First track day with Z4MC: Impressions

[donoman]

I had a fun time with the Z4MC at my track day on Friday at Laguna Seca. Everything worked really well and this is the most modern car I've driven at the track. Past cars were Miata, E36M3 and 964, with the 964 being my all-time favorite car to take out on the track.

I felt like the Z4MC was a bit anemic at times, it definitely does not have the same torquey feeling that my 964 has, and that's to be expected. You really have to rev the snot out of the car above 5K RPM to get her going, and I wasn't really comfortable doing that until a few sessions into the day. After this track day, I have decided that I definitely want an exhaust upgrade as the car just lacks that raw sound that I'm expecting from a performance vehicle. (I have stock exhaust/intake right now). I suspect that my lack of driving skills kept me from really being in the right part of the rev range for a lot of the day, but as I got more comfortable with the line, I felt less like the car was slow.

I did have trouble passing a certain Audi S6 V10, as he could totally walk on me on the straights. I was amazed!

I have a Ground Control suspension coil over kit and Apex ARC-8 wheels with S-04's. The suspension felt good, supple, but had some rubbing issues in turn 6, but that's it. I would say it's a good compromise between track and street. I'm running 375/525 springs and spent many days tuning the rebound on the Koni Yellows. I don't think I came close to bottoming out much anywhere other than turn 6, but I think it would be really hard not to bottom out there because there is a dip and it's such a fast turn. The S-04's were pretty good, but I was reminded that they aren't R-compounds and that was kinda disappointing. My 964 has Toyo RA1's that stick like nobody's business... but anyway, S-04s were very predictable and never felt like they were getting slippery on me.

Brakes (Stoptech street pads + SS lines) were really damn good. Surprisingly good, actually. Not much feel compared to my 964 but they stopped the car damn fast. Even at the end of the day they were surprising me, and I had many situations where I would brake and then have time to get on the gas again to make the turn. Hee hee. Must have looked funny but I figured it out at the end of the day. Threshold braking was excellent, I had plenty of feeling through the front wheels and could really pull it off. Heel-toe was easier than I remember in my E36 M3 (the pedals are all wrong for it!!).

Tranny was a little tricky, I had some problems getting into 3rd a few times, had to really deliberately let the shifter find the center position before pushing up, which I guess is the right way. It was so weird having an engine that will do 8K RPM in a car. I kept wanting to shift around 6K...

TRACTION CONTROL:
Man, I had trouble with DSC. First session, I had it on and had absolutely no idea what the car was doing. It felt so weird, like I was trying to rotate the car and it wasn't happening, or I was expecting it to react a certain way but just kept going in a pre-determined arc. Very strange experience, but it's my first car with such advanced DSC. I'd have to say I'm impressed what kind of stuff it can save you from, but I had to turn it off after just one session because I felt like I couldn't feel what I was doing. With DSC off, the car felt normal again, and since it's a new car to me, I felt like I got to know its dynamics a little better. I know that's overdriving the car, but to find out how the car responds I feel like I needed to turn DSC off. Next time, I will drive with DSC on and see if I'm any better.

I pussyfooted around all day, trying to be as smooth as possible, only got bend out of shape once coming onto the front straight when I put on the power too hard while still turning. There was lots of traffic (thank God for miatas!) and lots of young dudes in kamikaze cars driving around. I was amazed that the S54 wasn't really that fast compared to cars like E36M3's or S2000's. I know, I know, I was probably setting up the turns wrong.

Another note: This baby sucks gas at the track! I had to fill up before the last session of the day ($6/gallon arggghhh).

I'm excited to learn more about this car. I was expecting to be able to hang the ass out like in all the You Tube videos with Richard Hammond but alas my wallet and my gonads prevailed.

[shock311]

Nice descriptive summary. Would you say the pads and lines are sufficient or do you eventually see a BBK upgrade?

I'll be experiencing my first track experience in my recently picked up 08 Z4MC at Sonoma late August...I'm a total newb as it comes to track driving so it should be interesting.

[Kgolf31]

You need DSC off in the dry if you want any normal things to happen. DSC will NOT let you track out and will cut power.

The S54 isn't so modern anymore, it was kind of hilarious how a Honda Accord with a V6 would be hard to catch up to until getting out of 3rd gear on a back straight. However, the engine is VERY linear and predictable, something that is hard to come by.

[donoman]

shock311, I think the car will be fine with a good bleed with some good brake fluid. If you're running street tires, I think the brakes will be able to handle it. As an aside, you'll be amazed how much heat the brakes build up with DSC on. You're gonna have a blast at Sears Point. I've never driven it but ridden motorcycle on it and it's a really nice track.

I'm not going to buy a BBK for this car. If it comes to that I'm just selling the car and getting a Cayman. Those come with real brakes. As an aside, I really think the Z4M has a much rougher ride than my equivalently equipped 964. It definitely makes it more exciting.

Kgolf31, thanks for the confirmation. I was feeling really uneasy with the DSC on... glad I turned it off when I realized it might be the culprit of my anxiety. Of course, had I spun the car into a wall, I might have been writing something different today. Thank goodness I didn't!

[The HACK]

Laguna Seca is a notorious HP track. It's not surprising that a car with 100 more HP but weighed 1,000 more lbs will pull away on certain areas of the track.

The S54 really comes alive past 4,000 RPM, and unlike FI engines BMW uses today, it'll keep pulling until redline and seem to get stronger rather than weaker.

[donoman]

Yeah, I was really amazed that I wasn't walking away from S2000's! I've never driven one on the track but I kind of assumed they were like a Honda Miata. Boy, was I wrong! Of course a few S2K's had turbos and that made them totally insane on the track.

The Z4MC did well but I'm not so sure I'm gonna track it again at Laguna. I'm gonna bring it to Thunderhill where there is a lot more run-off. I was super worried about all the gravel traps and walls. I guess Sears Point is even worse!

Do you guys get into the ABS often when braking before a turn, or do you try to avoid it? I try not to brake quite that hard, but my coworker disagrees.

[The HACK]

Braking after a turn? You mean trail braking?

[Finnegan]

It's always cool to hear impressions!

As to S2000s, if you're talking ones with R rubber, coils, and supercharged, and a full APR wing setup, that's going to be hard to keep up with, just too much grip and with SC comparable power.

Lastly, I'd check rear toe in. RTAB limiters and some good toe in really improve the driving dynamics IMO, improving mid-corner a bit as well as exit speed (settles the tail a bit allowing more throttle input). It's quite a difference using Kgolf's specs vs. less toe in.

http://www.zpost.com/forums/showthread.php?t=968488

Do tell more about braking. Not clear on what you mean.

[donoman]

Originally Posted by The HACK

Braking after a turn? You mean trail braking?

Yarghhh I meant BEFORE a turn. Will edit.

[3002 tii]

I did Laguna few years back, in fact it was my first time on track and I had flown out to California and done a Skippy school during my vacation. Had a blast out there, I wish I could take my Z4 out there. Nicest track around me is probably the Glen.

[dschultz]

Originally Posted by donoman

Do you guys get into the ABS often when braking before a turn, or do you try to avoid it? I try not to brake quite that hard, but my coworker disagrees.

I was under the impression that regularly getting into ABS was a sign that you're probably too abrupt onto the brakes. Kind of a "mash it and forget it" style. It's hard (impossible?) to modulate the brakes once ABS kicks in.

The conventional wisdom used to be that maximum braking occurred just before ABS kicked in, but I don't know if that's still true today.

[fullerra]

For any car with ABS, physics dictates that maximal braking occurs with ABS on as deceleration will occur at maximal value immediately prior to the onset of sliding/kinetic friction (as opposed to static friction) as typically the coefficient of static friction between any two objects is higher than the coefficient of kinetic friction between the same two objects) The computer in the abs system dances around that line between lockup and (sliding) and threshold braking much faster than you or I could. Repeated engagement of ABS, will likely ruin your unit though.

Race cars typically do NOT have ABS, and their drivers must sense when their tires at any of the four corners are about to approach the limits of breaking prior to onset of lockup, and slowly back off of the brakes (that is, unless that is what is desired i.e. drifting / rally, employing the E-brake).

[David70]

Originally Posted by fullerra

For any car with ABS, physics dictates that maximal braking occurs with ABS on as deceleration will occur at maximal value immediately prior to the onset of sliding/kinetic friction (as opposed to static friction) as typically the coefficient of static friction between any two objects is higher than the coefficient of kinetic friction between the same two objects) The computer in the abs system dances around that line between lockup and (sliding) and threshold braking much faster than you or I could. Repeated engagement of ABS, will likely ruin your unit though.

Race cars typically do NOT have ABS, and their drivers must sense when their tires at any of the four corners are about to approach the limits of breaking prior to onset of lockup, and slowly back off of the brakes (that is, unless that is what is desired i.e. drifting / rally, employing the E-brake).

Thanks for the thorough reply but why on the part in bold?

[fullerra]

Typo. That should not have been in bold, but it's important to know.

[David70]

No, I put it in bold, just wondering why repeated use of the ABS would cause it to fail.

[Shipkiller]

Repeated engagement of ABS, will likely ruin your unit though.

I really want to know and understand WHY this happens. What is the thought process on this?
This is just the opposite of what I was told by several master mechanics in the GrandAm series.

[fullerra]

I believe I have been mistaken ( I had been told this by several people in the past) but when I just did a little independent research myself today, I could not find clear evidence to substantiate this.

consider this a formal retraction of the second part... the first part with the shorter stopping distance with abs still holds true.

[donoman]

fullerra,

If you get into ABS that means you are crossing the static/kinetic friction boundary. Wouldn't it be better to stay in the static regime, just before you start slipping?

I don't believe ABS can pre-empt slippage, therefore I think stopping is probably faster just before you get into ABS.

[Finnegan]

My two cents:

The way to most efficient braking isn't using ABS.

Whacking the hell out of the brakes for maximum braking isn't the best way to manage brakes for a session. Min stopping distance and max braking efficiency aren't as important as how you come off the brakes, or how you manage heat lap after lap.

Smoothness and balance of the car off braking is more important that whether you save a few (or more) feet with some max braking approach--corner entry and transition are more important. Abrupt release of the brakes bobbles weight back and forth--something that causes a loss of traction and makes corner entry much more difficult, resulting in lost time and lost control. The smoother you come off, the more traction you have. Simple as that.

If you're up for some good reading on the topic, and some great ideas on managing brakes as well as increasing traction during and after braking, this long (but very useful) explanation by The Hack covers it really well. (The book "Speed Secrets" discusses similar things, and others, and is a great read for any track junkie IMO.)

Using what I learned, applied, analyzed, and practiced from this piece alone (thanks Hack) I cut 10+ seconds from my lap times, while managing brakes better (no fade, even though I was faster), and ended up with a hell of a lot more traction into corners, better control, and hence faster out. More fun too. Several Zpost members I've driven with have had similar results when learning and applying these techniques--I hear things like "I'm not fighting with the car into the corner", "wow, it's so much more balanced and easy to control". YMMD.

Now I just need to manage about 25 other things to improve my driving, and then another 25, and so on! (Right Sean? )

[inTgr8r]

^This!

[Barryb97]

Great write up. Something else to add to the list of things to work on.

[heligarret]

donoman did you do the track day with speedventures?