Atkinson's Cycle

Dean724 · Nov 6, 2015

Broccoli said: ↑

If the ect was for towing (always has been always will be) @BlueT why would they have put it on multiple cars in the 90's early 2000's such as avalon...
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@BlueT ??

robertbank · Nov 6, 2015

Just for the record my old 1991 4Runner has an ECT button. I use it often when faced with a long steep hill to keep the transmiaaion from jumping from 2nd to 3rd frequently. My wife`s Avalon has the button as well, although it is hardly ever used.

The 3.5L engine has been put into other vehicles made by Toyota so so it is hardly a new engine. First time in the Tacoma but not a stranger in outher Toyotas around the world.

Take Care

Bob

First Taco · Nov 6, 2015

cougsfan[OP] initial post: ↑

Guess I am doing research after the fact because I have bought the truck.... But looking into the Atkinson cycle engine; it is kind of a neat concept. The intake and power stroke are different lengths for supposedly better efficiency. However looking at the actual fuel mileage people are reporting, it doesn't appear to be much, if any better than the older trucks. It appears to have a lot more moving parts and many more bearings. I am wondering if increased internal friction eats up the supposed efficiency gains?
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cougsfan[OP] initial post: ↑

Guess I am doing research after the fact because I have bought the truck.... But looking into the Atkinson cycle engine; it is kind of a neat concept. The intake and power stroke are different lengths for supposedly better efficiency. However looking at the actual fuel mileage people are reporting, it doesn't appear to be much, if any better than the older trucks. It appears to have a lot more moving parts and many more bearings. I am wondering if increased internal friction eats up the supposed efficiency gains?
Click to expand...

First Taco · Nov 6, 2015

cougsfan[OP] initial post: ↑

Guess I am doing research after the fact because I have bought the truck.... But looking into the Atkinson cycle engine; it is kind of a neat concept. The intake and power stroke are different lengths for supposedly better efficiency. However looking at the actual fuel mileage people are reporting, it doesn't appear to be much, if any better than the older trucks. It appears to have a lot more moving parts and many more bearings. I am wondering if increased internal friction eats up the supposed efficiency gains?
Click to expand...

My 2011 TRD 4.0 V6 4x4 I traded would hit 20 MPG. With new 3.5 TRD I hit 23.76 the first tank. Much better MPG and it is the faster of the two trucks.

heyphillip · Nov 7, 2015

David K said: ↑

This is why it is never a good idea to buy the first year of a new model... bugs need to be worked out!
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Would be nice if in 2017 they add a 8 speed transmission and a aluminum hood to reduce weight

dirtnsmores · Nov 7, 2015

Rock Lobster said: ↑

The F150 already has the aluminum panels for the current Tacoma price.
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Every chance you get LOL!

David K · Nov 7, 2015

What is a Tacoma then? Or did you finally sell it since you dislike it so much?

cougsfan · Nov 8, 2015

Tharris242 said: ↑

Presumably, they chose the duration based on maximizing Otto cycle power. The VVT system cannot change duration; so, that would significantly affect max power. Probably more pumping losses with shorter duration, too.
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Oh, so VVT only changes the timing not the duration (makes sense from a "do-ability" standpoint). So when they go to the "Atkinson" Cycle, they just delay the duration sequence of the intake valves in the stroke. So the valve probably does start opening well past TDC along with closing after BDC. It is all starting to make sense now.

heyphillip · Nov 8, 2015

Rock Lobster said: ↑

The F150 already has the aluminum panels for the current Tacoma price.
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From the numbers I've seen the gas milage isn't any different than the Tacoma

Tharris242 · Nov 8, 2015

cougsfan[OP] said: ↑

...So the valve probably does start opening well past TDC along with closing after BDC. It is all starting to make sense now.
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Just 33° after TDC; but, the exhaust valve can be open until 46.5° after TDC probably eliminating the need for an exhaust gas re-circulation system.

You can learn all about it in the link here:
2GR-FKS more 'Atkinson' than Prius.

Daytona Coupe · Nov 8, 2015

cougsfan[OP] said: ↑

I hate to admit it, but I have a degree in Mechanical Engineering too. And I know internal combustion engine theory fairly well. Conventional "Otto" cycle engines don't open their intake valves at exactly 0 degrees and close them at 180 degrees of the cycle either. Nor do exhaust valves do the opposite. They have valve overlaps that vary all over the place depending on what characteristics the engineer wants the engine to have. The stroke is the stroke, no matter what the valves do. Look at a two cycle engine; No one determines the stroke or displacement by port position, that would be preposterous.

What we are dealing here is with names. And names really don't mean much. What Toyota (and probably others) have done is cleverly mimic the characteristics of original Atkinson cycle without the excess baggage. That is good. But IMO it is sort of misleading to call it an Atkinson cycle. It is an Otto cycle with an unusually long closing duration on the intake valve. By definition, an Atkinson cycle has two different length strokes. The Atkinson Cycle name appears to be more of a marketing ploy than anything to acknowledge they are doing something different, which from that viewpoint, is probably OK.
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This is the most accurate post yet.

addicus24 · Nov 8, 2015

Isn't the 3.5 the same engine Toyota has been putting in their Sienna minivans?

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