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Best Engine RPM for minimal FE loss.

1 bar burn 2 bar burn RPM

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99 replies to this topic

#1 OFFLINE   John Sparks

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Posted 23 December 2013 - 01:28 PM

Okay, so I used to drive a Civic Hybrid, and adjusting to this car has been a little bit of a challenge, (Operates completely different) however I love my Cmax! I've seen a lot of discussion about a 1 bar burn vs a 2 bar burn, and while charging and power is better on a 2 bar burn, I don't think it is the most efficient method.

Something I learned with my Civic is that keeping the ICE at or below 2,000 RPM kept my efficiency up. Although the Cmax doesn't have a prominent tachometer, it can be selected in "My View". I'm finding that I have minimal FE loss when I do not allow it to go over 2000 RPM. Not great up hills, I sometimes get down to 25 mph and would never attempt it on a 2 lane highway or interstate, but gain great speed on the way down. On flat groud I find that the longer you burn at 2000 RPM the more speed you gain and often time will get up to 65-70 and a 90% battery and 55-65 instantaneous FE before dropping back in to EV mode.

So this is basically how I roll. I use Empower and run EV until my threshold falls below one bar and then switch to my view and maintain a 2000 RPM burn until my battery is up and it switches to EV assist or I come to a "decent" downward run. As the battery charges the engine RPMs will slowly drop below 2000.

After filling up the other day I ended my trip at 59.8 mpg for 27 miles, my tank is now at 49.3. It would be much higher if it wasn't for the short runs to the store over the weekend, short trips kill FE.

Anyway, I would like to get other drivers input on this or if anyone else has tried it, what they think.

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#2 OFFLINE   ptjones

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Posted 23 December 2013 - 07:44 PM

Okay, so I used to drive a Civic Hybrid, and adjusting to this car has been a little bit of a challenge, (Operates completely different) however I love my Cmax! I've seen a lot of discussion about a 1 bar burn vs a 2 bar burn, and while charging and power is better on a 2 bar burn, I don't think it is the most efficient method.
Something I learned with my Civic is that keeping the ICE at or below 2,000 RPM kept my efficiency up. Although the Cmax doesn't have a prominent tachometer, it can be selected in "My View". I'm finding that I have minimal FE loss when I do not allow it to go over 2000 RPM. Not great up hills, I sometimes get down to 25 mph and would never attempt it on a 2 lane highway or interstate, but gain great speed on the way down. On flat groud I find that the longer you burn at 2000 RPM the more speed you gain and often time will get up to 65-70 and a 90% battery and 55-65 instantaneous FE before dropping back in to EV mode.
So this is basically how I roll. I use Empower and run EV until my threshold falls below one bar and then switch to my view and maintain a 2000 RPM burn until my battery is up and it switches to EV assist or I come to a "decent" downward run. As the battery charges the engine RPMs will slowly drop below 2000.
After filling up the other day I ended my trip at 59.8 mpg for 27 miles, my tank is now at 49.3. It would be much higher if it wasn't for the short runs to the store over the weekend, short trips kill FE.
Anyway, I would like to get other drivers input on this or if anyone else has tried it, what they think.


On my last two record runs I used the two bar method, I use a ScanGauge, most of time I'm 2000rpm's or less. That was 65.4mpg/909mi./13.9gal.

Paul

#3 OFFLINE   ScubaDadMiami

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Posted 23 December 2013 - 07:51 PM

First:  Excellent first post, and welcome!  :thumbsup: I am guessing that your C-MAX was not used, and therefore has next to no miles.  So, you will definitely be up in the 60's after break-in.  Nice! 

 

I've never used the tachometer.  So, I can't directly comment.  Is there not a correlation between RPMs and bars?  If so, what does 2,000 RPMs come out to be, somewhere between 1.75 and 2 bars?

 

I have found that there are different ICE burns that I use for different purposes.  For example, I tend use lower bars for longer burns when going up a very long incline, or if I am at a low SOC.  I go with 2 bar burns when going up a shorter significant incline (we have lots of bridges around here), or where SOC is higher.  If SOC is very low (after I have just done a really long glide), I can go with a few pulse and glides at about 1.75 bars.  If I am doing well at keeping up the SOC, I will go at least 1.75, often 2. 

 

If I am traveling a memorized route, I can do burns that don't quite fit with the above, because my goal is to keep moving.  For example, I am willing to waste a squirt of gas in order to hit the traffic light in sequence, more than making up for the gas consumed by not having to stop and start. 

 

In general, my main rule is to have ICE operating the least amount of time possible.  I find that more important than plus or minus .25 bars.

 

Looking forward to reading more of your posts!


Edited by ScubaDadMiami, 23 December 2013 - 08:08 PM.

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#4 OFFLINE   ptjones

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Posted 23 December 2013 - 09:06 PM

There doesn't seem to be any direct connection between rpm's and bars, lots of variables.

Paul

#5 OFFLINE   Tdefny

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Posted 23 December 2013 - 11:27 PM

They are generally (but not perfectly) proportional except the bars lead the RPM. The bars represent load on the drive system in KW. The greater the load, the faster the computer will run the ICE to provide the power that you are requesting. Thus there is validity in using a 1 bar vs. a 2 bar burn as compared to constantly looking at the faculty.

#6 OFFLINE   John Sparks

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Posted 23 December 2013 - 11:38 PM

First:  Excellent first post, and welcome!  :thumbsup: I am guessing that your C-MAX was not used, and therefore has next to no miles.  So, you will definitely be up in the 60's after break-in.  Nice! 
 
I've never used the tachometer.  So, I can't directly comment.  Is there not a correlation between RPMs and bars?  If so, what does 2,000 RPMs come out to be, somewhere between 1.75 and 2 bars?
 
I have found that there are different ICE burns that I use for different purposes.  For example, I tend use lower bars for longer burns when going up a very long incline, or if I am at a low SOC.  I go with 2 bar burns when going up a shorter significant incline (we have lots of bridges around here), or where SOC is higher.  If SOC is very low (after I have just done a really long glide), I can go with a few pulse and glides at about 1.75 bars.  If I am doing well at keeping up the SOC, I will go at least 1.75, often 2. 
 
If I am traveling a memorized route, I can do burns that don't quite fit with the above, because my goal is to keep moving.  For example, I am willing to waste a squirt of gas in order to hit the traffic light in sequence, more than making up for the gas consumed by not having to stop and start. 
 
In general, my main rule is to have ICE operating the least amount of time possible.  I find that more important than plus or minus .25 bars.
 
Looking forward to reading more of your posts!


Thank you for your reply. I did buy my C-max new. (I'm actually a Ford Sales Rep) I have about 3300 miles on it at this point. I do believe I have noticed some difference in it in the last 500-600 miles. One thing that is so very different about this car vs my Civic Hybrid is the way it works and charges the battery. My initial reaction to the Cmax was a bit negative. With my Civic, if the ICE was running I was able to easily keep the instant mpg around 50....so naturally was concerned at first when the engine would come on with the Cmax and my instant FE would drop to 20 or below.

Realizing that the Cmax is charging the battery and becoming more experienced with how it worked, I understand better, the Civic didn't charge the battery near as much and this is probably why the batteries in those cars fail so often. (I had 2 failures in mine). Anyway you can see why this was an adjustment.

To get to your question about the bars vs RPM. The bars merely represent load on the engine. Sometimes I can be at 1 bar and be at 2000 RPM, or 1.5, 1.75, or 2. Generally when I drop out of EV the engine is right at or right below 2000 RPM, and in most cases I can tell when I'm at 2000 merely by the way the engine, sounds/feels, if that makes any sense.

I can totally see where a 2 bar burn is practical up short steep hills however given that I have enough momentum I can make it up many hills pretty quick keeping it at 2000. Temperatures here are ranging from 50 (65-75) the last day or two, down to 17 degrees. I have noticed that when it's that cold the instant FE will get really high if the battery is charged and the heat is on. Anyway, I was wondering around what mileage would you consider the vehicle "broke in" the manual says not to bother worrying about FE until after 1000 miles and we generally tell everyone break in is 5000-6000 miles. I'm just curious what people are finding to be the most accurate, on average how much difference you noticed, and how much warmer climate temperatures affect FE, warmer as consistently over 70. I just got mine in November and it will be several months before I get to find out for myself. (I'm a little impatient)

Thanks
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#7 OFFLINE   Jus-A-CMax

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Posted 24 December 2013 - 01:12 AM

1 bar burn, 2 bar burn... crikey...do we have an AA pyromaniac here out for REVENGE!? Who would coin such terms, lol.

Welcome to the forum John :)


Edited by Jus-A-CMax, 24 December 2013 - 01:20 AM.

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#8 OFFLINE   MacGyver

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Posted 24 December 2013 - 01:36 AM

Hey John, great post- I tested your 2000rpms method some today with encouraging results- it's interesting because I've used "Torque", an android app, and a bluetooth OBD sensor to determine that the optimum speed/gearing is between 70-73mph, which results in 40-60mpg on level ground (minimal engine load=instant mpg volatility), and even remains the most efficient when going uphill- Torque has an instant MPG readout accurate to a tenth of a gallon (well, I'm assuming it's accurate anyways, and you know what happens when you do that) and 70-73mph=20-23mpg whereas slower speeds=19mpg or less.

 

Yes, I know that seems counterintuitive, but those are the numbers I get from Torque.

 

Torque also has a Load readout so you can more accurately guage how much work those rpms are doing... and lots more- for a total investment of $15

 

I was surprised to find that 65mph was more efficient than 55, and in general, had been finding that faster was better than slower for FE, butt still was failing to reap really high FE #s, so am quite excited to find almost 20mpg during accelleration whereas before I was following the quick accelleration to speed then cruising at much higher FE. So far, this seems to be more efficient.


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#9 OFFLINE   MacGyver

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Posted 24 December 2013 - 01:39 AM

1 bar burn, 2 bar burn... crikey...do we have an AA pyromaniac here out for REVENGE!? Who would coin such terms, lol.

Welcome to the forum John :)

 

A rocket scientist or a science fiction reader- "burn" is slang commonly used for seconds of rocket thrust expended to change direction and/or velocity...


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#10 OFFLINE   MacGyver

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Posted 29 December 2013 - 05:44 AM

I've been testing the heck out of your 2000rpm lately, with very encouraging results, on the order of 50-60mpg regularly. Thanks!



#11 OFFLINE   John Sparks

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Posted 29 December 2013 - 05:01 PM

That's good to hear! I wonder if anyone else in the forum has tried it extensively? Around here the temperature has dropped, so has my mileage. Has anyone else ever noticed a drop in mileage when it's raining? I had some drop with my civic but on this thing it seems like I can barely get over 43 or 44 MPG when we're having a decent storm.

#12 OFFLINE   ptjones

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Posted 30 December 2013 - 09:33 AM

That's good to hear! I wonder if anyone else in the forum has tried it extensively? Around here the temperature has dropped, so has my mileage. Has anyone else ever noticed a drop in mileage when it's raining? I had some drop with my civic but on this thing it seems like I can barely get over 43 or 44 MPG when we're having a decent storm.

I can loose up to 5mpg in the rain caused by the increased resistance of water on the road. The wider the tire, the more surface area, the more drag. :) 

 

Paul



#13 OFFLINE   fbov

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Posted 03 January 2014 - 07:44 PM

1 bar burn, 2 bar burn... crikey...do we have an AA pyromaniac here out for REVENGE!? Who would coin such terms, lol.

 

A rocket scientist or a science fiction reader- "burn" is slang commonly used for seconds of rocket thrust expended to change direction and/or velocity...

 +1

 

The analogy is quite apt, especially considering the relative thrust available.

 

ICE is analogous to a chemical rocket engine, what most folks consider a "rocket" because they have enough thrust for lift-off. That means thrust levels must be greater than vehicle weight, and with all that thrust, timing is critical to getting the right trajectory. Timing is also critical for fuel conservation, as you're burning it at a tremendous rate, and once you're out, you're out. Think of any Apollo movies; it's all chemical rockets and reaction jets (release of gas under pressure). Kind of the ultimate "pulse and glide."

 

EV is analogous to an ion drive engine, a more recent development that works the opposite way, very low thrust, but with very, very long burn duration. The craft carries a gas "fuel" and solar panels. The solar panels generate electricity, which is used to ionize the gas and accelerate the ions to very high speeds, so high that the ions' tiny mass still transfers momentum to the craft. It uses grams of fuel/hour, not millions of pounds/minute.

 

So next ime you take off from a stop sign, think in terms of ICE as a high thrust engine that needs to run a limited amount of time, and EV as a low thrust engine that won't get you up to speed anytime soon, but will maintain speed against parasitic losses. I've gotten to timing my burns... sometimes only 5 sec. of ICE is enough to top the next hill or reach the next light. I almost feel like a rocket jockey!

 

Have fun,

Frank


Edited by fbov, 03 January 2014 - 07:56 PM.

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#14 OFFLINE   MacGyver

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Posted 04 January 2014 - 03:46 AM

Thanks again John, I've increased my mpg by about 7-10% so far by slowing down and using this method, but my android app that gets data from a bluetooth OBD is seeming to indicate that the CVT changes the formula for best mpg to make it more complex, such that "load" may be as or more important than simple rpm (or some combination of the two), since with the CVT we go faster and faster with the same RPM given careful acceleration and level ground...

 

I've seen my instant MPG actually go UP by increasing my speed and level of acceleration, which kind of makes sense given my discovery that the C-max's most efficient speed is 75mph... however, I think I need to calibrate my Torque better to work with the C-max, it's very much a work in progress, the hybrid battery level readout doesn't even work yet... suspect C-max specs are different than prius, maybe that's all the torque can understand at this point?

 

More news and data as I get it! I think I should be able to get line graph readouts from Torque of "burn" levels and acceleration, enabling easier analysis of efforts to maximize MPG!


Edited by MacGyver, 04 January 2014 - 03:47 AM.

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#15 OFFLINE   Ryan McEachern

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Posted 04 January 2014 - 06:45 PM

MacGyver,

I have followed this thread with interest, but I need you to explain to me slower and more carefully how you came to decide that 75mph is the C-Max's most efficient speed. As a physics guy, I just can't make sense of it. I have an open mind about these things, so lay it on me.
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#16 OFFLINE   John Sparks

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Posted 05 January 2014 - 02:48 PM

Thanks again John, I've increased my mpg by about 7-10% so far by slowing down and using this method, but my android app that gets data from a bluetooth OBD is seeming to indicate that the CVT changes the formula for best mpg to make it more complex, such that "load" may be as or more important than simple rpm (or some combination of the two), since with the CVT we go faster and faster with the same RPM given careful acceleration and level ground...

I've seen my instant MPG actually go UP by increasing my speed and level of acceleration, which kind of makes sense given my discovery that the C-max's most efficient speed is 75mph... however, I think I need to calibrate my Torque better to work with the C-max, it's very much a work in progress, the hybrid battery level readout doesn't even work yet... suspect C-max specs are different than prius, maybe that's all the torque can understand at this point?

More news and data as I get it! I think I should be able to get line graph readouts from Torque of "burn" levels and acceleration, enabling easier analysis of efforts to maximize MPG!


I'm glad to hear this is working for you. I would agree that the formula is constantly changing as load changes and battery level increases. Once battery level increases as well as speed, load decreases and your Instant FE goes up. You should also notice that if you have been holding the accelerator at a steady position, instead of 2000 rpm you will have dropped to 1700-1800. As a matter of fact if you apply more pressure to bring it back up to 2000 it will go into EV Assist mode.

I'm glad that I was able to contribute. Look forward to seeing more of your posts and I hope others out there are having success as well. I wonder what ever happened to scuba dad

#17 OFFLINE   ScubaDadMiami

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Posted 05 January 2014 - 08:36 PM

 I wonder what ever happened to scuba dad

Was I supposed to get back about something?  :waiting:


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#18 OFFLINE   Jus-A-CMax

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Posted 05 January 2014 - 08:43 PM

Was I supposed to get back about something?  :waiting:

lol, I dunno either...

 

Hey SDM, remember my ole "My 2c: EV" thread...we talked about 1 bar and 2 bar. I didn't check the tachy either but lately I've been flipping between the EMPOWER and the MyView where I set the tachy. I noted that it all depends on the road and speed, a 2 bar could be 2K rpm or 3K rpm. My rule of thumb now - as I sit mostly with the EMPOWER, is about 1 3/4 bar burn after my 15mph EV start...that gives me 2K rpm. Its all relative. Somehow for me...at the end of the day....I still prefer the 2 bar (or 2.1 bar) straight burn as the sweet spot for the decent acceleration & charging...but lack the scangauge to prove this.


Edited by Jus-A-CMax, 05 January 2014 - 08:44 PM.

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#19 OFFLINE   ptjones

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Posted 05 January 2014 - 11:41 PM

Two Bar worked for me and it is simple to do. :)

 

Paul


Edited by ptjones, 05 January 2014 - 11:41 PM.


#20 OFFLINE   John Sparks

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Posted 06 January 2014 - 01:55 PM

Was I supposed to get back about something?  :waiting:



LOL. No, I suppose not. For some reason I thought you would chime back in. :D






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