Octane Adjustment Ratio - Ecoboost

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The turbos move more air when its needed to add more hp/tq. The reality is much of the time that extra power is not needed at all - all you have to do is watch a boost guage to understand it. (Hint: RPMs may never change but the boost can vary considerably) You can make power when you need it, or be efficient when needed.
 
Originally Posted By: Olas
Talk of turbocharging for MPG is insane! If turbos move more air, and more air needs more fuel, how is the economy better?


If you are in the boost then the MPG drops accordingly. However, by turbocharging an engine you are able to reach the performance goals with a smaller displacement. Therefore, when you are not in the boost you are effectively using a smaller engine. It's all about sizing the right engine for the right application. If you go too small then you are always in boost and losing MPG.

Bottom line, if you are using the turbo you aren't gaining any MPGs but when you aren't using the turbo you are gaining MPGs. Engines like the Ecoboost that can control things such as OAR are just able to fine tune everything a bit more.
 
Originally Posted By: 09_GXP
Originally Posted By: Olas
Talk of turbocharging for MPG is insane! If turbos move more air, and more air needs more fuel, how is the economy better?


If you are in the boost then the MPG drops accordingly. However, by turbocharging an engine you are able to reach the performance goals with a smaller displacement. Therefore, when you are not in the boost you are effectively using a smaller engine. It's all about sizing the right engine for the right application. If you go too small then you are always in boost and losing MPG.

Bottom line, if you are using the turbo you aren't gaining any MPGs but when you aren't using the turbo you are gaining MPGs. Engines like the Ecoboost that can control things such as OAR are just able to fine tune everything a bit more.


Industry semantics!

If I have a 1.2 litre 4 cylinder it will be quite good on fuel because of its small displacement. Adding boost will not improve the MPG over what it was when the engine was normally aspirated. It will add more power/torque, but it will not achieve higher MPG than it did pre-boost.

If we take the peak power number and find a normally aspirated engine with the same peak power, the boosted engine will only be more fuel efficient when driven off boost but also much slower. To achieve the same performance requires using boost and with it more fuel, dropping the fuel economy to a similar level to the normally aspirated motor.

They're being very clever with their industry terminology, as is always the case.
 
Originally Posted By: Kawiguy454
Originally Posted By: 440Magnum
Originally Posted By: MNgopher
. The non-oxy delivered better fuel mileage (as expected), but it appears it does not unlock better performance at the same time.


Absolutely no surprise there. Non-oxygenated fuels have a higher energy density, so miles/gallon is generally better.

Alcohol is a tremendously effective octane booster, so although it has low energy density requiring more to be injected on each cylinder firing, it delivers more power because the engine can set the timing with less regard for detonation. The most extreme example is a flex-fuel vehicle like my Ram. Mileage drops like a rock on E-85 (from ~16 in regular commuting to roughly 12 under the same conditions), but power and throttle response are both better because E85 is far higher octane than even E0 premium.



I think your idea of why alcohol makes more power is incorrect. 91 alcohol blend and 91 pure gas have the same octane/knock resistance so the ECU will use the same timing control settings. The reason alcohol makes more power especially on turbo applications is due to its cooling effect on incoming air charge as it is atomized.


Mayyyybeee.... alcohols have about 1.5x the latent heat of vaporization of hydrocarbons like kerosene and gasoline. I don't think that's enough to significantly change the "cooling effect" (which is entirely due to heat of vaporization) when it only accounts for 10% of the blend. The only thing that has a truly significant cooling effect on the incoming charge is water injection, since water has a much greater latent heat of vaporization than either alcohol (3x) or gasoline (4-5x), and also doesn't add heat to the combustion chamber by burning. Its an inert heat-buffer.

The octane ratings posted on the pump are a *minimum*. I think the E10 blends tend to over-shoot and have a higher real-world octane rating than the E0 blends, since its so much harder to boost the octane without ethanol now that MTBE is no longer available. When alcohol can be part of the blend, its a lot easier to bump the octane up without adding a lot of cost to the final product, so there's less motivation to hit the bare minimum requirement.
 
So, tried out another fuel, and to be blunt, not impressed. Most BP stations in this market carry 93 octane premium. The vast majority of premium fuel here is 91 octane, with most being E10, and non-oxy premium 91 octane available pretty readily if one knows where to look.

So, went and filled up with 93 octane BP fuel, which is E10. I've run a few hundred miles on it, and the OAR is stuck at -0.6. Not impressive when 91 octane from Superamerica hits -0.7, and Shell 91 octane is -0.8. The 93 octane from BP is also priced about 30 cents a gallon higher than the premium 91 octane fuels from SA in particular.

Don't think I'll be going out of my way to purchase this fuel again anytime soon...
 
Was this in the tow section of OM ? For 3.5L eB in Explorer Sport - I only found 87 and </=15% corn juice ... ?
 
Originally Posted By: Kawiguy454
Originally Posted By: 440Magnum
Originally Posted By: MNgopher
. The non-oxy delivered better fuel mileage (as expected), but it appears it does not unlock better performance at the same time.


Absolutely no surprise there. Non-oxygenated fuels have a higher energy density, so miles/gallon is generally better.

Alcohol is a tremendously effective octane booster, so although it has low energy density requiring more to be injected on each cylinder firing, it delivers more power because the engine can set the timing with less regard for detonation. The most extreme example is a flex-fuel vehicle like my Ram. Mileage drops like a rock on E-85 (from ~16 in regular commuting to roughly 12 under the same conditions), but power and throttle response are both better because E85 is far higher octane than even E0 premium.



I think your idea of why alcohol makes more power is incorrect. 91 alcohol blend and 91 pure gas have the same octane/knock resistance so the ECU will use the same timing control settings. The reason alcohol makes more power especially on turbo applications is due to its cooling effect on incoming air charge as it is atomized.


But we are talking about direct injection engines for the ecoboost and many other new engines. The fuel is injected into the cylinder AFTER air intake is complete. Not trying to dispute you, just trying to understand how your explanation above may change based on direct injection vs port.
 
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