znod

Great on the project. But, otherwise, I am confused by what you said. The raw data do result from actual testing--going full 1/4 miles and, of course, to 62.14. There is no straight-line approximation involved. The adjusted data also employ no straight-line approximations. I mention this point because it seems like you may be thinking that something was interpolated on a straight-line basis. But, no.

Ricracing

I was not thinking you would be messing with the data!

OK, I know my english is not what it should be and therefore maybe
my meaning gets foggy.
(I'm partly working with a dictionary all the time).

As long as you guys accelerate your fine automobiles to 62,14 mph and past
to a 1/4 mile we hopefully can compare the data later on!

I love your enthusiasm.

znod

Yes, all data should be comparable. And, thanks.

grogan545

The passport GT2 can be set up to measure in metric.I read the instructions to do this but I don't think I will try this because the instructions say it will erase all data and settings that are presently stored for English measurements.I trust that Znods method of calculating 0-100 km is accurate.He is very meticulous with his calculations and is obviously well schooled in mathematics.

znod

Hi g-man:

I can read raw 0 to 62.14's right off the download from the Pro RR. And, the regression approach for obtaining adjusted values works the same way for 0 to 62.14 as any other value--e.g., 0 to 60 or 1/8 mile time/speed.

znod

Hi Again g-man:

I want to think about your point. I'm too tired to do a credible job tonight.

znod

OK, I thought about your point, and I don't have any really great thoughts. One thing I know is that 2 of the auto mags. apply weather corrections to the newer cars. In this regard, I don't know how the generic weather correction factors are obtained. But, apparently the auto mags think they apply to the newer cars.

Also, I wonder how much actually is gained on our cars through automatic retuning for weather and altitude. And, note that historically manufacturers have never suggested that retuning for weather and altitude would make significant differences in the performance of "ordinary street cars." In your drag racing experience, was much, if anything, gained on the muscle cars you raced by fine tuning for weather and altitude?

I noticed that weather adjustment on the vast majority of my passes affects my performance negatively. Given your thoughts, those effects would be too negative. Surely, my results couldn't be any more positive. As it is, they look overly positive since we adjust to sea level. I think I will look at my results assuming an abritrary, but more realistic altitude--say 500'. I think that there is a calculator that allows adjustment to any given altitude. What do you think the average drag-strip altitude would be?

znod

Hi g-man and All:

I don't have anything new to add except I am thinking that we might want to start reporting at an arbitrary, but more realistic altitude, than sea level. It dawns on me that my results look too good if one does not realize that the implied altitude is sea level, and, while there are some, most drag strips are probably above sea level. I am thinking of using 500' for reporting. There is a calculator that lets one adjust from one density altitude to another.

Let me know if you understand things the way I do. When using the adjustments I have been using, I know I am adjusting to sea level. In this context, I think I also am adjusting to standard weather conditions at sea level. So, I think the idea of using the "new" calculator is to adjust from sea level/standard weather conditions to another altitude under standard weather conditions--on the basis of previous obtained values adjutsted to sea level/standard weather conditions. If I am right, then I think 500' would be a good altitude upon which to base reporting. I think our results would be more comparable to what might be expected on an average drag strip/average day. And, our results should be more comparable to what the magazines reported at least for the 545i. What do you guys think? Would another arbitrary altitude be better? What's your best quess about average drag-strip altitude?

Aha, I just found the following on SMOKEmUP.

"Predictions - With accurate log book information including weather conditions, namely DA, you can compare your timeslips removing one of the variables, weather. NHRA ? has chosen the density altitude of 'sea level' as a altitude standard ( 59 ?F, 29.92 inches mercury, 0% humidity). Using this information SMOKEmUP.com has written some calculators to determine Density Altitude, Correct 1/4 Mile Timeslip to Sea Level, Correct 1/4 Mile Timeslip from one DA to another DA, and SMOKEmUP's 1/4 Mi. timeslip correction auto lookup calculator. Using these calculators you can accurately compare your timeslips removing one of the variables, weather."

"Let's walk through a couple of examples using the calculators. First you made a run at the end of the season last year and ran 11.8 with a DA of -2500 feet. In the off season you do a cam swap and in the begin of the season you run a 12.1 with a DA of 2000 feet. On the surface last years run was faster by 0.3 seconds. Now factor in the weather for the runs and you'll see the cam swap did in fact pay off and the car is running faster since the corrected ET is approximately 0.3 seconds faster.

Another example would be a friend went 12.88 the night before you went 13.2 he had a DA of -1236 yours was -396. Who went faster? Using Correct 1/4 Mile Timeslip from one DA to another DA. Enter ET 13.2, DA of run -396 feet, and new DA of -1236 feet. The result is 13.085 corrected to -1236 feet DA, and sorry to say he went faster than you did .
TABLE 2
Run #....ET (actual).....Density Altitude (DA)......ET (corrected)
1............11.8 sec.........-2500 feet........................12.11 sec
2............12.1 sec..........2000 feet........................11.822
3............13.2 sec...........-396 feet........................13.085 corrected to -1236 feet DA

Summary - As you can see from Table 2 above you need to consider weather conditions to accurately determine if the changes you made helped or hurt performance."

znod

Here are my best 5 passes data--first unadjusted.

.................................................. .................................................A verage
1/4 Speed...102.710...104.050...103.640...103.710...10 3.660...103.554
1/4 Time.......13.629.....13.564....13.663.....13.631. ....13.657.....13.629
1/8 Speed.....82.450.....82.880....82.530.....82.490.. ...82.390.....82.548
1/8 Time.........8.853.......8.810......8.859......8.8 58.......8.881.......8.852
0 to 60............5.149......5.079.......5.145......5. 161.......5.190.......5.145

Second, adjusted for weather to 500'.

.................................................. .................................................A verage
1/4 Speed...105.212...105.008...105.027...104.931...10 4.931...105.022
1/4 Time.......13.453....13.467.....13.471.....13.497. ....13.479.....13.473
1/8 Speed.....83.140.....83.041....83.050.....83.003.. ...83.003.....83.048
1/8 Time.........8.732......8.742......8.744.......8.7 63.......8.750......8.746
0 to 60............4.966......4.981......4.985.......5. 011.......4.993......4.987

Third, adusted for weather to sea level.

.................................................. .................................................A verage
1/4 Speed...105.778...105.572...105.674...105.592...10 5.495...105.622
1/4 Time.......13.382.....13.396....13.439.....13.400. ....13.408.....13.405
1/8 Speed.....83.416.....83.316....83.365.....83.326.. ...83.278.....83.340
1/8 Time.........8.682......8.692......8.722.......8.6 94.......8.700......8.698
0 to 60............4.894......4.908......4.952.......4. 912.......4.920......4.917

I kind of like the adjusted to 500' data better; they look and, in fact, are (I think) more real worldish. And as mentioned, I think they would be more comparable to the magazine data. What do you guys think?

Edit: All adjusted values above have changed by small amounts because I changed my altitude value by a small amount, etc. (more on the other thread soon). Nevertheless, the above data still illustrate the my points.

grogan545

Hi Zman.I agree that weather does affect newer cars with computer controls.I am just not sure the effect is as great as older cars.On carbureted cars we would change the jets and fiddle with the timing to adjust for weather conditions.This would minimize the effects but not cancel them totaly.

The NHRA corrections are a good way to compare runs made in different weather conditions with the same car or different cars.Somewhere in the smokemup forum there is discussion on the accuracy of these correction factors.They seem to be saying that although they might not be perfectly accurate they are a good way to evaluate changes made to your car.

I like your idea of using 500' altitude as a base.It is probably a lot closer to real world than sea level.The weather here has become unexpectedly warm.I hope to make some runs on monday.The temp is supposed to be about 60-70 F.I'll log the conditions and ask you to correct to 500' altitude.What I would like to do is compare raw data under very different weather conditions and then use the correction factors on the same runs to see if they correlate to the raw data.I'll use my runs made at 26 to 30 F vs the runs I expect will be around 60F.I hope this will show if the correction factors are valid.I suspect that they overcorrect in either direction but I am not sure.

I thought about where to apply these correction factors.I think it is valid to apply them to all of the "time to distance"points but not to "time to speed" points.

I am still hoping for under 5 sec 0-60 in the warmer weather.If I can't achieve this I'll concede that the weather effects are greater than I thought.