130 MPG Ninja 250

[alvaro84]

Originally Posted by renault_megane_dci

Oil pressure :
car iddle setting is usually a tad under 900 rpm
bikes iddle setting is usually around 1500 rpm

Bike engines usually revs up to 10.000 rpm and up.
Their oil pump has to cope with these high rpm meaning they are either small or under geared or a combination of both, requiring for a higher iddle setting.

...

Over-square engine :
just my opinion but the shorter the stroke, the least destabilized it gets at lower rpm.
More cylinders helps too.

I have two interesting vehicles, then

• The YARDIS idles at 500rpm with 4 cylinder when warmed up. Can be a bit shaky down there
• Teresa idles at ~1500rpm, even though the engine is a short stroke one with a redline of 7k. But she's kind of lacking at the cylinder count department (being a single)

[sendler]

Originally Posted by MPG_Plus

oversquare rules of thumb

What use of the term "over square" are you talking about?
.
Why "Over Square" Is Good
.
To me, over square means that the bore is bigger than the stroke. Which makes it a higher revving engine with more peak power output. Under square engines such as the new Honda NC700X have a stroke which is longer than the bore. Which moves the power band and redline lower for better fuel economy at the expense of peak power.

[renault_megane_dci]

By oversquare I meant the usual engine layout we use down here on the ground ;-)

[sendler]

Originally Posted by renault_megane_dci

By oversquare I meant the usual engine layout we use down here on the ground ;-)

Did you follow his link? What is that about with the airplanes.

[beatr911]

Apples and oranges on the airplane engine reference. The point refers to propeller pitch and rpm. Not bore/stroke.

On an ecomodder note though they are extolling the virtures high pitch and wider throttle opening (high manifold pressure). The same thing as gearing tall to slow the engine and opening the throttle wider.

Those Lycoming engines are like super reliable air cooled VW engines. Pretty basic low speed engines built to never fail. I don't know the bore/stroke often used in the Lycoming engines though, guessing they are undersquare.

[sendler]

Originally Posted by beatr911

wider throttle opening (high manifold pressure).

So high manifold pressure is another way of saying low manifold vacuum.

[renault_megane_dci]

(VW flat four are oversquare engines)

Who needs idle anyway ?

[MPG_Plus]

I am not trying to debate the definition of oversquare which is cut and dry and very clear and was only pointing out the associated rules of thumb have gray areas which can be very useful for economy. I believe the link is a well written article by the editor in chief of a pilots association and I respect the guy. His statements about reduced engine speed reducing friction are spot on and germane to the topic. I possibly could have gone on the low side of a safe idle and I plan to play with it a bit and see how much it affects my city mileage, because that is the reason I want for a lower idle. I don’t mind being the guinea pig or canary so to speak if others can benefit from my data, just don’t shoot the messenger. This also could lead to other solutions to the low oil pressure such as an electric oil pump that is set to kick in at low RPMs. Obviously the best savings at a light is to turn the engine off but then you have to be concerned about starter wear and tear. It seems that there are many examples on this site of thinking outside the box to gain efficiency.
Cheers,

[Grant-53]

Alan Smith posted 144 mpg in the latest Vetter Challenge event with his 2005 Ninja 250 streamliner this weekend so 130 mpg is not so outrageous anymore. See craigvetter.com for details as they become available.

[MPG_Plus]

Look's like they are going to post Allen's story in the near future. It should be interesting to see how he got the 144MPG and I'd like to know more about the winning diesel also.+