Deactivating the Atkinson cycle

Too much too soon I know but I want to do some research on this. I'm looking for someone to steer me in the direction of some useful information.

• "Recently, the term "Atkinson cycle" has been used to describe a modified Otto-cycle engine in which the intake valve is held open longer than normal to allow a reverse flow of intake air into the intake manifold."

• "The goal of the modern Atkinson cycle is to allow the pressure in the combustion chamber at the end of the power stroke to be equal to atmospheric pressure; when this occurs, all the available energy has been obtained from the combustion process."

• "The disadvantage of the four-stroke Atkinson-cycle engine versus the more common Otto-cycle engine is reduced power density."

• https://en.wikipedia.org/wiki/Atkinson_cycle#Modern_Atkinson-cycle_engines

So with that and the fact that we know the new V6 is able to switch back and forth between Atkinson and Otto it can reasonably be concluded that it would be possible to program the ECU to run the engine on an Otto cycle permanently. Obviously this would result in MPG reduction.

1. My questions to anyone who knows, how accessible have Toyota ECU's been in the past?
2. How much data can be flashed onto them?
3. Are they locked up for the most part or has someone managed to break into them?
4. Who makes good replacement ECU's for Toyotas?

I'll admit this is probably a fruitless endeavor but I'm interested in Toyota ECU's none the less so hopefully this thread can get two birds stoned at once.

 

What are you trying to acomplish? There is ZERO benefit to disable Atkinson cycle. Its nothing more than a different way to use the VVT system.

 

4.0 swap.

 

2jz swap

 

Why get rid of it? Isn't it the main reason the Tacoma is punishing the Colorado in MPGees? Oh wait.

 

Don't think that method will do anything except void your warranty.

 

Probably would get better MPG than a turd gen.

 

This. You're not going to make it any faster, just less efficient. So what's your goal here?

 

Right but it reduces power density in the cylinder and thus reduces motor output, if I understand it correctly. As Rock Lobster insinuated the motor operates in an Atkinson cycle at low RPM's... my thought process was that if you could have it running an Otto cycle at all times you might see an increase in low end power, albeit insignificant most likely.

Yeah it certainly is there to produce better MPG but I'm willing to trade MPG for power.

 

Doing it right would be a 1GZ-FE:

 

I was going to suggest LS, but was trying to stay with a yota engine.

My 550+HP G8 does 25mpg highway at 80mph. My TRDOR does 17, tops, at 70mph

 

I think you're misunderstanding what this engine does. It doesn't run on the Atkinson cycle at low RPMs, rather low load. Everything changes when you put your foot down

 

correct. Atkinson cycle only runs while at highway cruising speed

 

Wow. Digging the C3-PO and R2-D2 colors!

 

If you want more powah and don't care about mpgs go get yourself a tundra and throw a supercharger on the 5.7.

 

Fair enough. Makes sense. I knew it was a low load thing. With an auto if it has low load it will be low rpm. Low load power is still desirable in my opinion. And unless I understand the Atkinson cycle incorrectly, an Otto cycle will produce more power than an Atkinson cycle.

 

Take the ECU only a few thousandths of a second to change between atkinson or otto. you'll never feel low on power due to atkinson. The lack of power due to 3.5 liters of displacement is a whole different argument

 

Do the benefits outweigh the risks?

 

Good point. I guess my initial concern is stemmed from the thought that Toyota programmed it to run in Atkinson more often than I'd like to produce better MPG numbers. Fwiw, the motor produced more than enough power for me when I sunk my foot into it on the test drive but it was weak as dishwater at low RPM. Not surprising at all but I figured the Atkinson cycle might be some what to blame for this. I've had a 4.0L I6, 4.0L V6, 3.8L V6 and 3.5L V6 in the past and present that produced lower peak power output (except the 3.5) and yet all felt far more peppy at low RPM's. Needless to say, none of them had Atkinson cycles.

 

Its the trans that kills the power. It wants to be in as high of a gear as possible. Stick it in manual mode and keep RPM around 3k, its plenty peppy