Autocross Feedback

[Phantom]

Went to Benton city, WA last Saturday to an autocross school put on by the Sand and Sage Sports Car Club. Really great group of guys and gals.They set up four different courses and then we got 3-6 runs on each course with an instructor on board and a good debrief at the ned. Things I discovered about my car:

LS1 power is very controllable and easy to apply smoothly. Also lots of torque so it was 2nd gear the whole time.

Suspension needs a little work. Not bad but a bit soft. I'm running the Techno Toys Eibach/Koni coil overs on each corner and had then set at mid range which is where I normally drive them. Thought about going stiffer but decided to stay with normal driving setting so I would get a good feel of what the car is going to do on the road. Have the stock 280Z sway bars so I probably should upgrade those a bit. Anyone with feedback on the MSA kit that has a 1" front and 7/8" rear bar? Good setup or should I look elsewhere.

Brakes - Lots of braking power but modulation is terrible and they are not balanced correctly front/rear. Running 12.2" vented rotors with 4 piston Willwoods on the front and the 300ZX rotor with the 2 piston 240SX caliper on the rear. Suggestions?

[BLOZ UP]

More power. Always more power.

[Rob L]

Check out the suspension FAQ ....for sway bars I think the prime choice is S/T 52095 it's for 70-73 but the preferred kit for all s30s......i also have that same spring/shock setup.....what spring rates are you using?

Edited April 2, 2014 by theatriks

[JMortensen]

How serious do you want to get?

[RebekahsZ]

JMortensen-that's a great question.

[jhm]

What tires are you running?  Don't know what class you're running, but V8 Z's often end up in XP, which gives you the ability to run ANY tire you want.  If you don't want to spring for new racing tires, used can be found aplenty on eBay and Craigslist for very cheap.  One of the easiest ways to reduce your times.

[RebekahsZ]

Yeah, but you need to have 18" wheels to use the Corvette cast offs. Otherwise you are looking at used 15" spec miata tires which are tiny. And they've ALL been heat cycled out.

[Phantom]

jhm - I'm running 225/50-16" Dunlop Direzzas which are great street tires. Since I put the coil overs in I could probably go to a wider tire but then I'd also have to buy another set of wheels with a different offset - not going to happen.

 

Theatriks - Thanks, that was my next step after I got the post done. Springs - they are 200/250.

 

JMortensen - Good question - not super serious. Went to have a good time and learn some things about my car. I figure sway bars will help a lot in the cornering without stiffening up the ride too much. The car is still primarily a daily driver. If I was really serious I'd set up the '70 240Z since it's already pretty much stripped. I am, however, open to suggestions by those that are doing it. Since I like to go to Maryhill and drive the loop having a better handling and braking car will help keep me alive. Kind of a major goal on my part.

Edited April 8, 2014 by Phantom

[JMortensen]

Based on that I'd suggest bigger sway bars and a larger rear brake kit.

[RebekahsZ]

Direzzas are the bomb.  Camber plates?  LSD?  I wound up ditching my rear bar-just too hard to fit around the axles, exhaust and driveshaft.  Losing the rear bar did not hurt me.  Plus, you want the rear loose (from a sway perspective) in order to get the power down.  I'm only on 225/250 springs and I like it.  Did the car understeer or oversteer?  Mine is neutral until I get on the power, then it oversteers even in a straight line, hoping to fix that with huge rubber in back.  What do you mean by "brakes are hard to modulate?"  I had stock fronts and maxima rears and I basically only had front brakes even with a prop valve giving full pressure to the rears.  I couldn't stop the car and the fronts locked up whenever I tried.  What pads are you running?  If you have no camber plates, that would be priority #1.  LSD would be priority #2.  Then brakes.  I set my front shocks full stiff and my rears full soft to help get power down.  I also run less tire pressure than you would think.  26# on all 4 corners.  AND, due to tire heat and temperature rises as the day heats up from the sun, I wind up having to let air out as the day goes on.  I use shoe polish on the tires to check for edge roll.  I confirmed it once with a temp probe pyrometer and 26 gave me even temps across the face and even tire wear across the tread with no tire rolling.  The need for high tire pressures really only applies to high-profile street tires.  Direzzas may be labeled as street tires, but they are race rubber that sticks across the temperature range.  I so wish they came in wider sizes.  Your old Direzzas are better than old Hoosiers, and a hell of a lot better on rainy race days.

Edited April 3, 2014 by RebekahsZ

[Phantom]

Rebekahsz - I have the Z31 Turbo 3.70:1 LSD R200. Car understeered and oversteered. I got understeer when I was on the brakes or light throttle. It oversteered when I lifted the throttle or nailed it. I was set up with 34 PSI front and 30 PSI rear per recommendations at the track. I went there with 29 on all four corners. Sounds like I was closer than they were.

Brakes basically seemed to lock prematurely. A little change in brake pedal pressure and it was the instant slide. It seems like the car has always done that, though, no matter what brakes I had. One of the guys watching me said that he would see the rear wheels lock up slightly before the fronts. That wasn't what I was experiencing in the car however because the rear never walked around on me except as previously mentioned with big power changes, not with braking.

Jon - I'm handicapping myself a bit on rear brakes because I want to retain the e-brake function. Is there something else out there other than the 240SX caliper/300ZX rotor that does that? I've looked but not seen that directly addressed unless I want to spring a bundle for a secondary system.

Can anything be done to affect braking with pads? I'm currently running a very hard pad in the front and soft in the rear.

[RebekahsZ]

From what you have shared, I think you have a fine setup to start with. My recommendation is to race it this year just as it sits. Take one aspect to work on per autocross weekend, but I don't think you need to change anything major. You may just need to practice driving it. Be sure to start slow on your first run, then on your last run, try to knock down every cone on the course. On that first run, be sure to get car slowed enough that you are off the brakes going into the turn. Try left foot braking. Try to turn the wheel once entering the corner, then try not to adjust it-that is what it means to "set" the car. If you are "driving" a lot thru a turn, your tires and weight balance never really get to work for you. If you are understeering sometimes and oversteering others, its not the car-its you. Once you get settled down, it will do one or the other. Try to be precise instead of fast. And you will start to feel in control. When I have a bad day, it is from entering corners too fast and you can't really recover the car from that. I think the only setup deficiency is camber plates. The rest is mostly driving.

Edited April 3, 2014 by RebekahsZ

[socorob]

Direzzas are grippy street tires. Last autocross I went to watch the faster guys were switching from direzzas to rivals for whatever that's worth. A couple said the rivals are a little faster when it's dry but direzzas were a little faster if its wet.

[logr]

Phantom, SSSCC is a great group. Was Ken your instructor since he has an LT Z? Any of the instructors there would have been good. I am with a club in Spokane where a bunch of the SSSCC guys come race at. You should come up and give it a try. We have a "Classic" class that SSSCC doesn't have. It is for 70's and older cars and I run my SR Z in it. It is 140tw or greater. Our school is this coming weekend on Sat which is free. It's a school in the morning and a T&T in the afternoon, all free. Sunday is a regular event. Hope to see you there. http://www.autosportsnorthwest.org/

 

I have 200/225 springs with Bilsteins and the ST bars. It is very neutral and easy to drive. I also have JSK hats with Superlights and 12.2 all the way around which with the ZX master is very modulationable and balanced, with a proportioning valve in the rear.

 

Hope to see you there as I need some competition in my class. Ken and Ricky say they are coming up a bunch this year, in the Z. Lynn, Harold, Mitch, Ian, Kelsey, Dan and others come up a lot. We run on a runway and it is more open than 3-cities.

[logr]

Many of us have tried the RS3's, Direza's and Rivals. For our area and we have a very grippy track, we feel the R1R's are the fastest. They can overheat but not easily in the NW. All of these tires are good so it's more up to the driver at that point.

[JMortensen]

I think AZC now has a parking brake option. Regardless, I don't think you're going to get your current system balanced, so going bigger in the rear is going to be the solution. Might check into some of the other options. Silvermine? 

 

The basic idea in autox is to keep the tires happy. On a more stock suspension, there is too much body roll and/or too little camber to prevent the tires from rolling onto the sidewalls. One very rudimentary test is to take some white shoe polish and dab a little on the corner of the tire and over onto the sidewall in a couple spots, then check after a run and see where the polish is worn away. 

 

Yours is obviously not stock, but we also don't know what adjustments you have available from your description. With no adjustability all you can really do is pump up the tires more. With adjustable camber you can lean the tires in, and with adjustable caster you get more neg camber out of the outside front when you turn.

 

jhm's suggestion of used slicks is what I run. A formula atlantic front fits a 15x10 and you can find them cheap online as he said. The problem with going to a sticky tire is that you increase roll, and the tires aren't as durable as a street tire. So you're faster, but you'll also find the limitations in the suspension as well. My Z was sprung too soft so I had way too much body roll. After a season my slicks looked like worn out skateboard wheels, visibly cone shaped due to the wear on the outside.

 

I run the Toyo R1R on my Miata and I love it. It sticks great, really good in the rain, etc. I have found that I can overheat it even at autoxes and badly overheat it at practice and schools, and when they overheat they lose grip, and if you make up for it by turning the wheel more, it tears up the treads. Many guys around here spray their tires with water between runs. It's really necessary on the R1R IME, but still a really good autox tire. I suspect there are better choices if you want to do track days too.

Edited April 3, 2014 by JMortensen

[Phantom]

Rebekahsz - yeah -I know - car is doing what I'm making it do. I got loose in the middle of the day and then went back to working the line and staying controlled the latter part of the day and not pushing so hard. Runs were much cleaner and times got a bit better. I'm still need to do some work on the brakes so I can get better braking coming into the corners and cut my between corners times a bit.

logr - I met Ken through this site and then in person about 5 years ago. Turns out I went to church with his sister here in Yakima for a while and then her new husband was the one who got me to go to the school. Brian was driving Ken's 240SX. Spent a lot of time talking with Ken that Saturday but he wasn't one of my instructors.

I got good feedback from the instructors. My biggest problem is just getting the right line through the cones - turning in soon enough, and getting that rear tire across the back edge of the cone. It was a real eye opener for one of my instructors when he drove my car. The manual steering threw him for a loop and he got too hot into a corner and we plowed like crazy trying to get slowed down.

Both instructors commented on the smoothness I have with the car. I get it set and hold it there and am very controlled with the throttle. 10 years with the car the way it is can do that.

Won't be able to make your school this weekend. I have a coolant leak inside the cockpit which is not good news and something serious going on somewhere in my drivetrain. I'm getting a noise and a vibration that is getting worse and I have not been able to identify. I'm concerned I might have cracked u-joint or bent shaft somewhere that is getting ready to detonate.

[Phantom]

Jon - Thanks for the additional input. AZC does have a parking brake option right now but it's pretty expensive. I'd be out nearly $1k with the 4 piston rear brake kit and the e-brake adaptors. I actually considered putting an adjustable proportioning valve on the front brakes just to try to balance things. I know - bad idea.

Suspension wise I have only the front toe adjustment. No camber plates or caster adjustment although I have considered that. The main thing is to get the car as predictable and tame as possible since 95% of the time it's just an around town driver. I originally built it to be able to enjoy my commute to work through the Dallas-Ft. Worth traffic. I definitely achieved my goal there.

 

I'm hoping that putting in heavier sway bars and setting my shocks stiffer next time out will give better handling - but that may be next year.

Question for everyone - what makes the ST sway bars worth $100 more than the MSA sway bars. Willing to spend the money but don't want to pay and not get any benefit.

Thanks,

Bill

Edited April 3, 2014 by Phantom

[jhm]

WRT used tires, I run 15" wheels and have never had trouble finding 10" slicks and 275 A6s in great condition at good prices. I even have a set of super light 13" wheels that work really well on tight courses. Good luck whatever you decide.

[RebekahsZ]

There is a JSK rear disc conversion in the classifieds right now.