more autox ruminations, or, "slip slidin' away"

[Sharp11]

Last weekend, I had the Z4 out for a second time at one of cart's (www.cartct.com) test and tune days.

I'm having fun with the Z4 as I'm learning its (and my) strengths and weaknesses.

Sport button on, manual mode on the step, mash the go pedal and your eyes sink back in your head - it's a nice feeling, launches like this, after last year's season of discontent off the line with the E46.

First turn was a 540 degree skid pad (one and a half times around a circle), the Z4's really good here, I could tighten up the line (circle) with the throttle and a slight adjustment of the steering wheel - around the circle was pretty fast indeed, got some good time here.

Slaloms were fast, no brakes, just about flat out (the last gate was always a bit scary though).

The downhill, off camber sweeper was a problem - here, the Z4's tail just kept wanting to come out - I finally found a solution in the engagement of the first level of DTC.

There were also a couple of moments where the car would understeer more than I thought appropriate.

Overall, it was a great day, I was pretty fast and clean, my best was a 75 while the two FTD's were just under 70 - I was beating guys on racing tires with my standard runflats. That felt good, but who knows, they may have been pretty sucky (I'm not supposed to care about this stuff, but who can help it?).

However, the runflats seemed to like to slide quite a lot, it was cold and the lot was sandy, but still, grip was relatively poor.

One of the Z3 guys felt I could pick up at least two seconds if I switched out the run flats............yes, but it's another 800 to 1000 bucks :( and there we go again $$$

Ed

[rumatt]

The downhill, off camber sweeper was a problem - here, the Z4's tail just kept wanting to come out - I finally found a solution in the engagement of the first level of DTC.


Dear god, say it isn't so.

One of most fun aspects of autocross is learning car control. This was an prime opportunity to work on not lifing.

[bren]

Generally a bit of slip angle (on any tires) is fastest.


Dear god, say it isn't so.

One of most fun aspects of autocross is learning car control. This was an prime opportunity to work on not lifing.

Unless there is a cone wall delineating said sweeper (sorry Clyde) :eeps:

[clyde]

Yeah, if it was oversteer (and not power oversteer), the solution was to keep your foot in it, perhaps even giving it more gas. If it was power oversteer, that's a different issue related to the lack of an LSD and lack of traction (the tires in combination with the course conditions that you described). The electronics will sort of help a bit in treating that symptom, but there's a heavy price to pay as you won't be able to apply full power until much later (you're straightened out and stable...wait...wait...wait...ok, computer is happy that you aren't about to kill yourself, and now it stops applying brakes, and now it stops killing power).

There were also a couple of moments where the car would understeer more than I thought appropriate

Should have slowed down more and/or used less steering lock.

[clyde]

Unless there is a cone wall delineating said sweeper (sorry Clyde) :eeps:

While your incident a few weeks ago was impressive, between John, Jane and myself, my car took out at least 25 cones (reported cone tally was an undercount and, of course, didn't include pointer cones) at the last event.

I put in a new fender liner Tuesday evening and have a new front lip in a box in my basement. The old fender liner had been dragging on the pavement at speeds over 30mph and a couple inches had been melted/worn away. I'll bring a souvenier to the next event for you as a keepsake. :D I also got a few bags of fasteners, so everything on the front underside can be resecured again.

The lip needs to be replaced because 7 of 8 fastener mounts are broken/missing as are a couple clips (I think). I'm going to replace the front bumper with the yellow one by the end of the weekend and keep that on until the end of the season so I don't have to keep cleaning off the cone juice. I'll put the new lip on the original bumper after it comes off the car. In the fall, it all goes on as a single undamaged unit.

[Sharp11]

Yeah, if it was oversteer (and not power oversteer), the solution was to keep your foot in it, perhaps even giving it more gas. Good point and something I'm still getting used to with this car - the E46 never had enough power, but the Z4 does. I've found this to work really well through slaloms, it's intoxicating. As for the sweeper, sometimes I'd keep my foot in it and it'd bite down and grip, at other times it'd go wide and reflex would have me lift.....I just couldn't quite get the rhythm here (I've got to keep working on this).

The electronics will sort of help a bit in treating that symptom, but there's a heavy price to pay as you won't be able to apply full power until much later (you're straightened out and stable...wait...wait...wait...ok, computer is happy that you aren't about to kill yourself, and now it stops applying brakes, and now it stops killing power). True. In this case with just DTC on (and not the full DSC), the system is more transparent, it works really well. I could definitely see it in the rain and on poorly swept courses.However, I only used it for my final couple of runs.


Should have slowed down more and/or used less steering lock. No question, I entered one corner at the end of a long straight faster than was humanly possible to negotiate - I'd "found the limit" (and then some) :) CART has a big lot with at least one high speed straight (think 70 to 80 mph depending upon the car) in this case, ending in a tight right-hander. I kept hitting this little box of a turn faster and faster, throwing the weight down forward, flicking the wheel, hitting the gas, it was all working beautifully till I'd exceeded the limits. Now I've got to buff all the cone crap off my pretty white bumper.

All in all, the whole issue with using the throttle more is something I really have to get used to with this car, so used to am I "lifting" when the tail starts to go. I wish I could just practice this one maneuver over and over.

Ed

[rumatt]

Hey Ed,

How bad is the CART lot? I've heard it's in horrible condition and that I should stay away. Potholes, cracked pavement, etc. Is it really that bad?

I'm thinking of attending tomorrow. I can also go to a BMW event in NJ, but their courses are so tight they're boring.

[Sharp11]

Hey Ed,

How bad is the CART lot? I've heard it's in horrible condition and that I should stay away. Potholes, cracked pavement, etc. Is it really that bad?

I'm thinking of attending tomorrow. I can also go to a BMW event in NJ, but their courses are so tight they're boring.

It's big, fast and very rough.

I do like the layouts, the Cart guys do a good job mixing it up with open sections and tight, technical bits.

It does get crowded, so arrive early.

I don't think you'll break the car, it might be worth a try (unfortunately, I can't be there tomorrow).

Enjoy.

PS: Conversely, I'd like to try one of the NJ events one of these days.

Ed

[rumatt]

Thanks for the info. Looks like I'm going to need to skip anyway. :(

In terms of heading down here, unfortunately I can't say the events in the NY / NJ area are anything special. The NY SCCA and NY BMW CCA events are OK, they are so damn slow that the event always starts late and there's a ton of down time. The Porsche club events at Meadowlands are decent too, but you have to deal with Porsche owners. :eeps: . But t I'm not saying you shouldn't, but don't expect anything extraordinary.