Date: Sun, 25 Nov 2007 15:29:16 -0800
Reply-To: Michael Elliott <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Elliott <camping.elliott@GMAIL.COM>
Subject: Re: Calculate fuel consumption when idling?
In-Reply-To: <008301c82f86$672e7480$0a00a8c0@OWNERMIKE>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Well, ya stumped me on this one. I have no idea whether this means that my
engine would consume more fuel than I calculated, or less.
--
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 9:12 AM Mike wrote:
> 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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