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Old 08-21-2007, 08:20 AM
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bwilson4web bwilson4web is online now
Engineering first
 
Real Name: Bob
Location: Huntsville, AL
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Wink Re: AC vs windows open mileage test

Hi,
Quote:
Originally Posted by fernando_g View Post
Pardon my ignorance Bob; but I've got two questions:

1) What are the units for g/sec? Grams/second?
2) How do you correlate air flow to fuel consumption? I think I know, to maintain a stochiometric ratio a higher air flow means also a higher fuel flow. Am I correct?
Sorry, I'm often so buried in the technology I often forget to 'speak human.'

Air flow is in grams per second based upon a sensor located just in front of the throttle plate. It is a critical part of injector timing to maintain a stochimoetric, 14.7 to 1, air to fuel ratio.

Take the air flow in grams per second and divide by 14.7 and you'll get the fuel flow rate in grams/second. However, this typically becomes a pretty small number:

2.00 g/sec -> 0.136 grams of fuel / second
2.45 g/sec -> 0.167 grams of fuel / second

When I posted the air flow I realized that it is technically more correct to post the fuel rate but it is often harder to visualize the difference between 0.136 and 0.167. So I used the source data, the air flow rate, which by inspection shows a 20% increase: 0.20 -> 10% of 2.00, thus 0.45 ~> 20% increase over 2.00. But it was somewhat sloppy engineering not to show the exact units and explain the relationship between air and gas flow.

Bob Wilson

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