Joe Dirt's Stock V8 economy findings thread

[vroomzoomboom]

Dale,

I'll try to post a vid of a couple of runs with differing acceleration levels. That might be helpful...

WHOOHOO!

can you say, SOUND CLIP!

 

[2000StreetRod]

FIND is correct

I'd swear that ECU fuel economy PIDs are generated using injector pulse width versus the signal from VSS. Since the VSS is supposed to work out to 4000 pulses per mile, and the fuel pressure is fairly predictable as is bench flow rate for injectors, it shouldn't be very far off. Granted, those values can vary by vehicle or injector slightly, and can vary slightly due to changes in vacuum to the FPR, but... It is about as close as one can get.

I am not 100% though of course. I suppose I'll have to troll some board where some of those homebrew standalone guys have hacked EEC-V and EEC-VI.

If found the following:

"26.1.3 PULSE CALCULATION (CRAH0)

STRATEGY MODULE: dol_pulse_calc_4
/*


FUNCTIONAL REQUIREMENTS: TBD

FUNCTIONAL DESCRIPTION:
The Data Output Link (DOL) provides fuel consumption information to the vehicle dashboard fuel economy display products
(Tripminder or Message Center). The output is the the variable DOL_COUNT, where each bit represents a PUL_PER_GAL amount of
fuel used since the last update. This information is used in calculating fuel economy and distance-to-empty for display to the
driver.

The injector fuel flow (in lbmf/(injector/port)) is accumulated in the register FUEL_SUM every time an injector port is
energized. Once a background loop, FUEL_SUM is converted to the appropriate integer number of DOL counts, and DOL_COUNT is
updated according to the equation shown below. The amount of FUEL_SUM which cannot be converted to an integer count remains in
FUEL_SUM for the next conversion.

Note: it is possible for FUEL_SUM to be a negative value. This may happen during certain deceleration or fuel cutout
situations. If it does happen, then do not execute this strategy module while it is negative. (For further information on how
this situation might happen, consult with the FUEL feature team.)"

 

[FIND]

I thought that was it. I didn't figure they changed their method since earlier versions of EEC. I don't think the ECU even has a strategy for calculating engine load in EEC-V or any older version.

 

[Joe Dirt]

I'm not anywhere near the level of either FIND or Dale as far as analyzing the ECU equations, so I"ll just ask- knowing what you guys do, if my average MPG is spot on to the tenth of a gallon based on a fill-up today, the instant seems to median out at the average MPG according to data logging should I continue posting info, or is the data irrelevant?

I think my thought for the thread was to get some visual to what people are claiming on a daily basis to be true, and if they were correct or not as much as albeit rudimentary data can provide a clue towards. Not that the discussion isn't both welcome and interesting, but I worry are we over-analyzing the data to the point that it clouds the initial intent?

I'll have some more different data today on vac pressures, volumetric efficiency, and MAF readings...

 

[2000StreetRod]

Your fuel economy data is accurate

. . . if my average MPG is spot on to the tenth of a gallon based on a fill-up today, the instant seems to median out at the average MPG according to data logging should I continue posting info, or is the data irrelevant? . . .

I'm sorry for the diversion but I was concerned that conclusions might be based on inaccurate data. I should have checked the source code before posting my comments. My opinion is that your fuel economy data (instant and average) is as accurate as it could be for the instrumentation installed. The only way it would be more accurate is with the use of a fuel flow meter that would compensate for low fuel pressure and restricted injector flow.

Please continue to post your fuel data since we all can learn from your results.

 

[Joe Dirt]

No prob Dale- Your info is much more accurate than mine probably is, I just didn't want it to get to the point where we were missing the forest for the trees... Even some sweeping generalizations form 'pretty accurate' data on this thing might help some people see what their Ex is doing some of the time.

How about a WOT snapshot... It was 86*F according to the overhead display, so my crap factory CAI was apparently working fine.

 

[SoNic67]

No, the mileage is calculated from gasoline flow (gallons/hour) and speed (miles/hour).

PS: Gasoline flow is known because of the MAF readings (air flow) that are used to compute the injector duty-time. All of this is corrected with O2 sensors in closed loop to achieve a air-fuel ratio of 14.7:1.

 

[Keeper0311]

Pretty interesting reading. Considering the time I'm posting I haven't grasped to much of it, but I'll have to go back and reread it all. Seems like I need to slightly change my acceleration habits. I'm sure I'll be able to get in the 20's with my SOHC.

 

[FIND]

Been running torque for a while...

This was the result of a 260 mile drive today, and is a pretty average one for me (though fill-up yielded me a figure of 22.4mpg) I reset the trip counter at the beginning of my drive when I filled up, and left it sit for the rest of the drive.

I kept that speed pretty constantly, except for 15 miles at 64. No following other vehicles, with AC on, windows up. AC off doesn't really make a big difference, even when I can keep the windows closed, maybe .5 - .8 mpg on average? I don't really have enough good data, and there are too many variables to compare it anyway. I feel like with a better tune, I should be able to get it up to 24. I'm also pretty happy that I have it reading only .3 mpg off, since that could just be that my tank got a different level of full each time.

 

[2000StreetRod]

light vs moderate acceleration?

Does anyway have comparison fuel consumption values for light acceleration for a longer period of time vs moderate acceleration for a shorter period of time to achieve a certain speed?

 

[FIND]

On my V8... There isn't a whole lot of difference. The differences are minor at best, though I will try and figure out a good way to track fuel consumption during acceleration only.