87 octane vs 93 octane - ECOBOOST

[fordtruckman2003]

heeeeeere we go

I'm just amused they can't admit they are wrong.

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[Chili]

I've actually never heard of that? Is it the cheapest gas you can get? I feel kinda slighted in Colorado. The dealer stated it can take regular, but I've come to find the 85 in Colorado/wy/NM aren't recommended. 85 is 3.45 a gal while 91 (max we can really get) is 3.99. Multiply that by 36gals. I couldn't care less how much power the engine has past like 270 or so HP, but reliability and efficiency are important.

You guys get lower octane due to your elevation. Around here 85 octane is called "farm gas" and only farmers buy it, never seen it at a gas station.

E15 / 88 octane is common at a big chain called Kwik Trip who also sells e85. I assume they're just mixing 87 octane and e85 but I'm not sure. The typical price breakdown is e15 is 20 cents cheaper than 87 and 91-92 is 80-90 cents more. We have 93 but you have to look for it.

 

[Gros Ventre]

Manual says for all motors 91 octane for best performance.

True, but irrelevant... If you haven't read the link I put up, you are taking a simplistic statement and turning it into something it wasn't meant to be. Go read that link.

 

[joejamesatou]

It comes down to do you want 20hp, a .6 faster 0-60 and .6mpg better mileage for $360 a year. That's the difference between 87 and 93 octane. The cost between them is even cheaper at Costco.

 

[boo radley]

I have watched videos about the effectiveness of Shell V Power and I begun buying a couple of tanks in the Spring and Fall.

 

[Gros Ventre]

It comes down to do you want 20hp, a .6 faster 0-60 and .6mpg better mileage for $360 a year. That's the difference between 87 and 93 octane. The cost between them is even cheaper at Costco.

No, the difference is that $360/yr pees out the exhaust pipe. There is no statement by Ford that hgher octane increases power output. What likely happened is that Ford so designed the engine, when in its perfect state right off the assembly line floor, that with 87 octane it is right on the edge. Read that link I put up, you'll find that as an engine ages it coud go over the edge on 87 octane, but if you up the numbers it'll still run smoothly. That's all there is. The thermodynamics is clear: octane higher than designed adds nothing to power. The power comes from the area under the curve. The ony way you make that area under the curve larger is by upping the compression ratio and therefore raising the "Brake mean effective pressure" in the engine. Octane just doesn't do this.

 

[Graygoose2021]

I go to the drag races all the time...not once have i seen an 87 or a 89 octane fuel for race cars...wonder why.

 

[Graygoose2021]

Octane just doesn't do this.

No, but a higher octane keeps the engine from detonation. Detonation kills the older engines when you read plugs. Nowadays, a computer pulls timing so you don't. Timing, equals power.

 

[Gros Ventre]

No, but a higher octane keeps the engine from detonation. Detonation kills the older engines when you read plugs. Nowadays, a computer pulls timing so you don't. Timing, equals power.

Timing does not equal power. Timing delivers design power, that's all. Timing cannot increase power above design. Why does timing even make a difference in an engine? Simply, it's that it takes a measurable amount of time for the fuel-air mixture to burn and reach peak pressure. Timing is set so that the spark is sent just before TDC so that peak pressure occurs an instant after TDC. That's a design feature. It doesn't "increase power," it keeps the engine from losing power. If the spark is late and peak pressure occurs while the piston is already well into going down, you've lost power. To increase power output you have to increase compression ratio and that can't be done on the fly.

 

[Chili]

Timing does not equal power. Timing delivers design power, that's all. Timing cannot increase power above design. Why does timing even make a difference in an engine? Simply, it's that it takes a measurable amount of time for the fuel-air mixture to burn and reach peak pressure. Timing is set so that the spark is sent just before TDC so that peak pressure occurs an instant after TDC. That's a design feature. It doesn't "increase power," it keeps the engine from losing power. If the spark is late and peak pressure occurs while the piston is already well into going down, you've lost power. To increase power output you have to increase compression ratio and that can't be done on the fly.

I think you stated your case and it has valid points.

Most engines have an amount of timing that will provide maximum power given other variables like AFR, temperature, amount of boost. Once you add more timing nothing really happens except a higher chance of pre-ignition. Keep pushing it higher and it becomes detrimental.

The question is, will 87 octane provide enough octane to avoid pre-ignition? Or does the ecu need to dial it back to avoid pre-ignition, meaning a higher octane fuel would result in making more power.

The other variable is boost. What is the max allowable boost with factory programming? If you are hitting max allowable boost and timing then higher octane won't make more power.

If someone were to run 93 octane for long enough for th ecu to adapt and then fill with 87 octane they could scan for pre-ignition, boost and total timing. Start seeing that pre-igntion (or sometimes called KR) and that's factual proof that the ecu was designed to go further than 87 will normally get you.

Judging by increased mileage, I'd say the higher octane is allowing more timing; as more timing will result in better fuel mileage. Octane itself doesn't allow for better fuel mileage. Ford could also have strategies that adjust AFR to make the truck run richer if pre-igntion is detected.

 

[Chili]

Modern engines also calculate how much power they're making and adjust parameters to safely meet that target. It's the reason I make less boost when it's cold. It can hit that target at a lower amount of boost.

 

[Graygoose2021]

Timing does not equal power. Timing delivers design power, that's all. Timing cannot increase power above design. Why does timing even make a difference in an engine? Simply, it's that it takes a measurable amount of time for the fuel-air mixture to burn and reach peak pressure. Timing is set so that the spark is sent just before TDC so that peak pressure occurs an instant after TDC. That's a design feature. It doesn't "increase power," it keeps the engine from losing power. If the spark is late and peak pressure occurs while the piston is already well into going down, you've lost power. To increase power output you have to increase compression ratio and that can't be done on the fly.

Go pull 5* of timing out of your ECU and get back to me.

 

[Gros Ventre]

I think you stated your case and it has valid points.

Most engines have an amount of timing that will provide maximum power given other variables like AFR, temperature, amount of boost. Once you add more timing nothing really happens except a higher chance of pre-ignition. Keep pushing it higher and it becomes detrimental.

The question is, will 87 octane provide enough octane to avoid pre-ignition? Or does the ecu need to dial it back to avoid pre-ignition, meaning a higher octane fuel would result in making more power.

The other variable is boost. What is the max allowable boost with factory programming? If you are hitting max allowable boost and timing then higher octane won't make more power.

If someone were to run 93 octane for long enough for th ecu to adapt and then fill with 87 octane they could scan for pre-ignition, boost and total timing. Start seeing that pre-igntion (or sometimes called KR) and that's factual proof that the ecu was designed to go further than 87 will normally get you.

Judging by increased mileage, I'd say the higher octane is allowing more timing; as more timing will result in better fuel mileage. Octane itself doesn't allow for better fuel mileage. Ford could also have strategies that adjust AFR to make the truck run richer if pre-igntion is detected.

So, do you really think Ford woud advertise an engine at less capability than its design? The point is that all of those variables have been calculated by Ford in designing the engine. They already know all of that. The engine is designed for 87 octane, the fact that Ford says it'll run better with a higher octane is intended to include the changes in those variables that Ford couldn't design for. For example climbing over the I-64 7-mile steady climb in West Virginia in late July with 110ºF ambient, low humidity, and enough miles on the engine to have some carbonization inside the cylinders while towing a max load......... The fact of Ford telling you that "Maybe, just maybe, it'll run better in that circumstance if you use 91 Octane..." Does that mean it's producing more power? No, it means that you've got some margin from detonation in a condition Ford did not design for. That's what Ford is really saying when they say it'll run more smoothly when pushed. What people are trying to say is that Ford designed the engine to produce more power if you run high octane fuel in it. If that were true, they'd say that. The illusion of high octane fuel giving more power without altering the desgin of the engine pulls money out of pockets. My first car, a Plymouth Duster with a 225 cubic inch slant six ran on "regular." In that day, long, long ago, regular was 91 octane and Sunoco sold "Dial-an Octane" topping out above 100. All of those things you've mentioned can cause detonation... But, the engine is designed to protect itself and it will, by reducing power. The engine will recognize when it has reached its max power production, and it will protect itself by reducing power.

 

[Gros Ventre]

Go pull 5* of timing out of your ECU and get back to me.

Go look at Figure 5 in this link... And you have your answer...

 

[Chili]

So, do you really think Ford woud advertise an engine at less capability than its design? The point is that all of those variables have been calculated by Ford in designing the engine. They already know all of that. The engine is designed for 87 octane, the fact that Ford says it'll run better with a higher octane is intended to include the changes in those variables that Ford couldn't design for. For example climbing over the I-64 7-mile steady climb in West Virginia in late July with 110ºF ambient, low humidity, and enough miles on the engine to have some carbonization inside the cylinders while towing a max load......... The fact of Ford telling you that "Maybe, just maybe, it'll run better in that circumstance if you use 91 Octane..." Does that mean it's producing more power? No, it means that you've got some margin from detonation in a condition Ford did not design for. That's what Ford is really saying when they say it'll run more smoothly when pushed. What people are trying to say is that Ford designed the engine to produce more power if you run high octane fuel in it. If that were true, they'd say that. The illusion of high octane fuel giving more power without altering the desgin of the engine pulls money out of pockets. My first car, a Plymouth Duster with a 225 cubic inch slant six ran on "regular." In that day, long, long ago, regular was 91 octane and Sunoco sold "Dial-an Octane" topping out above 100. All of those things you've mentioned can cause detonation... But, the engine is designed to protect itself and it will, by reducing power. The engine will recognize when it has reached its max power production, and it will protect itself by reducing power.

So your response to fact is opinion? Great response. Do you know that the 21+ 3.5 Ecoboost now uses the same larger turbos as the previous HO engine and the Raptor? (450hp/510 tq). Raptor is rated on premium fuel though

Guess you have another 5 paragraph response of nothing relevant for when a dyno of stock 87 vs 91+ shows gains of 20-30 HP at the tire. Which is of course, 30-40 at the crank.

Please. Tell us more about your 40 year old Plymouth.

Yes I do believe Ford would go with a lower number to not require premium fuel on a regular truck. Both due to the fact most don't want to pay for premium and to protect Raptor and Power boost sales as well as already making more power than the competition. Bet you see a jump in numbers when Ram releases a boosted 6.

But since you decided to ignore all the facts I posted, can you explain the dyno gains?

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