[Chance]

Attached is fuel consumption data used to compare naturally aspirated versus EcoBoost engines. This first picture is of a NA engine used as baseline. It may give some insight as to what EB can and can not achieve and why.

Data is in the form of a Brake Specific Fuel Consumption map on the right, and a more detailed section taken at 2000 RPM on the left. I wish this map had more data on it as is typical but it doesn't.

A member requested a copy, and I thought a few others may be interested as well. I'll have to do one picture at a time so EB will follow.

 

[Chance]

What can you do with this type of data? To put it in context for those new to this:

Let's assume I have a 3.7L with 3.73 running at 2000 RPM, and hence 63 MPH.

Let's also assume that based on load, van size, and wind conditions, that I need 50 horsepower to maintain this 63 MPH. That's 131 lb-ft X 2000 RPM.

Running through numbers, I find BMEP is approximately 6 bars, and hence BSFC to be an excellent 260 grams per kW-hour. In English that's .427 pounds per HP-hour.

So that's 21.4 lbs/hour of gasoline, or 3.56 gallons per hour.

Since van is traveling at 63 MPH, then instantaneous fuel economy is 17.7 MPG.

 

[rbisch]

3.5L ecoboost and HD-5

Chance, below is information from Southwest Research Institute regarding the ecoboost engine and propane.

http://www1.eere.energy.gov/cleancities/pdfs/patf14_ross.pdf

I would appreciate your opinion as to the value of purchasing a conversion if and when one becomes available.

 

[Chance]

Using the naturally aspirated engine as a baseline, we can then see what differences it makes with EcoBoost of "equal" engine displacement. Comparing the two gets a little more complicated; or so it seems to me.

 

[Chance]

By the way, we can see that with everything else being equal, and with load of only 6 bars, EcoBoost fuel consumption would be slightly higher at roughly 270 versus 260 grams of fuel per kW-hour.

 

[Chance]

Chance, below is information from Southwest Research Institute regarding the ecoboost engine and propane.

http://www1.eere.energy.gov/cleancities/pdfs/patf14_ross.pdf

I would appreciate your opinion as to the value of purchasing a conversion if and when one becomes available.

I'm not the right person to ask because I'm biased against most aftermarket modifications of significant scope. My preference is towards the OEM doing all the hard work and testing, and then if they think it's still a good idea, for them to stand behind the product under their brand.

The last thing I personally want is to get caught in the middle between two companies that point fingers at each other and leave the customer dissatisfied.

 

[VinceP]

Thanks for posting these.

I agree it would have been nice if they had put a few more of the curves on these graphs, but this is still enough to give a good idea of the relationships and to illustrate the relevant concepts.

It's a pretty impressive difference and a heck of a BSFC sweet spot.
If you were to scale down the turbo-DI engine to have a similar peak power output, you would see some real efficiency gains at lighter loads, while still holding on at the high end of the load range. Which I suppose should be no surprise at all when you consider what we have been experiencing over the last few years in the newer cars we drive.

 

[Chance]

....cut....

It's a pretty impressive difference and a heck of a BSFC sweet spot.
If you were to scale down the turbo-DI engine to have a similar peak power output, you would see some real efficiency gains at lighter loads, while still holding on at the high end of the load range. Which I suppose should be no surprise at all when you consider what we have been experiencing over the last few years in the newer cars we drive.

Exactly why I've been saying that axle gear ratios aren't as critical with EcoBoost once enough load is reached to make BMEP high enough to operate inside the broad "sweet spot" on curve. You can easily double the torque on engine, like when towing, and remain in sweet spot of efficiency. So EB doesn't need to downshift as often. The NA engine can accomplish the same efficiency range but has to downshift and use RPMs to develop the same power.

It can be seen from these curves that EB can save fuel relative to larger NA engines of equal power at low loads, but at high loads it can't save much because the larger engine can also be efficient. If always towing a large trailer, a 5.0L V8 can be operated as efficiently as the smaller 3.5L EB.

So 3.5L EB doesn't really save fuel over 3.7L NA. But if EB was downsized to 2.3L from Mustang, which has equal power, it could save fuel under normal driving conditions. The slower you drive the more it would save relative to 3.7L NA. Towing, not so much. That's my take anyway.

I'll try to post the "downsize" engine option tomorrow.

 

[orton]

So EB doesn't need to downshift as often.

Very obvious when driving the EB. It does not downshift often. Very wide range of loads before it requires help from a transmission ratio change.

 

[Chance]

Very obvious when driving the EB. It does not downshift often. Very wide range of loads before it requires help from a transmission ratio change.

Yes, it's obvious based on numbers also. I personally wanted to compare both V6s under typical driving conditions to see why things happen the way they do. So first I assumed typical driving at 50 HP at 2000 RPM (63 MPH with 3.73 & SRW), and then if load goes up to 100 HP due to hill or by towing a large trailer.

As before:
50 HP
2000 RPM
131 lb-ft torque
63 MPH

3.7L V6
BMEP = 6 bars
BSFC = 260 g/kW-hour
Fuel rate = 3.56 gal/hour
MPG = 17.7

3.5L EB V6
BMEP = 6.4 bars
BSFC = 265 g/kW-hour
Fuel rate = 3.63 gal/hour
MPG = 17.4

Within accuracy of reading data let's call it even.

 

[Chance]

To avoid getting timed out due to my slow typing.


Now changing power from 50 to 100 horsepower as if towing or climbing hill:


100 HP
2000 RPM
262 lb-ft torque
63 MPH

3.7L V6
BMEP = 12 bars
"Engine can't handle load and must downshift"

3.5L EB V6
BMEP = 12.8 bars
BSFC = 245 g/kW-hour
Fuel rate = 6.71 gal/hour
MPG = 9.4 MPG

3.7L in 5th gear instead of 6th
100 HP
2500 RPM
210 lb-ft torque
63 MPH
BMEP = 9.6 bars
BSFC = +/- 245 g/kW-hour
Fuel rate = 6.71 gal/hour
MPG = 9.4 MPG

We don't have data for 3.7L at 2500 RPM, but at that speed and torque/BMEP it falls in the very middle of its fuel efficiency sweet spot, so we can assume the same BSFC -- more or less.

Although 3.7L requires a downshift, fuel consumption remains about the same. And it's the greater amount of work being done that drops MPGs roughly in half, not whether the engine is EcoBoost or not.

 

[alarmist]

If I type (chrome browser/win7) in the reply box and don't post it, the text is still there next time I hit reply, even after logging off the site for a few days.

 

[PeterR]

If I type (chrome browser/win7) in the reply box and don't post it, the text is still there next time I hit reply, even after logging off the site for a few days.

Do you delete cookies and clean your Internet cache in between log ins?

 

[alarmist]

Nope. Don't surf porn

 

[Chance]

If I type (chrome browser/win7) in the reply box and don't post it, the text is still there next time I hit reply, even after logging off the site for a few days.

I'm on iPad. From home I can type on desktop and then cut and paste.

I guess I could edit previous post by adding additional information. Hopefully a long post with numbers is something that won't happen too often.

 

[alarmist]

I think they might have changed something after a few complaints about that short window of opportunity. Test it out.

 

[Chance]

VinceP, almost forgot about "downsize" EcoBoost option. These curves are most revealing of what I think was the original intent for EB -- to improve Fuel economy which requires significant displacement reduction. As such the 3.5L EB V6 is comparable to 5.0L V8.

Edit: Note that since different size engines are shown on same graph, that the data is no longer shown on a "per liter" basis. This one shows actual torque instead of being converted to BMEP.