Originally Posted by grogan545' post='260855' date='Mar 27 2006, 04:19 PM

Hi all.I made another run today,weather conditions have changed enough to see if they somewhat affect performance.I had an excellent start in D with traction "off".The temp is finally warm enough for my goodyears to stick.Results below.
1/4..........13.41/105.5
1000'....... 11.19
1/8.......... 8.69/82.7
330'..........5.65
60'............ 1.95
0-60......... 4.97
temp.........52F
dew point... 19F
barometer.. 30.18
altitude...... 400'
humidity.... 24%
Zman,please work your magic with the corrections and let me know.

Originally Posted by Znod' post='260969' date='Mar 27 2006, 07:21 PM

Good deal g-man. I am glad your weather is shaping up. Mine is starting to get hot, but I will continue to do passes to see what happens when it does so. Your pass was an excellent one. Here is your density altitude.

Your results:
Air Temp 52 (?F)
Altimeter Setting 30.18 (in)
Dew Point 19 (?F)
Altitude 400 (Feet)
Density Altitude -211.8 (feet)

Here is your adjustment to sea level.

Your results:
Density Altitude -211.8 (feet)
Uncorrected ET 13.41 (sec)
Uncorrected MPH 105.5 (mph)
Corrected ET 13.44
Corrected MPH 105.26

Here are your excellent results adjusted to 500'. The same thing almost always happens to me. I start out below 13.5 and over 104.999 after the density altitude adjustment top sea level, then, the adjustment to 500' almost always take me back over 13.499 and to less than 105--even when using 42% adjustment.

Your results:
E.T. 13.44 (sec)
Trap Speed 105.26 (mph)
Measured DA 0 (feet)
Corrected to 500(feet) DA
Corrected ET 13.511 (sec)
Corrected Trap Speed 104.697 (mph)

My best estimate of your 0 to 60 is: 4.97 - (13.41 - 13.511) = 5.071

Using 42% adjustment for weather, you get:

For your density altitude: 400 + -.42(400 - (-211.8)) = 143.044

Now, your adjustment to sea level gives:

Your results:
Density Altitude 143.04 (feet)
Uncorrected ET 13.41 (sec)
Uncorrected MPH 105.5 (mph)
Corrected ET 13.39
Corrected MPH 105.662

Here is your adjustment to 500':

Great pass. Way to go.

Your results:
E.T. 13.39 (sec)
Trap Speed 105.662 (mph)
Measured DA 0 (feet)
Corrected to 500(feet) DA
Corrected ET 13.461 (sec)
Corrected Trap Speed 105.097 (mph)

Here, my best estimate of your 0 - 60 is: 4.97 - (13.41 - 13.461) = 5.021

I assume that I should post your 42% results on the other thread. Let me know for sure. The 42% method is 99 and 44/100 % pure--just like Ivory Snow.

I am very glad that you finally got a good chance to show what you and your car can do. 550i's watch out for the g-man.

EDIT: Too late. I have already posted your new results under the 42% method on the other thread. I did it while I had the time this evening. I also converted your earlier posted data to the 42% method. I can change both to the 100% method if you prefer. Just let me know. Also, I have not yet "announced" the posting of your latest on the other thread. So, no one will even notice the change to 100% if that is your preference. Just let me know which you prefer.

Originally Posted by grogan545' post='260994' date='Mar 27 2006, 09:01 PM

Thank you again Zman.You are a magician with numbers!!.Use the 42% correction numbers.I think they are the most accurate.

I need to do more testing ,but todays run gives me the impression that my original thought that the NHRA factors are overcorrecting for our cars is valid.I think my best unadjusted run(13.26) when corrected 100% was 13.56.This run was done in very cold weather(26F) with a dew point of 5F.Today with the weather near "standard" conditions gave me my best to date numbers.

Originally Posted by grogan545' post='260994' date='Mar 27 2006, 09:01 PM

Thank you again Zman.You are a magician with numbers!!.Use the 42% correction numbers.I think they are the most accurate.

I need to do more testing ,but todays run gives me the impression that my original thought that the NHRA factors are overcorrecting for our cars is valid.I think my best unadjusted run(13.26) when corrected 100% was 13.56.This run was done in very cold weather(26F) with a dew point of 5F.Today with the weather near "standard" conditions gave me my best to date numbers.

Originally Posted by Znod' post='259843' date='Mar 25 2006, 10:51 AM

Good work g-man. I wasn't aware of the small problem with the NHRA altitude adjustment table, but, as you say, the error looks like it would not be at all significant. I'll look more closely at the table. And, I agree about your nonlinearity conclusion. Everything that I have been able to infer about the all the tables implies that they are based on a linearity assumption.

On the weather correction issue, I adjusted each of my 38 passes so that each allows for only 25% of the weather correction and calculated the resulting averages. The averages are given below. Ignoring a rounding error, the procedure I used yields exactly the same results that are produced when adjusting my averages for the 38 passes using a 25% weather correction applied to my average density altitude of 1360?. For example, a 25% weather correction based on the 1360? value yields an adjusted density altitude of 1540 = -.25(1600 ? 1360) + 1600. Using 1540, adjusting 13.727* (see * below) to sea level gives 13.493. Then, adjusting this value to 500? yields 13.564 = approximately 13.562** (see ** below).

...........................1...................... .......2.......................................... ....3.........................................4
..................Unadjusted.....Weather/Altitude to 500'.....25% Weather/Altitude to 500'....Altitude to 500'
1/4 Time.........13.727*..................13.592...... ...............................13.562**........... .................13.556
1/4 Speed.....102.878..................104.046........ ............................104.351............... ..............104.134

Taking the altitude effect of .171 (13.727 - 13.556) out of 2 and 3 gives:

2 = 13.592 + .171 = 13.763 adjusted to 1600' given standard conditions or
3 = 13.562 + .171 = 13.733 adjusted to 1600' given standard conditions

Now, the question is whether the weather conditions, on average, were better than standard so that:

a. they imply a .036 increase ? time at 1600' assuming standard conditions (i.e., 13.763 - 13.727) or
b. they imply a .006 increase in ? time at 1600' assuming standard conditions (i.e., 13.733 - 13.727)?

The more reasonable answer depends on how my car?s HP is affected by weather over the 1360? (my average density altitude) to 1600? (my actual altitude) range of altitudes. If the answer is .036, then, crudely, my car?s performance should be handicapped, in effect, by the absence .036(HP) = .036(325 HP) = 11.70 HP [(= RWHP of 9.36 = .8(11.70 HP)]. And, if the more reasonable answer is .006, then, crudely, my car?s performance should be handicapped, in effect, by the absence of .006(HP) = .006(325 HP) = 1.95 HP [(= RWHP of 1.56 = .8(1.95 HP)].

The values below show my car?s Pro RR-measured average RWHP for each of the given density altitudes (DA). The range of these values approximates the range mentioned .above.

..............Average
...DA........RWHP
1695.0.....243.3
1554.4.....239.3
1516.0.....244.8
1509.3.....240.0
1415.4.....248.0
1239.0.....244.1

The average of the RWHP values associated with the density altitudes averaging close to 1360? [(1415.4 + 1239.0) / 2 = 1327.2?] is 246.05, while the average of the RWHP values associated with the density altitudes averaging close to 1600? [(1695 + 1554.4 + 1516.0 + 1509.3) / 4 = 1568.7] is 241.85. The difference between the two averages is 4.2?which is closer to 1.56 than to 9.36 (i.e., 4.2 ? 1.56 = 2.64, while 9.36 ? 4.2 = 5.16).

The above observations suggest that the more reasonable answer to the question raised above is .006. In turn, this conclusion suggests that adjusting for 25% of a density altitude adjustment is more reasonable than adjusting for 100% of the adjustment.

From an overall perspective, what seems to be implied, for my car, is finding the percentage of the 1360? density-altitude adjustment that yields a RWHP decrease of 4.2 RWHP. Trial and error reveals that 42% yields a decrease of 4.28 RWHP?which actually is as close as one can get using the tables. The density altitude yielding this decrease is 1499.2 = -.42(1600 -1360) + 1600.

I believe that the above procedure is appropriate for use on my car. But, I am uncertain about whether it applies to the cars of others running especially at greatly differening altitudes. On the other hand, I would bet that using my procedure on other cars, etc., at least would improve accuracy. Also, I would bet that the use of my procedure could not hurt accuracy appreciably since the average results produced should differ very little from what 100% adjustment yields--i.e., my 40%-adjustment values compared to my 100%-adjustment values for the 1/4 are as follows.

........................100%........42%
1/4 Time..........13.592.....13.572 (difference .02)
1/4 Speed......104.046....104.077 (difference .31)

Thus, the advantage of my procedure does not subsist in it effects of averages, but rather in its effects on the identification of superior passes. Using the 25% adjustment caused some rearrangement, and minor changes in times/speeds, for my superior passes. I am not yet sure if the 40% adjustment will have the same effects.

Ultra conservatism is implied by using 100% adjustment. However, as shown above, the effect of doing so is not likely to be significant.

Originally Posted by cobradav' post='261963' date='Mar 29 2006, 12:45 PM

I'm sorry I do not have time to do any of my own analysis on these first runs, but I have three upcoming launches I am working requirements on and just cannot afford the time right now. Hence I could not even put these into tabular form - just a snap shot.

I believe my weight to be off. Vehicle is only 22 pounds lighter than 545 per unladen weight in BMW specs so I believe I need to increase weight.

Also think pitch is too high. I believe this suspension could easily be a 1.8 or 1.9.

After some experimentation I determined my best runs were DSC OFF and in Steptronic (Manual Mode) starting in M1 and letting it auto shift at Redline. ANy attempts with D or DS were far slower

Wx
Temp = 67 degrees
DewPt = 49 degrees
Wind Sp = 1 MPH
Bar = 30.32" or 1026.7mb
Height = 20 feet
Hate to hit and run but gotta go.