Landracing Forum Home
October 19, 2017, 12:21:21 AM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with username, password and session length
News:
BACK TO LANDRACING.COM HOMEPAGE
 
   Home   Help Search Calendar Login Register  


(Note: Donations are not tax deductible)







Live Audio Streaming and Archives of Past Events
Next Live Event: TBD
Pages: [1] 2   Go Down
  Print  
Author Topic: what does DA: 5016ft mean?  (Read 2497 times)
0 Members and 1 Guest are viewing this topic.
mtiberio
Jr. Member
**
Offline Offline

Location: Arlington, VA
Posts: 38





Ignore
« on: May 25, 2017, 01:59:35 PM »

Its on my timing slip from last weekend
Logged

Every programmer occasionally, opens up a file on their computer. Sometimes they wrote it, or they found it and knew they had to save it. They read over the lines, and weep at their beauty. This file is Good Code. It has sensible names for functions and variables. It's concise. It has never had to answer to a sales team. It does exactly one thing, and it does it well. It reads like poetry.
Dynoroom
Global Moderator
Hero Member
***
Offline Offline

Age: 60
Location: Chino Hills, Ca.
Posts: 1975




« Reply #1 on: May 25, 2017, 02:01:34 PM »

That is the "Density Altitude" of the on site SCTA weather station. It is there to assist you in future tuning.
Logged

Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...
mtiberio
Jr. Member
**
Offline Offline

Location: Arlington, VA
Posts: 38





Ignore
« Reply #2 on: May 25, 2017, 02:15:12 PM »

I thought it had some relation to altitude, or air density, just couldn't figure it out from the value and units...

So when this goes up, the air density is down?

Better to know before the run, wouldn't you say?

m
Logged

Every programmer occasionally, opens up a file on their computer. Sometimes they wrote it, or they found it and knew they had to save it. They read over the lines, and weep at their beauty. This file is Good Code. It has sensible names for functions and variables. It's concise. It has never had to answer to a sales team. It does exactly one thing, and it does it well. It reads like poetry.
Peter Jack
Hero Member
*****
Online Online

Age: 74
Location: Calgary, Alberta
Posts: 3441





Ignore
« Reply #3 on: May 25, 2017, 03:34:09 PM »

Not necessarily. If you know the density altitude that the engine was tuned for and you know the actual when you run, you can then tune with that information for future runs.

Pete
Logged
Milwaukee Midget
Global Moderator
Hero Member
***
Offline Offline

Age: 57
Location: Beerhaven, Wisconsin
Posts: 5911


Bonneville I/GT record holder - 122.539 mph


WWW
« Reply #4 on: May 25, 2017, 09:54:05 PM »

It will vary startlingly during the day.  I've got runs logging anywhere from 5800 to 7200 feet.


Better to know before the run, wouldn't you say?


If you're able to make quick adjustments in line, post a team member over by the timing shack and just ask what the DA is.  We changed out jets on the Weber 3 times in one day in 2013.

If you're running EFI, for most systems, it's automatic, and not a big concern.

But it's a very useful tool with carbs, if you're looking for that last 1/10th.

Logged

"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!
mtiberio
Jr. Member
**
Offline Offline

Location: Arlington, VA
Posts: 38





Ignore
« Reply #5 on: May 26, 2017, 06:05:03 AM »

... post a team member over by the timing shack and just ask what the DA is.  We changed out jets on the Weber 3 times in one day...


good idea on getting the info from the shack before the run. so a 10% increase in altitude translate into a 10% smaller jet?

m
Logged

Every programmer occasionally, opens up a file on their computer. Sometimes they wrote it, or they found it and knew they had to save it. They read over the lines, and weep at their beauty. This file is Good Code. It has sensible names for functions and variables. It's concise. It has never had to answer to a sales team. It does exactly one thing, and it does it well. It reads like poetry.
jimmy six
Hero Member
*****
Offline Offline

Age: 73
Location: SoCal
Posts: 2479





Ignore
« Reply #6 on: May 30, 2017, 10:49:38 PM »

It means your going run shitty without a blower or fuel....
Logged

First GMC 6 powered Fuel roadster over 200, with 2 red hats. Pit crew for Patrick Tone's Super Stock #49 Camaro
RansomT
Sr. Member
****
Offline Offline

Age: 58
Location: Georgetown, KY
Posts: 457





Ignore
« Reply #7 on: May 31, 2017, 07:20:16 AM »

It means your going run shitty without a blower or fuel....

But you will push through the air easier....
Logged
GH
Sr. Member
****
Offline Offline

Age: 76
Location: Springfield, Missouri
Posts: 830





Ignore
« Reply #8 on: June 02, 2017, 08:42:37 PM »

I'm with JD, stick a blower or turbo on it.
Logged
Stainless1
Administrator
Hero Member
***
Offline Offline

Age: 66
Location: Wichita KS
Posts: 6421


Robert W. P. "Stainless" Steele Wichita, Kansas



« Reply #9 on: June 03, 2017, 07:59:42 AM »

While that seems like a poor DA for EM, it would be welcomed at Bonneville.

 
good idea on getting the info from the shack before the run. so a 10% increase in altitude translate into a 10% smaller jet?


It would be nice if it really worked that way, but I don't remember that ever working for us back in the carb days.  The way to do it is data.... lots of data written on charts.  I remember one day we changed jets 3 times in line at the salt. 
If you want a better DA, run earlier in the day  rolleyes
 cheers
Logged

Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
SPARKY
Global Moderator
Hero Member
***
Offline Offline

Age: 75
Location: Phoenix
Posts: 6235




« Reply #10 on: June 03, 2017, 08:06:42 AM »

"While that seems like a poor DA for EM, it would be welcomed at Bonneville"



Hear Yee! Hear Yee! Francis and I are now working on our air intake system to try to get rid of about 1000'of those DA---we are hopeful  that we are not the DAs .
« Last Edit: June 03, 2017, 08:11:00 AM by SPARKY » Logged

Miss LIBERTY,  changing TKI  to noise, dust and RUST!!!

The # 1 issue is: TO KEEP THE REPUBLIC      
   Center for Self Governance            tncsg.org     mrspowell.org

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller
Rex Schimmer
Hero Member
*****
Offline Offline

Age: 74
Location: Fulton, CA
Posts: 2117


Only time and money prevent completion!




Ignore
« Reply #11 on: June 15, 2017, 10:54:30 AM »

Stainless said: "If you want a better DA, run earlier in the day" and it is true that the cooler air will be more dense and you motor "should" make more power but the down side of the denser air is that it also will increases aero drag which many times can be greater than the hoped for horse power increase. We have all watched record runs in the early morning and the car will actually go slower than its qualifying run, could it be the denser air aero drag increase? Probably need some input from Woody here.

Rex
Logged

Rex

Not much matters and the rest doesn't matter at all.
Dynoroom
Global Moderator
Hero Member
***
Offline Offline

Age: 60
Location: Chino Hills, Ca.
Posts: 1975




« Reply #12 on: June 15, 2017, 11:14:52 AM »

To add another twist to what Rex is saying, as the day warms, the water table rises and the salt can become even more damp creating drag on the tires.
This of course depends on how wet the season has been before an event.
Logged

Michael LeFevers
Kugel and LeFevers Pontiac Firebird

Without Data You're Just Another Guy With An Opinion!

Racing is just a series of "Problem Solving" events that allow you to spend money & make noise...
jacksoni
Sr. Member
****
Offline Offline

Age: 73
Location: Annapolis, Maryland
Posts: 958




Ignore
« Reply #13 on: June 15, 2017, 11:21:37 AM »

Stainless said: "If you want a better DA, run earlier in the day" and it is true that the cooler air will be more dense and you motor "should" make more power but the down side of the denser air is that it also will increases aero drag which many times can be greater than the hoped for horse power increase. We have all watched record runs in the early morning and the car will actually go slower than its qualifying run, could it be the denser air aero drag increase? Probably need some input from Woody here.

Rex
I have seen this slower in the morning phenomenon many times and have considered Rex's explanation as the likely answer but Dynoroom's comment above also makes sense and adds to the puzzle- but would make things faster in the morning.  huh
Logged

Jack Iliff
 G/BGS-250.235 1987
 G/GC- 169.741  2009
 G/GMS-178.835 2010
Milwaukee Midget
Global Moderator
Hero Member
***
Offline Offline

Age: 57
Location: Beerhaven, Wisconsin
Posts: 5911


Bonneville I/GT record holder - 122.539 mph


WWW
« Reply #14 on: June 15, 2017, 12:20:20 PM »

I know my little brick ALWAYS ran faster in the thinner air of the afternoon, and that was normally aspirated.
Logged

"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!
Pages: [1] 2   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!


Google visited last this page September 21, 2017, 11:01:02 PM