Which engine should I order?
#16
Well for those touting the gas mileage on the Ecoboosts (both 2.7 and 3.5) as a reason to get it over the 5.0L you REALLY REALLY need to look at where the person is going to live. If you are living in a mountainous area the gas mileage on those engines often turns out WORSE than the 5.0L because the engine is constantly in boost to go up the inclines and has to work harder.
Yes the torque numbers on the 3.5L Ecoboost is better and provided you don't care about the warranty you can get CRAZY with that thing. You can also put a tune on your 5.0L that puts it right at the level of the 3.5L Ecoboost without paying out the nose for the "optional engine".
Now if you live in a flat state without a lot of hills and do a majority of highway driving the 3.5L and 2.7L are good choices.
Yes the torque numbers on the 3.5L Ecoboost is better and provided you don't care about the warranty you can get CRAZY with that thing. You can also put a tune on your 5.0L that puts it right at the level of the 3.5L Ecoboost without paying out the nose for the "optional engine".
Now if you live in a flat state without a lot of hills and do a majority of highway driving the 3.5L and 2.7L are good choices.
That got me to thinking back to a college text on the Fundamentals of Internal Combustion Engines wherein the advantages of Brake Mean Effective Pressure were discussed. And the upshot is that a higher BMEP gives higher efficiency.
There are lots of ways to increase BMEP, and one is to increase compression ratio. So, all else being equal, the engine with the higher compression ratio should be more efficient. But, you shouldn't compare compression ratios between naturally-aspirated engines and turbo-charged engines since the effective compression ratio of a boosted engine can be much higher than the static compression. For instance, this site's calculator says that an engine with a 10:1 static compression but with 10 psi of boost, which an Ecoboost can do, has an effective compression ratio of 16.8:1 - assuming it is operating at sea level.
And, there's another flaw in your thinking - altitude, which comes with mountainous areas. The above-linked site says the same engine running at 10,000 feet would still have 14.8:1 effective compression ratio. But, a naturally-aspirated engine with a 10:1 static compression ratio at sea level would have an 8.0:1 effective CR at 10,000 feet.
So, the bottom line is that being "in the boost" can actually increase the efficiency of an engine, as Tom reminded me.
#17
I would have agreed with you save for a recent discussion that I started in this thread. Tom said "I remember a good technical discussion with one of the engineers on the EcoBoost engine here on FTE a few years ago that talked about this. Low boost levels don't necessarily enrichen the mixture, so often it's more efficient to run under boost than to run in the vacuum at high RPMs."
That got me to thinking back to a college text on the Fundamentals of Internal Combustion Engines wherein the advantages of Brake Mean Effective Pressure were discussed. And the upshot is that a higher BMEP gives higher efficiency.
There are lots of ways to increase BMEP, and one is to increase compression ratio. So, all else being equal, the engine with the higher compression ratio should be more efficient. But, you shouldn't compare compression ratios between naturally-aspirated engines and turbo-charged engines since the effective compression ratio of a boosted engine can be much higher than the static compression. For instance, this site's calculator says that an engine with a 10:1 static compression but with 10 psi of boost, which an Ecoboost can do, has an effective compression ratio of 16.8:1 - assuming it is operating at sea level.
And, there's another flaw in your thinking - altitude, which comes with mountainous areas. The above-linked site says the same engine running at 10,000 feet would still have 14.8:1 effective compression ratio. But, a naturally-aspirated engine with a 10:1 static compression ratio at sea level would have an 8.0:1 effective CR at 10,000 feet.
So, the bottom line is that being "in the boost" can actually increase the efficiency of an engine, as Tom reminded me.
That got me to thinking back to a college text on the Fundamentals of Internal Combustion Engines wherein the advantages of Brake Mean Effective Pressure were discussed. And the upshot is that a higher BMEP gives higher efficiency.
There are lots of ways to increase BMEP, and one is to increase compression ratio. So, all else being equal, the engine with the higher compression ratio should be more efficient. But, you shouldn't compare compression ratios between naturally-aspirated engines and turbo-charged engines since the effective compression ratio of a boosted engine can be much higher than the static compression. For instance, this site's calculator says that an engine with a 10:1 static compression but with 10 psi of boost, which an Ecoboost can do, has an effective compression ratio of 16.8:1 - assuming it is operating at sea level.
And, there's another flaw in your thinking - altitude, which comes with mountainous areas. The above-linked site says the same engine running at 10,000 feet would still have 14.8:1 effective compression ratio. But, a naturally-aspirated engine with a 10:1 static compression ratio at sea level would have an 8.0:1 effective CR at 10,000 feet.
So, the bottom line is that being "in the boost" can actually increase the efficiency of an engine, as Tom reminded me.
It seems that the guys around here that I know with Ecoboosts (about a dozen or so and all 2013 and older mind you) are all complaining about their gas mileage and when I ask them what they get they are averaging the same or lower than my 2015 5.0L.
After a couple complained I made it a point to ask anyone I talked to with one just to see. Yes there are other variables to it (i.e driving style, towing, etc...). I personally haven't grown out of my Mustang Lead Foot so I know I could easily get better gas mileage if I tried.
Right now on long trips down the highways up here I'm getting 22-23mpg in my 5.0L which is respectable, but around town on the island I'm on it drops to about 15-16 because everything is about 35mph average.
#18
#19
I think when you factor in the capability of the 3.5, the real world mileage is somewhat impressive. I've driven a 4x4 cc at 80 mph on the interstate and got just under 18. My 7.3 same configuration won't touch that at 80. No, not fantastic fuel economy, but when you get into the trucks that do better mpg wise, the towing/hauling ability drops off pretty quick.
#20
I think when you factor in the capability of the 3.5, the real world mileage is somewhat impressive. I've driven a 4x4 cc at 80 mph on the interstate and got just under 18. My 7.3 same configuration won't touch that at 80. No, not fantastic fuel economy, but when you get into the trucks that do better mpg wise, the towing/hauling ability drops off pretty quick.
And yet it'll tow anything I'm likely to ever want to tow, carry anything I'm likely to want to carry, and do so in luxury and with 5-star safety. Compared to Rusty's 12.5 MPG and no creature comforts and little safety, I feel like I made the right choice.
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10-13-2002 11:01 AM