Potential engine mod? Otto to Atkinson conversion

[theunchosen]

Ah that makes sense. marketing deception. . .

[Allch Chcar]

Now that we've got that all cleared up and this has had a good long cooldown period I can safely say we need to figure this one out. I will admit this topic has all the markings of an internet based argument. Something needs to change it's course.

The Atkinson cycle still uses fuel "better" than the Otto cycle. Even 20% would be substantial enough to warrant the spending of money. I don't see anything in the logic for the Miller cycle, you've trading 1/4 of the power for fuel economy but now you're boosting it. You're better off upgrading the engine size. A 2.5l 4-banger could easily replace a large number of the v6's out there if there was a power assist. There would have to be substantial efficiency gains to be worth it. And the usage of a supercharger/turbocharger reduced fuel economy overall unless in the rare case of downgrading displacement. The best case scenario, you're swapping it out of a V6 or V8 stock vehicle. I'm more averse to using an electric motor with the added weight of batteries in the case you just need something to boost stock MPG from a fuel miser. A supercharger/turbocharger is better than living with a V6 but you're trading engine life and reliability for it. Which really depends on how the person actually drives the car. If they rev it to compensate, you're digger bigger holes to fill in bigger problems. I should probably keep my examples to first person and what I'd do, but I'm trying to figure this out myself. I personally believe a 4-banger needs two torque peaks; 2500rpm and 5000rpm. A supercharger eats power despite what you do with it and the power difference between 2500rpm and 5000rpm is enough that you can cover all your bases.

[hyperyaris]

I thought Atkinson was a highly modified Wankel? Or am I thinking of another type?

[Allch Chcar]

Mazda did market a Miller Cycle engine with a supercharger, I believe. But Atkinson has nothing to do with the Wankel rotary. Rotaries are designed to be fuel hogs so nothing has been attempted to reduce their fuel usage.

Atkinson cycle was just a competitor's attempt at making a gasoline engine that didn't infringe the Otto cycle copyright. At least so I understood. The basic engine running on Atkinson cycle is similar to an Otto cycle engine, what is necessary to convert is where we're stuck.

[hyperyaris]

Ooh ok so Miller is the weird rotary one?

[Christ]

No, Miller Cycle is basically an Atkinsonized Otto Cycle engine (late cam events) with forced induction to make up the power loss.

[hyperyaris]

Then what is the strange one that turns in a circle and has uneven parts moving to make weird shaped combustion chambers lol?

[Christ]

A Miller-cycle engine is very similar to an Otto-cycle engine. The Miller-cycle uses pistons, valves, a spark plug, etc., just like an Otto-cycle engine does. There are two big differences:

* A Miller-cycle engine depends on a supercharger.
* A Miller-cycle engine leaves the intake valve open during part of the compression stroke, so that the engine is compressing against the pressure of the supercharger rather than the pressure of the cylinder walls. The effect is increased efficiency, at a level of about 15 percent.

Taken from: HowStuffWorks "How does a Miller-cycle engine work?"

There are two types of Atkinson Cycle engines, the RA, or Rotary Atkinson, and the PA, or Piston Atkinson. A true PA engine has a crankshaft that is modified from the Otto Cycle design, as a means to bypass patent restrictions, which often ends up giving the engine an expansion ratio that differs from it's compression (concentration) ratio.

Reference (although not a good one):Atkinson cycle - Wikipedia, the free encyclopedia

Adding a supercharger to an RA-type Atkinson engine would presumably serve to increase the dynamic compression, but it would not qualify as a Miller Cycle engine, since the Miller Cycle is designed to use a piston which begins the compression stroke against a supercharger's air charge rather than against the cylinder head.

[hyperyaris]

thanks...but there is another one that is really strange...I will research it

[Christ]

Image of Rotary Atkinson design:

From the Wiki link above.