Horrible MPG's

[MT19RANGER]

I am surprised at how many of you take the computers word for what you’re getting for mileage.
It’s bound to have some “wishful thinking algorithmic bru-ha-ha” programmed in. Be sure to check it occasionally with the trip meter, gas pump and a calculator. Unless of course you just don’t want to be disappointed perhaps.

https://www.ranger5g.com/forum/threads/fuel-calculator-adjustment.2996/

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[CoastieN70]

No. With the turbo, you get more power because pushing more air into the cylinders allows you to also push more fuel into the cylinders. Thus, you aren't get more complete combustion of the same amount of fuel, but combustion of more fuel.

But wait there's more! Since you're actively pushing more air into the cylinder and injecting more fuel, you're increasing the cylinder pressure. This increases the risk of pre-ignition. One strategy to avoid such pre-ignition (not sure if this is Ford's approach?) is to make the mix a little bit fuel-rich, thus making the combustion a little less efficient.

All a turbo does is push air, period. It has nothing to due with the amount of fuel that enters the cylinder, it just provides denser air for more complete combustion. The fuel amount is determined by throttle position, more throttle more fuel, it's that simple. Boost can be at its prescribed maximum and the throttle cam be at any position other than closed or idle. The amount of fuel entering the cylinder actually dictates MPG.

Equating boost with anything other than power at a given RPM is in error.

As to your second statement about increased cylinder pressure, yes pressure is increased but pre-ignition is a product of heat, a hot spot in the cylinder that causes the fuel to combust a split second before the spark plug fires. Pre-ignition is controlled with timing, both valves and ignition and has nothing to due with boost.

 

[jsphlynch]

All a turbo does is push air, period.

Yes. On this point we are in complete agreement.

The amount of fuel entering the cylinder actually dictates MPG.

On this point we are also in complete agreement.

It (the turbo) has nothing to due with the amount of fuel that enters the cylinder

Here is where we disagree, but possibly just because I was clumsy in how I described it before. The turbo itself does not control how much fuel goes into the cylinder, exactly as you said. However, to get efficient combustion, and thus actually extract energy from the fuel, you must have the proper ratio of air to fuel (roughly 14:1). Therefore, under natural aspiration, the maximum amount of fuel that can be used per ignition cycle is ~1/14th (by weight) of the amount of air that atmospheric pressure can push into the cylinder. If you add more fuel than that, it does no good because there's no oxygen to react with it, and therefore the injection system is programmed to not add more fuel than that. The way around this is to use the turbo to add pressure and push additional air (by weight) into the constrained volume of the cylinder. With more air to react with, the injection system can push more fuel in, and that fuel will burn and provide energy.

Thus, to summarize, the turbo itself does not increase the amount of fuel that enters the cylinder, but when it engages it is because the power demanded of the engine requires pushing more fuel into the cylinder than can burn without providing the additional air. You aren't getting more power from the same amount of fuel, but power from combustion of more fuel in the same small engine.

yes pressure is increased but pre-ignition is a product of heat

The ideal gas law is relevant here.

 

[CoastieN70]

Yes. On this point we are in complete agreement.

On this point we are also in complete agreement.

Here is where we disagree, but possibly just because I was clumsy in how I described it before. The turbo itself does not control how much fuel goes into the cylinder, exactly as you said. However, to get efficient combustion, and thus actually extract energy from the fuel, you must have the proper ratio of air to fuel (roughly 14:1). Therefore, under natural aspiration, the maximum amount of fuel that can be used per ignition cycle is ~1/14th (by weight) of the amount of air that atmospheric pressure can push into the cylinder. If you add more fuel than that, it does no good because there's no oxygen to react with it, and therefore the injection system is programmed to not add more fuel than that. The way around this is to use the turbo to add pressure and push additional air (by weight) into the constrained volume of the cylinder. With more air to react with, the injection system can push more fuel in, and that fuel will burn and provide energy.

Thus, to summarize, the turbo itself does not increase the amount of fuel that enters the cylinder, but when it engages it is because the power demanded of the engine requires pushing more fuel into the cylinder than can burn without providing the additional air. You aren't getting more power from the same amount of fuel, but power from combustion of more fuel in the same small engine.

The ideal gas law is relevant here.

You are reading too much into this.
Simply stated: Turbo moves air; Throttle position moves fuel; the combination of both produces more HP per Cubic Inch; Boost from The Turbo does not effect MPG because you can have max Boost at 1/2 throttle or at Full throttle at any given time BUT at Full Throttle you push more gas and concurrently lessen MPG.

 

[Ranger12]

Just got 443 miles on a tank of all highway driving. Put in 16.1 gallons to fill it up. 27.5 mpg

 

[R G]

You are reading too much into this.
Simply stated: Turbo moves air; Throttle position moves fuel; the combination of both produces more HP per Cubic Inch; Boost from The Turbo does not effect MPG because you can have max Boost at 1/2 throttle or at Full throttle at any given time BUT at Full Throttle you push more gas and concurrently lessen MPG.

I'm sorry, but in my opinion you are way oversimplifying things. Fuel delivery is based on load, which includes throttle position, but also other factors. I've been working on tuning my fuel injected and supercharged MG Midget. I wish throttle position alone dictated fuel. That would make life tons easier. Sadly, it doesn't work that way.

 

[Hllll]

This has been my experience as well. Currently sitting around 17.7mpg (computer) with this tank, very light acceleration, no WOT hard pulls, and monitoring the instant fuel gauge. All mostly city commuting. I still think its a great truck, but 20mpg in the city isn't happening for me. I'm glad if other people can get it, but I have to assume that its based on geography, road type, traffic ect.

Others here are misrepresenting their commute...their definition of city driving must be very different than the one you guys are experiencing...

 

[CoastieN70]

I'm sorry, but in my opinion you are way oversimplifying things. Fuel delivery is based on load, which includes throttle position, but also other factors. I've been working on tuning my fuel injected and supercharged MG Midget. I wish throttle position alone dictated fuel. That would make life tons easier. Sadly, it doesn't work that way.

Supercharger is not a turbo and in that case throttle position is your main factor due to the engine power required to run your Blower. Modern engines use their ECU to control both but your Midget is a whole different animal. Except on drag track engines most are :clutched out below a certain RPM and again on a modern engine this is too usually a function of the ECU.

Most of my supercharge experience is on aircraft reciprocating engines and then the blowers are used at altitude. I had a friend who was a "wizard" at supercharging automobile engines but sadly he is no longer of this world. Best of luck with your MG...

 

[t4thfavor]

Supercharger is not a turbo and in that case throttle position is your main factor due to the engine power required to run your Blower. Modern engines use their ECU to control both but your Midget is a whole different animal. Except on drag track engines most are :clutched out below a certain RPM and again on a modern engine this is too usually a function of the ECU.

Most of my supercharge experience is on aircraft reciprocating engines and then the blowers are used at altitude. I had a friend who was a "wizard" at supercharging automobile engines but sadly he is no longer of this world. Best of luck with your MG...

The other guy is completely correct about modern turbo engines. The throttle position has a lot to do with it, but modern ECU's definitely anticipate boost, and as such squirt lots of fuel BEFORE the turbo gets spooled so that you don't have a lean condition and detonate.

On the gas off the gas WILL waste lots of extra fuel because the turbo won't completely spool to burn that extra fuel, and it will be shot out to be burned by the cat.

The 4 cylinder GTDI engines of today have ~5 knock sensors, can control the precise amount of fuel in each cylinder, timing of each cylinder. It will add or remove both fuel and timing if detonation is even remotely detected.

I spent 60K miles watching the AFR wideband, and individual knock sensors on my previous car seeing how it would react to changes in atmospheric temp, pressure, type of fuel, etc.

The initial "stab" of the throttle would send the AFR to 10-11:1, at which point the boost would come on, and the AFR would head towards 13-14:1 when letting off the gas and coasting, the AFR would hit "infinity" (read on the meter as ~99:1) because all of the injectors turn off.

I should note that this was a Ford 2.0L GTDI with a manual transmission.

This control is part of the reason it's so easy to force 26PSI through today's factory engines whereas 20-30 years ago 26PSI meant you got to meet one or more of your connecting rods (for the most part).

 

[CoastieN70]

The other guy is completely correct about modern turbo engines. The throttle position has a lot to do with it, but modern ECU's definitely anticipate boost, and as such squirt lots of fuel BEFORE the turbo gets spooled so that you don't have a lean condition and detonate.

On the gas off the gas WILL waste lots of extra fuel because the turbo won't completely spool to burn that extra fuel, and it will be shot out to be burned by the cat.

The 4 cylinder GTDI engines of today have ~5 knock sensors, can control the precise amount of fuel in each cylinder, timing of each cylinder. It will add or remove both fuel and timing if detonation is even remotely detected.

I spent 60K miles watching the AFR wideband, and individual knock sensors on my previous car seeing how it would react to changes in atmospheric temp, pressure, type of fuel, etc.

The initial "stab" of the throttle would send the AFR to 10-11:1, at which point the boost would come on, and the AFR would head towards 13-14:1 when letting off the gas and coasting, the AFR would hit "infinity" (read on the meter as ~99:1) because all of the injectors turn off.

I should note that this was a Ford 2.0L GTDI with a manual transmission.

This control is part of the reason it's so easy to force 26PSI through today's factory engines whereas 20-30 years ago 26PSI meant you got to meet one or more of your connecting rods (for the most part).

I concede because at this point this is an unwinnable discussion. If you look at this in the context of on and off the throttle HARD you definitely have a point about boost being a driving factor in gas mileage but normal daily driving with the throttle being rolled on and off in a comparatively gentle manor boost influence on gas mileage is negligible.​

 

[Roofhopper]

Regardless of how you slice it we can all probably agree that the MPG on these trucks is all up to how you drive it as an individual. If you put on a ton of city miles, drive aggressively, disable auto start/stop, idle a lot, use cheap fuel, etc you are going to get poor MPG. Whereas if you drive mostly highway, easy on throttle/brakes, use cruise control, premium fuel etc you will get excellent gas mileage. The name EcoBoost rings very true, stay outta the throttle for economy, or stay on throttle for the boost. But don’t complain about not getting 20+MPG from this truck if you aren’t doing your part to get it there

 

[Lunchbox88]

Regardless of how you slice it we can all probably agree that the MPG on these trucks is all up to how you drive it as an individual. If you put on a ton of city miles, drive aggressively, disable auto start/stop, idle a lot, use cheap fuel, etc you are going to get poor MPG. Whereas if you drive mostly highway, easy on throttle/brakes, use cruise control, premium fuel etc you will get excellent gas mileage. The name EcoBoost rings very true, stay outta the throttle for economy, or stay on throttle for the boost. But don’t complain about not getting 20+MPG from this truck if you aren’t doing your part to get it there

Except, this truck is rated at 20-21mpg city, and if we do use best practices and still don't come close I see a reason to at least discuss it. Just bashing people (not saying you specifically) because they experience different real world fuel consumption is unnecessary and unproductive.

 

[Msfitoy]

87 versus 92 octane...which would get better milage?

 

[Lunchbox88]

87 versus 92 octane...which would get better milage?

Under normal driving conditions (not towing/heavy loads ect) you will see minimal improvements of fuel economy by switching to higher octane fuel. Many people chose to use higher octane fuel because it can allow the truck to make a bit more power since the higher octane is more resistant to pre-ignition.

 

[Polar Bear]

87 versus 92 octane...which would get better milage?

Here locally I have the options of 87, 89, and 93. I've been running 89 for the better part of the last 3 weeks and have pretty happy with it. With my long highway test run and experimentation with other variables I find that MPG's are consistently where I expect them to be. FWIW my truck seems to really like the 89.

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