Just over a month of owning my '09 Hycon and I'm begging to understand how to drive to maximize fuel economy but the AVG MPG is deceiving (I think).

The other day I was driving in my neighborhood under 29mph/on pure electric and I reset my AVG MPG. So the instant MPG shows 99mpg but when I selected the newly reset AVG MPG it was pinned at 20mpg.

So every time you are on pure electric power your AVG MPG is only going up by 20mpg and not 99mpg that your instant shows.... so I assume we are actually getting better MPG's than what the AVG MPG actually shows?

 

It's actually an integrator. The longer time between re-sets of the AVG the more accurate. Maxing out pure electric may not always be the best strategy. You need to pay the battery back at some point and burning gas to do that is not as desirable as kinetic-to-electric during Re-Gen braking.

Long easy decelerations allow for the most kinetic recovery. Fast hard braking exceedes the battery power limits and just makes hot brake rotors.

Likewise hard accelerations puts the engine in power enrichment like the old carburetor power valve days.

 

But no matter how you drive it.... the 99mpg when you are in electric only counts for 20mpg for AVG MPG.

So when I am accelerating at 12-15mpg on gas or hybrid it counts for 12-15mpg on my AVG, but when I am reaping the rewards of driving in a way to keep the battery charged.... out of the 99mpg, I'm only getting 20mpg counting towards my AVG.

I think these things get better MPG than my DIC is saying I'm getting.

 

I put a good top tier premium gas, switch to 2wd, go up fast to speed limit and cruise from there. I also use the AFM by not putting it cruise control and keep it on V4 longer. maximum mileage range was 587 miles. the efficiency gauge is also a good indicator and make sure to keep it in the middle as much as possible.

 

The 99 is not actual for that instant. Mathematically moving without using fuel is an instantaneous infinity. But you need to use l'hopital's rule since division by zero is undefined.

When are you benefitting by optimizing? Electric only with engine off is not the only electric propulsion. Since you like to watch the instantaneous number, pay attention to decelerations without braking from 70 mph or lower. You will also notice 99 mpg on the DIC in V8 and V4 operation. This is fuel cut off. In a normal V8 like my Suburban V8 fuel cut off pumps air across the catalytic converter elements. This deceleration fuel cut off boosts fuel economy but the cooling and oxygenating of the cats limits the amount of time in fuel cut. So a conventional even on long mountain grade needs to”burp” some fuel in to keep the cats hot and operational.
On a long down grade the 2 Mode can go into V4 fuel cut. The 2-lane road down from Estes Park in Colorado is a perfect road for this. 44 miles and 1.2 gallons. Why? The late intake closing cam phaser can further reduce the non-firing air flow across the cats. The result is that it stays in fuel cut much longer than a conventional. Plenty of power on the way up I-70 to the tunnel and fuel cut on the other side. Net result ~20 mpg at posted speed from Denver to other side of Vail Pass.

With regard to the charging and discharging of the HV battery. It is not sized for long EV distances. It is sized to absorb kinetic stopping energy and then return the energy to accelerate the vehicle later. It is sized to run the vehicle loads and AC at the long stop light rather than burn fuel making a torque converter hot. Then the engine will sometimes stay in V8 a little longer to “pay the battery back”. If the system decides it is an efficient thing to do. Once you get “the knack”, you can drive a slight down grade at 50 plus mph in V4 fuel cut (99 mpg) and use battery energy ~10 to ~15 kW to stay in this V4 engine not firing late intake valve closing state. A real light pedal foot is required. At 50 mph and NO fuel used, you will benefit much more long term than 28/29 mph pure EV. It's just math, time and distance.

Time, energy, Brake Specific Fuel Consumption, BSFC and the calculus thereof is what is going on under and around you. So don’t obsess. Just drive it. Enjoy.

 

that's why I always see 99 not in the DIC but in the speedo?

 

Hillbilly, I understand but correct me if I'm wrong: theoretically if I were able to use electric mode 100% of the time at any speed with a full tank of gas what would my AVG MPG be.... infinity right? I could go on forever and not use an ounce of my full gas tank. BUT (and that's a big but) in my Yukon my AVG MPG would pin at 20mpg.

I'm still gaining distance (Miles), be it in pure electric mode or fuel cut-off mode, while using 0 gas (I understand "instantaneous infinity")... so you can't divide miles by infinity to obtain my AVG MPG (miles/∞=MPG)... but it sure as heck shouldn't only be giving me 20mpg for using 0 gas!

All I'm saying is the Yukon gets better MPG than stated on the DIC.... that's a good thing right?

 

"All I'm saying is the Yukon gets better MPG than stated on the DIC.... that's a good thing right? "

It may be getting better in that instant, but the best indicator is odometer divided by gas pump.

If you were up on top of a mountian and Re-Set the DIC, then drove down, you would see some impressive numbers. But that would be just for that interval. Conversely if you reset at the bottom and drive up, pretty depressing numbers.

Pure electric in a 3.1 Ton SUV with your battery is maybe 7/8 mile. So a short amount of "infinity" over a longer operating range.

The 20 number may be a built in starting point after a fresh re-set. You may have to experiment with that.

No matter what you need at least 20 miles to see a stabile average fuel economy number. And that may be a couple % off.