Can a 240Z with unmodified chassis compete with more modern cars on the track?

[blue_leaf]

Have been reading a fair bit on springs selection for 240Z and have heard that you can't put really hard springs (more than 5-6 kg/mm spring rates) on these cars because then the chassis itself will start twisting - hence my question - will the preformance of 240Z on a racetrack suffer much from relatively low spring rates and a relatively non-rigid body? Would a well setup 240 with basic suspension mods such as coilovers with say 5kg springs and matched shocks etc. be comepetetive (cornering wise) against cars such as a well setup AW11 MR2 or 240SX with coilovers with higher or same spring rates? How did your cars go against more modern cars on the racetracks?

[260DET]

What sort of racing do you want to do? Because mostly a cage will be required and than can be used to stiffen up the body.

 

Second point, with a seam welded body up to ~300 pound springs can be used and thats plenty, with appropriate ARB's.

 

Finally, in AU we don't have the sort of rules which enable a S30 to compete with modern cars like in the US.

[blue_leaf]

What sort of racing do you want to do? Because mostly a cage will be required and than can be used to stiffen up the body.

 

Second point, with a seam welded body up to ~300 pound springs can be used and thats plenty, with appropriate ARB's.

 

Finally, in AU we don't have the sort of rules which enable a S30 to compete with modern cars like in the US.

 

I am not planning to do any "proper" racing - all I am interested in is just track days so roll cages arent required officially and there will be plenty of more modern cars on the track at the same time. Also I have read somewhere that a cage doesnt stiffen up the body by much - something like only 15% on average which seems quite unrealistic in my opinion plus there are a lot of variables involved - how effective is a rollcage in your opinion? The reason I am intersted in stock chassis is beacuse atm I do not have the funds to get a proper rollcage - still have plenty of other parts to upgrade and fix first. So in your opinion S30 with 300lb springs will be quite competetive? And whats ARB?

 

And how did your fj20 260 compare to sr20 silvias etc. on the racetrack?

[evildky]

well I know it's not the same but I am an avid autocrosser, and have a stock un braced early 71 (series one) chassis, running sectioned struts with coil overs, 440lb springs up front with 350lb springs in the rear, and msa sway bars, and I welded a piece of tube between my rear shock towers as the solid camber plates requires I remove my msw strut bars, anyhow it seems to handle quite well compared to newer cars, at this weekends autox I raw timed all but 1 fendered car and 3 or 4 of the c mod cars, so yes it can be made to compete with newer cars with out additional bracing, but I'd be afriad to have my car on a track at track speeds with the potential to hit something if I got out of shape, the car would fold up like a tin car with me in it! I wouldn't want to track a datsun without a cage for saftey reasons

[JMortensen]

You can add strut tower bars, that stiffens up the chassis quite a bit. Then run near the max spring rates before the chassis twist starts to become an issue, say 250-300 in/lb springs. In order to make that stay flat in the corners you'll need some big sway bars. Then you need to make the suspension adjustable to keep the tires happy. Camber plates and adjustable control arms/TC rods gets you most of the way there. At this point you'll have a pretty fast car. I basically ran my car about like that and I had a couple 2nd overalls at track days and autoxes.

 

I finally got tired of running a compromise setup and am in the process of going the full cage route and I'll up the spring rates considerably and get some real shocks on there. I've also reengineered the suspension to a large degree, and modded the sway bars and control arms quite a bit. You can see basically what I had and where I'm going on my project thread: http://forums.hybridz.org/showthread.php?t=117235

 

Don't get me wrong, the car was fun before, but I would have saved a ton of $$$ had I just done it right the first time or better yet I could have purchased an obsolete 240 GT2 car. Those might be harder to come by now that the Z has been reclassified to GT3, but you might start with an ITS car that needs some freshening up. Then you wouldn't have to shell out for the cage, and I've seen some pretty amazing deals go by over the years. I could have been driving for the last couple years instead of working in the garage, although I suppose you could argue that now I know it's all done correctly, or at least to my own satisfaction.

[johnc]

I am not planning to do any "proper" racing - all I am interested in is just track days so roll cages arent required officially and there will be plenty of more modern cars on the track at the same time.

 

At track day events, lap times have much more to do with the driver then the car. Mark Skaife in a stock 240Z will probably lap an entire group of no-hopers driving STis, Evos, etc.

 

 

Also I have read somewhere that a cage doesnt stiffen up the body by much - something like only 15% on average which seems quite unrealistic in my opinion plus there are a lot of variables involved - how effective is a rollcage in your opinion?

 

That may be a true generalization for more modern vehicles, but for a 240Z you can get a much better stiffness improvement with a proper 8 or 10 point roll cage. Spring rate at the 600 lb. in. level have been successfully run in 240Zs that have an extensive roll cage installed.

[tube80z]

The posts above have some good info but it will be hard to find an ITS or GT-2 car in Australia since those are specific US classes.

 

If you don't have money to add a cage and still want the suspension to work best I would suggest working out your spring rates so that the car has equal front and rear roll angles in a corner. This will help with a car that's not as torsionally stiff. If you don't know how to do this you might consider contacting the folks at http://www.racing-car-technology.com.au, they are located in NSW.

 

Cary

[260DET]

I am not planning to do any "proper" racing - all I am interested in is just track days so roll cages arent required officially and there will be plenty of more modern cars on the track at the same time. Also I have read somewhere that a cage doesnt stiffen up the body by much - something like only 15% on average which seems quite unrealistic in my opinion plus there are a lot of variables involved - how effective is a rollcage in your opinion? The reason I am intersted in stock chassis is beacuse atm I do not have the funds to get a proper rollcage - still have plenty of other parts to upgrade and fix first. So in your opinion S30 with 300lb springs will be quite competetive? And whats ARB?

 

And how did your fj20 260 compare to sr20 silvias etc. on the racetrack?

 

 

Track days are fun, speed costs money so at present it may be best to concentrate on learning to drive fast with what you have, as John indicated.

With my 260Z I could not beat well driven Silvias, GTR's, Supras and RX7's but not all such cars are well driven, plus there are plenty of others to own. Joining a Z club is a good idea too.

 

Link to some pics of our clubs Zeds in action. http://www.digitalrealism.com.au/supersprintb/gp19and20/gp19-20.htm

Most of those cars have cages with spring rates between 220 and 275 pounds, 22 to 24mm front ARB's, light or no rear ARB's. Most of them are sitting nicely on the track as you can see.

The 71/72 car has a RB30ET engine, the 70 car is running 220 pound springs and a 22mm front ARB, see the body roll but a quick car.