I think after say 50K miles milage should be more accurate.

 

OBC's are there just as a guide, not for representing actual
MPG. you can get a nice ball park figure though... 20mpg vs
30mpg and so forth.

there are too many variants in real world conditions to expect
accurate readings just from that computer, imo.

 

"Seems that whenever I'm above 30mph and let go of gas, the meter goes up to 80mpg, which is not really possible because my speed is decreasing as I'm coasting."

That's because anytime you release the throttle fully and the rpms are above 1,500 there is NO fuel used at all. No fuel goes into the cylinders. So your instant mileage would literally be infinite.

 

Hence the overoptimistic calculations. They could easily put in a realistic constant in the formula to account for this real-world loss of energy, but they don't because it's to Honda's benefit to overestimate on intention. The reason I say it's intentional is if it wasn't, there would be reports of under-reporting, but everyone has over reporting, which points to intentional fudging of the numbers to make them look better.

 

Maybe for manual, but the fuel doesn't seems to cut off for auto. I did see the fuel cut off a few time, but not on a consistent base when I coast.

 

The problem is not related to fuel cut-off. My auto does not cut off fuel when coasting and I still get the same 10% error.

 

According to my spreadsheet the BSM is a consistent 12% "optimistic" tank to tank.

I disturbs me that no one has figured a way to "adjust" the BSM to allow it to reflect more accurate readings. Just like it irritates me to know there is a trip computer built in my nav system I paid for but it is simply locked out because its more accurate than the BSM !!!

COMON Honda! Lighten up! We all know it just a lie! Let us USE the tools we paid for properly!

 

The Dec 2008 copy of Car and Driver contained a brief discussion on fuel cutoff.

When Coasting to a Stop, do Not Shift Into Neutral - Feature / Gas Pains: Mileage Myths and Misconceptions - Feature / Features/Classic Cars / High Performance / Hot Lists / Reviews / Car and Driver - Car And Driver

 

FWIW, mine is 3-4 MPG too high. Both the cummulative and instantaneous readings are still useful, however.

 

Hi, an unusual request however having read your work on members.rennlist your knowledge of car electronics may hopefully answer a question for me that no one seems to be able to (my apologies for such a long letter). My name is Ian and I live in Scotland.
I have a VW Sharan 1.9TDi ANU engine and have had an intermittent engine misfire for 4 years (only happened once or twice per yr) then late last year onwards it became more prolonged until recently it became permenant. I had intially replaced the injector wiring loom as this is the common cause and while it fixed it for around 6 weeks it came back. I then put the car into an electronics specialist as I just wasn't convinced it was the injector although symptoms suggested it was. The report is as follows:
Initial fault codes thrown up where:

(18074) P1666 Valve for pump/cylinder1 injector -N240
(17675) P1267 Valve for pump/cylinder 3 injector -N242

Fault Codes detected for Engine Electronics

(18074) P1666 Valve for pump/cylinder1 injector -N240
(16685) P0301 Cylinder 1

Mearsuring Dynamics

Group 13: Idle speed smooth running control

Cylinder 1 2.99mg/H
Cylinder 2 -1.62mg/H
Cylinder 3 -0.75mg/H
Cylinder 4 -0.99mg/H

The Report:

The engine ECU (computer) had 5 faults stored relating to various circuits, noted and cleared the codes. Ran the engine and one fault returned relating to an intermittent fault with injector 1 circuit, the engine had a perminent misfire. Basic testing showed a classic mechanical injector fault and the ECU trying to compensate for it but more in depth electrical testing was showing a different problem.
Tested the injector current flow and found that injector 1 was "switched off" and not operating at all. When the engine was shut off and restarted, injector 1 tried to fire for approx 3 seconds and then was shut off again.
Each injector is opened and then held open in 2 seperate operations by the ECU to control fueling, the faulty injector circuit was only operating the hold open control ie the injector open phase was not operating at all.
Removed the ECU and sent the unit out for test. The unit was faulty. Unit repaired and returned.
The normal testing of the injector and circuit showed no fault. However, carried out an inductance test on all the injector circuits and found that there was a slight difference in the circuit for injector 1 which was the problem circuit.
Injector 1 - 0.138mH
Injector 2 - 0.129mH
Injector 3 - 0.129mH
Injector 3 - 0.129mH
Advised to renew injector 1 as there is no warranty on the repair without a new injector.

My question, could the difference of the value of injector 1 have caused damage over time to the ECU? Is the difference acceptable? or could the damage to the ECU have been caused by a faulty wiring loom. I'm just trying to establish whether or not I need to shell out £700 ($1000) on a new injector as no one can answer the question they've advised me to renew it. The car is at the moment running better than ever!
I hope it all makes sense, in that I have described it all properly.
If easier to reply my email is the marshycrew@yahoo.co.uk
In anticipation many thanks for your time
Ian
PS apologies guys for using this forum but am at the desperation stage

 

Finally a fix!!!

https://www.fitfreak.net/forums/2nd-...tml#post778186

 

Thanks for the update! I have been away for a while, and didn't catch it earlier. I will check with the dealer in the morning to schedule a firmware update.

 

Well I guess I can no longer dub it the BSM. Honda finally came thru with a patch! I'll give em credit for that!

I did mine in December. MPG corrections went from 112% to 101%! Which equates to about .5 mpg variance from accurate!

Still on the positive side But ya can't argue the fact they are CLOSE! Cudo's to Honda for coming thru!

Now Give us our TRIP computer back in the NAV System!!!

Thanks!

 

dude when i drive a fresh tank in the mtns my computer says like 25 mpg but it works out to really 34mpg sometimes

 

I just had the ECU flashed with the update during a minor service at 20K, and it does seem to match more closely to my (calibrated) ScanGauge. I am still on the same tankful, and have not done any manual calculations. I may not bother.

 

i have 2009 honda fit sport manual...
i just put about 4300 miles on the car. at first total miles i got from a full tank of gas was bit low. however for last 5 fillups i have been getting around 350-360 miles on a full tank of gas. the computer on the guage panel indicates about 42mpg. does this seem normal?

 

I had the same issue on 2009 manual. The dealership updated the software for about 15 minutes and it is solved now. I have less than 1 mpg diffference between actual and computer reading.

 

thanks for the info. i guess i better have it checked out...