| redbaron303 |
This is just from a site I ran across on the net... is this good information to run with??? Is it fairly accurate in the description of how the car will benefit from each part???
How to set up a 300ZX
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The 300ZX From the Factory
There is no good way to write this section without making Z owners mad, but here it goes. Nissan blew the suspension set-up on the Z31. They took a fairly stiff frame, then put a weak, misconfigured suspension under it. Instead of catering to the t rue sports car fans, they sought to please the people that would be impressed by the digital dash in all its 80's "funkiness".
The suspension isn't "bad", but it would have been SO easy to make it "right". First, the springs are way too soft, it's no wonder they sag so easily. Second, the sway bars are about as stiff as wet noodles. Third, the rear suspension is sem i-trailing arm. That in itself isn't good, but shouldn't destroy the car's handling(the Z3 has semi-trailing arms too). However, combine a semi-trailing rear suspension with soft springs and sway bars that let the car roll around too much, and you have a car that just doesn't handle as well as it COULD. And let's not forget that all non-turbo 300ZXs come with an open differential.
Now that I'm done bashing some of the many things Nissan did wrong with the Z31, let's look at some of the things they did right. First, the engine is actually pretty good for autocross purposes. In the non-turbo Z's classes (DS, CSP) it is no slouc h. And it has low-end torque going for it, something its competition doesn't have much of. The Turbo Z is in a peculiar position when it comes to autocrossing. In stock form, it's put up against Mustangs and Camaros. These "pony" cars dominate F-Stock , and even the Supra Twin Turbo(also in F-Stock) fails to keep up. When modified, the Turbo Z runs against new RX 7 Twin Turbos, 911 Turbos, Vipers, and the rest of the very expensive, very fast cars you can name. Scary proposition...
Another good trait about the Z31 is the brakes. Supplied with a decent set of brake pads(Autozone lifetime warranty pads don't cut it on the track), the brakes work very well and don't fade. The Z also has a very good weight distribution and supplie d with the right suspension gadgets, can turn quite well.
How to Set Up a 300ZX To Perform Well
Unfortunately, when you're dealing with the prospect of autocrossing a 300ZX, you are looking at trying to be competitive in a car with suspension pieces that are up to 14 years old. More than likely, the springs are weak, your sway bar bushings are dried up and shrunk, and if you still have the original shocks/struts, chances are, they are probably weak too. You could still have a lot of fun on the track in this situation, but being competitive will be difficult.
Running in a "Stock" Class
If you plan to run in a stock class, you'll need to take a long, hard look at the suspension pieces on your car. Does your Z sag every time you give it gas? That motion will seriously hurt performance. You might consider buying some OEM springs, ev en cheap replacements will likely be better than your worn out original springs. If your springs are still "tight" and your Z doesn't sag, don't worry about it.
In an autocross, you want the car to react as quickly as possible. The shocks and struts are a key in how "quick" your car responds. Some sort of high performance shock and strut might be advisable. You don't have to buy adjustable shocks, but your average Monroe shock will eventually become noticably soft as you become more experienced. This doesn't mean the shock will wear out, but as you become more experienced, you begin to see where the car is lacking and where you as a driver need help.
Take a look at your sway bar bushings and see what their condition is. On most aged 300ZXs, the bushings are dried up, rotten, shrunken, and in need of replacement, regardless of where you drive. Under the guidelines of the stock regulations, you ca n replace your sway bar end-link bushings and the frame bracket bushings with polyurethane bushings and still remain legal. As I have noted in other sections of this site, these bushings are the single most beneficial modification that can be made. Doll ar for dollar, nothing beats the improvement in feel and response than the bushings.
In the stock classes, you are free to change your front sway bar to whatever diameter you want. For some vehicles, changing the front sway bar is beneficial, on the 300ZX this creates an unknown(so far anyway) result. Reducing roll in a vehicle is g enerally beneficial, but adding a stiffer front sway bar tends to promote understeer.
Running in "Street Prepared"
Forget everything you know about the handling of the stock 300ZX. It's time for a change. Remember those complaints about the shortcomings of the stock suspension? It's time to fix them.
The street prepared classes allow quite a bit of modification to the suspension and it is my personal opinion that this is where the 300ZX has the potential to suprise some people. The key to accomplishing this is to not cut corners. While choosing a spring, you must decide whether you want good all-round performance, or to achieve maximum autocross performance and sacrafice in other areas. Ideally, you would want a linear spring, as progressive springs tend to change their charachteristichs slight ly as they compress.
The Danger of Shorter Springs
Stiffer springs will increase performance in most cars, however, with the 300ZX, there is a catch. As you lower the 300ZX, the rear tires' camber becomes increasingly negative. In turn, this gives the rear tires much more cornering grip than the fro nt tires. The result is a medium-severe understeer condition, slow "turn-in" response, and an unwillingness to rotate. The good news is that this condition is correctable, and relatively cheaply. Motorsport Auto sells kits that will correct your rear c amber, all you need to do is get an alignment, determine where you'd like your rear camber to be set, and order the correct kit. Keep in mind that you need to put some thought and research into which camber kit to buy, and you'll need an alignment to see where your camber is BEFORE you adjust it, in order to purchase the right kit.
Shocks and Struts
The stock shocks and struts on a 300ZX are probably not up to the task of handling a stiffer spring. For ultimate performance, spend the extra money and order a set of adjustable shocks/struts, or a very good non-adjustable unit. Without beefier sho cks and struts, it will be hard to keep spring oscillation under control, and this deteriorates handling ability.
A Heavy Car on Small Wheels
This modification is easy to figure out. An Integra GSR weighs ~2600lbs and comes from the factory with 15x6 wheels. The 300ZX weighs 3000-3300lbs and has 15x6.5 wheels(unless you have an 86+ turbo or AE). You don't have to be a physics genius to f igure out which combination of weights/width works best. The Integra(and the rest of the competition) will have smaller sidewall widths too. This reduces sidewall roll and increases turn in response. The Street Prepared rules allow any size wheel that will bolt onto the car. Depending on your horsepower level, you should buy wheels that are substantially wider than what you currently have.
The weight of 300ZX wheels is suprisingly heavy. While helping a friend remove the wheels off of his Integra GSR, I noticed that they were half the weight of my wheels/tires. This occurs for two reasons. First, the wheel is manufactured to be light er. True, it is 1/2" narrower, but the difference in weight was beyond what 1/2" of metal would provide. Second, the tire is smaller, tires of course, have a weight. However, most of the weight difference comes in the wheel manufacturing. As times pro gress, wheel material becomes stronger, thus allowing lighter wheels.
Rolling Around
This is not a 300ZX with a stock suspension. It has Eibachs and polyurethane sway bar bushings, as well as Tokico shocks/struts. It rolls far too much. The next time you hear someone say "I bought new springs and the car corners perfectly flat." yo u can feel free to show him this picture and say "Either your equilibrium is distorted or you don't corner very hard."
If you take another look at the photo, you will notice something. The outside or "compressed" side of the car isn't where the lean originates. The springs are keeping that side of the car "up" fairly well. The inside, "uncompressed" side creates th e lean. It has risen up and this will occur regardless of how stiff your springs are. Springs do not have any control over the chassis rising. The task of keeping roll under control is up to the sway bars.
The way sway bars work is simple. The bigger, stronger, the less your car will lean. Some are made of ultra strong material and can be made thin, some are simply huge. The job of a sway bar is simple. Keep the car from rolling around. This in tur n, gives you better/faster weight transfer, and better suspension geometry relative to the road/track surface.
On my Z, which is pictured above and has stock sway bars, I can literally turn the wheel, feel the car start to turn, then lean, then reach the roll limit. It all happens very slowly. This is a component to "turn in response". Of course, in a perfo rmance car, the faster the turn-in response, the better. Sway bars increase response by not allowing the car to roll so much. Basically, what you feel is more grip and substantially faster response to driver input.
Also note, all known aftermarket sway bar manufacturers include polyurethane bushings with the bars.
Strut Braces
This modification is simple and cheap and provides a noticeable benefit. Basically, it reduces chassis flex during hard cornering. The benefit here is that it noticeably improves turn-in response. Rear tower braces are currently unavailable, but sh ould you make one yourself, and it is secured in only two locations, it should be legal and strengthen the rear of the car. |
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| MrHeavyFoot |
I don't know anything about the 300ZX specific details, but the general principles all seem about right. Just a couple of points.
1. If you are worried about what class your car falls into, the information here is SCCA class specific. Canadian rules/classes are similar but a little different.
2. "The car is as fast as the driver makes it." No offense, but at this point in your autox career, there's probably a lot more to be gained from improving the driver than improving the car. |
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| redbaron303 |
Oh ya! Driver skillz superceed the car sometimes :)
I will learn, and the more I attend and race in, I shall have my practice :)
Somethings on my car need to be replaced any how, I've got tired shocks and springs, and bushings (probably). I figured I'd do some checking around to see how I can add better aftermarket parts that won't be as lame as my oem ones. :) I'll be practicing my "mad skilz" on the current setup, as the new setup isn't in the budget just yet... ;) Nothing wrong with dreaming (and researching). |
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