280zx Autocross Street prepared setup

[bigbreak_2000]

I am very tempted to get my vehicle ready for Autocross and want to see if there is someone on the forum with experience re. proven setups on their 280ZX. My car is a 1981 2+2, 5 speed and stock in all regards except the following: 3.2L NA stoker engine (225whp) on street gas, lightened flywheel, standalone ECU, non stock exhaust system. I would truly be a beginner in the Autocross classifications. Other than the modifications mentioned the car is stock as it came from the factory: the car has 20k original miles on so original disc brakes setup (NOS pads however upgraded to DOT4 fluid), Nissan 6 spoke alum wheels with new 195/70 - 14 michelin tires, and appears to have the very original shocks and in as-new condition - perfect height level front and back per FSM - no sagging yet that I can tell). It is a late 81 production so it has power R&P steering. The diff is 3.9 R200 and the gearbox is the 5 sp with low 1st and long OD 5th. I do have an optional set of aftermarket wheels and tires that I put on as a summer setup; those are BFG GForce Sport 205/55-15 (7 wide front) and BFG GForce Sport 225/50-15 (8 wide rear). These tires have excellent grip, no scrubbing with the wider wheels, but rather large fender gap as you can image with the stock springs and shocks. I do drive the car on the street and it is tuned well for city driving (lots of torque in lower RPM and exhaust has 2 mufflers so it is not too load even with header) however I can tell the brakes and suspension are not on par with the performance level of the engine. It is not a car I would dare go fast into corners. Ive been couple times to the track at CMP and there is no way this car, even with the abundance of power, can be competitive with much lesser powered stock class modern cars. My goals are far from professional road racing, so my question is really what can be done as a Phase 1 project for decent upgrade to get braking performance and better handling and steering? Many had told me the brake setup on the 280zx is good, just need better pads (hawk or another brand?). The car is not a daily driver so I won't mind a stiffer or somewhat lower ride as long as it is not bone jarring hard or too low. I've also been told the aftermarket bushings may make the ride very hard but I cannot decide if that is more important to upgrade vs. installing modern gas struts, thicker sway bars, or stiffer springs. All I know is the car will hold its own to many performance cars on a straight line, but nose dive heavy on braking, pushes very very wide on power-on fast cornering, suspension feels soft and feels like a boat compared to my other newer cars. I'd like to avoid too many modifications with the first project, for ex. don't want to start cutting or welding to the suspension component, but looking for advice on relative easy to do mods that would give good results such as which pads, bushings, sway bars, shock and spring combinations might be good for a beginning. Thanks

 

I've read of other 280zx owners being successful in the ITS class, apart from them being good drivers I wonder what changes they had made, and what the SCCA allowed them under the Stock or Street Prepared classes.

Edited February 26, 2012 by bigbreak_2000

[BluDestiny]

I was within 3 seconds of some s2000's ( a lot I know, but they're freaking S2000's) and beating some BMW's today. I have a pretty much stock engine, but highly modified suspension. I would love to have your engine. I could probably take them then.

 

I would suggest that you first get some actual time behind the wheel at some events. This was only my second event and I was running in the novice class. Talk to the instructors, they are their to help and teach you.

 

A decent suspension upgrade is the tokico HP shocks and tokico springs, along with a swaybar kit. That and your 15" tires should defiantly get you going. Hawk also makes pads for 280zx brakes just search for them. Everything I just listed is literally just remove and replace.

Edited February 27, 2012 by BluDestiny

[RebekahsZ]

Don't modify anything else this year. Autocross as often as possible in Novice class (stay there as long as they will allow it). Put car in second gear and leave it there for the whole race. Learn to drive with both feet. Get some of the better guys/girls in the club to ride along with you. Slow down going into turns and accellerate out and you'll stop pushing and diving. Try to drive slower and you'll go faster. For most cars, stock brakes and pads are fine in autocross. True race spec tires (225/50/15) will help a lot, like Hoosier A6 or BFG R1. You might even be able to get some from somebody else used in your club. If you came to race in Alabama, I'd race in the morning session and let you borrow my tires for the afternoon-I bet you'd drop 2 seconds on the first try. If you learn to drive, you can go plenty fast with your stock setup. Get the fastest guy in your club to drive your car and then try to learn to drive as fast as he/she did. This year save up for stiffer springs (stiffer than all the cheap "lowering springs" that you see advertised) bigger swaybars and good shocks. Ask JohnC for a source and a recommended spring rate. Install the springs and shocks next winter. Year after that, put in camber plates.

[260DET]

There was some good info on this forum posted a year or so ago by Frank about modifying the rear suspension like BMW did with the E30 for racing. It was more than just adding the usual bolt on stuff, it was about changing the rear suspension arms sweep angle. Other than Frank I have never heard of anyone doing this with their 280ZX which is surprising as it would not be difficult to do.

[JMortensen]

Go look at what 510's do, and ape that. 510s have basically the same suspension, but they have a spring/shock combo in the rear instead of the coilover setup like the 280ZX. 510s are a very popular autox car and almost all of the same tricks apply. You can do springs/shocks/swaybars and make it handle better. If you just want better, that is a pretty good suggestion. If you are really wanting to be competitive, you'll need different springs and shocks, and more modifications than that. By researching now, you can save yourself from having to buy parts twice later.

 

Frank's thread on the rear suspension is very good. I'd look hard at it, and in the 510 world the "penultimate crossmember" if you want to really get serious with it.

Edited February 27, 2012 by JMortensen

[BluDestiny]

Holy cow, googles that crossmemeber thinking it was like a modified one that some member did, not an actual product.

 

http://datsun510.com/photopost/showphoto.php?photo=8005

[bigbreak_2000]

I misstated in my original post, the problem is not going to fast into corners. My main frustration with the stock suspension setup is that now with the added engine power, power on existing a corner, the front becomes very loose. It is just plain frustrating to hold much of that power back till I'm down to a full straight. Applying power in corner and the the car would start to push wide. I noticed with the summer wheel/tire setup with the rear diameter slight higher than the front it is a bit better. In part may be better gripping and stiffer sidewall tires in the front, but also I think with a slightly higher roll center in the back it may have helped. But I want the rear end to stiffen up more. So to get more steering, do I need to add a stiffer rear sway bar, or do I just need to add stiffer rear springs or is truly going to take a combination of all those things? I called a few Z car part shops and the very first recommendation is replace the stock oil filled shocks with gas filled shocks. I am at a total loss understanding how changing to new shocks will help. Should I just accept that the Tokico HP shocks for the rear will be noticeable stiffer and more responsive than the old oil filled shocks? Since the Illumina (what I heard is better than HP's) is no longer available for the rear, I'm afraid with the Tokico shock kits to put Illumina's in the front and HP's on the rear that stiffening the front is what I think I don't want to do. All my local club members are familiar with the S30s but have very little experience with the 510 or S130. Maybe I just need to call John at Beta Motorsport. Any other recommendations?

[h4nsm0l3m4n]

I think your summer tires are simply able to sustain more speed in a corner than your 14s before they finally break loose and you start to understeer. Yes, roll center and stiffer sidewalls may be a factor but since youre on stock suspension you have lower hanging fruit thats causing you more trouble. Youve gotten some good advice already on where you can start improving your car's handling.

 

Springs, shocks, swaybars are all variables in your car's suspension. I suggest reading about how these things work and what they do to your car's handling.

 

As far as illuminas vs hp. Illuminas have adjustable damping which is nice for tuning your car's balance. They are also able to control higher spring rates.

Edited March 4, 2012 by h4nsm0l3m4n

[BluDestiny]

Definitely call john at beta. It is a matter of stiffening your suspension. The tokico HP's will blow away your stock shocks.