The Official 370Z Autocross Thread

[ChrisSlicks]

Originally Posted by Ruff

I get it even with DA Koni's... what's your setup Chris? It's mainly the crappy stock diff's fault

Stock struts and springs, Hotchkis swaybars, stock diff (for now). Probably the main difference is I'm only running RE-11's ATM. I'll be getting some different tires as the season warms up.

[Ruff]

Lol, I think mine is just fried period.

[AutoX Z]

I never noticed inside wheel spin on street tires but the moment I started running on A6's it was everywhere. I've got a hotchkis front bar now and it's made a world of difference. I was able to get on the power much earlier and more confidently however I was still getting alot of push through the sweepers combined with some horrible lines cause I missed my braking points, hence the slowness.

[Ruff]

Originally Posted by AutoX Z

I never noticed inside wheel spin on street tires but the moment I started running on A6's it was everywhere. I've got a hotchkis front bar now and it's made a world of difference. I was able to get on the power much earlier and more confidently however I was still getting alot of push through the sweepers combined with some horrible lines cause I missed my braking points, hence the slowness.

I think the inside wheel spin on A6's is partially caused by them being much shorter then stock. So bad understeer eh? Iirc the Hotchkis is a pretty big bar for the 370 over stock, that might cause some understeer, but I'm betting still a worthwhile mod. Without shocks you're just going to have to drive around it. But one important factor is what tire pressures were you running? I noticed a feelable and drivable change on just a few pounds of difference.

[ChrisSlicks]

The Hotchkis front bar will cause pretty bad push as it reduces the body roll generated camber. Unfortunately I don't think there is much you can do to add static camber up front in stock class.

[AutoX Z]

I've driven with the hotchkis bar on street tires and its undrivable with that amount of push. However with the A6's on the car become MUCH more neutral.

I'm willing to bet that my tire pressures are still way too high but I had enough to focus on at the NT and didn't feel like opening up that can of worms so I just set them at 37 and tried not to think too much about it. I'll definitely start doing some more experimentation with that back at the local events.

[Ruff]

Originally Posted by AutoX Z

I've driven with the hotchkis bar on street tires and its undrivable with that amount of push. However with the A6's on the car become MUCH more neutral.

I'm willing to bet that my tire pressures are still way too high but I had enough to focus on at the NT and didn't feel like opening up that can of worms so I just set them at 37 and tried not to think too much about it. I'll definitely start doing some more experimentation with that back at the local events.

Try around 36-38 front, and 32-34 rear, around a 3-4lb stagger. That'll help your push a little.

[pgrmstr]

If I am hard on the gas, the diff locks and the rear drifts, its when I'm rolling on the gas coming off corners that the inside wheel spin becomes evident. With street tires, the few times I ran it last year, I didn't feel much inside spin, but with the reduced grip, any throttle input would cause the tail slide so it was kinda masked. Coming from BMW's with open diffs (330i ZHP), it's nice to have even the weak diff in the Z....comparatively speaking.

As far as push goes, I too have the Hotchkis bar up front, and imagine if I charged into a corner, I'd see the push come out, but I guess maybe my driving style has adapted over the years, having been in FWD camber challenged cars, or RWD front heavy camber challenged pigs...where you're forced to drive around the issues.....and part of that has been getting the car slowed down getting into a corner, and then rolling on the gas through a turn, increasingly so as the steering wheel comes unwound. So I did not notice any push, and was quite impressed with how it stuck in the sweepers and accepted my throttle.

Hopefully some shocks will be out by mid season and we can start tinkering in more earnest, and I have yet to mess with the alignment....

As far as pressures go, having only been on the A6's once, in cool temps, I ran 38F and 35R....and dropped the rear to 34 for my last two runs. The rear still had lots of tread untouched on the outside edge so I will likely bleed more pressure off at the next event (hopefully with warmer temps) and see how it goes. I would expect to settle somewhere in the 32-34 range on the back. Not sure how much lower you'd want to go up front though as even in the cool, I used up ever bit of treadwidth up front at 38lbs...

[Ruff]

Heading to San Diego, talk to everyone later!

[cotizi]

need opinions on an AutoX wheel/tire setup. My AX events I attend are 1-2 hours away and i want to get a 2nd set of tires and wheels for autocross itself. My Z is not my daily driver, but I do drive it on the weekends on the street. Being in Texas, this means the car will still see 10k miles a year easy. I want to use the stock wheels with cheaper tires for road trips and street driving.

Saying all that, I gather the best setup for dedicated AX use is a square setup in the 18" 275/285 width range? Any suggestions on affordable wheels? I don't really care what they look like. I care much more about function than looks. Also, i personally don't think I'm ready for R compound tires yet as I'm still pretty new and would rather just get another set of good street tires and learn to drive better. I do want wheels that wont have a problem fitting Hoosiers in the future.

Thanks!

[AutoX Z]

What wheels you get depends on what class you want to run in and how competitive you want to be. To stay in stock class you must have wheels that are the same diameter and width as stock while being within .25" on offset. There are pretty much zero options that meet all these criteria so as far as I know most everybody uses the stock rays for autox duty, they are pretty lightweight forged aluminum after all.

If you don't care what class you run in then I would definitely look into getting some good 18" wheels, maybe 10" width all around and use 295's for street tires and 315's for hoosiers.

[cotizi]

the idea is to run in street prepared until its supercharged next year. that or a local street tire class we have at a local AX i do.

[pgrmstr]

fuel starvation with 1/2 tank....

Was getting cut out at the turn around on course yesterday. Oil temps were at 220 starting the run, 245 at the end....thought I was getting some momentary limp mode, but after reading fuel starvation posts this morning, I'm convinced it wasn't limp mode, but fuel starvation...with 1/2 tank of gas!

Looks like I need to add more weight in the rear.....people have gotten it with as much as 3/4 of a tank on the track

[ChrisSlicks]

Welcome to the fuel starvation club! For a typical auto-x course as long as I keep it just above 1/2 I'm fine. On the track it can cut out at 3/4 because of the longer corners.

Limp mode doesn't kick in until 280, and I've regularly reached 260 during a run during the summer. Turning on the A/C at the end of the run kicks on the extra cooling fan which seems to help speed up the cool down.

[pgrmstr]

Originally Posted by ChrisSlicks

Welcome to the fuel starvation club! For a typical auto-x course as long as I keep it just above 1/2 I'm fine. On the track it can cut out at 3/4 because of the longer corners.

Limp mode doesn't kick in until 280, and I've regularly reached 260 during a run during the summer. Turning on the A/C at the end of the run kicks on the extra cooling fan which seems to help speed up the cool down.

When it was happening, I started thinking about the quickest way to cool things down, and was wondering if the temp would come down quicker with the engine running or turned off (hood open of course).....so I'll have to keep the A/C mode in mind at the ProSolo when the runs come quicker!

I remember running my Honda's with the fuel light on and never got starvation...oh well, I'd rather have fuel starvation than limp mode so am glad it turned out to be an easy fix