conversion question +

[Michael McBroom]

Todd King wrote:
> 
>      A couple of questions; a) what is the conversion for gal/hr to
>      pounds/hr for gasoline?

Whenever you want to convert from the volume of a substance to the mass
of that substance (or vice versa), you must know the density (or
specific gravity).  In the case of gasoline, according to one of my
references, the density of gasoline can vary from 0.66 to 0.69 gm/cm^3
(at STP).  Split the difference, and call it 0.675gm/cm^3.

I've worked out a conversion that will take one from ml/min to lb/hr,
which is handy when comparing Bosch to US injectors.  Dividing ml/min by
11.2 will give you lb/hr.  Conversely, multiplying lb/hr by 11.2 will
give you ml/min.  

In your case, you will need to arrive at the density of gasoline in US
units.  I figure it to be 0.675gm/cm^3 x 4546cm^3/gal x 1 lb/453.6gm =
6.765 lb/gal of gasoline, on average.  I'm sure someone else here will
have a chart listing the density of gasoline in US units.  I don't.  But
my calcs should be close.

The rest is easy.  Divide lb/hr by 6.765 to get gal/hr, multiply gal/hr
by 6.765 to get lb/hr.

>      b) Also, with the turbo cars we see a dramatic
>      rise in EGT during a 1/4 mile pass, with EGT typically rising to
>      1550-1700F by the end. Can anyone comment on the big picture here,
>      energy, phyics or otherwisewise, as to what is going on with turbo
>      engines and EGT at wot? I realize that the exh manifold up to the
>      turbine is at much higher pressure than for n.a., the turbine is
>      extracting energy from the exh flow, etc. but is this EGT rise
>      "necessary" for the turbo to keep up at wot/high compressor pressure
>      ratios/high flows, ie is the high EGT sort of indicative of the
>      potential energy "well" existing in the manifold, necessary for the
>      turbo to draw from to "keep up" with it's chores on the comprssor
>      side? Wow, I'm clear as mud here, right? :-)

First off, the spike in EGT you're seeing isn't because of what you've
theorized.  It's because at elevated boost conditions, your fuel system
is going lean on you.  Overly high O2 concentrations can superheat your
EGT, causing melted pistons and other wonderful byproducts.  I would
recommend that you go with larger injectors, additional injectors, or a
rising rate fuel pressure regulator to counteract the lean condition
your engine is experiencing.

Secondly, the exhaust side of the turbo should not be seeing
significantly high pressures.  High backpressures on the exhaust side of
a turbo *kill* performance.  If you're running a low restriction, or
open, exhaust, and a turbo that's been properly sized for your
application, high back pressures are most likely not your problem.

-- 
Best,

Michael McBroom

'87 745T 123k w/APC (batoutahell!)
'88 765T 154k 
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Graduate Student, Linguistics                         Author of 
Research Interest: Biological Origins       =McBroom's Camera Bluebook=
of Language                                     http://mcbrooms.com
California State University, Fullerton                        
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