://autozine.kyul.net/technical_school/aero/tech_aero.htm#Drag%20and%20Lift Steven

I've spent $8500 on body and paint, this was the only work I had done for me, then about $13000 on parts, engine, gearbox, brakes, suspension, wheels and tyres, dash, rubbers, emblems, and a hundred and one little bits you forget about. Note Aust dollars. $1 AUST=78cents US Steven

Yes its quite a bit. I removed the springs set it at ride height on a jack and graphed the toe change up 50 mm and down 50mm till i found the least change. I used a slotted crossmember and once i had found the best spot, i redrilled a second cross member and rechecked. Steven

I Also drive through an area which has bad gusty cross winds, and very early on I found that once I modified the inner lower control arm points to reduce "Bump steer", the problem of swerving in my lane durring cross winds went away. If you think about it, ever with a small amount of bump steer this problem is worse in a cross wind situation as you have one side of the suspension compressing and the other side dropping. I know this is slight but you have both wheel toeing in two different directions which will cause it to steer. If it steers in to the wind , its not to bad, but if it steers with the wind it will be all over the lane as mine did. I raised my pick up points 30mm and I have very little trouble with cross winds now. What do you guys think? Steven

If any one is interested in the 4 cyl Nissan twin cams of old, then this is a good page to have a look at. http://www.datrats.com.au/lz_twin_cams.htm Steven