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I have noticed a sweet spot at about 68mph, 2800rpm. MPG goes up to about 75 and I can keep speed.

Has anyone else noticed this spot? am I just imagining it? Any other sweet spots to know about?
 

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I often manually-cruise at 70-75 mph and get mileage in the mid- to high-60s, a/c on Econ at 72°. With the Rostra cruise on, that can drop to the high-50s to low-60s. See #6:

http://www.insightcentral.net/forums/mpg-issues/17233-whats-your-normal-mpg-55mph.html

Between 35-45 mph, normal city cruising, however, I can get substantially better mileage than other ranges. My ScanGage II frequently shows mileage in the 200+ mpg range, and the FCD display can max out for blocks on end without dropping speed on flat-to-slow-rolling Dallas streets. Here's what I recorded for a doubting Thomas last week on the way to his office:

 

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I have noticed a sweet spot at about 68mph, 2800rpm. MPG goes up to about 75 and I can keep speed.
My best MPG spot is about 45MPH but there is probably a reason for the sweet spot that you noticed @2800 RPM. Even though you may not get the best mileage at that speed and RPM, the VTEC kicks in at 2700 RPM when under engine load. At a point just before VTEC under engine load, your MPG may be a bit lower until the secondary valve changes providing a bit more power allowing you to ease off the throttle just a bit but still continue with VTEC engaged.

JoeCVT = Just your average CVT owner
 

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Discussion Starter #4
My best MPG spot is about 45MPH but there is probably a reason for the sweet spot that you noticed @2800 RPM. Even though you may not get the best mileage at that speed and RPM, the VTEC kicks in at 2700 RPM when under engine load. At a point just before VTEC under engine load, your MPG may be a bit lower until the secondary valve changes providing a bit more power allowing you to ease off the throttle just a bit but still continue with VTEC engaged.

JoeCVT = Just your average CVT owner
This spot is a transitory thing on my commute, as there is no real flat part for any considerable distance. (not to mention that part of it is highly patrolled.) But the VTEC was my suspicion as well.
 

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Kevin, that BSFC plot is off a CVT, and may be tainted by IMA. And if you draw horsepower isolines, you find that cruising at 4000RPM puts you in the >280g/kWh range.

I really wish we had a useable BSFC plot, because it would answer these questions authoratively.

@ac7ss: Your mpg figure sounds quite a bit high for steady state cruising on flat land. Try using the FCD button to record mpg across a predictable part of your commute, and do it in the opposite direction on your way home. Record the mpg using different techniques, and you'll be able to tell what works.
 

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Wow, I don't know how you're doing that well. I get about 47 when I'm at 75 and the A/C on 76.

My sweet spot is probably around 45 or so- I can get about 52.
 

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Wow, I don't know how you're doing that well. I get about 47 when I'm at 75 and the A/C on 76.

My sweet spot is probably around 45 or so- I can get about 52.
I'm not sure to whom that was directed, but... make sure your tires are at 50#s, like mine; watch your fuel bars, keep them above 75 mpg; immediately release the accelerator when you see an upcoming stop, whether potential (e.g., a red light a block away that could change to green) or actual (a stop sign); don't pass other cars; drive away from a stop as though you had an egg under your foot that you didn't want to crush; "pulse and glide," accelerate slightly to just past your desired speed, then release your foot off the gas slightly once you reach your desired speed, and as you slow down, repeat; and whenever possible, follow traffic (I'm not advocating drafting like a race car, but even at slow speeds, following another car two-three-four car lengths back makes a difference. Two seconds back on the highway, please). Do those, and you may see a decrease in your consumption... :D
 

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Here is what I did yesterday with an average speed of 45MPH on a 25 mile round trip:



This was with some hilly areas and some stop and go....I wish I had a long flat area to try this on a hot summer day....Temp was about 85F and both windows fully open. OEM tires at 50 psi.

For a six mile stretch of road, I was at 99.4MPG :) I took this picture at the end of my trip while in AutoStop.

I think for a CVT, the best sweat spot range is at 40-45MPH.

JoeCVT = Just your average CVT owner
 

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For a six mile stretch of road, I was at 99.4MPG :) I took this picture at the end of my trip while in AutoStop.
Wow, those mpg's are amazing!!

I think for a CVT, the best sweat spot range is at 40-45MPH.
I think the same is true for the MT, or possibly even a touch slower.

JoeCVT = Just your average CVT owner
Maybe you need to change "average" to something else???
 

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I know that it is nothing like what you can achieve in the MT Insight but not too shabby for a CVT model. When I first got the car back in 2004, I took off the OEM tires because I thought the rear was a bit unstable on certain areas of the highway (right hand lanes where trucks usually travel). I saved those oringal tires with only 5K miles on them just just put them back on the car this spring and immediately saw an improvement in mileage. The best I could do on non-OEM tires (that were still considered Low Rolling Resistance tires) was 74-75MPG on the same trip.

Now that the OEM tires are back on, I don't feel as unsafe as I initially felt. Must be all the years of driving the car.

I need to find a nice long flat road in New Hampshire with a 45MPH speed limit and no stop lights to see what the max mpg I could do. I would really like to see a 100MPG run one of these days :) I would also need hot weather and no wind.

JoeCVT = Just your average CVT owner
 

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Kevin, that BSFC plot is off a CVT, and may be tainted by IMA. And if you draw horsepower isolines, you find that cruising at 4000RPM puts you in the >280g/kWh range.

I really wish we had a useable BSFC plot, because it would answer these questions authoratively.
Someone with a scangauge should be able to offer some ball parks figures for rpm againt MAP at various speeds to populate the graph with some isobars.

Could be useful in confirming observations on the road or highlighting sweet spots that are worth trying out.
 

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Johnny, the left axis is labeled "indicated mean effective pressure", which is linear with torque. Since power equals torque times rotational velocity, the isolines have the same shape for any BSFC plot:


All that says is, if you need, say, 15HP to get the job done, choose the lowest RPM and widest throttle opening that provides that. I.e. put it in the highest gear you can. Good advice, but what about lean burn, and when should you use assist even if you know you'll have to pay it back with gasoline? The plot doesn't answer these questions.
 
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