How much does Autostop really save?

[aisbell]

Originally Posted by bibendum

100 cc of fuel is about 100 grams?

The specific gravity of gasoline averages about 0.75 g/cc, so 100 cc of gasoline has a mass of about 75 grams.

Originally Posted by bibendum

at 28 grams per oz that is a little more than 3 oz per minute
.... that seems a little high.

So it would actually be about 2.7 oz/min which is a little lower.

Originally Posted by bibendum

maybe you meant a cubic milliliter?

A milliliter (ml) is already a volume measurement which is equal to 1 cubic centimeter (cc). So there is no cubic milliliter.

[bibendum]

Originally Posted by aisbell

The specific gravity of gasoline averages about 0.75 g/cc, so 100 cc of gasoline has a mass of about 75 grams.


So it would actually be about 2.7 oz/min which is a little lower.


A milliliter (ml) is already a volume measurement which is equal to 1 cubic centimeter (cc). So there is no cubic milliliter.

yeah aloha.

ok so I missed a conversion from oz by volume to grams by weight
by about 25 percent. oops.
The fact it was part of asking for a clarification of an even bigger possible error is ignored...

The funny part is that one guess missed by an order of magnitude
and another soul missed by 200 percent minimum
Yet you felt no need to point out those errors.

Even using your numbers and conversions,
I will point out the claim of fuel used at idle was in a unit of volume.
and as I buy my fuel by the volume in oz and gallons and not by the mass...
so 100 cc of fuel is 3.3 oz by volume (also known as fl.oz)
(1cc = 1 gram and the basis is volume of pure water.
Same basis for the volume 1 oz of fluid.
so you tell me where the conversion of volume of cc to oz by volume is not 1 oz to 29cc....)

when I run my car at 60 mph I get about 64 mpg (close enough ...)
so I use 2 oz by volume per minute.

so we are clear, that 100 cc per minute, also known as 3.3oz per minute,
is not an engine idle rate.

Care to hazard a guess the volume of fuel an insight uses at an idle?
I am thinking .15 oz per minute is very low. how about you?

victor

[theaveng]

Originally Posted by RedJellyBean

Hi Mr. Engineer, I'm an engineer too and I've disagreed with almost everything you've had to say since registering.

That's okay. I doubt the Honda engineers agreed on everything either & had some serious debates about various decisions made (on engine size, # of cylinders, whether the motor should be 10 or 20hp, etc). On the most-recent Insight some engineers wanted it to be a standard sedan with a trunk. There is no "correct" answer on anything, when it comes to design decisions.

[Bugone]

A tv show over here called 5th gear tested a car with autostop on the same commute against it with the autostop disabled. It worked out as about 10-15%. I would imagine the results are similar in the Insight.

It really all depends on your drive how much it will save. The Insight restarts from an autostop with considerable ease - so its a perfectly useable everyday feature. My mate has a 318 BMW with the feature, and its a complete emissions fudge - as the restart process is nowhere near as smooth as on the insight.

[theaveng]

As I said in my first post..... "unless you're stuck in an hour of stopped traffic"

[jonnyvtec]

The injectors run constant pressure compared to the inlet port pressure, the regulator changes the pressure based on manifold vacuum such that if you have 7psi of vacuum the rail pressure is lowered by 7psi to maintain the same pressure differential between the fuel rail and air it's injecting into.


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[Willie Williford]

Johnny Vtec
Don't you mean "7 in of vacuum the rail pressure is lowered by 7 psi?"

Willie

[Cobb]

Yeah, inches of mercury or "Bars".

Ive been stuck in traffic, auto stop didnt help much, I find the old fashion way of turning the ignition off and on worked best.


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[aisbell]

Originally Posted by bibendum

yeah aloha.

No alohas to you for your snarky response.

Originally Posted by bibendum

ok so I missed a conversion from oz by volume to grams by weight
by about 25 percent. oops.
The fact it was part of asking for a clarification of an even bigger possible error is ignored...

I don't care about how much fuel an Insight uses at idle. I rarely let mine idle. So I haven't been following your calculations in detail. As a former chemist, I did recognize one calculation error that you made which I politely pointed out. I won't bother in the future…

Originally Posted by bibendum

The funny part is that one guess missed by an order of magnitude
and another soul missed by 200 percent minimum
Yet you felt no need to point out those errors.

And I won't be pointing out any of your errors in the future.

[bibendum]

yeah aloha again.

Before you fire off a claim of 'snarky' you may want to re-read your post and see if it passes the snarky test.

I have no problem with being corrected.
I kinda wished you had been more clear about your corrections.
Because as I saw it, your correction was wrong at the end point,
which I thought was funny.

I made my mistake while trying to be both nice and considerate.
It was an attempt to get Willie Williford to see that his numbers were out of range or some how mis-calculated.
You on the other hand, found no need to be nice or considerate.

Back to idling... If you ever bother, you will most likely be using from .3
to .5 fluid ounces per minute.
When you drive my insight, your idle will definitely be over the .5 fl.oz per minute side of that guess.

victor