MPG? (Hypermiling, Scanguage question)

[forestacademy]

Thanks guys.

In gear, foot off gas turns off the gas better than putting it in N.

Good to Know. Now the only question left is while sitting at a stop light, is it better to keep it in gear with foot on brake hard enough to disengage creep, or pop it into N with a light brake? I prefer N because my foot gets tired pushing on the brake.

[tvengineer]

Originally Posted by forestacademy

Thanks guys.

In gear, foot off gas turns off the gas better than putting it in N.

Good to Know. Now the only question left is while sitting at a stop light, is it better to keep it in gear with foot on brake hard enough to disengage creep, or pop it into N with a light brake? I prefer N because my foot gets tired pushing on the brake.

Sounds about right.. I too like to use N while stopped..
And I coast in N quite a bit...

I do belive the readings that people are reporting here from the Scan Guage (and I do not have one)... but ... I have read the scan guage setup instructions.. and there is a setting IN THE GAUGE that assumes fuel cutoff below a user defineanble throttle postition point.
So.. the readings of 0 gallons per hour.. are really the SG assuming that the fuel is cut off... no where have I seen a definitive answer as to whether or not the Smart does cut the fuel.. (guess I could hook a scope up to the injectors to find out)...

I do coast.. I have a tall overpass just after I leave work.. followed by a stop light 3 blocks away.. I switch to N at the top of the overpass.. and if the light is red.. I coast to it without loosing enough speed to be going much slower than ordinary traffic.. if the light is green I simply apply a little throttle and drop back to D.. the smart figures out the gear perfectly.

Louis

[John_H]

Originally Posted by NCC1701

John, I haven't checked to compare the two conditions yet (coasting in N v.s. in gear) but, the SGII can show GPH.

From a given speed, 0gph (in gear, no gas) will give you 0.0x miles of travel before you come to a stop. From that same speed, the 0.44gph will allow you to travel 0.0y miles (y>x) before coming to a stop. The difference in distance (miles) and the fuel used in neutral (gallons) will give you a miles per gallon rating that just isn't calculated in a scanguage.

I'd suggest that the braking will exert a much larger effective use of fuel than the idling in neutral.

[tvengineer]

Not arguing about it.. I suspect it's like a bunch of other things... comes down to personal opinion. The Scan Gage just isn't going to give us the answer to this one.

I just drive the smart much like I did my old Miata... I would put the clutch in and coast to a stoplight or down an overpass..
Smart has no clutch.. so i bump it to N. If I am coming down a hill and need the engine braking.. I certainly would stay in gear.

Originally Posted by John_H

From a given speed, 0gph (in gear, no gas) will give you 0.0x miles of travel before you come to a stop. From that same speed, the 0.44gph will allow you to travel 0.0y miles (y>x) before coming to a stop. The difference in distance (miles) and the fuel used in neutral (gallons) will give you a miles per gallon rating that just isn't calculated in a scanguage.

I'd suggest that the braking will exert a much larger effective use of fuel than the idling in neutral.

[NCC1701]

Originally Posted by forestacademy

Now the only question left is while sitting at a stop light, is it better to keep it in gear with foot on brake hard enough to disengage creep, or pop it into N with a light brake? I prefer N because my foot gets tired pushing on the brake.

According to SGII: I checked this evening. There appears to be no difference in GPH between stopped in N and stopped in gear. With the A/C turned off, I got 0.30 to 0.31 either way.

BTW, my earlier report of 0.44 GPH coasting in N was with the A/C on. Without A/C, it probably would've been 0.30.

[NCC1701]

Originally Posted by John_H

From a given speed, 0gph (in gear, no gas) will give you 0.0x miles of travel before you come to a stop. From that same speed, the 0.44gph will allow you to travel 0.0y miles (y>x) before coming to a stop. The difference in distance (miles) and the fuel used in neutral (gallons) will give you a miles per gallon rating that just isn't calculated in a scanguage.

OK, so the question goes unanswered, if I understand correctly. Could be a Calculus problem with more data available. (Just a wee bit rusty in that department).

[John_H]

I'd love "real" data on fuel consumption versus horsepower at the wheels across the RPM range as well as typical drag forces across the speed range. That could produce some real information on ideal hypermiling techniques as well as best gear selection at various inclines.

It's not a problem, it's an exercise.

[Dave777]

I believe the ScanGauge is reading correctly when coasting in gear...0.0 GPH. In my Toyota Echo the same gauge read a measurable amount, as the Echo engine did not have injector cutoff.

It doesn't really matter much. Fill your tank with 9 or 10 gallons, drive conservatively and enjoy.

(Still waiting for someone to exceed the 505 miles I did on one tank. )

[rfernatt]

Originally Posted by tvengineer

I have read the scan guage setup instructions.. and there is a setting IN THE GAUGE that assumes fuel cutoff below a user defineanble throttle postition point.
So.. the readings of 0 gallons per hour.. are really the SG assuming that the fuel is cut off... no where have I seen a definitive answer as to whether or not the Smart does cut the fuel.. (guess I could hook a scope up to the injectors to find out)...

If you're coasting in N with your foot off the gas or coasting in gear with your foot off the gas (assuming no difference in load due to A/C, etc), the throttle position should be the same (even if it's not 0), correct?

So, if a SG reports minor fuel usage in N, but not in D under these conditions, I would say that the fuel is actually cutoff since everything else is equal. My 2008 Nissan truck with automatic also reports no fuel usage while coasting in D, but some usage while in N.

[craven3557]

Ow You guys make my head hurt or maybe it's just tired head.:] Does really make a big difference if you get 36 mpg or 36.2?