Throttle Position During Acceleration and its effect on FE

[SVOboy]

<p><small><font face="Verdana,Arial">You'll get the best efficiency
around town by accelerating with full throttle, and shifting up to
the next gear quickly, before engine RPMs rise too high.</font></small></p>
<p><font size="2" face="verdana,arial">There are
two reason why this works. One is that the higher the gear, the lower
the frictional losses. By getting to 5th quickly, the total number
of engine revolutions is reduced, with a corresponding reduction in
frictional losses. The second reason is pumping losses. This is the
work done to force air past a partially closed throttle plate. The
more closed the throttle is, the higher the losses. Accelerating quickly
reduces throttle losses, because the throttle is open. In addition,
engine speed is lower in fifth, so to generate the same amount of
power, you have a larger throttle opening (and hence lower throttle
losses) - this is another reason to get to higher gears as quickly
as possible.</font></p>
<p><font size="2" face="verdana,arial">The best fuel economy is gained
by a combination of the gas petal to the floor with shifts at as low
an rpm as possible to sustain your desired acceleration. This ensures
a fully open throttle during the entire acceleration event and gets
you out of the lower gears as quickly as possible, for lower frictional
losses. It also gives you even more electric motor assist, as the
acceleration takes longer. There is only one problem with this technique
- its virtually impossible to do. You have to shift like a race car
driver, except that the shifts are at low rpm instead of high rpm.
You wind up going through gears like a maniac. It can be a lot of
fun, but you have to be really involved with driving (no cell phones)
and the technique is extremely counterintuitive. The combination of
mashing the accelerator and shifting at 2500 or 3000 rpm just doesn't
feel right. However, if someone is willing to practice this, they
can get a nice boost in FE around town.</font></p>
<p><small><font face="Verdana,Arial">After accelerating this way in
1st &amp; 2nd gears, you'll often be up to your desired cruising speeds.
Now it is time to switch modes, using as little energy as possible
to maintain this speed. Typically you'll now want to be in fifth gear.
The <strong>1-2-5 shift pattern</strong> (or 1-2-4 as the case may
be) may seem strange at first. After all, why are those other gears
there if you shouldn't use them? The answer is to think of them as
passing gears or cruising at slower speed gears. In most cases, this
is the way I use the five gears:</font></small></p>
<blockquote>
<p><small><font face="Verdana,Arial"><strong>1:</strong> Accelerating
gear<br />
<strong>2:</strong> Accelerating gear<br />
<strong>3:</strong> Even slower cruising / quick passing gear<br />
<strong>4:</strong> Slow cruising / slower passing gear<br />
<strong>5:</strong> Cruising gear</font></small></p>
</blockquote>
<p><small><font face="Verdana,Arial">Once you're up to speed, in addition
to quickly getting into your cruising gear, you'll also want to begin
feathering the throttle. Since you should have done all your acceleration
before going into cruising gear, you now want to use as light a throttle
as possible that will still maintain your current speed. If you find
that you want to accelerate further, you may be better to downshift
for a quick blip of acceleration, and then shift back into your cruising
gear.

</font></small></p><p>&nbsp;</p><p>&nbsp;Does this sound right? Am I crazy? Slam it to 50 mpg in second then shift into 5th? Huh? What? It is from insightcentral so they know their stuff, but really? <br /></p>

[diamondlarry]

I have heard of this technique before so I think you are probably on the right track. This is the technique that I normally use but have never thought to test the mileage differences between &quot;normal&quot; shifting and this method. Depending on conditions, I either do 1-2-5, 1-3-5 or some variation. I rarely use all 5 gears unless I am puuling onto a crowded highway.

[Matt Timion]

<p>I've actually done this before.&nbsp; The difference for me, however, is that I didn't take it up to 50mph in 2nd gear.&nbsp; I took the 87 CRX Si to about 3000rpm and them went into fifth gear for cruising around town.&nbsp; I followed the 1-2-5 pattern.</p><p>The engine didn't mind at all.&nbsp; Performance wasn't affected.&nbsp; A few other times I've just skipped 4th gear and done 1-2-3-5.</p><p>I usually save about 500 RPM by crusing around in 5th gear, so it's worth it to me.</p><p>&nbsp;Now, the WOT theory is something I'm not sure about.&nbsp; For the insight I believe flooring the gas will click on electric assist (their electric motor will give an extra 10hp when it's assisting the gas motor), thus making it easier to accelerate and also will not affect their gas mileage as much as WOT affects a standard car's gas mileage.&nbsp; So in reality the insight owners are cheating a little with their little electric motor.</p><p>I think moderate acceleration and the 1-2-5, 1-2-3-5, or 1-3-5 shifting pattern is going to help a lot more than WOT.&nbsp;</p><p>&nbsp;</p><p><br />&nbsp;</p>

[SVOboy]

I agree with everything that has been said, it is just I wonder how much difference it will make. Sometimes is I have to hustle I will rev to 2500 and skip a gear but usually I just 2000 all the way. I can't test it out myself because I'm auto (for the time being), but hopefully some sort of test can be figured out, though I think it should be pretty hard to pull off. <br />

[Matt Timion]

Eventually it would be a fun test to do one tank of 1-2-3-4-5 shifting (and never to cruise in 5th in the city) and another tank of 1-2-5 shifting.&nbsp; I think that this is doable down the road as an experiment.

[SVOboy]

Yeah, I tried 1-2-5 WOT shifting today and not only did I take off like crazy so that it would be impossible to do under normal traffic and [i]I just don't understand. Can anyone tell me why this would help for gas mileage? It seems like the camry musta dumped a cup of gas in there when I had it at WOT for those 4 seconds. It was fun though, but not worth getting 20 mpg.

[Flatland2D]

I have a suspicion that the fuel mix goes way rich during this style of driving. It might be more efficient to accelerate when the engine is actually producing some power (~3000rpm) so it doesn't have to compensate with the mix. It's just an idea though. Hopefully I can test this when I install my AFR gauge.

[SVOboy]

That actually makes a lot of sense to test it then, good thinking.

[SVOboy]

So, guess what? In my quest for ecu tuning I found this thing that says WOT acceleration is the best for gas mileage, and some who say it is, whaddya think about either side of the argument:

<a href=http://forum.pgmfi.org/viewtopic.php?t=7342&highlight=fuel+economy target=_blank>PGMFI Stuff</a>

[Flatland2D]

Can you copy and paste? You have to register to view that link. I've got nothing against that, I'm just lazy.

Only way to know for sure is to test it.