Ideal RPM Range???

[madapple]

Hello again,
I have been experimenting with the RPM range I was running in to get better mileage. I think i have been "lugging" the engine down to much and running it with a little higher rpm's and a lower gear might get better MPG's.
I live in a very hilly area and use 3 & 4th gear a lot, I go to 5th anytime I am going down hill or can for a while.
What do most of the "veterans" here do? I have heard that about 3000rpm is the sweet spot for this engine.
My last tank was 62.7mpg and the current is about 59.9, the temps here are running about 25 degrees in the morning and mid 40's for a high. I also just checked my tire pressures again today and I am at 44psi, I had one low tire.
Thanks
Darrell In Indiana

[02insight]

3000rpm might be ideal for torque and power, but for MPG I try to keep it at or below 2000rpm, and above around 1300 to prevent it from lugging.

You dont want to keep it at 3000rpm also because at that point it is also running on all 4 valves per cylinder for more power.

but since you are in a hilly area, you probably need the power, but try keeping it under 2500rpm, because thats the point where VTEC engages.

[Eli]

VTEC engages at 2800RPM in my experience, but it does depend a little on other factors since it's oil pressure based.

Keeping it below 2,000RPM will give you the best fuel economy, but sometimes you can't do this if there are hills around.

Hypermilers keep it around 1200RPM.

You can't really lug the Insight engine. If a lugging situation is imminent, assist will be activated.

[IamIan]

For my 2 bits....

Originally Posted by madapple

I think i have been "lugging" the engine down to much

'lugging' the insight engine has a good chance of putting it into rich burn ... as the dynamic air to fuel ratio of the I1 would try to give you more power at the cost of energy efficiency ... not what you want for better MPG.

You are also likely ( without MIMA ) as others have posted to trigger the IMA assist ... which depending on the specifics of the larger context may or may not be a MPG good idea ... when IMA is a efficiency benefit and when it is isn't is kind of it's own discussion... one that's come up from time to time.

Originally Posted by madapple

I have heard that about 3000rpm is the sweet spot for this engine.

The BSFC chart for the non-Lean Burn state of the I1 ICE puts the highest tiny ~38% efficiency point just bellow 4,000 RPMs ... in non-lean burn and ~3,000 RPMs the best you can hope for would be ~35% ICE efficiency.

Lean Burn is significantly more efficient than just about any non-Lean Burn state for conversion of chemical energy of the gasoline into mechanical energy to move the car ... no matter what RPM or load you are at.

Originally Posted by madapple

running it with a little higher rpm's and a lower gear might get better MPG's.

Higher RPMs have higher amounts of frictional losses ... this can be countered / balanced if you happen to be in the right set of conditions ... for example if you have the choice between either:

#1> Higher Gear with low RPMs , but not in Lean Burn.
#2> Lower Gear with Higher RPMs , but in Lean Burn.

Under most contexts ... the efficiency benefits of Lean Burn are larger than the additional frictional losses of higher RPMs.

If you can maintain LB in the higher gear with lower RPMs , you would get a bit of both , LB efficiency benefits and lower RPM friction befits.

However ... that is not a guarantee that lower RPMs in LB are always more energy efficient ... that other RPM points in LB ... with both the Air to Fuel ratio and the Ignition Timing both changing dynamically in our I1 engines ... a conventional BSFC chart is not able to properly display the range of operating conditions.

- - - - - - -

All that having been said...

For myself ... it depends on the context ... but generally as my logs have shown me ... I spend my RPM time as follows:
~63.1% of my driving is bellow 2,000 RPMs.
~36.8% of my driving is between 2,000 RPMs and 3,000 RPMs.
~0.003% of my driving is between 3,000 RPMs and 4,000 RPMs.
~0.00007% of my driving is over 4,000 RPMs.

I don't have a set rule for every context ... different situations I drive differently ... The one general rule ( with very few exceptions ) more Lean Burn ( no matter what RPM or load ) is better for your efficiency and MPG.

[3-Wheeler]

I rarely run above 2000 rpm.

When I first bought the car, I used to think that running at 45 mph in fifth gear was "lugging" the engine. For me it was a matter of perspective.

Before the Insight, I had a Chevy Cavalier that had lower gearing than the Insight, so it took some time to get used to how low the Insight engine can run.

Now I regularly run at 30 mph in fifth gear based on circumstances. The important thing is to get a feel for throttle control.

This year I had six tanks over 1000 miles based on the above technique.

Jim.