Let's be sure we all stay calm and civil to one another.

While this is a topic near and dear to all our hearts, let's also keep in mind that we all live in very different areas with very different climates, roads, and distances. What works for one person may just be impractical for another.

That's where personal experimentation comes in to find which techniques work best for you and your vehicle on your commutes.

 

Hi Scott

The torque in the Atkinson cycle engine in our FEH/MMH is much different than what they call the standard Otto cycle engine in most cars. The Atkinson cycle is not generally used because they have much less torque at low RPM's. However, they do have better efficiency (I think it's around 10%) than the Otto cycle engine. In a hybrid, the electric motors "assist" the torque of the Atkinson cycle so you have near or even more torque than the Otto cycle engine of the same size. This is why Ford says that we have almost the same power as the V6 Escape. You will get the best FE without using the electic motors for assist, but they are there if you need them for added torque and speed.

If you look at the torque curve of both engines, you can see why at certain RPM's, the Atkinson does not develope it's best torque for acceleration. In addition, if you are driving at higher speeds where headwinds and other things like wind from a passing vehicle tend to slow you down, the RPM's can drop faster in the weak RPM ranges. This causes you to accelerate harder and burn more fuel. 1,900 to 2,200rpm is not as bad as 3,000 to 3,500rpm, but 2,400 is much better for accelerating if you need to go above 1,900rpm. What I'm saying is you might as well go to 2,400 and get to the desired speed rather than dick around at 1,900 to 2,200rpm's and waste fuel while accelerating. Also, after 4,000rpms, the torque curve heads south on the graph, so there's no need to go there either.

Like Pravas Prime stated, there are many factors that play a role in why you can only get 34mpg, but I'm only addressing acceleration here.

Here is the torque graph your looking for:
http://www.cleanmpg.com/photos/showp...to/864/cat/508

Again, for those who don't understand "Pulse" as in P&G, it is accelerating to your desired speed the most efficient way possible. See above.

GaryG

 

Oh, that must make you a lot of friends. You pull over into the passing lane, and not pass the truck as you should (if common courtesy isn't enough reason, its a $100 to $300 fine here in PA if you don't). Instead you block the normal flow of traffic in that lane so that the truck can move over too.

No wonder hybrids have gotten such a bad rap.

 

It's all about traffic flow and common sense Walt. What good is it to make that big rig come to a stop or slow down the traffic flow? It takes him much more time to get back to the flow of traffic and alot of others suffer behind him. It's not common courtesy to block and force a trucker to come to a stop here in Florida, and it's not a violation to not pass. Slower traffic should remain in the right lane, but if the traffic just to the left is moving at the same speed, no problem. Anyone with any common sense would also know you don't halt fast moving traffic in the left lane just to let someone ahead of you change lanes. If you pay attention like the truckers and I do to traffic flow, it would make your commute much more safe and economical. It's when the driver isn't paying attention and driving along the side of trucker at the same speed that causes problems.

There is a reason I get the mileage I do, it's called defensive driving along with common sense. It doesn't make any sense to get behind bad drivers, but truckers generally have good records and good reasons for changing lanes. When they put their turn signal on, it's not the time to change lanes and speed up to pass IMHO.

GaryG

 

Not sure just how truckers got into this conversation but to chime in...

In europe, at least what I observed, truckers STAY in that right land regardless, PERIOD.

For myself I will often "pause" to allow a trucker to pull out and pass, mostly only when my lane is not moving all that much faster than the trucker's lane. Keep in mind that it will take the trucker quite a distance to come up to the new speed if there is a large difference between the left and right lane speeds. In the latter instance I will more often block the trucker, match speed and drive alongside the "tractor", until the car behind me reaches the "block" point.

But on an uphill climb or if I see or know one is upcoming I will not "pause", to allow a trucker in, EVER. The right lane is "reserved" for slow traffic and slowing, holding up, the higher speed left lane traffic, allowing that trucker to bring them to the lower speed of the right lane, even temporarily, is just plan wrong.

 

Atkinson cycle engines....

Remember the old saw that a turbocharger is run using FREE energy?

There is some truth to that, a turbocharger uses energy, HEAT energy, that would other wise be WASTED. Basically in the otto design the exhaust valves are opened before the ignited fuel air mixture has complete burned. So absent a turbocharger every modern day engine out there in use is WASTING energy, FUEL.

WHY?

Compromise.

If you look up the actual atkinson design you will see that it is a lot more complex mechanically than today's otto engines. The original actual Atkinson implementation has ~30% longer power/exhaust strokes than the intake/compression strokes.

The basic idea of the Atkinson cycle is to use ALL of the energy in that burning F/E mixture before opening the exhaust valves. So, if you consider the FUNCTIONAL displacement of an Atkinson engine instead of the actual displacement, the torque/HP curves of an atkinson engine are pretty much the same.

If you look at the referenced, linked, engine torque versus RPM you can see that at the point of peak torque, considering that the functional displacement of the Atkinson engine will be as much as 30% less than that of the otto engine, the Atkinson is a great deal more efficient, 170 vs 200 for the 30% "larger" otto engine.

A 2.3L otto engine becomes a ~1.6L Atkinson engine. There was a follow-on design modification, the Miller cycle, to the Atkinson design in 1947 by a fellow named, guess who, Miller. A 2.3L Miller cycle engine was used in the Mazda Millenia S a few years ago. The Miller Cycle makes use of a SuperCharger to increase the input charger level, effectively maintaining the engine "functionality" at 2.3L while still gaining ~23% FE advantage.

I admit that I have been puzzled, mightily, as to why someone hasn't yet converted on of these Atkinson Cycle to the Miller Cycle. Given the level of hybrid voltage/power readily available it seems to me it would be quite easy to throw in a synchronous A/C motor energized by yet another variable frequency drive system. Then the SC could be completely out of the "loop" only called upon to produce "boost" at half-throttle or greater.

Add this SC implemention, drop the engine actual/real displacement an additional 30%, remain at the current 0-60 times, and still improve FE by as much as another 20%.

And.

Have a "mode" switch (is Edson DeCastro still alive?) wherein if the driver foresees that highway "cruising" will be the dominant mode for a period of time the SC will be used as first choice when accelerating or regaining a set speed of the cruise control system. Or activating cruise control could "switch" automatically.

 

When accelerating, at ANY level, the CVT control system "wants" to get the ICE into the highest operating RPM possible. Keep in mind that an ICE is at its MOST efficient at or near WOT wherein pumping losses are minimized. The designers used a very unique CVT implementation so this procedure could be programmed, embedded, into the system firmware and here you are trying to defeat its core purpose.

 

Yes, but given the power curve, you can use it and try to control the rpm to be in the most efficient range by varying your acceleration for the best FE...that's the whole point. THe computer maximize the best efficiency for a given condition, but you're controlling it even further by changing the conditions (faster or slower acceleration for most efficient FE...so that's not defeating the purpose, it's enhancing what the computer doesnt know)

 

WOT is the point where the engine produces the most torque but is that necesarily the same point as when it is producing the CORRECT amount of torque to maintain the requested speed with the least amount of fuel consumption which is the point at which the engine would be acting most efficiently.

NOTE... I'm not contradicting what anyone has said. I'm not a mechanical eng or a mechanic. I'm just listening in and asking questions so I can understand the conversation. When I'm driving mine it doesn't seem like the engine is always running at wide open throttle because to me it would seem like it should be reving a whole lot more... I'm missing something in my understanding and just wondering what it is.

 

"...WOT is the point where the point where the engine produces the most torque but is it necessarily...."

WOT, or near WOT, is the most appropriate for any level of ACCELERATION in a CVT equipped vehicle, hybrid or no. WOT, pumping losses are reduced to a minimum. On the other hand when just cruising along at a constant speed WOT should NEVER be used, and isn't. At least not by any controlling ECU.

In non-CVT vehicles that's what O/D is all about, reducing the engine frictional losses by operating the engine as close to the absolute minimum RPM that will still produce enough torque to overcome the overall losses at that speed.

A CVT, especially the unique hybrid CVT implementation, is designed to give you the very best of both "worlds". The proper, lowest, engine RPM throughout a very wide range of cruising roadspeeds and also the abilty to go WOT for acceleration. Remember that your hybrid CVT has an infinitely variable ratio between minimum and maximum.The hybrid control ECU chooses the best CVT ratio for the ICE to just "barely" produce enough torque during cruising.

On the other hand the fixed O/D ratios in most non-CVT vehicles will almost always result in some level of compromise, only being optimal at specific roadspeeds.