Is there a firmware upgrade for the FCDs on the 2003 HCH I's? I've seen mention of it in various posts but they were unclear as to what year of HCH I. I've also looked on the NHTSA site and can't find a bulletin that addresses this. The closest I have found is one that mentions an odometer issue (# 10013805). My local Honda dealer didn't think there was any such upgrade.

On 4 tanks and 2000 miles I find my FCD to be about 10%+ optimistic (45.0 on the FCD vs. 40.4 calculated). I think my first tank was an underfill because the numbers are slightly better for the last three tanks but its still not even close.

thanks
Shawn

 

The FCD can never be that accurate. It's just an estimation. I wrote a paper on it if you want to see it. 10% off isn't that bad, that's about what I get.

 

I would like to see that paper.

From what I've read, it seems that most people on here are reporting their FCD mpg and not the calculated mpg. this is fine if people realize the discrepancy but also from what I've read it seems that in later models this problem has been corrected (or at least improved) which makes it hard for anyone to compare mpg between cars. Its also made harder because the threads that have mentioned this don't appear to show much consistency in how far off the FCD is from actual (I've seen 10% over estimation to 5% under estimation reported).

I'm trying to figure out just what sort of mileage I should expect given my driving conditions but when I look at others' results, even if I assume they are reporting the FCD, I still don't know how inaccurate their FCD is. (Of course, the other big unknown is what speed they are driving since that seems to be the biggest factor affecting fuel efficiency).

shawn

 

Mine is off by 10% as well. I report calculated not displayed MPG.

 

I report calculated MPG, also. I keep a log of it both ways, and thus far (3 tanks!) the calculated is averaging about 1 MPG higher than FCD (0.6, 0.8 and 1.3, in fact).

 

Regarding your statement about speed affecting gas mileage -

I can give you an estimate for an extreme. I drive between 80-90 mph going up mountain passes and get low 40s averaged over the tank still. (I calculate my mpg and ignore the dash)

 

My calculated and displayed MPG vary quite a bit. I usually fill at the same station from the same pump whenever possible, and still the display is sometimes over, sometimes under. It's pretty irregular. If you're going to track your mpg the only accurate way to do it is to use the calculated figures and all the other variables even out over time. I figure the display is really there to give you a rough indication of how you're doing between calculations.

 

Mine is way off. Mine said 60.9 and calculated out to 53. Quite the discrepancy. I wish I knew how to get it just a tad closer to reality.

 

It's just an estimate. I'm sure it's a lot closer than a lot of other FCD's.

 

I just experienced an awesome skewed mileage today....

I filled up my tank, same station as usual. The readout said 47.3 mpg. I calculated my actual as 58 mpg! I'm trusting my actual because I had 550 miles on just over half a tank. And yet, ever other tank so far this summer has been the 47 or worse... And I didn't change my habits... Weird.