Higher gear not always good for mpg?! - Fuelly Forums

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Old 05-16-2006, 07:54 PM   #1
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Higher gear not always good for mpg?!

Found this somewhere, I forget where:
"If you are at 35mph and in 5th gear (Around 1800RPM in the average car), you will actually be wasting more gas than if you were in 4th or even 3rd. Every car has a certain range where it gets the best fuel economy, and it is usually right before the secondary air system opens up (on newer FI secondary intake runnersor carburated secondary "power" venturis cars with more than one barrel). Most cars have secondaries that open around 2800-3500 RPM, and this lets more air, and thus, fuel into the engine. The best RPM to be at to achieve best fuel economy is at right below this point."

I don't have a scangauge...or even a tach, somebody feel like verifying, or hopefully discrediting this statement. I usually upshift from 1st or 2nd into 4th @ 20mph. I have a 4spd std.


Frank.



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Old 05-16-2006, 07:56 PM   #2
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I'll discredit it for

I'll discredit it for you...

Dan has tested and he tells me that no matter what the slower you go in 5th the better your gas mileage, even if you're madly lugging.

I've heard that also, and it's bull****, doesn't even make sense. And you definately do not have IABs on your car, so don't worrya bout this. I don't even see the logic in why higher rpms is better. I think Jangeo and metrompg have tested this also.
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Old 05-16-2006, 08:02 PM   #3
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*Sigh of relief* ..Anyone

*Sigh of relief* ..Anyone else?
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Old 05-16-2006, 08:08 PM   #4
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at constant speed, lowest

at constant speed, lowest engine speed in the highest gear is most efficient.

see -

mini experiment: rpm/gear choice VS MPG at constant speed
http://www.gassavers.org/forum_topic/rpm_gear_choice_vs_mpg_at_constant_speed.html

mpg vs. speed - metro graph
http://www.gassavers.org/forum_topic/mpg_vs_speed_metro.html

the jury is still out on the issue of best gear/RPM for most efficient acceleration however.
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Old 05-16-2006, 08:16 PM   #5
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Quote:the jury is still out

Quote:
the jury is still out on the issue of best gear/RPM for most efficient acceleration however.
This is why I need a scan gauge! First I'd have to switch to obd1 or obd2 though.
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Old 05-16-2006, 08:20 PM   #6
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OBD1 won't get you a

OBD1 won't get you a scangauge. An electronic VSS will get you a superMID though.
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Old 05-16-2006, 08:22 PM   #7
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How many pesos for the

How many pesos for the SuperMID? elec vss can be substituted easily?
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Old 05-16-2006, 08:27 PM   #8
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160 shipped from japan land,

160 shipped from japan land, it can be. However, you have Sucky Injection System, so I dunno how it'd work for you,
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Old 05-16-2006, 08:37 PM   #9
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I think the 91 ef already

I think the 91 ef already has elec vss, no? What are you thinking might be affected by dpfi?
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Old 05-16-2006, 08:41 PM   #10
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No, electronic began in 92,

No, electronic began in 92,

Anyway, the MID works by taking a 240cc (usually) injector pulse and multiplying it by four for total usage, but you've got weird size **** and two of them,
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