Atkinson cycle question
 

Hey Guys,

My C-Max has in interesting trait that I wanted to share with you.

I have noticed that on the highway (70 to 75mph) the car will show a relatively low mpg at times and all of a sudden jump around 8mpg without anything changing in SOC, wind, speed, elevation, etc. I have found if I gradually increase and decrease my speed just a tiny amount, I can trick it into that mode, then hit cruise and it will stay there for miles, then depending on any steep hills, it may jump back out of that mode. My RPM only changes slightly when it goes into that high mpg state. So, I am thinking I am tricking the engine into an efficient state by hunting for it as I drive.

I am not an engine expert. So, I wanted your take on this.

Matt

Lean burn? Many cars it helps for the vvt to adjust if you accelerate past your desired speed, then coast down to a slower one. :eek:

Just a guess but they may be using the valve timing to control air flow and eliminate the throttle position and some pumping losses due to manifold vacuum.

This is an animation of the original Atkinson design which is completely different.

Animated Engines - Atkinson

regards
Mech

Yes, variable valve timing reducing pumping losses is what this engine does. My question is, is this what is happening when I suddenly see my MPG go way up without any outside conditions changing?

Matt

I don't know what a c-max is. If it is a hybrid, can you tell if it is dumping battery power when the mpg goes up?

Edit, looks like the The electric drivetrain can produce do 85mph by itself (68kw), so maybe.
http://en.wikipedia.org/wiki/Ford_C-...i#C-Max_Energi

Oh, don't forget your $550 rebate :)
They used a different model for testing, apparently that is "OK" with the EPA :/
Ford to Pay 2013 C-Max Owners for Efficiency Miscalculation | Edmunds.com

Yes, I recieved my $550 check. :)

Actually, I had no desire for a rebate. My mileage has always far exceeded the EPA numbers. The 47mpg has never been an issue for me. My in town MPG has always been far above 50mpg (in summer). My MPG on the expressway (65mph) is normally in the mid 40s. At 50mph, I can average nearly 50mpg and this was before my aero mods. Since my mods I am seeing far higher. To give you an idea, yesterday averaged 35 degrees F and I averaged 55.5mpg for the day (in town). This would normally be 48 or so when the car was stock.

Yes, I can watch my electric consumption. This car has an almost laughable amount of technology on board..... When the mileage jumps, it is not from electric system dump into the drive. The mileage jump is with the battery charging or at steady state.

Oh, though the car is capable of EV up to 85mph, the electric system in the non-plugin is 44kw. The plug in Energi is higher powered. The benefit of 85mph EV running is traveling down a hill or drafting. Under those conditions the car will drop into EV up at 85mph. Otherwise, on flat ground without wind, 75mph is about the max speed that the car will sustain any distance in EV.

As a side note, the car used to only run a max of 62mph in EV mode. However, Ford updated the software and now it runs up to 85mph in EV. That addition has given at least 1.5mpg gain on the expressway. So, it was a good update.

Matt

No surprise that smash the pedal and go joe is not making even epa numbers...

can you tell how much the battery is charging when the mpg is boosted vs not?

Yes, to a certain degree.

is there any correlation to the amount of charging going on and the mpg reading?