grogan545

Great to here from you jim.The chart that Znod refered you to says it all.At your altitude(4000') there is about a 5% correction in both time & speed in the 1/4 mile.In other words if you had a time of 14.00 secs in the 1/4 it would correct to 13.31 secs at sea level.Quite a difference.The NHRA monitors temp,pressure,humidity and comes up with an equivilent altitude.In other words if your actual altitude is 1500',but because of high temp and high humidity and low barometer reading your equivilent altitude may be 3500'.You would look at the chart and apply the factor for 3500' to your speed & times.

DD694

So, ZNOD needs to go back and review historical data for barometric pressure on the days he ran previous tests. Maybe the speed anomolies are barometric pressure related and have nothing to do with CIP change. Learning could still be a factor.

znod

Hi g-man:

Thanks.

I guess I never discussed altitude before just to keep things simple. But, when the issue came up today, I looked at the NHRA chart and realized that its adjustments would make a significant-looking difference in my times speeds. The way I understand the NHRA chart is that straight adjustment would yield times and speeds as though all other factors, such as temp, humidity, etc., are held constant. Thus, if we both adjusted using just this chart, then there still could be unaccounted for differences--e.g., temp, humidity, etc. To some extent, the unadjusted factors might or might not tend to cancel out. For example, your recent tests have been done when colder than here, but my humidiy is likely have been lower--thus, producing a cancellation effect.

But, you mention above that "the NHRA monitors temp,pressure,humidity and comes up with an equivilent altitude.In other words if your actual altitude is 1500',but because of high temp and high humidity and low barometer reading your equivilent altitude may be 3500'.You would look at the chart and apply the factor for 3500' to your speed & times." Is the "equivalent altitude" value, the same as what SMOKEmUP refers to as "density altitude?"

In this regard, where do you get the adjustments for equivalent altitudes?--at the dragstrip?--by paying the membership price at SMOKEmUP? And, once adjusted to sea level, what would the implicit values for the other factors, such as temp and humidity, be?--e.g., 60F and 20% humidity. If our other factors were similar to the NHRA standards for them, then it looks like we could avoid the equivalent altitude adjustments.

Here is another question that gets at what I am interested in knowing. Under what conditions, or sets of conditions, would the NHRA indicate that no adjustment to equivalent altitude is needed? Also, I know at least one big three US auto mag makes adjustments. I am going to try to figure out what they all do--probably with no luck on all though.

I don't guess the NHRA has an octane adjustment too, huh?

znod

Thanks E60VTA. But, note that I have been reporting on tests where I held virtually everything constant except first the CIP change and second the mods change. Normally, one would not have much luck holding the weather constant, but the weather has been essentially constant in Phoenix for many days--including the period of time after the CIP change. Also, I did tests a few days before, including the day before, and a few days after, including the day after the CIP change. Same with the mods change.

znod

g-man and all:

I registered for SMOKEmUP and paid for 3 mos. of calculator usage. I am getting my answers now. So, far I have been able to find hourly weather data for Phoenix for today. Using the 3:00 a.m. values, which should be similar for the whole month, my density altitude would be about 1429 rather than 1500. I have not been able to find hourly data for, say, the last month, but I imagine I will find it soon. Still researching, but this is my busy work day.

grogan545

Hi Znod
You are correct with your analysis of the "equivilent" altitude.Your actual altitude has a minimal input as to your times.When I was at the drag strip last July the "equivilent" altitude was 3750" even though the actual altitude was only about 300'.For now I am going to ignore corrections until i can verify what actual conditions are while testing.All I can say now is it is cold with low humidity and an average barometer reading.

NOW FOR THE BIG NEWS.I HAVE DONE IT ZMAN CHECK OUT THESE NUMBERS !!!!!!!!!
...........................run 1(N)...............run 2(S)...............ave
0-10..................... .27....................... .30...................... .285
0-20..................... .90....................... .95...................... .925
0-30..................... 1.58..................... 1.62.................... 1.60
0-40..................... 2.68..................... 2.75.................... 2.715
0-50..................... 3.65..................... 3.75.................... 3.70
0-60..................... 4.80..................... 4.98.................... 4.89
0-70..................... 6.32..................... 6.53.................... 6.425
0-80..................... 7.85..................... 8.07.................... 7.96
0-90..................... 9.50..................... 9.83.................... 9.665
1/8 time................8.60..................... 8.70..................... 8.65
1/8 speed............ 83.1..................... 82.2......................82.65
60'...................... 1.92..................... 1.97....................... 1.945
330'.................... 5.60..................... 5.67....................... 5.635
1000'.................. 11.13................... 11.30...................... 11.215
HP..................... 368 @ 57 mph....... 360 @ 57 mph......... 364 @ 57 mph
1/4(grogans form) 13.26.................... 13.42..................... 13.34
estimated spd 1/4. 105.5................... 104........................ 104.75
Temp was 26F,humidity about 35%.All runs with controls on and in D.Shift points appear to be at 6500 rpm

I am now thoroughly convinced of my method I believe I can get the "super start" 2 out of 3 tries.I really believe you should work on my method .I know it is discouraging when it doesn't work but with patience I think it will work for you.The most important thing is to go to full throttle in a "SLOW"manner.This is harder than it sounds because the tendency is to mash the throttle when you let off the brake.This will cause the controls to overreact and cause the car to bog and hesitate(5.4 0-60 for me).

Bokke

Gman - great numbers!

You are so correct about applying the throttle.....I really struggle with this and I tend to mash it and then I get wheel spin an there goes the run.....although I do think it's a little harder with a manual, but once perfected I hope to get times similar to yours.....

Cheers,

znod

You really did do it. Way to go!!!!! All three of your 1/8's are better than my original three 8.71's (uncorrected) and the same, of course, with your 0 to 60's. I am very confident in your forumula so I think your 1/4 mi predictions would be right on. Did you actually get to 100? I assume so since you do not imply otherwise.

I will try your method--first in DS I suppose. I doubt that I will improve my actual times anymore without colder weather. If the weather gets colder, then I probably will do what I have been doing or mix things up. I suspect that I will start adjusting for weather and altitude since I want my runs to be comparable. Otherwise, when summer arrives, there would be no point to testing in Phoenix at all.

And, again, congratulations on doing what no one, as far as we know, has done.

Oh, and did you see my post #165? And, if you can get approximate dew point and barometric pressure (i.e., altimeter setting), then please give them to me along with their units of measure.

Bokke

Perhaps we should have a separate "best results" thread, so that everyone will see his numbers without going all the way to page 12.

They are pretty impressive

znod

I'll start a thread like that. Give me a while though. I think we are about to embark on a new era--adjusting for weather and altitude. You might check with the data I asked grogan for above. Whenever you do runs, then I could provide you with the pertinent adjustment factors, and we can post both adjusted and unadjusted data both here and on the new thread.