Brought to you in part by:

.

Shop Eastwood for your Auto Restoration Needs!


  Mustangsandmore Forums
  Ford Racing
  Just want to get something straight.

Post New Topic  Post A Reply
profile | register | preferences | faq | search

UBBFriend: Email This Page to Someone! next newest topic | next oldest topic
Author Topic:   Just want to get something straight.
70coupe
Gearhead

Posts: 277
From: Toronto,Ontario,Canada
Registered: Aug 2000

posted 09-09-2002 10:01 PM     Click Here to See the Profile for 70coupe     Edit/Delete Message   Reply w/Quote
Standard pressure is 29.92" of mercury. When the pressure rises (ie.30.00") higher pressure,does this slow down or speed up your ET. I was under the impression the higher the barometer the higher the pressure the better the air? Do I have this backwards?

IP: Logged

Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 09-09-2002 10:12 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
You are correct.

------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA/MCA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl

Quote: "I never met a magazine mechanic I liked."

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 09-09-2002 11:33 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Yep,

Of course he's right. Higher barometer equals denser air which means more oxygen molecules in the air.
Lower humidity also equals more oxygen in the air(less water vapor), and lastly lower temp means more air density/more oxygen per cfm of air.

SteveW

IP: Logged

Big D
Gearhead

Posts: 3286
From: WELLS, NEVADA
Registered: Nov 2000

posted 09-10-2002 01:15 AM     Click Here to See the Profile for Big D   Click Here to Email Big D     Edit/Delete Message   Reply w/Quote

Are you sure Professor Steve...

Don

IP: Logged

kid vishus
Gearhead

Posts: 3894
From: middle of NC
Registered: Oct 2000

posted 09-10-2002 11:07 AM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
Aad the best is high barometer, low temperature, and low humidity all at the same time.

yeah, like that happens in the summer. But that's what the fall is for.

IP: Logged

TomP
Gearhead

Posts: 4637
From: Delta BC Canada
Registered: Dec 99

posted 09-10-2002 12:21 PM     Click Here to See the Profile for TomP   Click Here to Email TomP     Edit/Delete Message   Reply w/Quote
i dunno about that low humidity one... my car has always run it's fastest in cool fog... 100% humidity.

We've had air 1000-1500ft below sea level on those occasions.

IP: Logged

Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 09-10-2002 12:37 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
You don't count Tomp! You are Canadian!
You guys also have a "metric" humidity level.

------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA/MCA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
Professional Manwhore
The Barry of BarrysGrrl

Quote: "I never met a magazine mechanic I liked."

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 09-10-2002 01:06 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Tom,

I guess you can only have two out of three up north. If you could get all three factors right you'd be in -2000' da.

SteveW

IP: Logged

70coupe
Gearhead

Posts: 277
From: Toronto,Ontario,Canada
Registered: Aug 2000

posted 09-10-2002 03:18 PM     Click Here to See the Profile for 70coupe     Edit/Delete Message   Reply w/Quote
So,if our track elevation is 600' and the barometer is 29.92" (not factoring in humidity and temp) then the altitude is 600'.
If the barometer goes to 30.02" then the corrected altitude is now 500'. Now that I have that straight. How do we factor in temp and humidity? I did a search but I'm still not completely comfortable. Anyone want to try. Maybe would could make a table that could be printed out for the track for those of us not wanting to pay $500 for a meter.
29.82" = 700
29.92" = 600
30.02" = 500
30.12" = 400
or is there a simple factor that you can multiply or divide the temp and humidity by?

[This message has been edited by 70coupe (edited 09-10-2002).]

IP: Logged

kid vishus
Gearhead

Posts: 3894
From: middle of NC
Registered: Oct 2000

posted 09-10-2002 03:31 PM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
I dont know. I bought a used ET predictor a few yrs back that does all that for me. It was $250 and works pretty dang good.

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 09-10-2002 04:23 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Here's my old thread before I broke down and bought a weather station.

https://mustangsandmore.com/ubb/Forum12/HTML/002531.html

SteveW

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 09-10-2002 04:28 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
From my old thread,

Air Density and Performance (Courtesy: Roger Copeland)

The Standard Day (SAE test standard J1349): 100% Air Density Temperature: 60 deg. F Humidity: 0% Barometer: 29.92

Barometer
Barometer readings have a linear effect on air density. If the barometer goes up or down 1% from the standard reading, so will air density.
Example:
30.22 (New) ? 29.92 (Std.Day) = 1.01 or 101% 29.62 (New) ? 29.92 (Std.Day) = .989 or 98.9% (Round up to 99%) A barometer of 30.22" gets you to 101% air density, 29.62" nets to 99%, etc.

Each 5 deg. F change in temperature (away from 60 deg. F), you get about a 1% change in air density. An 80 deg. F day means 96% air density, and a 40 deg. F day means 104% air density.

Temperature goes up... The air gets thinner. Temperature goes down...Air gets thicker.

(Air Density) This is not linear, but it's close enough for racing considerations.

Ever notice how much better an engine runs on a cool damp day?

At 60 degrees, jumping from zero to 50% humidity will cost you roughly 1% in air density. That same 50% humidity at 90 degrees will cost you more than 2% in air density. The reason for this is that it requires much more water vapor to get you to 50% humidity at 90 degrees than it does at 60 degrees, since air can hold more water as it's heated.

"Relative humidity" is expressed as a percentage of water in the air compared to how much it can hold at a given temperature. All 3 figures need to be considered. A 50 degree day with 50% humidity and a 29.62" barometer nets you to just about 100% air density, since the 2% you pick up in temperature is offset by the losses from the barometer drop of 1% and the humidity loss of 1%.

Power
Figure around 75-80% power change compared to the air density change. An 8% drop in air density will cost you about 6% in power.

Barometric changes give you about a 1.2:1 change in power.
Temperature changes give you about .7:1 change in power.
Humidity is about 1-1 change in power.

SteveW

IP: Logged

70coupe
Gearhead

Posts: 277
From: Toronto,Ontario,Canada
Registered: Aug 2000

posted 09-10-2002 08:57 PM     Click Here to See the Profile for 70coupe     Edit/Delete Message   Reply w/Quote
Hey Steve, I just spent the last 3 hrs making up a spreadsheet for the track. I used that link that you had posted. It should work as well as a computer but a little slower. Oh well, not like you dont have enought time sitting around at the track to figure out a few calculations.

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 09-10-2002 09:02 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Very cool!

Can you post it? Or e-mail it to SteveL for publishing as an article?

SteveW

IP: Logged

70coupe
Gearhead

Posts: 277
From: Toronto,Ontario,Canada
Registered: Aug 2000

posted 09-10-2002 10:10 PM     Click Here to See the Profile for 70coupe     Edit/Delete Message   Reply w/Quote
After all the help you guys have given me,no problem! I'll take it to work tomorrow and scan it. Then I'll try to post it or email it to you. I've got every other degree from 61 to 79F done so far but will do more over the next few days.

------------------
351c 4v clsd heads
60'1.619
1/8 [email protected]
1/4 [email protected]

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 09-10-2002 10:22 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
Great Brian,

Got your e-mail, what program is it written on? Maybe I can open it at work tomorrow.

SteveW

IP: Logged

70coupe
Gearhead

Posts: 277
From: Toronto,Ontario,Canada
Registered: Aug 2000

posted 09-10-2002 10:23 PM     Click Here to See the Profile for 70coupe     Edit/Delete Message   Reply w/Quote
It a program called Ability Office 2000. Its not a very popular spreadsheet. Let me know becuase I will still scan it at work tomorrow.
Brian

IP: Logged

steve'66
Gearhead

Posts: 5659
From: Sonoma,CA,USA
Registered: Mar 2000

posted 09-10-2002 11:34 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by 70coupe:
It a program called Ability Office 2000. Its not a very popular spreadsheet. Let me know becuase I will still scan it at work tomorrow.
Brian

OK,

Please do, I'll forward it to our leader.

SteveW

IP: Logged

Ryan Wilke
Gearhead

Posts: 1115
From: Stanton, Michigan 49707
Registered: Oct 2000

posted 09-11-2002 09:18 AM     Click Here to See the Profile for Ryan Wilke   Click Here to Email Ryan Wilke     Edit/Delete Message   Reply w/Quote
How do these conditions sound to everyone????

Today's Forcast:
Mostly Sunny. Barometric 30.05" & rising.
@ 4pm, 72F @ 45%RH.
@ 8pm, 63F @ 66%RH.

Do ya think I'll be at Test n' Tune tonite???

IP: Logged

Ryan Wilke
Gearhead

Posts: 1115
From: Stanton, Michigan 49707
Registered: Oct 2000

posted 09-12-2002 05:07 PM     Click Here to See the Profile for Ryan Wilke   Click Here to Email Ryan Wilke     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Ryan Wilke:
...these conditions.....Do ya think I'll be at Test n' Tune tonite???

Folks were running hard last night!! ...I saw a BBC '68 Chevelle pull the biggest wheelstand I've ever seen,,,I'm saying over 5ft high!! You could see the whole fuel tank! The 're-entry' resulted in blowing out a front shock mount and pan-caking the oil pan (while goughing a hole in the track!) but after returning to tera-firma, he got back on 'er and ran a 10.68... ...I talked to the fella after; he said it normally lifts 1-2ft,he stays on 'er without any problems. But he's never had it go THAT high before! Too Bad no one got a pic of it!!!!

IP: Logged

TomP
Gearhead

Posts: 4637
From: Delta BC Canada
Registered: Dec 99

posted 09-12-2002 08:09 PM     Click Here to See the Profile for TomP   Click Here to Email TomP     Edit/Delete Message   Reply w/Quote
A pet peeve of mine

Nobody ever gets pictures when i do decent wheelies... and somehow i manage to miss getting shots of anybody elses

IP: Logged

All times are ET (US)

next newest topic | next oldest topic

Administrative Options: Close Topic | Archive/Move | Delete Topic
Post New Topic  Post A Reply
Hop to:

Contact Us | Mustangsandmore Front Page

Copyright 2003, Steve LaRiviere. All Rights Reserved.


Ultimate Bulletin Board 5.47d

Amazon Honor System Click Here to Pay Learn More

[The M&M Gearhead Gear Store]

[Build a free Mustangsandmore.ws Home Page!]

[About M&M][Acronyms][Calendar][Chat][Classifieds] [Links] [Members' Pics] [M&M Mug Shots] [Tech] [ Mustangsandmore.com Bookstore] [Advertise on Mustangsandmore.com] [Mustangsandmore.com T-Shirts]