znod

Hi B32:

I know what you mean. There is a lot of info here. We could easily get you up to speed. Just buy a meter, and ask us about set up. We'll take you there and lead you through what else to do one step at a time. There's really not much for you to do except to find a level, flat, and safe test site and then point and shoot your car.

cobradav

We're at 90 degrees, 95% humidity now so I am breaking off my 6er testing, unless time and weather really give me a good opportunity. I am still trying to do the special HP measurements as recommended by Gtech (short WOT run in 1st & shift at 3000 RPM and then WOT in 2nd gear to 3rd and shut down, take HP measurements in 2nd gear).

And I may have a chance to test a 335i (I6 with twin Turbo). I want to lay hands on the STEP version as they are claiming "faster" shifts than conventional Auto - whatever that means.

Also still trying to find the opportunity to test the new JAG XK Auto box. The sales folks want me to, but I have to get my wife out of town & that will not occur until she heads to Brazil in early June.

Meanwhile I have to study all the stuff Znod has put together. So until any one or all of the above happens I will be reading, but probably not contributing here.

znod

Hi cd:

If you have things to discuss, how about raising the issues on the other thread--the "Straight-Line Performance Thread?" Given no very active testing right now, I am going to be posting some ideas, etc., on that thread as they come to me. Tesla's HP test idea is a good one except that HP/TQ below about 4500 RPM is irrelevant for our cars except in first gear if talking about straight-line performance. So, except for below about 4500, using the 2nd gear HP/TQ values from normal passes is just as good as what Tesla recommends. And, if fact, it seems to me that 3rd gear might be the best single indicator of HP/TQ curves, for straight-line analysis, since our cars spend the longest time, at the highest load, in third gear. Coincidentally, HP/TQ curves are one of the things I am working on now. Among other things, one issue is adjusting from the Pro RR values to US standard values--e.g., those claimed by BMWNA.

cobradav

I think Tesla's main objection into the higher gear range for calc of HP was wind resistance due to higher speeds found there compared with same RPMs in lower gear. I am just looking for a consistent and reliable test method so I can have some hope of comparing before / after events whether software upgrades, repairs or actual mods or configuration changes such as the charcoal filter removal. One really needs to lay out a strategy that permits you to do your b/a testing in as near identical circumstances as possible. Ususally that means quick turnaround, but it may also mean as near similar conditions (wx, place, direction, etc) if pressed to extend the time between b/a testing.

znod

Right, their method is perfectly appropriate for what you want to do. But, for example, if trying to assess optimal shift points, then, assuming one had a choice, allowing for the effects of air resitance in all gears would provide a great advantage. That's the reason I looked at each gear specifically when posting info on optimal shift points.

znod

Hi All:

I am doing an update on optimal shift points for the Steptronic 545i. Note that such analyses can, at most, indicate whether (or not) the Step 545i's programmed shift points are optimal for straight-line performance unless one is interested in buying a shift program (assuming one becomes available). If such interest exists, then optimal shift-point analyses can influence one's decision on whether or not to buy a shift program.

From a straight-line perspective, there are two reasons why one might buy a shift program: (a) to provide enhanced manual shifting capabilities to improve on the Step's automatic shift points and (b) to allow faster shifting in general. If the Step shifts optimally automatically, then reason (a) evaporates.

Previously, I have done 3 optimal shift-point analyses. The first two, found in posts #34 and #45 of this thread, imply that the Step shifts optimally automatically. These two analyses are deficient because they use only BMW's engine dyno 545i torque curve. Thus, they ignore the sources of differential engine loads and differential mechanical inefficiencies in the various gears. The primary factor ignored is aerodynamic drag. In contrast, the analysis in post #293 of this thread utilizes Pro RR all-loss rear-wheel torque (RWT) values for each gear and yields mixed results. That is, this post implies manual shifting is superior when shifting from 1st to 2nd and that automatic shifting is better when shifting from 2nd to 3rd and from 3rd to 4th.

The analysis shown in the attached file, which is similar to the one contained in post #293 mentioned above, provides similar results. That is, it implies that manual shifting is marginally better when shifting from 1st to 2nd and that automatic shifting is better when shifting from 2nd to 3rd (marginally) and from 3rd to 4th (significantly better) under the optimal shift-theory maxim that one should either minimize the decrease in RWT that occurs when shifting to a higher gear or maximize the increase in RWT that occurs when shifting to a higher gear. In this regard, it seems especially important to allow automatic shifting when moving from 3rd gear to 4th gear. Note that (1) through (3) below reflect the actual automatic shifting that occurred on a single pass, while (4) through (6) below reflect hypothetical manual shifting on the same pass. In the future, I plan to extend the analysis to the average of my best five passes.

vegastrashed

Znod,
Any advice you can give me about using the G-Meter? I finally got one and will be using it at the Socal Meet on Saturday. Yes, I know it's here somewhere but looking over 31 pages is too much.

TIA,
jiio

znod

Super!!!! It will be great to see some new results. Definitely, yes, I can and will help, but which meter did you get?

vegastrashed

Passport G-Timer GT2.

The drive Saturday will be in La Canada Flintridge, CA. The temperature supposed to be in upper 80s/lower 90s. We will be driving along on Angelus Crest Highway. I'll provide all the other details that I'm sure you'll ask for like dew point, altitude, etc... for adjusted times when I report back with my raw numbers.

znod

Check out the posts up to #16 on this thread. Here is the way I was setting my GT2 up.

"My setup values for the time/speed related GT2 settings are as follows.

1. Rollout distance for both 0 to 60 and the ? mile?12??which is a "shallow-staging" standard that often is attemped on dragstrips and often is used in magazine tests.

2. Pitch correction?1.9?I used this correction factor because the GT2 manual indicates that, in trying to develop pitch correction factors for the C5 Z06 and the Audi S4, values of 1.5 and 2.0 had worked well. Note that my manual indicates that an increase/decrease in the pitch correction factor of .2 will result in ?a .03 slower/faster ? mile time. So, I am trying to be conservative in setting the pitch correction.

My setup values for the flywheel-horse power (FHP)-related GT2 settings are as follows.

1. Test weight of car?4,150 lbs. In this regard, Car and Driver test used a test weight of 4,150 lbs for a car equipped similarly to mine--but with some + and - adjustments needed. Since I don't have all the values needed for the adjustments, I decided just to use the Car and Driver value.

I now am using 4200 lbs because my car has heavier options than the CD car.

2. Drive-train loss?.20?because of my Steptronic?the value recommended by my manual for an automatic transmission

3. Rolling resistance--.13?the GT2 default?left it alone since I had no idea what better to assume

4. Aerodynamic drag?6.5?I assumed a value .3 lower than the one that worked well for Passport on the Audi S4."