Ecoboost engine question

I personally think that for ecoboost motors to return the fuel economy they tout, they must stay out of boost. My personal experience was with my 07 saturn sky redline. That car was rated at 29mpg freeway. However, if you could stay out of boost, I was able to eek out 34mpg. If you put the ecoboost in a heavier rig like the F250 and higher, the heavier chassis and possibly increased drag of components and aerodynamics (as far as I know, Ford hasn't put much Aero effort into its HD trucks) would more than likely keep the turbo's spooled or closer to being spooled. For a gas motor, this would actually decrease efficiency. The more time an engine can spend off of turbo (acting like a naturally aspirated motor of its displacement) and provide enough thrust to maintain speed or perform modest acceleration, the more fuel saving the motor is. The idea of the high horsepower and torque rating on the ecoboost is that the power and torque would only be needed for heavy loads and acceleration. From many rags like pickuptrucks.com, there isn't any gain in towing fuel economy in ecoboost vs. 5.0 v8 (some reported a slight detriment in mpg). However unloaded the ecoboost shines as it doesn't need to dip into boost for daily driving unless the driver feels like having some "Fun". Putting the motor in a superduty would be like towing a small weight at all times and diminishing the ability of the 3.5 to save fuel over the 6.2.

Basically turbocharging is just another method of displacement-on-demand. For every 14.7 psi of boost, you've added another engine of the same size. Only thing bad about turbocharging is that you do need to run a little richer than 14:1 afr. Even with direct injection (though with old-school port injection you needed to maintain 11:1 afr, I beleive the dip is only down to 12.5 or 13:1 for gasoline direct injection).

Wes Tausend wrote:
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On the other hand, I believe that a turboed engine is slightly more efficient than a NA (normally aspirated) motor for the same hp and/or equivalent displacement. The reasoning is that the end exhaust is slightly cooler on the turbo, meaning it derives more power (more is used to do work) out of the same fuel that must be equally burned to provide identical propulsion of a pair of trucks. One of the pair is assumed to be turboed, the other NA in this imaginary test.
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You would be incorrect. BSFC is quite a bit higher with a supercharged engine.

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The reason Ford doesn't offer the 3.5 EB in a 250 is that the heavier rear axle in these trucks irrevocably drags the mileage down. A 3/4 ton with a 1/2 ton axle would get similar fuel economy as the 1/2 ton itself, or visa-versa, the 3/4 ton axle in a 1/2 ton would suffer the same poor fuel economy as the average stock 3/4 ton.

So the expensive variable displacement, aka turbo, in the EB would seldom run at the economy of only 3.5L normally aspirated, and not achieve the EPA target that the 1/2 ton does. It would always have to run at slight boost.

In other words, 20 hp might move a easy rolling 1/2 ton at 65 mph, but the 3/4 ton would require 30 hp to roll the same conditions. It is just as well to use a cheaper larger displacement engine at low throttle than a small engine always at slight boost.

On the other hand, I believe that a turboed engine is slightly more efficient than a NA (normally aspirated) motor for the same hp and/or equivalent displacement. The reasoning is that the end exhaust is slightly cooler on the turbo, meaning it derives more power (more is used to do work) out of the same fuel that must be equally burned to provide identical propulsion of a pair of trucks. One of the pair is assumed to be turboed, the other NA in this imaginary test.

So for that "efficiency" reason I would like to run a 3.5L EB in my Excursion, instead of the V-10, just to see.

Wes
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Fordlover wrote:

Turtle n Peeps wrote:

johndeerefarmer wrote:
3.5 eco is not maxed out power wise. Lots and lots of guys are running tunes with 80 or more extra hp and 120 ft lbs of torque.
Ford overbuilt the 3.5 block so it can handle this extra power. I have heard of no tranny's failing but one guy lost a rear end probably becaus he towed 15k

That's like saying my blown SBC is not maxed out at 600 HP. I could always go 40% over on the blower and make 1,000 HP. :R

This is an easy formula:

When power goes up, duty cycle goes down.
When power goes down, duty cycle goes up.

How high of a duty cycle do you want? How much power you want?

And how many Ecoboost F-150's have you seen pulling a 53' reefer trailer long haul?

LOL Well that is true but can't that be said of ANY of the little light duties (yes, that includes 1-ton diesels) sitting on dealer lots?

The private-use benchmark these days among pickups seems to be the 2013/2014 Ram 3500s with their 37000lb GCWR, but if I see one coming down the highway with a 53' van behind it I'm changing lanes and giving it a whole lot of breathing room.

Turtle n Peeps wrote:

johndeerefarmer wrote:
3.5 eco is not maxed out power wise. Lots and lots of guys are running tunes with 80 or more extra hp and 120 ft lbs of torque.
Ford overbuilt the 3.5 block so it can handle this extra power. I have heard of no tranny's failing but one guy lost a rear end probably becaus he towed 15k

That's like saying my blown SBC is not maxed out at 600 HP. I could always go 40% over on the blower and make 1,000 HP. :R

This is an easy formula:

When power goes up, duty cycle goes down.
When power goes down, duty cycle goes up.

How high of a duty cycle do you want? How much power you want?

And how many Ecoboost F-150's have you seen pulling a 53' reefer trailer long haul?

Gotta revise and repost this.

WHO CARE'S????


chevman

Me Again wrote:
"Do you have any idea why Ford does not put their big beast 400 freeking HP fire breathing 6.7 in a class 8 truck? I do. It's called duty cycle............or lack there of."

And what diesel goes in the F650? That's right a midium duty Cummins 6.7. Both the PS and Duramax are consided light duty engines.

Chris

And Fords V10 engine that's used in these F650 trucks are considered "medium duty"? I believe your analysis is a failure and your motives are obvious! :W

Class 6 is a Medium Duty truck. Ford offers a 200hp Cummins or a 362hp gas engine in their F650. Have no doubt which one will tow faster up the hill. Cummins offers the 6.7L for small motorhomes. The 8.3L, ISL9 and ISX15 are offered for the big guys. On our next cruise, I'll ask if the 6.7L is pushing our ship through the Caribbean. The Cummins B series does make a cool novelty engine for the family car though.:B

Hannibal wrote:

pronstar wrote:
The proof is in the pudding.
There's a reason why we don't yet see high boost, small displacement gas engines in heavy-duty/high duty cycle applications.

Until we start seeing them en masse, large displacement gas and/or turbo diesels are where it's at for heavy duty/heavy duty cycle applications.

Until that time comes, it's a moot discussion.

We don't see small displacement car sized turbo diesels such as the 1.8L TDI or 5.9 CDT in heavy duty/high duty cycle applications either. But keeping it in perspective, a 14L TD is small displacement for a 70k lb OTR truck. Much like a 3.5L engine for a 15k lb GCW pickup and camper.
Imagine the size of engines OTR trucks would require if trucking companies had to please truckers' irrational fears of the forbidden downshift on every hill or God forbid, not towing in top gear. They too would start losing carrying capacity due to engine weight.

Class 6 truck not heavy duty enough? Motor home? Marine applications not high enough duty cycle?