87 octane vs 93 octane - ECOBOOST

[fordtruckman2003]

I believe in modern variable timing motors all brands tune for higher octane for peak power. Then they just let the computer figure it out for lower octane to avoid detonation cutting the timing back. It will keep cutting back on timing when it sees detonation until it gets to a lower limit of timing then you'll see flashing engine light on dash because it can't compensate further for all the detonation.

Tune for 91 (as indicated in the truck manual for ours) and you have plenty of range to retard timing for 87 or tighten it up for 93 if not detecting any detonation.
Designed for higher octane, capable of surviving on lower grade for most users.

Sponsored

 

[Gros Ventre]

The issue can be seen in Figure 5 of the link I've been posting. Bottom line is that the way an engine produces more power is by moving the Power line farther away from the Compression line. The area between those two lines represents the work done to the face of the piston. The way you do that is by raising the compression ratio which moves the Power curve away from the Compression curve and this then requires higher octane. Unless you control dyno testing to the same parameters that Ford used, dyno testing is anecdotal. Nice to have but irrelevant. The only purpose octane serves is to prevent fuel-air detonation prior to the ignition point during the compression curve. If you want more power you have to raise the power curve farther away from the compression curve (Recall that a gallon of gasoline contains the same energy regardless of octane). So you have to change the design of the engine. How do you do that? You increase compression ratio (which requires a higher octane). Note: the Compression curve repsents work into the cylinder; the Power curve represents work out of the cylinder. Note: moving the ignition point (the spark) either way from the design point of the engine reduces power. Merely advancing the ignition point doesn't add power since, with the same engine compression ratio, the peak firing pressure will go down. (Why is that? The purpose of advancing the spark is to allow combustion time to be complete by the planned peak firing pressure point.) If you don't increase the peak firing pressure, the area under the curve doesn't change.

 

[Chili]

The issue can be seen in Figure 5 of the link I've been posting. Bottom line is that the way an engine produces more power is by moving the Power line farther away from the Compression line. The area between those two lines represents the work done to the face of the piston. The way you do that is by raising the compression ratio which moves the Power curve away from the Compression curve and this then requires higher octane. Unless you control dyno testing to the same parameters that Ford used, dyno testing is anecdotal. Nice to have but irrelevant. The only purpose octane serves is to prevent fuel-air detonation prior to the ignition point during the compression curve. If you want more power you have to raise the power curve farther away from the compression curve (Recall that a gallon of gasoline contains the same energy regardless of octane). So you have to change the design of the engine. How do you do that? You increase compression ratio (which requires a higher octane). Note: the Compression curve repsents work into the cylinder; the Power curve represents work out of the cylinder. Note: moving the ignition point (the spark) either way from the design point of the engine reduces power. Merely advancing the ignition point doesn't add power since, with the same engine compression ratio, the peak firing pressure will go down. (Why is that? The purpose of advancing the spark is to allow combustion time to be complete by the planned peak firing pressure point.) If you don't increase the peak firing pressure, the area under the curve doesn't change.

No. Just no. You're over explaining and not addressing one question. Is the engine designed to make max power on 87? We know that's not the case. Better question is, will 87 octane allow you to extract the maximum amount of power allowed by factory programming.

You can't answer that and your info doesn't prove that. Lots of anecdotal info points to "87 doesn't". You speak in absolutes you don't have any info on.

 

[Snakebitten]

Ford has been leveraging "Premium" for additional performance with turbocharged engines for a long time.

My 1984 SVO Mustang had a toggle switch on the centerstack for when you were running Premium fuel.

It wasn't a placebo switch. ?

 

[SilverPigeon]

...My 1984 SVO Mustang had a toggle switch on the centerstack for when you were running Premium fuel....

Man, why did they think so small, should have been

 

[Snakebitten]

That would have been way cooler!

 

[Gros Ventre]

No. Just no. You're over explaining and not addressing one question. Is the engine designed to make max power on 87? We know that's not the case. Better question is, will 87 octane allow you to extract the maximum amount of power allowed by factory programming.

You can't answer that and your info doesn't prove that. Lots of anecdotal info points to "87 doesn't". You speak in absolutes you don't have any info on.

Trouble is you don't know that, thus you are just plain wrong. Ford advertises that the engine will run on 87 and produce full power. Read the owners manual. When you say "we know that's not the case" you're seeking to paper over ignorance with fancy words. Try again.

 

[nrmedic]

Treated my Powerboost this morning.

 

[nomarhits400]

Trouble is you don't know that, thus you are just plain wrong. Ford advertises that the engine will run on 87 and produce full power. Read the owners manual. When you say "we know that's not the case" you're seeking to paper over ignorance with fancy words. Try again.

Against my better judgment, I'll ask this question then:

Your stance is that the plethora of examples of these engines (take your pick) with physical dyno graphs of increased power using higher octane fuels (under the exact same conditions) are....what exactly?

 

[Snakebitten]

He's not budging gents. I tried to warn Yaw. ?

He's a smart fella, but he's dug in deep on this. You ain't getting him out of his bunker.

 

[Chili]

Treated my Powerboost this morning.

That's the spendy stuff! Our ethanol free is 91 or 92.

 

[Chili]

Man, why did they think so small, should have been

Remember the little red button? Push the little red button.

 

[JExpedition07]

The F-150 3.5 EcoBoost power output is not certified per the SAE J1349 Standard, but the Expeditions is. The Expedition base 3.5 Eco is 380 horsepower/470 lb ft per the J1349 Standard and utilized premium fuel to do so per the website. The same footnote is made on the Platinums 400 horsepower/480 lb ft version. Since the F-150 is even more torque I’d say it’s safe to say that’s on premium even though that torque is not certified per the SAE standard. The F-150 5.0L V8 says right on the website that is it certified per the J1349 Standard on premium fuel, so that 400 HP/410 lb ft is certainly on premium fuel. Nowhere in my owners manual for my 5.0L does it say 87 makes full power. It says 91 or higher is recommended for best overall performance.

Look up dyno results on both the 5.0 and 3.5 on 87 octane. Both made 330 rwhp on Livernois pre-tune runs with regular unleaded. Both made 350-360 rwhp on premium stock. Sorry bro. Premium is called for on both motors for full power. Both are running serious cylinder pressure (12:1 static compression on 5.0 and upwards of 15 psi available boost on the 3.5) detonation resistance helps these motors a lot. You’re just cheap.

 

[Graygoose2021]

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

No, I will run 91 in my truck, and 89 in wifes Highlander.
I've helped plenty of buddies over the years from reading plugs, to now everything is on a laptop tuning. And sadly, consensus, they all us premium octane or E85, or racing fuel.
I tried to tell em..."guys, I swear by 87..."

they wont listen.

 

[nomarhits400]

He's not budging gents. I tried to warn Yaw. ?

He's a smart fella, but he's dug in deep on this. You ain't getting him out of his bunker.

I’m pretty sure that’s spot on.

However, I’m really not trying to bait him: I’m genuinely too stupid (but still really curious) to ascertain whether he thinks the physical evidence presented is just lies- or if he just doesn’t approve of the science.

Sponsored