The '09 2nd Gen Nav Sys seems to me does not measure total Fuel Cut. The more I use fuel-cut, the Nav sys average MPG drops as compared to both the SGII's in my '09 FEH. I really seen this on the highway while doing Pulse and Glide in "D" and seeing 9,999MPG on the SGII Instant MPG readings with Open-Loop during the glide.

Now that I confirmed Fuel-Cut in my '09 FEH, I've been taking advantage of it more and I can see the results between the Nav sys average MPG go even lower than both SGII averages. I reset the SGII's with my first fill-up at 592.6 miles and my SG's showed an average of 46.4mpg and my Nav average was 44.3mpg, which was 2.1mpg lower. Since that time, I've used more fuel-cut techniques on average and can see a bigger difference in just 133.7 miles after the reset of all three Gauges. Now my SG's are reading 48.7mpg Tank averages and the Nav sys is reading a 46.4mpg, a 2.5mpg average lower than my SGII's.

One good thing that Ford changed in the new Nav sys was they increase the data memory so that the data does not drop off before an entire tank is used. My '05 FEH loses data after a little over 200 miles after a reset. The 40 Gig Map system and the 10 Gig song and picture system must have allowed Ford to increase the MPG average data also. What I think has happen is the Ford Engineers who designed the new Fuel-Cut features didn't communicate that to the new Nav Sys Engineers. I know Ron Delong the designer of the SGII was getting an ear full about how the SG needed Fuel-Cut and he came through a year ago. Let me be the first to give Ford an ear full on not thinking of the Nav Sys average MPG and Fuel-Cut.

GaryG

 

#1 your car is still new and not broken in yet
#2 you are still new at driving it
#3 fuel cut on a ScanGauge is an assumed value, it is not measured directly, thus
#4 you may not actually be in fuel cut every single time your SG says so, it is likely your SG is being fooled some of the time.

The SG in my 2005 reads fuel cut sometimes when I am going uphill and the car is at, or near WOT. Open loop is expected, but with a high TPS reading, this is not supposed to occur and it still does at random times. Other persons have reported this also. Thus, I feel the SG is not perfect.

I can confirm ( in a 2005 ) the SG does NOT use fuel trim to calculate MPG, and the 2005 Nav unit DOES.

When I go to the Colorado Rockies ( 10,000+ ft. ) and then to Omaha ( 2000? ft ) my fuel maps change quite a bit with changes in oxygen levels. The SG will show the fuel trim values changing with a PID ( xGauge ) but the MPG does not change. It changes as expected in the NAV system MPG.

This is a case where the Ford Factory unit is smarter than a SG. In a 2005, anyway.
You may need to trust the Nav more and SG less.
Only more months and miles will tell.

 

Don't get me wrong, I love this new 2nd generation Nav sys, but it has problems with not only Decel Fuel Shut-Off (DFCO), I think it has problems with partial DFCO also. My '05 FEH had the same SGII for 9 months that I put in my '09 and my son gave me a new one in July for my birthday. They both read Fuel-Cut or DFCO the same. When I decelerated in "D" in my '05, I've never seen the kind of Instant MPG readings on my SGII that I'm now seeing in my '09. The SGII reads much higher Instant MPG while still in Closed-Loop than the graph on the Nav sys. The graph moves say from 40mpg to MAX at 60mpg in like 3 seconds. The SGII instantly goes to a Instant MPG reading to say 112mpg while it takes the Nav sys 3 seconds to get to MAX (60mpg).

Here is what Ford said about the new system and I can verify it's true from what I'm seeing:

"Idle-stop and start events are much quicker, and enable greater efficiency with as many as two times the starts and stops in a given driving cycle as the previous system. The quicker engine shut-downs and pre-positioning (for the next start) also reduces O2 build-up in the engine’s catalyst. Decel Fuel Shut-Off (DFSO) mode and electric-only mode have also been expanded."
http://www.greencarcongress.com/2008...reviews-n.html

The same SGII that was in my '05 matched the Nav sys in my '05 FEH pretty close except when data started dropping from the Nav sys MPG average. Ford said it expanded DFSO in the new system and the SGII has verified that. The 2nd generation Nav sys does not recognize DFSO like the SGII which I believe is correct. The SGII matches the average MPG as the 2nd generation Nav sys pretty close at a steady state speed until performing Fuel-Cut techniques or when normal DFSO occurs.

Also, I think Desertdog (Carl) has explained that TPS has nothing to do with WOT. Econoline (Don) corrected the false readings by adjusting the Fuel-Cut settings in his SGII. The SGII has worked excellent in the FEH and continues to work excellent in the '09 FEH with DFSO. In fact, many other Makes and Models use the SGII now to confirm their factory MPG gauges with DFSO adjustments.

GaryG

 

Update...

The '09 FEH/MMH will go instant EV with a shift to Neutral at 40mph and below with a SoC of 41.9% or higher. Shifting to neutral above 40mph prevents Fuel-Cut (DFCO) when decelerating, so there is no benefit there.
My second tank MPG average is looking like a little over 49mpg and close to 700 miles. Considering we had ~4 days of high winds and heavy rain with Tropical Storm Fay, this is excellent for this time of year in So. FL on E-10 gas.

Based on my present tank miles on the trip OD of 604 miles, a MTE of 71 miles, and knowing I have 1.3 gallons of fuel left at 0 MTE, I will burn 15 gallons at 735 miles. My SGII Tank reading says I burned 12.2 gallons so far and have 132 miles TTE. My SGII Tank Size is set at 15 gallons. Based on the present Tank miles and the MTE projection, I'm getting a little over 49mpg. The Nav Sys says my average is 46.5mpg. This confirms my earlier difference between the SGII and the Nav Sys MPG averages. It is still my opinion that the OEM gauges don't recognize Fuel-Cut (DFSO) and will always read lower MPG averages. Since the new Nav Sys can be reprogrammed, Ford should have a recall and update the system for DFSO.

GaryG

 

I think calling for a recall is a bit much! Let's save those for something a bit more important than a few missing ticks on the Average MPG meter.

 

More than likely the dash MPG ECON doesn't measure fuel-cut or DFSO either for those without the Nav Sys. This could mean Ford's entire fleet of '09 vehicles with DFSO is going to read 5% lower MPG averages. You can bet Toyota and Honda love the fact Ford made a 5% lower MPG average mistake in their OEM gauges. It is to Ford's best interest to have a recall so new owners are aware their vehicles are really getting better mileage than their gauge reads. Those people who feel it's no big deal like yourself will most likely choose not to have a repair or wait till another problem causes the vehicle to go in for warranty work. Ford may not even have a way to correct the gauges, but letting buyers know that their most likely getting better mileage instead of worst according to the gauge could help sales in the future.

I can't say for sure that fuel-cut is what's causing the lower MPG readings, I just know the miles (distance) traveled are very close (within 1/2%) between the SGII and the OD. Going 2 1/2 miles further with every gallon of gas is a big deal to me at todays gas prices. I'm expecting to exceed well into the 50mpg lifetime average as the '09 FEH gets broke-in based on my experience with my '05 FEH. As I play with DFSO techniques, that 5% could increase and I don't even have hills here in So. Florida. Those that drive long hills may see much higher than a 5% difference in mileage readings for the worst.

GaryG

 

I don't disagree that having the Average MPG gauge be off (especially low) is bad for Ford but I can tell you that any time the word RECALL is mentioned Ford will get even worse press. In this case I don't think that is worth the bad press.


My '08 Average MPG gauge is consistently 4%-6% higher than my hand calculations, I've just learned to expect ~2MPG difference. I'd love to be able to add MPG to what my Average MPG gauge said like you feel most '09 owners will.

 

you don't recall for something like this.

however, you can issue a tsb. and by the way, the differences you are talking about here are within a margin of error.

 

This weekend I did two 250mi tanks at ~95% highway (500mi round trip with fill ups at each end) and at one end the FE display was almost correct (within a few tenths) while on the last fill up the FE display was off by +3MPG. At this point I just think of the FE display as a ballpark guess of tank FE (even under 200mi) with a rule of thumb that it's 2MPG high. YMMV...

 

Big surprise today on my way to fill-up my second tank on my '09 FEH. I thought I had plenty of gas left because I only had 37 miles past 0 MTE. In my '05 FEH, I have ~1.3 gallons left at 0 MTE and thought it would be near the same in the '09 FEH. I was wrong and ran out of gas about a half mile from the gas station (Sams Club). The engine died and I lost power to a max speed at around 20mph and the warning "Stop Safely Now" came on. I made it to the gas pump in EV with a SOC of ~35% remaining. Even had to come to complete stops at stoplights and still got going again. This was much different than when I ran out of gas in my '05 FEH a few years ago.

The total miles on the OD was 1301.1 when I made it to the gas pump today. The first fill-up by the dealer must have been much less that 15 gallons because I only made it to 592.6 miles and the gas needle began dropping within a few miles from delivery with 4 miles on the OD. This second tank lasted 708.5 miles before fill-up on an empty tank.

The Nav Sys. average read 46.4mpg and the trip was 708.5 miles before reset. The SGII Tank average read 49.0mpg with the miles at 706. This still means the two gauges are consistantly off by ~2.6mpg. The SGII read I used 14.4 gallons with .6 gallons TTE with a setting of a 15 gallon tank size. Now I'm leaning that both SGII's are reading DFSO too agressively. Has anyone compared DFSO in other models OEM gauges to the SGII? This would mean the Nav Sys is nearer to correct.

GaryG