Date: Sun, 25 Nov 2007 12:12:48 -0500
Reply-To: Mike <mbucchino@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike <mbucchino@CHARTER.NET>
Subject: Re: Calculate fuel consumption when idling?
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The flaw here is that no naturally-aspirated engine has 100% volumetric
efficiency. So, you'd have to factor the actual VE, which is probably about
as low as it ever could be while running at idle. (Even a super- or
turbo-charged engine has no boost at idle.)
Mike B.
----- Original Message -----
From: "Michael Elliott" <camping.elliott@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, November 25, 2007 11:01 AM
Subject: Re: Calculate fuel consumption when idling?
> Hmmm.
>
> Each piston will still suck in 475 cc of air/fuel per intake cycle. But
> instead of the air being at normal atmospheric pressure, it sucks on the
> intake manifold/plenum, which is at around 11'' Hg of vacuum, or 11'' Hg
> less than the outside air pressure (Bentley's does not come right out and
> say that 11'' Hg is the normal vacuum inside the plenum but it can be
> inferred from from several of their measurement procedures). Mean sea
> level pressure is about 30'' Hg, so the plenum contains 19'' Hg of
> pressure, which is about the same as being at 12,000 feet elevation
> according to the online Density Altitude Calculator at
> http://wahiduddin.net/calc/calc_da.htm -- if I'm using it right. 70F,
> 30''Hg altimeter setting, 40F dew point.
>
> Under these conditions, air density is 62% of sea level air. So my Junior
> Engineer's cocktail napkin result of 1.6 gallons per hour of fuel
> consumption when idling (below) needs to be reduced to 1 gallon per hour.
>
>
> --
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> KG6RCR
>
>
>
> On 11/25/2007 12:06 AM John Connolly, Aircooled.Net wrote:
>
>> but we have a throttle limiting the amt of air entering the engine
>> (unless
>> you have a diesel).
>>
>> John
>> Aircooled.Net Inc.
>>
>> ----- Original Message -----
>> From: "mike elliott" <camping.elliott@GMAIL.COM>
>> To: <vanagon@GERRY.VANAGON.COM>
>> Sent: Saturday, November 24, 2007 5:26 PM
>> Subject: Re: Calculate fuel consumption when idling?
>>
>>
>>> Do you win? Heck, I don't know. I'll take a shot at it. Watch me get
>>> it spectacularly wrong.
>>>
>>> The 1.9L engine has 475cc displacement per cylinder. I think two
>>> cylinders fire per revolution, so at 900 rpm we got 900 x 2 x 475 =
>>> 855cc of air per minute being sucked into the engine. If the mixture
>>> is a good stoichiometric one, we'd have about a 1:15 fuel:air mass
>>> ratio. Air has a mass of 1.3g per liter, so that's .855 x 1.3 = 1.1kg
>>> of air per minute, with being one-fifteenth of that, or 74g per
>>> minute. At 60 minutes that's 4.4kg of fuel. Gasoline masses roughly
>>> 740 grams per /liter, so that's 6 liters, roughly 1.6 gallons U.S. per
>>> hour.
>>>
>>> Those are the numbers I come up with and I bet they're within an order
>>> of magnitude of being right.
>>>
>>> Mike "Rocket J Squirrel" Elliott
>>>
>>> On Nov 24, 2007 3:52 PM, Matthew Snook <matt@snooksband.com> wrote:
>>>> 0.9375? Is that right? Do I win?
>>>>
>>>> :)
>>>>
>>>> At 60mph, mine's turning @ 3200rpm. It will burn 3 gallons doing that.
>> 3
>>>> gallons per hour at 3200rpm. But it idles at 1000rpm. So that comes
>>>> to
>>>> 0.9375 gallons per hour at 1000rpm. Of course there's no wind
>> resistance at
>>>> that speed, so maybe less...
>>>>
>>>> Matthew Snook (@ ~3000 ft)
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Michael Elliott
>>>> Subject: Calculate fuel consumption when idling?
>>>>
>>>> A properly-tuned 1.9L WBX engine would consume how many gallons of
>>>> gasoline per hour when idling at sea level? Would this be significantly
>>>> different at 6,000 feet?
>>>>
>>>>
>>> !DSPAM:4748b1c081151569112627!
>>>
>>>
>>
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