Normalizing ET's
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Normalizing ET's
This is a tech question, so I'll ask it here.
When figuring out your ET's and MPH's in the 1/4, you take into account...
1) Barometric Pressure
2) Temperature
3) Humidity
4) Elevation above sea level
right?
If so , how much does sea level change things? I mean, I realize that in Colorado where it's 5300 + feet it's a big change, but what about 50-350 ft. above sea level....would you encounter much of a change between 50 and 350?
Is there a formula to add the variables into?
Just trying to learn, and this is the place...
[Modified by black_89_vette, 3:44 PM 8/22/2003]
When figuring out your ET's and MPH's in the 1/4, you take into account...
1) Barometric Pressure
2) Temperature
3) Humidity
4) Elevation above sea level
right?
If so , how much does sea level change things? I mean, I realize that in Colorado where it's 5300 + feet it's a big change, but what about 50-350 ft. above sea level....would you encounter much of a change between 50 and 350?
Is there a formula to add the variables into?
Just trying to learn, and this is the place...
[Modified by black_89_vette, 3:44 PM 8/22/2003]
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Normalizing ET's (black_89_vette)
The three weather important parameters are:
-baro
-temp
-RH
There are equations on my site to normalize ET & trap speed for baro & temp. There are also equations to calculate effective chp from trap speed. This is nice for comparing runs from week to week to see results of mods.
For RH you can subtract about .050-.060 sec to the ET for each 10deg F above 40% RH. Since .1sec ET change is about 10hp you could subtract 5-6hp for each 10% rise in RH.
Elevation realy dosn't matter as the effects of the "thinner air" are accounted for in lower baro readings as elevation increases.
I've noticed another factor not accounted for in these corrections; namely coolant temp. My trap speed and ET also depend on coolant temp, i.e. they get worse as coolant temp goes up from 160deg F.
-baro
-temp
-RH
There are equations on my site to normalize ET & trap speed for baro & temp. There are also equations to calculate effective chp from trap speed. This is nice for comparing runs from week to week to see results of mods.
For RH you can subtract about .050-.060 sec to the ET for each 10deg F above 40% RH. Since .1sec ET change is about 10hp you could subtract 5-6hp for each 10% rise in RH.
Elevation realy dosn't matter as the effects of the "thinner air" are accounted for in lower baro readings as elevation increases.
I've noticed another factor not accounted for in these corrections; namely coolant temp. My trap speed and ET also depend on coolant temp, i.e. they get worse as coolant temp goes up from 160deg F.
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
Likes: 6
From: Winchester Ontario
Re: Normalizing ET's (65Z01)
Ok, for temp you are reading it in terms of F, but what about your barometric pressures? What unit is that in? kPa?
By your calculations, it appears that your ET on time slip will always be lower than normalized ET. I figured that since the day I went , it was 90 F and like around 55-60 % RH (If I remember correctly) that my normalized time would be lower.
I must have some calcs wrong.
By your calculations, it appears that your ET on time slip will always be lower than normalized ET. I figured that since the day I went , it was 90 F and like around 55-60 % RH (If I remember correctly) that my normalized time would be lower.
I must have some calcs wrong.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Normalizing ET's (black_89_vette)
Sorry, baro in those equations is in in-Hg.
When you look at those equations you can see where the "normal" values are set.
If you look at my mods results you will see actual time slip data and normalized data.
Usually, at least in summer, normalized data is better than actual data. But in early spring and late fall I've made some passes with much better numbers than normalized data.
You can see in my sig below that the normalized data wasn't as good as the actual numbers; that was because on that evening we had crisp air combined with a killer baro (near 31 in-Hg, I believe).
[Modified by 65Z01, 5:01 PM 8/22/2003]
When you look at those equations you can see where the "normal" values are set.
If you look at my mods results you will see actual time slip data and normalized data.
Usually, at least in summer, normalized data is better than actual data. But in early spring and late fall I've made some passes with much better numbers than normalized data.
You can see in my sig below that the normalized data wasn't as good as the actual numbers; that was because on that evening we had crisp air combined with a killer baro (near 31 in-Hg, I believe).
[Modified by 65Z01, 5:01 PM 8/22/2003]
