NorCal UFO June event.

[RC240z]

Okay, I watched the video, it seems when you got up into the powerband that the car got tail happy on you and would step out quickly, as it looked like you almost spun on that run and had to completely get out of the throttle.

[SLOroadster]

Ron, You got it, as soon as it comes on cam it breaks the back end free. I'm running a 4.11. I know it makes good power, but its not a massive amount of power. Yes I had to get off the power, and catch the thing before it spun. Then the whole left turn before I went for 3rd was a power induced drift. When I was trying to run the whole course in 2nd, you can imagine how much of a handful it was. The big turnaround sweeper was still right on the verge of a power induced drift.

Last year at the same location I was .2 of a second off TTOD, same suspension setup aside from the traction bars. Smaller tires with about the same amount of stick. This really makes me wonder whats going on here? The pavement is not smooth here, so if the car is too stiff its going to skip around. (It does, power induced) If I go to stock springs that should calm the back end down as it will both raise the back end leaving more room for suspension travel, and soften the suspension so it will work rather than packing and skipping. By pulling the traction bars I might loose some spring rate (due to bushing bind ect) and if I get faster, I think I'll be onto something. When I get the stock springs again, I'll start over full stock then add the panhard and traction bars.

I have 3 sets of wheels so I can mount the Street TDs on my 6.5s and run them. I'll keep the 225s on the Panasports and run them till they cord. The Libres will continue to be the street wheels. I have to admit 2 sets of race wheels with 8 bikes in a one bedroom apartment is getting a little much.

Will

[RC240z]

Since my car has an ultra close gearbox I am never off the cam, and I must admit my car is not that squirrely when it gets up onto it's cam. Your car is like an OFF then ON switch..In this case that might be a problem...Maybe a more gradual cam would be a benefit? If I recall you have a Z-196 Isky cam?

My car with it's ultra close gearbox does 50+ in first gear so, I could roast the tires like that if I wanted to.

My question is what does Tim say? I know he has driven your car, and I know he is fast, what does he think? I do know he generally likes a tighter setup than most because he is a very good driver and is used to the handling characteristics of a tight car.

Your car should push with the locker, in an on the throttle situation. As the locker should work like a spool...My car does that...it will push the front end. I lift off the throttle to rotate the car in a corner.

[SLOroadster]

When Tim drove the car it had sticker tires on it and just flat out stuck. It didn't have the traction bars on it at the time either. He did say it was tail happy, but it wasn't nearly this bad. The only things I have changed since then have been stepping from the 39 to the 40 mm venturis, and adding the traction bars. I haven't touched the front suspension settings and only set the rear shocks to full soft (from full hard). In its current state, I have no wish to go run it on the track. It would be way too scary (especially at Sears Point, I can see it now, crest 2, the back end steps and off I go into the wall... No thanks. I'll get this sorted first.)

The car has never been known to understeer with this rear end in it. I know it should plow, but the only time I can get it to is when I have overcooked a sharp corner and turned the wheels far too far to get it to turn, until it burns off speed.

Something must be binding in the rear causing this. I'm not sure what else it could be. Its not fun to drive like this, it makes me look like a lousy driver, its slow, and darn it I like to win.

Will

[RC240z]

It is frustrating when you go backwards....but there is something to be learned from every failure too.

I still point to the rear springs. But now all you can do is try different things and look for a positive change.

Just so I know, what do you have in the front of the car for suspension?

R

[datsunrides]

(especially at Sears Point, I can see it now, crest 2, the back end steps and off I go into the wall... No thanks. I'll get this sorted first.)Will

Not exactly on topic, but I have to say, I f'n HATED turn 2 at Sears when I raced motorcycles there in the early to mid 90's. That turn and cold tires scared the s*** outta me more than a few times. "Yeah, let's put a turn at the top of a hill and make it off camber while we're at it" The exit of 3A gave me some moments too! I will say I loved flying up turn 1 off the dragstrip WFO, knee on the ground. What a rush!

Mark

[Alvin]

I vote for softer springs.
With all of the rapid weight transfer in auto-x the comp springs just don't have enough travel....I think Will's analogy of behaving like it has a rear sway bar is right...
Combine that with today's tires with stiff sidewalls and you get a really bouncy setup.
-You don't need power to make a car slide you just need to upset the chassis. imho making the transitions less violent might help!
-swap out the springs for early ones
-drive a course with a set of tires you can use repeatedly while making suspension mods
-try to keep at least one constant(ie tires)
-then add the panhard rod or other aids

also, if someone else drives your car be careful how you take the feedback. What works for them may not work for you

[dbrick]

Will, how much of a difference did the traction bars make on the cornering? And did you add them by themselves or with other changes? I was thinking the the combination of the bars you added and the factory torque link above the axle could be causing a bind or an imbalance under accelleration.

[SLOroadster]

The traction bars went on by themselves. It was the last thing I did. I noticed immediatly that the back end was binding just drivign down the street. I pulled the torque rod following that. It made things better.

The front setup is a set of Mike Youngs comp springs (680# I think, might be a little higher, not as high as the Nissan comps.) with Konis set full stiff. 23mm front anti-sway bar. 0 toe, -2 degrees camber.

Mark, I'm still trying to find some time to run down your way to pick those springs up.

Will

[dbrick]

OK, so the rear bind isn't a possibility with the torque link off. Have you tried a large change in the compression dampening on the shocks? Try to go alot softer and see if there is a positive or negative change. It's a no cost test and can be easily reversed.

[oilleak]

For what it's worth, Elliot Harvey told me that he and Bill tried a locker... Once. They couldn't get it out of the car fast enough. He described basically the same problem you look to be having. The problem is that you can't predict when the locker will actually lock. So you alternate from an open diff to a fully locked diff with no transition - and it happens mid corner on tight auto-x courses. Seems like you don't have the problem in the faster, more open "race track" like corners. It's further complicated in the tight stuff by the fact that you've got more power than a CSP 2000 can make.
The springs may be part of the problem too but there's not a huge difference in the rates. I'm running '66 springs and was using the stock '69's prior to that.

[dbrick]

In a perfect world, it would be great if Will could "borrow " a rear from one of the racers with a LSD, and if it works, maybe swap for the locker rear. Not a fast thing to install, but it may be the ticket.
I keep having the same thought, locker on a tight course and it upsets the balance.

[RC240z]

Will I have a couple of LSD's. None of them are 4.11's though. You are welcome to borrow one to test. The lockers are different...more effective if you ask me, but I don't drive the ultra twisty stuff. Road courses are much more open than auto-x.

I have the heavier front springs in my car BTW. With the same sway bar. Same allignment settings with 2.5 degrees of negative camber.

Ron

[SLOroadster]

As far as the locker goes, I tend to brake early and roll onto the gas as I start into the corner. That should lock the diff. I can't soften the rear end without chaning springs or revalving the shocks themselves as they are already set full soft.

I have to say the car is slowly getting pushed to the back burner. I have the season championship wrapped up in the Alfa, and I've been racing the bicycle instead lately. I'm not going to really make a big deal out of it at this point. If/when I get the stock springs on it I'll give it another go.

Will

[RC240z]

Fair enough.

Let us know when you get your springs.

R