Honda Insight Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter #1
I frequently see comments like:
"For some reason, the Insight gets extra good mileage in mountainous areas. This may be because, while it takes extra gas when climbing a hill, this is more than offset by the fact that the Insight is smart enough to use no gas at all when you're going down hill."

The problem is that average fuel economy (i.e. for 2 segments of a trip) is not just the average of the fuel economy for each segment (mpg average does not equal (mpg1 + mpg2)/2).

For example, if I drive to work (mostly down hill) and get 70 mpg, and drive back home (taking the same route so that the distance is the same) and get 40 mpg for that segment, the average fuel economy for the round trip is not (70+40)/2 = 55 mpg. It is actually (2*70*40)/(70+40) = 50.9 mpg.

That is, the average fuel economy for the two legs of the trip is :
2*mpg1*mpg2/(mpg1 + mpg2)

(This assumes that each leg of the trip is the same distance, otherwise you need to include the distance in the calculation.)

The reason that this is significant is that, no matter how high mpg1 is, a low value of mpg2 will cause a serious decrease in roundtrip fuel mileage. As an extreme example, let's say that you drive up a steep mountain and get 10 mpg on the way up, even if you get 10,000 mpg on the way back down, your average fuel economy will be less than 20 mpg (instead of the mean mileage of 5,005 mpg). Therefore, you can never offset bad fuel economy for a segment with good fuel economy for the next segment.

You can check this using 2 of the Insight trip meters and recording the segment mileage and total mileage for a round trip (hopefully with significantly different mileage for the two legs).

Randy
 

·
Premium Member
Joined
·
830 Posts
personnaly...

Hi,

I think that it does get good mileage in mountanious area. I think that the car is lite and does offer the best efficiency with the big load of going up. And does not use fuel going down.

An engine with medium load is not using the power at maximum efficiency.

Just like most people say that to get best MPG on flat, they use gears 1-2-5 with gas pedal almost to the floor. Accelerate fast to cruise using the maximum time possible.

Personnaly I think that using this method is good for MPG but bad for the engine and transmission (peak tork from engine and IMA in that situation will cause wear)

The MPG shown is only mesuring fuel used for the trip. Then for display, it is divided by distance. The fuel injector "On" time represent the fuel mesurement.
 

·
Registered
Joined
·
652 Posts
In regards to mountainous terrain the Insight losses efficiency. I live in the Appliachian foothills (Greenville, SC) and work in DC. The flat terrain along the coast always delivers better efficiency than the mountains or foothills. I also believe lower elevations will deliver better fuel economy than higher elevations such as on a plateau. (Coastal Virgina vs El Paso). I know the air density would be less at the higher elevation but it doesn't seam to offset the reduced engine efficiency.
I also disagree with the 1-2-5 shift pattern. The problem is that it takes more energy to accelerate rapidly than slowly. Those that believe in the 1-2-5 shift pattern say that the battery is delivering more of the power which is true but then again the battery draws its energy from the engine eventually (REGEN braking is just recovering part of the energy expended by the engine). Have fun,
 

·
Registered
Joined
·
25 Posts
Discussion Starter #4
Effect of Altitude on Fuel Economy

When I moved to the Denver area (5000-8000 feet asl) from Detroit (640 feet asl), I noticed a large improvement in fuel economy for both of my motorcycles (one that was averaging 52 mpg is now averaging 63 mpg).

This could be due to:
+ less wind resistance (motorcycles have very high drag)
+ improved engine efficiency (but, since they are probably running richer, it seems like this would have the opposite effect and result in lower efficiency)
+ different traffic patterns
+ climate
+ other ??

It would be interesting to see a poll of fuel efficiency vs. typical driving elevation and to plot the data, though so many other factors that effect fuel economy (terrain, climate, commute length, traffic, driving styles, etc.) could obscure differences due purely to altitude. Perhaps someone would like to come up with a formula that would include the effects of all these variables?

Randy
 

·
Premium Member
Joined
·
498 Posts
IMA limits in mountains

The only problem I've seen in the mountains is that, the IMA goes into overheat or battery protection mode after a few miles of serious slopes.

I drove across Frankonia notch in NH last fall. On the way up, assist worked great, pulling me effortlessly up in 5th gear, until it did a recal. From there on, next to no assist until I reched the plains around Quebec city. I couldn't recover as much energy as I would like on the downslopes, either: The IMA limited charging to 4-5 bars soon so I had to use friction brakes most of the time.

I agree, though, moderate, rolling hills are great fun!

Armin
Y3085
MYBRID
 

·
Premium Member
Joined
·
1,658 Posts
My Calculations.....

I have just finished my first tank of Insight petrol and I averaged 46.5 mpg.

If the averages in the messages above looked complicated (it did to me) at least you don't have to do my conversions. My Japanese Insight has been 'chipped' to show miles and mph on the dash. Unfortunately is still shows km/litre on the rest of the display (14km/litre lifetime average).

Therefore I had to take the mileage (327) and divide by the amount of litres it took to fill up (32 - (Sold in the UK in litres at around 79pence per litre)). Then multiply by 4.546 (No. of litres in a UK gallon) to get my mpg figure.

In case you think the mpg figure is poor, I should point out that I do short journeys with cold starts in an urban environment. My tires were at low pressure (29 psi) for three out of four weeks and there were also numerous examples of hard acceleration (showing off!).

I will try and drive more sensibly on this second tank and then carry out my calculations all over again....
 

·
Registered
Joined
·
25 Posts
Discussion Starter #7
Uk gallon vs. US gallon

Christian,
I believe that there are 1.25 US gallons in a UK gallon (3.6368 l per US gallon/4.5461 l per UK gallon). So 46.5 miles per UK gallon would be:
46.5/1.25 = 37.2 miles per US gallon.

Randy
 

·
Premium Member
Joined
·
1,658 Posts
Thanks Randy....that makes my MPG look even worse! I will definitely have to make more of an effort on my second tank of fuel.

By the way, if you enjoy doing UK / US conversions then you could make you and your fellow American drivers feel much better about the price of your petrol by comparing it against mine (79 pence per litre).

Cheers
 

·
Registered
Joined
·
25 Posts
Discussion Starter #9
High cost of Gas in UK

At the current exchange rate of $1.57 US/British pound, that's $4.69 US per gallon. And to think that some people are whining about $2.00/gallon in California (not Insight owners, of course)!

Randy
 

·
Premium Member
Joined
·
1,658 Posts
Just for the record I have now completed my second tank of fuel and averaged 52.5 UK mpg or 42 US mpg. An improvement on my last tank but still a long way to go to catch some of you fellow Insighters.

I have my tires on 44psi all round now and am looking to do an oil change soon to ensure the right, clean stuff is in the engine.
 

·
Registered
Joined
·
223 Posts
And to think that some people are whining about $2.00/gallon in California (not Insight owners, of course)!

Ha, this cheap California Insight driver whines of course it doesn't help I remember being able to buy gas at 29.9 cents a gallon.
But on a serious note the mileage is one of the main reasons I bought both Insights My family has now. MIZR has cut My comute fuel from approximately 120 gallons a month to normally no more than 32 a Month (this includes numereous trips to store and trips to San Diego or Yuma). The wife will burn maybe 1 tank a month, so I am very pleased with mileage.
As I told guys at work the other day "you all laughed at My *funny* looking car when I got it. Now who is laughing at gas pumps[/quote]
 
1 - 11 of 11 Posts
Top