Pete's 1/4 times: 3.45@GLD vs. 4.10@BG

[Paul Workman]

Just an observation:

Pete (in the electric water pump thread) provided his 11.04 & 11.09 sec times at GLD (Great Lakes Dragway) were with his 3.45 ratio differential. And, if I recall correctly, Pete ran an 11.0 "something" (Pete pls correct me) at BG with the 4.10 gear.

Well, the thing that leaps out at me is the ETs were practically the same, yet the weather and gear circumstances were signifcantly different.

Just trying to get a feeling for the effect the weather conditons might have had on Pete's horsepower, I took the liberty of estimating the conditons for each the GLD and BG runs and plugged them into one of the popular calculators (http://wahiduddin.net/calc/calc_hp_dp.htm), typical of the kind used on dynos.

Using the following:

GLD:

altitude = 600 ft AMSL
temp = 40F
Hg = 29.0
Dew Pt = 30F

Relative HP = 100%
DA = 615'

For BG:

altitude = 547 ft AMSL (at the airport)
temp = 80F
Hg = 29.0
Dew Pt = 60F

Relative HP = 94.4%
DA = 3306'


SO! Relative to the discussion about the difference between quarter mile times with a 3.45 vs. a 4.10 gear (which comes around more times here than a carousel pony), it would appear Pete's 4.10 gear overcame a 5.6% effective HP loss (due to conditions).

OK, one datum (BG) does not a trend make, but isn't it interesting that the ETs were so close - hell, practically the same - when Pete's motor was producing something like 27* rwhp LESS at BG than it did at GLC.

Some claim little or no practical ET difference between the 3.45 vs. the 4.10 gear in the quarter; usually centering around loss due to the extra shift. The debate will go on I'm sure. But, these results of Pete's intrigues me. All things are held as close to common as possible, far as car and driver experience goes. Yet the ETs are pratically the same in spite of significant differences in conditions at the track. It suggests there IS a difference - a difference in favor of the 4.10s, - just like Bob G (aka Gillig Racing) recommends for the 350 ci ZR-1s.

Yeah, bench racing... But, what the heck...It's snowing outside, and I'm having ZR-1 withdrawals!!

P.

[efnfast]

Thanks Paul, that was great. You also helped me out, being a novice, what all the abbreviations were, except "DA"? Reading the post on the electric water pump I was getting pretty lost. Now I feel better, and learned something.:dontknow:

Steve

[Aurora40]

BG seems to be "different". I've run 115-116mph there before several times, on days that were 90F+, and the DA was measured at over 3000'.

I have never run that fast locally, even on days that were like 50F. BG has always seemed to me to be a "fast" track. I don't think the weather completely explains it.

[Pete]

Paul,the run @ Bg was 11.1 i also ran a bit less MPH.

Here's BG video
http://www.youtube.com/watch?v=ZlRIOMwaDYY

Pete

[bdw18_123]

... You also helped me out, being a novice, what all the abbreviations were, except "DA"? ...

"DA" is Density Altitude. From Wikipedia:

Density altitude is the altitude (http://en.wikipedia.org/wiki/Altitude) in the International Standard Atmosphere (http://en.wikipedia.org/wiki/International_Standard_Atmosphere) at which the air density (http://en.wikipedia.org/wiki/Density_of_air) would be equal to the actual air density at the place of observation, or, in other words, the height when measured in terms of the density of the air rather than the distance from the ground. "Density Altitude" is the pressure altitude (http://en.wikipedia.org/wiki/Pressure_altitude) adjusted for non-standard temperature.
Both an increase in temperature (http://en.wikipedia.org/wiki/Temperature) and, to a much lesser degree, humidity (http://en.wikipedia.org/wiki/Humidity) will cause an increase in density altitude. Thus, in hot and humid conditions, the density altitude at a particular location may be significantly higher than the true altitude.

[efnfast]

Thanks BDW :handshak: