Honda Insight Forum banner

1 - 20 of 24 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
Hey all,

Has anyone ever checked to see how accurate the MPG data output is by

1. Comparing it to actual use - saving the receipts and doing the math, or
2. Any other method?

Greg
 

·
Registered
Joined
·
652 Posts
Mine has fallen within .1 mpg for well over a 100K miles. Individual tanks will show a greater difference but I trust the mpg guage far more than the gas guage. Have fun, Rick
 

·
Registered
Joined
·
79 Posts
MPGs

I did the math to see if my MPG display was correct and it was very close (within 1 MPG). My father didn't believe that I was getting as much as the display said so I did the math twice. One time it fell 1 MPG below and one time above (I'm sure the amount of gas pumped in the tank could vary a little when you are figuring with math).
 

·
Registered
Joined
·
222 Posts
Yeah, they never want to believe it, that sounds so familiar.

But once you convince them it's real, their next statement is always "But I hear your battery has to be replaced and it will cost you $5000"
 

·
Registered
Joined
·
95 Posts
their next statement is always "But I hear your battery has to be replaced and it will cost you $5000"
Tell them that you use the batteries that have the little bunny on TV, they last a long time. See what they say then. ;)
 

·
Registered
Joined
·
66 Posts
My indicated milegae at my last fill up was off by about 4 mpg against what I calculated via gallons to fill tank devided by miles traveled. The indicated mileage was optimistic.

But...

Variance in odometer and how full the tank is filled from one time to the next impedes an exact enough figure to know which is right and which is wrong.
 

·
Premium Member
Joined
·
4,942 Posts
This is an ooold topic. You'd have to go way back when...

Members did keep long term records and averaged them on paper vs. the MPG gauge. Its accurate (with OEM tires) to 1-2% on _average_ over the long term (fill-up variations and the like).

The HCH1 is 5-7% optimistic.

HTH! :)
 

·
Registered
Joined
·
224 Posts
While this may indeed be a topic that has been "discussed" on other threads in the past, it's no doubt a question that many Insight owners, who haven't searched the forum archives will continue to ask.

I have some information based on Tour de Sol calibration data that may be of interest.

It would seem that the Bridgestone Potenza RE-92 LRR tires (Insight OEM) don't change the indicated FE when inflated up to 45 psi. However, at 50 psi or more inflation pressure, there seems to be a consistent error in the order of 2%. Specifically, the indicated distance travelled (and consequent FE) shows about 2% higher than the actual.
This is assumed to be due to tire shape distortion.

I have no data in relation to underinflation (not recommended for those of us who are FE conscious).

-Brian
 

·
Registered
Joined
·
222 Posts
Hey nemystic, I think you got it backwards. The bigger you inflate the tires, the indicated distance travelled will show LOWER than actual.

That's why the cabbies in NY run their tires at about 10 psi or something, so that the indicated distance travelled shows HIGHER than actual.
 

·
Premium Member
Joined
·
2,332 Posts
Sounds like an urban legend Paul. The steel belts should determine the circumference even if dimensionally distorted. The tires would wear out quickly and the gas mileage would decrease. That would cost money. The ride would be smoother though, so perhaps they would get a better tip.

Putting on undersized tires or messing with the electronics sound like much more effective techniques.
 

·
Registered
Joined
·
131 Posts
I keep track and I've had tanks with a lower FE first half and a really good FE second half that caused the FCD to read a lower mpg than calculated. it's not significant, though, maybe 3-4 mpg max difference?
 

·
Registered
Joined
·
222 Posts
Yeah, it might be, Kip, but urban legends are a favorite topic of mine, and I can't find any reference to it being one.

My recollection is that a news crew along the lines of 20/20 went around New York with a tire gauge to show this dangerous practice. But I can't find any record of that, either.

Plus, I never said cab drivers always act in their own best interest :)

But my real point remains, a larger tire will result in a low-reading odometer.
 

·
Registered
Joined
·
5 Posts
FCD has about a 300-500ms (not scientific) rise/fall time

In regards to accuracy.....

One thing I have noticed is that the FCD has a rise and fall time of about 1/3 - 1/2 of a second. Try this out for yourself. While coasting to an autostop resting position watch the FCD.

Normall you will be at 150MPG (or pegged) when coasting to a stop. When you do stop note how long it takes for the FCD to go from 150 to 0. There is a noticble delay. (fall time)

Why does this matter you ask? When using pulse and glide you are giving small shots of assist to keep the car at speed then letting off. all while keeping your focus on Instaneuos FE. If you hit the gas too hard, then let up quickly, the FCD wont react quickly enough to let you know you just gave the car to much throttle.

Peace out and much love
-Jonathan
 

·
Registered
Joined
·
340 Posts
As Tranquility said:
Variance in odometer and how full the tank is filled from one time to the next impedes an exact enough figure to know which is right and which is wrong.
I think the biggest difference between what I calculate and what the car calculates is not being able to fill the tank to the same place each time, and like Rick says, over a year, the difference is minimal.
Robert
 

·
Registered
Joined
·
34 Posts
Agreed with the other posters who've said the onboard mpg meters are accurate. Here are my records, and the order is odometer rating, mpg-meter, mpg calculated from odo & gas receipt:

442, 59.0, 59.12
755, 66.1, 66.48
1117, 69.1, 66.83
1490, 67.4, 66.31
1788, 68.6, 67.68
2035, 74.4, 72.60
2353, 71.6, 69.89
2728, 72.6, 72.28
3168, 70.2, 69.35
3654, 71.9, 72.11
4128, 72.1, 71.14
4745, 73.0, 72.57
5301, 69.0, 68.85
5697, 75.9, 75.77
6179, 75.2, 75.35

The average variance is only 0.65mpg, with the onboard meter being just a tiny bit optimistic. Of course, the next thing the naysayers say is that it will be awful in winter. Still waiting to see!
 

·
Registered
Joined
·
224 Posts
Hi Ethicalpaul,

I realize that it seems counterintuitive, but the data appears to confirm that the RE92 tires actually decrease slightly in diameter when over-inflated to 50 psi or beyond. Other reports of reduced tire wear in the center (when the tires are over-inflated) would appear to further reinforce these data.

I'm interpreting Insightful Trekker's message as another confirmation.

I'd encourage anyone to conduct experiments to confirm these data or to prove us wrong.

With regard to those "underinflated" cab drivers, it would seem that with fuel prices these days, their questionable practice would yield a net loss despite the higher fares.

-Brian
 

·
Registered
Joined
·
222 Posts
I don't recall any reports of reduced tread wear in the center, other than people reporting that despite overinflation, their tires continued to wear more on the edges despite some people's thoughts that overinflation should cause wear in the center.

I don't recall that anyone reported increased edge wear.

Your challenge to conduct an experiment to prove or disprove that these tires get smaller when overinflated is intriguing. I plan to do so just after the end of my other two experiments that I have going.

The first is that one loses weight the more ice cream one consumes, and the second is that by driving slower and slower to work, I arrive earlier and earlier. I do look forward to publishing these results, then I can test to see if my tires shrink the more air I stuff into them.

As for Insightful Trekker's response, I was more than a little confused as to what exactly he was referring. Maybe he'll clarify for us...I think he has gone overboard in his dislike of the /quote tag ;)
 

·
Premium Member
Joined
·
2,332 Posts
If our tires are steel belted it should make no significant difference to the circumference whatever pressure we use. The distance of the tread around the tire should be the same even if the tire is flat. Only the shape would be distorted. As long as the tread does not slip with respect to the pavement, the car should cover exactly the same distance every time the drive shaft rotates the wheel through 360 degrees. The only thing that will change the distance covered is slippage of the tread with respect to the pavement. Slippage can occur if the tire is over inflated. Anyone who has experienced the ABS kicking in as a result of putting too high a pressure in the tires will understand this principle. The effect of this slippage would be an increase in calculated mileage versus a decrease in real mileage. I propose that this explains the mystery of the "shrinking" tires. :idea:
 
1 - 20 of 24 Posts
Top