280 ZX in STR class

[f1race79]

OK guys would like some feed back.

SCCA Solo is creating a new ST class called STR.

It is a street tire class created for roadsters.

I have an 83 280ZX I would like to build for this class.

Class rules:

Max wheel size 9” with 255 tire, no rolling or flares, can roll lip.

No internal engine work but can do add-ons with cat.

Any LSD.

My thoughts:

I might be able to fit 245’s all the way around, could go staggered but couldn’t rotate.

Will have to go to 17’s to get competitive tires in these sizes, looking at cheap, light wheels, yeah I know, doesn’t exist…OK looking for light wheels.

Thinking maybe larger throttle body, would triples give me more?

I thought management system but with no internal add-ons don’t think I would gain enough for price.

Larger cc injectors?? Remember no cam or valve work.

Headers with performance cat with 2.5” exhaust.

LSD, would disk be better than Quaife in autox?

Suspension in open, will go with coil-overs and plates on front, anyone know spring rates for a ZX?

MSA has some rear camber kits.

I am looking for suggestions or improvements.

Thanks,

[gira]

Hello F1race79,

Here are my first impressions. Roadster and ZX don't really go together. The ZX unibody is a little frail in my opinion and taking the roof off would kill the chassis strength. I built an IT car that was pretty fast and we spent a lot of time patching the underbody and working on the rollcage.

Get the engine to breath by taking the emissions off. Throwing triple webers at a stock engine might not gain you much. Make sure to use the torque of the engine when setting up for the course, seriously don't worry about screaming it to redline all the time and those engines fall flat at 6500.

The semi trailing arm rear suspension is a bear to work with. Jump up and down on the bumper and watch it go negative camber by way too much AND toe out. A lot of negative camber might work good for autocross but the wheel also will toe out which will make you loose. Limit the movement by using stiffer than normal spring rates, somewhere in the 400 pound range.

hope this helps

greg ira

[John Coffey]

STR is not just for Roadsters. That nomenclature is obsolete.

http://my350z.com/forum/autocross-road/441838-rumor-350z-classed-in-solo2-str.html

The 280ZX may be competitive locally but won't stand a chance Nationally against a lot of these cars:

Eligible vehicles are:

- Honda S2000

- Mazda Miata (except Mazdaspeed)

- Mazda MX5 Miata (’06-‘09)

- Toyota MR2 (non S/C, non-turbo)

- Toyota MR2 Spyder

- BMW Z3 (non-M)

- BMW Z4 (non-M, non-turbo)

- BMW M Coupe & M Roadster (1998 to 2000)

- Mazda RX7 (non-turbo)

- Porsche 924 & 944 (non-turbo)

- Porsche 911 (1984 to 1989 Carrera 3.2)

- Porsche 968

- Pontiac Solstice (non-turbo)

- Saturn Sky (non-turbo)

- Datsun 240Z & 260Z & 280Z & 280ZX (non-turbo)

- Nissan 350Z

Edited September 16, 2009 by John Coffey

[gira]

Golly, that doesn't seem like a very fair fight against that list. What's wrong with that rulebook? I am certain I am missing something, like different levels of preparation...

Greg

[John Coffey]

Levels of prep are similar. Its the start of a new class and of a new philosophy in Solo2. There's some discussion of competition adjustments being used in STR to level the cars out but no firm commitment yet. The advocates of a specific car need to build for the class, compete, and then lobby for adjustments.

If the 280ZX is your passion and you want to compete in this class, build the car to the rule limits and bring it to the Nationals next year. That will provide a basis for efforts to get some kind of competition adjustment.

FYI... SCCA does not guarantee all cars classed will be competitive. They just guarantee a place to compete. Its taken 7 years to get a Solo2 class where the 350Z has a good chance to win. It won't be an easy effort and will take a couple years but it can be done and there are at least 5 national caliber drivers building the car for next year. The 280ZX and 240Z need that kind of effort if they want to be a player.

[260DET]

You would need a slicktop for body rigidity, T top would be a disadvantage. Are you allowed to rework the rear suspension angles? While the semi trailing arm rear suspension is now obsolete, with some reworking it can be made to perform well, as Prodrive/BMW found

On wheel width, try and go for the widest, 9" should fit, rolling the guard lips will help. Good luck and keep us informed. Love the S130