87 vs 93 Octane

[Babbage]

Trouble is you're wrong. The atkinson cycle is a different engine than an Otto cycle. Nothing I've said is out of date. It is the theory of the engine in your F150. I'm well aware of the differences between my GM 350 and more modern engines. Come on, it's a '92 and isn't even an OBD-II. Increasing compression ratio is the feature of design that enables extraction of more power out of fuel with a higher octane rating. The theory is straight forward: a gas engine becomes more efficient than a diesel engine with a high enough compression ratio... it's just that the cost of that octane rated fuel is too high... So how do theyuse 87 octane in a 10.5:1 engine? Well... that thing called gasoline direct injection is the basic element that sidesteps detonation problems... Think that might be related? All heresy begines with grains of truth and that's what you're doing. C YA...

Ok, it's about timing, when the engine is hot and/or under high load (floored it) 87 octane gas will pre-detonate or knock. The PCM (powertrain control module) knows this and PULLS timing, to save the engine from blowing up. Now you have less power and no ping. The PCM can lower timing causing the engine not to knock (and grenade) once it "knows" you have 87 octane gas based on on CHT (cylinder head temps etc) the PCM is watching all of this all of the time. So now you are down on power and may not even notice it.

This is especially true for 3.5 and also true for the 5.0 which was designed for 91 or better with factory tune, yes you can run 87, and may not hear the knock because the PCM knows it has already pulled timing and loosing power.

Higher octane gas burns slower, so that the PCM can command maximum timing and the piston comes up higher in the bore the - ignition sequence is at a 'perfect timing cycle' this means more power. 3.5/5.0 Modern F150 with 87 the piston does not come up as high in the bore and to stop the 87 fuel from burning too early the PCM pulls timing and tells ignition to light it up early. (and this stops the engine from breaking stuff). This happens on all modern engines. A car that was designed to run premium 10.5:1 WITHOUT Direct Injection, can be flash tuned to run 87 (yes it's just less timing and less power) grain of truth...

For an older OBDII car that was designed for 87, the 91 or 93 will hurt you as the PCM has a max timing curve designed for 87. Also the PCM can learn about this 87 gas and advance or retard the timing still within a range, perhaps only a few (2) degrees.

The ford PCM has a wide range of timing tables to learn about the fuel it is using and having 91 or 93 will lead to the best possible timing table, once a 3.5EB or 5.0 learns you have 87, you no longer have 400hp, perhaps only 380hp (%5)


Anyway, hope this helps.

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[Samson16]

the increase in OAR

Like when the wife steps out of the shower and my OAR increases. Check.

 

[Gros Ventre]

Ok, it's about timing, when the engine is hot and/or under high load (floored it) 87 octane gas will pre-detonate or knock. The PCM (powertrain control module) knows this and PULLS timing, to save the engine from blowing up. Now you have less power and no ping. The PCM can lower timing causing the engine not to knock (and grenade) once it "knows" you have 87 octane gas based on on CHT (cylinder head temps etc) the PCM is watching all of this all of the time. So now you are down on power and may not even notice it.

This is especially true for 3.5 and also true for the 5.0 which was designed for 91 or better with factory tune, yes you can run 87, and may not hear the knock because the PCM knows it has already pulled timing and loosing power.

Higher octane gas burns slower, so that the PCM can command maximum timing and the piston comes up higher in the bore the - ignition sequence is at a 'perfect timing cycle' this means more power. 3.5/5.0 Modern F150 with 87 the piston does not come up as high in the bore and to stop the 87 fuel from burning too early the PCM pulls timing and tells ignition to light it up early. (and this stops the engine from breaking stuff). This happens on all modern engines. A car that was designed to run premium 10.5:1 WITHOUT Direct Injection, can be flash tuned to run 87 (yes it's just less timing and less power) grain of truth...

For an older OBDII car that was designed for 87, the 91 or 93 will hurt you as the PCM has a max timing curve designed for 87. Also the PCM can learn about this 87 gas and advance or retard the timing still within a range, perhaps only a few (2) degrees.

The ford PCM has a wide range of timing tables to learn about the fuel it is using and having 91 or 93 will lead to the best possible timing table, once a 3.5EB or 5.0 learns you have 87, you no longer have 400hp, perhaps only 380hp (%5)


Anyway, hope this helps.

Your description ignores the contribution of the GDI. Knock, ping, or detonation is self ignition (eg before the spark) in the cylinder caused by the heating of the mixture from compression. Just retarding the spark doesn't necessarily fix this. But... ya know, if the fuel isn't yet in the cylinder because of GDI... then no knock, etc.

 

[MJG44]

I'm a 5.0 Livernois tuned. I ran 93 for the first few tanks and now back to 91. I wonder what the difference in output I'd between the two fuels.

I'd love to dyno test but that's just too much time and dedication.

 

[Babbage]

Your description ignores the contribution of the GDI. Knock, ping, or detonation is self ignition (eg before the spark) in the cylinder caused by the heating of the mixture from compression. Just retarding the spark doesn't necessarily fix this. But... ya know, if the fuel isn't yet in the cylinder because of GDI... then no knock, etc.

Oh, sorry you were saying wrong things and I tried to help you understand. Strange how you state things like above but insist 87 is fine in a modern F150.

 

[Babbage]

I'm a 5.0 Livernois tuned. I ran 93 for the first few tanks and now back to 91. I wonder what the difference in output I'd between the two fuels.

I'd love to dyno test but that's just too much time and dedication.

2 Tunes? one 91 and one 93? - I hear that Livernois knows their stuff.

Almost 552 on 93 Octane - Gross Venture: call Livernois and tell them to run that tune with 87 because G14 F150 has PFDI etc

 

[Yves]

Can a mod remove his blatant lies? Yes so. Quite literally backed up by fact. Backed up by Fords engineers, dyno results, and experienced tuners. Your bullshit is backed up by nothing, and you are an old head who doesn’t understand how modern engines work. Can’t teach an old dog new tricks as they say…

Maybe you should take a breath.....

 

[MJG44]

2 Tunes? one 91 and one 93? - I hear that Livernois knows their stuff.

Almost 552 on 93 Octane -

I have the flex tune so just 1 performance tune. I throw in 93, well actually 94 with up to 10% ethanol, but switched back to 91 since I drive so much and 91 is more easily accessible.

 

[WhiteLightningnshitshadow]

Well, the computer running the engine will detect any detonation and retard the spark, and maybe some other things. Plus at altitude, eg Colorado and Wyoming , 85 actually makes little difference because of the lowered inlet air pressure. This lowered inlet air pressure translates into lower cyinder pressures and thus greater protection from detonation. My thought, and how I ran my engine, is while under warranty, use 87 octane minimum. Why? Well you just don't want to give Ford or a dealer an excuse to refuse to honor the warranty. After you're out from under the warranty... well let your conscience be your guide...

Thats definitely true of carbed cars, but unfortunately the new stuff, turbo or not, actually just lets more air in to compensate for the lack of density.

 

[Samson16]

2 Tunes? one 91 and one 93? - I hear that Livernois knows their stuff.

Almost 552 on 93 Octane -

Have we actually watched the video? I didn't hear any mention of fuel octane rating and the engine most certainly never flirted with 600hp. 455whp reported post tune. That's impressive enough, there is no need for exaggerated reporting.

 

[WhiteLightningnshitshadow]

Ok, it's about timing, when the engine is hot and/or under high load (floored it) 87 octane gas will pre-detonate or knock. The PCM (powertrain control module) knows this and PULLS timing, to save the engine from blowing up. Now you have less power and no ping. The PCM can lower timing causing the engine not to knock (and grenade) once it "knows" you have 87 octane gas based on on CHT (cylinder head temps etc) the PCM is watching all of this all of the time. So now you are down on power and may not even notice it.

This is especially true for 3.5 and also true for the 5.0 which was designed for 91 or better with factory tune, yes you can run 87, and may not hear the knock because the PCM knows it has already pulled timing and loosing power.

Higher octane gas burns slower, so that the PCM can command maximum timing and the piston comes up higher in the bore the - ignition sequence is at a 'perfect timing cycle' this means more power. 3.5/5.0 Modern F150 with 87 the piston does not come up as high in the bore and to stop the 87 fuel from burning too early the PCM pulls timing and tells ignition to light it up early. (and this stops the engine from breaking stuff). This happens on all modern engines. A car that was designed to run premium 10.5:1 WITHOUT Direct Injection, can be flash tuned to run 87 (yes it's just less timing and less power) grain of truth...

For an older OBDII car that was designed for 87, the 91 or 93 will hurt you as the PCM has a max timing curve designed for 87. Also the PCM can learn about this 87 gas and advance or retard the timing still within a range, perhaps only a few (2) degrees.

The ford PCM has a wide range of timing tables to learn about the fuel it is using and having 91 or 93 will lead to the best possible timing table, once a 3.5EB or 5.0 learns you have 87, you no longer have 400hp, perhaps only 380hp (%5)


Anyway, hope this helps.

I was under the impression that higher octane means higher ignition point rather than slower burn rate.

 

[Gros Ventre]

I was under the impression that higher octane means higher ignition point rather than slower burn rate.

Octane measures the resistance to self ignition or detonation. That's all.

 

[Gros Ventre]

Thats definitely true of carbed cars, but unfortunately the new stuff, turbo or not, actually just lets more air in to compensate for the lack of density.

The inlet size is not variable. If the ambient pressure decreases the air charge into the cylinder has lower oxygen content. From this the peak cylinder pressure just prior to ignition is lower.

 

[Samson16]

I know we've all seen it, but just dang. 492whp and 594lb./ft. with just a tune

 

[wayfarer556]

I’m always 93. My trucks runs noticeably better with it. Costco or QT always has it at a good price. There’s a subtle change with 87 that’s noticing when you need to put your foot down.

Wanna know what really made my truck come alive? 0 eth 93 octane. They sell it at Buccees in Galveston.

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