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Old 05-07-2008, 01:55 PM   #21
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1993: "I think gentle/moderate acceleration is ideal"

I think you're wasting fuel if you pulse with something other than a rather large throttle setting (as Pale suggested). But this should be in a high gear, so the acceleration will probably still be moderate. So maybe you're already doing this. After all, 'moderate' is a very subjective term.

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I imagine he'll speak up, but I think he modified his VX.
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Old 05-07-2008, 01:56 PM   #22
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gary: "The way I used a DVOM to measure fuel was to measure the resistance of the sending unit"

OK, very interesting, thanks for explaining. I never would have thought of that. You had to be very patient to collect all those calibration readings. And then when you take subsequent readings, you have to make sure the car is on a level surface, and you have to give the fuel a few moments to settle in the tank (stop sloshing around). I'm sure you know this.

Also, couldn't the float mechanism have some significant hysteresis? That is, it might not respond in a smooth, accurate way to small changes in level. If you drove a relatively short distance, and are therefore measuring a very small change in fuel level, then the error could be significant, I suppose.

Then again, when you did your calibration procedure, you may have observed the float responding in a smooth and sensitive manner. So I could be all wet!

Anyway, I wish there was simple, quick, accurate way to measure fuel level, on an ongoing basis. Waiting for the next fill takes too long, and it's also not very accurate (until you average a bunch of tanks together).

You probably realize the pros use a small bottle, and they weigh it, before and after. Too bad we can't do something like that.
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Old 05-07-2008, 02:16 PM   #23
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Another way would be to siphon fuel out of the tank in measured increments, with stable battery voltage (ignition off) . One of the problems I ran into was the fuel in the tank would gradually get hotter especially if the vehicle was sitting still, with no airflow to cool the tank. Over a couple of tripss the temp rose 15 degrees, which almost made the consumption 0 due to expansion.

It would be nice to have a means of determining consumption over very short periods of time. My guess would be to have a small "test" tank that was on a scale, maybe one or two gallons. Constand weight measurements could be easily converted to percentage of total volume, which would give precise consumption figures regardless of temp variations.

The downside is the possibility that the fuel could get much hotter quickly if you tank volume is low, but that does not seem to be an issue with people who run cars with low fuel levels in the tank.

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Old 05-07-2008, 02:17 PM   #24
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Quote:
Originally Posted by 1993CivicVX View Post
I think the RPM at which the no fuel cut off point is varies gear to gear. I thought it was around 1500RPM? Is it really as low as 1000?
yes, my scan gauge confirms 1K RPM. below that, the MPG drops quickly from 9999.
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Old 05-07-2008, 02:22 PM   #25
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I usually do 75-100% throttle in the highest gear possible without lugging or straining the transmission. So it's good to hear that that is best. Rather than the light acceleration I just offered. I'm always torn about which to do.
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Old 05-07-2008, 02:28 PM   #26
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Just don't go to full throttle. On mine, anything below about 90% is good. Above that, it goes into Open Loop and starts dumping fuel in.
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Old 05-07-2008, 02:43 PM   #27
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I think the best throttle percentage is 70-75 %. If you are using the highest practical gear you are filling the cylinders with that percentage, without getting fuel enrichment that comes in at higher percentages.

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