[s-cars] RE: Density altitude calculator

[Ulrich L. McKenzie]

Hey Hap,

Doesn't your fancy nancy flight computer have a density altitude function?
I know my old circular slide rule type did.  Now if only I could find it....

Searching for my old FC

Len

-----Original Message-----
From: s-car-list-admin at audifans.com
[mailto:s-car-list-admin at audifans.com]On Behalf Of mlp qwest
Sent: 10 October 2002 18:10
To: Mock, Bruce J (Bruce); Frank Amoroso; Michael Pederson (E-mail); Hap
Maguire Emerald '93 (E-mail)
Cc: s-car-list at audifans.com
Subject: [s-cars] RE: Density altitude calculator


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Now I think I remember some of this now.  Doesn't this have something to do
with the molecular weight of water (H20 - two hydrogen + one oxygen) being
very light, as a gas or vapor, by comparison to "dry" Nitrogen & O2, the
most common form oxygen takes in free atmosphere? i.e., I.e. Nitrogen, @ 72%
of air, in its common form as N2 has an atomic weight of @ 28; and O2 an
atomic weight of 32 vs. water's measly,by comparison, 18.  Ergo, humid air
is lighter, or better said, less dense than an equal volume of dry air at
the same temperature.

Now the conundrum, while injecting water may serve to lower the charge air
temperature due to water's "high specific heat capacity" and "latent heat of
evaporation" I guess it must also have the detrimental effect of lowering
the incoming air's overall density?  There must be a break even point where
the loss of density due to water vapor is over come by the drop in
temperature occasioned by the water's "latent heat of evaporation?"   One
other "source" points to water injections potentially further performance
deleterious effect of ".... absorbing a tremendous amount of heat from the
combustion reaction, helping cool the engine internally.... buffer the
combustion event... thus help{ing} regular pump gas behave much like
controlled burn high-octane racing gas."
http://www.se-r.net/about/200sx/scc/feb99/water_injection.html  ... maybe
not so much  a loss if your boost goals are aimed at running up to 3 bar (44
psi) of boost.  The SE-r project guys concluded their set up worked out "...
almost like having a tank full of race gas all the time except without the
$5 per gallon cost."

Sorry Bruce, still no formulae, but the closest I've seen to that are some
charts offered by Aquamist at
http://www.aquamist.co.uk/rescr/faq/airmass/airmass.html  with some maths
towards the bottom.  Please let me know who wins, temperature drop vs.
density reduction & heat absorption as a result of the liquid to vapor phase
changes in the combustion chamber  :-).

HTH

Mike "looking for Bob, Oh Bob Pastore, where are you" Pederson

BTW, $2.75 for Hawaiian Shirts?  You gotta be kidding me.
That seems awfully expensive


http://www.noswizard.com/water.php

http://aquatune.com/overview.html
  -----Original Message-----
  From: Mock, Bruce J (Bruce) [mailto:bmock at avaya.com]
  Sent: Thursday, October 10, 2002 1:53 PM
  To: Frank Amoroso; Michael Pederson (E-mail); Hap Maguire Emerald '93
(E-mail)
  Subject: RE: Density altitude calculator


  Frank -

  I agree  COLD, DRY air  - I still have that issue of European Car myself

  So Hap - What is the 'no hand waving allowed' explanation of why wet air
is better.   I know there IS something to be said for H2O injection...  but
why, Why, WHY!
  Give me some mathematical formulae baby!

  BTW - garish Hawaiian shirts???  I just picked a Hawaiian shirt up at
Target the other day...   Couldn't resist for $2.75 on Clearance - Now THAT
is garish!!!  :)

  Bruce
    -----Original Message-----
    From: Frank Amoroso [mailto:FAmoroso at svbank.com]
    Sent: Wednesday, October 09, 2002 5:17 PM
    To: Mock, Bruce J (Bruce); Michael Pederson (E-mail); Hap Maguire
Emerald '93 (E-mail)
    Subject: RE: Density altitude calculator


    Interesting site.



    I’m still not buying Hap’s humidity argument though. SAE paper J1349
that was reviewed, including altitude, temperature, and humidity correction
factor charts, in the 8/97 European Car, clearly states that lower
altitudes, lower temps, and lower humidity make the most factor.



    Even if there review is flawed, the tables show the correction factor
percentages (to get back to a standard number for comparison purposes)
increasing as you go up in altitude, temperatures, or humidity.



    What is the Society of Automotive Engineers missing?



    Frank--






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