This car is difficult to drive and scares me

[letitsnow]

Let me start out with this, I'm pretty new to autocrossing and I still drive this car almost every day. I've driven a few events in other cars over the past few years and this is the first year that I've run nearly the whole season. I'm in the process of putting an LSD in and didn't finish for today's event so I borrowed my dad's LS1 FC RX7, after that, I'm positive that the Z is much tougher to drive fast than any other car I've ever driven. I co-drove with one of the fastest guys in the region and he agrees that it's very tough.

 

I've kind of developed a reputation for spinning, I'm afraid of getting near the limit because once it starts to spin I have to be super quick to catch it or I exit the corner backwards. It doesn't seem all that unbalanced but once it starts to go it's hard to catch.

 

My car is setup as follows:

 

Bilstein struts in sectioned housings

200/225 f/r springs

stock bars

225/50r16 kumho ecsta spt's on all 4(not very sticky)

poly bushings everywhere except the T/C rod, they're rubber.

 

I don't know where the toe is and I haven't corner weighted it, rear arms are stock and the rear alignment is wherever it ended up.

 

I'm hoping the LSD will make the car easier to control and get upset less by boost coming on when the car isn't pointed perfectly straight, maybe make it easier to catch.

 

Edit:I guess by difficult to drive I mean difficult to place on the line I want to take.

Edited July 16, 2012 by letitsnow

[Xnke]

I have the same problem with my car...and I have far less horsepower than you. If mine gets loose in a corner, and I don't catch it before it comes out more than 8-10 degrees, I won't be able to get it back on the straight and narrow. I've currently got an open diff, but I'd also like to know what can be done to keep the S30 chassis from quickly becoming unrecoverable in a slide.

[zlalomz]

I had my Z with about the same spring rates and street tires. It was very loose, almost to the point of drifting. I put in my lsd and it was a changed car. It became much easier to autocross.

[RebekahsZ]

I checked your content trying to learn a little about your car, but came up short. You really want help getting your car handling better? Tell us more about your car: suspension mods, motor, alignment settings, etc. Subscribing.

[letitsnow]

The only thing I didn't say was L28ET, the suspension and known alignment settings(none, LOL) are listed. Is there anything specific you'd like to know? here's a dyno sheet, just for good measure. http://i44.photobucket.com/albums/f12/letitshow/Dat-SON.jpg

 

 

Based on times from today, I'm pretty sure the rx7 is slower(roughly 3sec/60sec course), but still far easier to drive than the Z. I think a better set of tires, like a set of rs3's or star specs, would bring my times down into the competitive range, I'm just curious about making the car a little less leery.

Edited July 16, 2012 by letitsnow

[h4nsm0l3m4n]

Making the power that you do the car will be very hard to drive. The LSD is going to make a huge difference in predictability at the limit.

 

Lack of power steering really sucks for autocross and makes the car more difficult to drive at low speeds. My club has lately done courses with back to back 180 degree turns very close together. I really envy how the modern cars can whip around their wheels to do these kinds of turns.

[RebekahsZ]

77 280z with turbo'd L28. OK. Do what you can to achieve johnc's recommended race suspension settings listed in the Suspension stickies. 3 degrees of camber front and back will help ALOT. Lowering the car from stock heighth increases camber in the back, but decreases it in the front. Fastest way to get there is DP camber plates from BetaMotorsports.com if you already have coilovers-lots more work if your springs are stock diameter. In my car, the lack of an LSD didn't make the tail twitchy, it just made it hard to get the power down (the inside tire just spun). LSD made my car faster by letting me get power down earlier coming out of turns, but it didn't make the car less twitchy. As you stated, race compound tires will help the car transition more gradually instead of having an abrupt change from traction to sliding to traction, you might be able to borrow or bum a used set from somebody in your autocross club; that's what I did at first. The other thing that might help is either less power or a lighter foot. Could you put a stiff spring somewhere in your throttle linkage to help you modulate throttle? Do you have stock (very slippery) seats? I had trouble with movement of my feet (causing me to stomp the gas in hard left turns and slalom) caused by movement of my butt sliding around on the seat. A race seat and/or a set of 5-point belts settled that down-a small block of wood screwed to the floor can help with that too. You are right-a high powered z with basically stock suspension drives like crap. Autocross is a suspension game, not a motor game.

[Sideways]

I don't know where the toe is and I haven't corner weighted it, rear arms are stock and the rear alignment is wherever it ended up.

 

 

This will probably end up being a huge portion of your issues.

[letitsnow]

I do have the stock seats, I've considered a kirkey just for autox. I listed spring rates bot forgot to say coilovers, the ride height is measured to be the same on all 4. I set the ride height to where the outer pivot of the control arms are about .5" lower than the inner pivot.

 

I do think the lack of power steering really doesn't help, but the rx7 lacks PS as well, but the steering on the Z feels so much heavier, especially on course.

 

I don't seem to have issues with stabbing the gas at the wrong time, the engine isn't terribly responsive and it takes about .3-.4s to get to full boost, longer at lower rpms, which is where it's been on the last couple courses. The power really hasn't been much issue, just trying to get on the gas early enough to use it has generally led to spinning the inside rear, then a rolling burnout from corner to corner.

 

This will probably end up being a huge portion of your issues.

 

The only adjustable alignment settings are front toe and ride height at the moment, aside from slotting things, which I don't really like the idea of.

 

Just for the heck of it, here are a few runs in my dad's rx7 from yesterday(which is a nearly stock 87 + an LS1)

Edited July 16, 2012 by letitsnow

[letitsnow]

and one of the Z(I had excellent instruction for this event because I was co-driving with the guy that generally wins our Pro class). What sounds like understeer, but doesn't look like it is spinning one of the rears.

Edited July 16, 2012 by letitsnow

[jt1]

If the inside tire is spinning, you don't get any lateral grip from that tire, so the outside tire is the only one working. Get a lsd.

 

Try a smaller rear bar, or maybe no rear bar. You may have to adjust spring rates.

 

Like said above, alignment with 2.5 - 3 deg neg camber, toe in on rear, and get the corner weights evened up, with the bars loose and you in the seat.

 

Throttle modulation is important, a quick gas pedal makes the car hard to drive. Work on the linkage to get it as slow and linear as possible.

 

Seat time, seat time, seat time. The connection between the steering wheel and throttle is important.

 

jt

[burninator]

You could try swapping your springs front to rear. Putting the stiffer springs in the front should make it over-steer less. Or unhook your rear sway bar. If you have the ability to adjust, a little toe in on the rear might help too. Like others suggested, an lsd would also probly cure most of it and is on my personal list as well. I have a stock 2.8L on my 240 and it over-steers like a son-of-a-gun in autocross too. It's a blast to drive though. With practice you can learn to manage it and not spin, but you'd probly still be faster if you got it sorted.

[letitsnow]

LSD is 'in' the car, but it's not connected to anything because I didn't have the M14 nuts for the mustache bar to rear cover. I'll finish that up sometime this week. The LSD has drained just about the whole car fund.

 

I do notice that the pedal is very quick, is there an 'easy' way to change the ratio?

 

Cheap rear toe adjustment, is it a bad idea to use cam bushings? They look like they'd bind things up. I guess I could look and see how much a pair of rod ends are and add them to the stock arms.

[johnc]

I don't know where the toe is and I haven't corner weighted it, rear arms are stock and the rear alignment is wherever it ended up.

 

Begin here. The S30 is very sensitive to alignment. The whole point of all the adjustable stuff we put on these cars is to get the alignment right. Check the alignment sticky I have in the Suspension FAQ.

 

A LSD will help but looking at the videos your car has the classic Z handling problem: Understeer and then lift throttle oversteer when the driver gets out of the throttle as the car pushes wide. Its exacerbated by the slow steering of a typical S30 which means you have to have very quick hands to catch the back end.

 

Enter the corner slower and squeeze the throttle.

[letitsnow]

A LSD will help but looking at the videos your car has the classic Z handling problem: Understeer and then lift throttle oversteer when the driver gets out of the throttle as the car pushes wide. Its exacerbated by the slow steering of a typical S30 which means you have to have very quick hands to catch the back end.

 

Enter the corner slower and squeeze the throttle.

 

I'd say that's an adequate description of what it does.

 

I think I'm going to focus on becoming a faster driver for now and see about adjustable suspension pieces next year.

[RebekahsZ]

I agree with everything that has been said, so I don't want to be a nag. But, the bang for the buck on the DP bolt in camber plates is really great. Check wit johnc, but since you already have coilover suspension, that is a really easy 1-weekend job with no welding. Basically, the DP camber plate replaces your top spring seat and your stock insulator. In the process, it lowers the car an additional inch. If you keep your stock lower control arms, the only tools you need to do a garage alignment is a camber gauge and a toe gauge, both of which are available from LongAcre Racing thru someplace like Jegs for a couple hundred bucks total. Johnc's camber plates transformed my car from an "also ran" to a front runner. Super dedicated racers will argue with me, but I see no reason at all to go to weld-in camber plates, so long as the DP is available. Now, everybody gets really excited about wide, low profile tires. But, you would do better with a set of used 195/60/14 tires in a BFG R1 or Hoosier A6 compound than you would with 275/50/16 street compound tires. The difference that you feel with race compound tires is amazing. You might find a used set laying around somebody's shop for as little as $100. Somebody gave me my first set because they felt sorry for me.

 

That run in your car looked pretty good. Post a video of your worst run?

Edited July 16, 2012 by RebekahsZ

[bjhines]

Alignment is important. You need to get that right first. You can use a combination of BOLT-IN upper and lower modifications to get the front end right. You will have to get a LOT of aftermarket parts to get a proper alignment.

 

A long time ago, I managed to get a decent handling 240Z with stock horsepower WITHOUT welding and cutting very much. I also managed to get a decent alignment with mostly stock parts by elongating a few bolt holes and adding some washers with a few KEY components. It was very hard on tires, I had to rotate and flip them often.

[letitsnow]

I know that the compound makes a world of difference, but I want to stay away from a dedicated race tire for now, until I learn a bit more. I shouldn't need them right now, I've been repeatedly RAW'd by a stock class '90 honda civic with a good set of street tires and shocks, I don't even want to talk about PAX. I'm planning on a stickier street tire for the next set. Slicks(*<140 treadwear in my region) puts me in pro as well.

 

Here are all the runs from that day. I co-drove that event with a very very fast local guy, his instruction helped a ton and I got to see the course more. Just for reference in the video, I'm Bob and he is Chris, the runs are labeled with who drove.

 

Maybe I shouldn't have said that the car scares me, but I think I've looped it at every event this year, except that bmwcca event. The last event I did turned out to be closer to rallycross than autocross, it was an old lot that had mostly disintegrated into gravel. It did scare me there. I think the parts I find difficult about this car are placing it on line(heavy slow steering, while hanging on for dear life), and the occasional lift throttle spin/slide scaring me for the next 2 or 3 runs. I've autox'd a z31 a few times, that car was very forgiving at the limit, but it had no power, a fair amount more tire, and power steering.

 

 

I thought about the lift throttle oversteer John mentioned a little, the s30 rear doesn't have any toe change with compression/extension, does it? Is that why when you lift and weight transfers off the rear it gets twitchy?

[jt1]

You can have a good bit of toe change in the rear in transition if you using rubber bushings, esp if they're the 40 yr old stock ones. That's why you see most of the track guys using aftermarket lca's with heim joints and no rubber. Downside is they're noisy and a bit harsh on the street.

 

To get a "long" gas pedal, you have to work with the linkage. Depending on your setup, you can shorten or lengthen various arms, pivots, whatever, to get more pedal movement for the idle to full throttle event. I've spent a good bit of time getting the pedal fairly slow, and getting the pedal heights right for a good heel-toe downshift. When you're doing this, pay close attention to make sure it always returns to idle smoothly, and that you're getting full throttle. A stuck throttle can ruin your day.

 

There's no point in going to race rubber until you get the chassis and driver as good as you can on street tires. Race rubber will make you faster and a lot poorer, but it won't make you or the chassis better.

 

jt

[RebekahsZ]

Your videos are great it looks to me like you are doing fine. How did your times compare between you, your co driver and your dad? I would kill to be able to go racing with my dad but that won't happen until we are racing among the clouds. Funny that the consensus is to wait on race tires. It was the first thing I did. It is just so little work and guys in my club had old tires just laying around. It only takes a few minutes to swap tires...took a couple of events to cord them but they were faster on cords than brand new street tires.