New to autocross.

[IceCold4x4]

and..... a 350z. It's so hard for a Nissan to get any respect around here

I'll just drive faster

Sorry I always forget about the Datsuns.

[Cholewa]

I'm glad you could tell a difference!

Mr W8's advice is sound. If you've got the bug to do modifications then I would take it a bit slow. Do one mod, and then do at least one event to learn how it changes how the car feels. Once you have a handle on that, then do another, and then learn some more. That way you keep the learning curve bent as shallow as you can, while you get your car prepared to your class, while you are still learning the sport. Or throw it all in now, just expect a very different car at the next event!

You may lag behind now, but so what? The thing about seat time is that it is very incrementally cumulative. You may walk the course 5 times at the next event and just 'know' which line you are going to take. And then on your first run, you find out that that line is impossible because your car becomes unruly, due to whatever reason [insert new tires, cold tires, wrong tire pressure, new anti-roll bar, stiffer suspension, locked up the brakes, entering corner too fast, forgot to disable Traction Control, not looking ahead, et al]. What more seat time does is it informs what you know you can do, not only with the car but with the course too.

I know the urge to prepare the car to be competitive to your class. But even if I had a gun to my head to enter into a national level event tomorrow, I wouldn't make any change to what I had right now. I'd go knowing I would be beat but at least I'd get good seat time, plus I'd have confidence that the car would act just like it did at the last event!

My $0.02

This is sound advice. The more you mod your car between events, the worse you will drive, because you have no seat time to really get a feel for what the mods have done. I would pick one mod that you really want, do it, and do nothing else for the remainder of the year. Unless that mod requires another one - like if you add a bunch of power, you probably need some better brakes.

It's best to just drive the car in stock configuration until you can figure out what your driving style is. It's even better to drive the car with less than optimal tires, so your grip isn't covering up fundamental mistakes. The saying goes if you can drive a slow car fast, you can drive a fast car fast. Getting to know the car and yourself is the best investment you can make for performance driving. When you know exactly how the car will react on street tires at full tilt, you'll have an even deeper grasp on how it will react with stickier tires, or beefier sways, or stiffer shocks, or whatever.

In the end, you're just throwing a bunch of weight around, and if you aren't used to feeling it move around, and you start modding away that feeling, you're not gonna have a good time.

KISS - but simple means stocks. For the first little bit at least.

[IceCold4x4]

So got some time to do a bit of "closed course" testing at the warehouse where i work, and the car is getting to the point where i'm wondering exactly how much harder i can push it. The limit is starting to get pretty high up there, mostly due to the tires i believe, but the strut braces and subframe inserts definitely made her more predictable. (i'm talking about talking a 90 degree right hander that is the approx equivilant to a standard 2 lane road at 50 mph and it's just obeying without a chirp or peep from the tires)

any good way to figure out correct pressure to run the tires at?
I'm at 38 psi cold now for the streets, I can't "feel" them rolling over and there hasn't been any chewing up of the sidewalls yet, but then again I haven't exactly managed to make them slide around yet either. So I don't know if I'm just still well under the limit of these, or they have really stiff sidewalls (doubtful as they ride too smooth) or if i might be on the high side which i doubt as stock pressure is 36psi.

[JohnW8]

any good way to figure out correct pressure to run the tires at?

Tire temp gauge. Measure the inside edge, middle and outside edge immediately after a spirited run. If it's rolling over the outside edge will be higher. If it's overinflated the middle will be higher, if it's under inflated the middle will be lower. Ideally the middle and outside edges should be similar temps and the inside slightly higher. It really helps to see what your tires are doing and then you can make alignment or pressure changes in an attempt to fix it.

Laser thermometers are ok but the digital gauges with a probe to stick into the tread are better since they measure the tire carcass and not just the surface temp.

[seanittner]

old school... Chalk.... across the tread face down the sidewall..

You want to use all tread and not go down the sidewall. If you are going down the sidewall, increase pressure... not using all the tread... decrease pressure. Normally in 1 lb increments.

Quick, Cheap, easy to understand. Does not require the "jump out of the car check the temps" step.

Used by autocrossers for decades.

[IceCold4x4]

found another way to do it, what do y'all think? up? down?

https://www.youtube.com/watch?v=gtcL3mynzu4&feature=youtu.be

[bimmertech]

The video gives you no data point for tuning.

The tire chalk is the most effective poor-man's tool.

Taking temps will give you lots of data, but it's important to understand how different surfaces, setups, and driving styles will affect them.

I would start with the chalk. It's easy to interpret and will give you exactly the data you're looking for. If you want to go deeper in air pressure adjustments buy a pyrometer.

[bimmertech]

Old video, but it's relevant to your question.

https://www.youtube.com/watch?v=eAaK3DQLWus&feature=youtube_gdata_player

[IceCold4x4]

neat series of videos btw thanks.