Honda is developing a variable compression automobile engine: MPG up 7.4%

[MetroMPG]

Originally Posted by MetroMPG

• The engine was durability tested to 1 million cycles.

That seemed low to me, so I did the math:

2500 RPM = 150,000 revolutions (cycles) per hour

= 6.6 hours of testing at that engine speed to get 1,000,000 cycles.

(... assuming 1 crankshaft revolution = 1 "cycle")

I trust Honda normally tests much more than 1 million cycles before things get into consumers' hands.

[some_other_dave]

I would be surprised if "cycle" was 1 rev. I would hope that one "cycle" was one engine start-load- engine off-cool cycle.

-soD

[jmonroe]

I would bet that 1 cycle was probably switching from low to high and back to low.

[NeilBlanchard]

Hi,

Are there any pictures or drawings of this? I'm a visual-type person...

[theunchosen]

Its one rotation of the crankshaft. One rpm=one cycle.

Its not being released to the public yet so no need to do 100 hr testing yet.

This was a scale test to determine whether or not the theoretical advantages would scale up and would be effective over time.

Now they'll run a system until they break it, since a 7.5% increase is pretty good.

On a related note its going to allow(coupled with V-TEC, GDI and stratified injection) a much greater spectrum of FE-HP. Higher compression(via adjustable heads) more aggressive valve timing and more fuel(via stratification) gives you more power while lower compression more aggressive valve timing and warmer charge(injecting little bits of fuel gradually to keep temps up as well as having less fuel evaporate overall) could yield substantial FE.

[Daox]

Here is my interpretation of what they said. The inner piston is the bottom one, the outer is the top part in the picture (I made it transparent). The outer piston rides up and down on the center shaft area.

[Deezler]

Originally Posted by theunchosen

Its one rotation of the crankshaft. One rpm=one cycle.

One complete 4-stroke engine cycle = TWO revolutions of the crankshaft

And I seriously doubt they are running at 1 rpm....

[theunchosen]

MM, lol sorry Deezler I should have specified. I mean that what they were counting were RPMs. Every time the crank shaft goes around your counter goes up one.

I doubt it too.. If you got that from me I'll be more careful in my phrasing in the future.

[Deezler]

No sorry I was just giving you a hard time, haha.

But if they were using engine cycles as their counter for test cycles, then it would still only count once for every two revolutions.

I am sure they durability test their engines for much more than 1 million engine cycles too. If it was idle to full load sweeps as "cycles" then 1 million would be an insanely high amount! Like, a few thousands hours or more...?

[Formula413]

Interesting stuff. All it needs now is a camless valvetrain and we might be able to keep using this inefficient lump we call an internal combustion engine for a few more years.