Gas Octane

[Paul McWhiskey]

…which allows more spark timing resulting in more power.

I will give you that. Can anyone provide dyno results that conclusively show that Gen 6 Mustangs produce more power using 93 vs. 91? I would be interested in seeing if the system can tell the difference and advance timing to do so. I am not disagreeing with you. I am more interested in if the car is smart enough.

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[shogun32]

are we pretending that gasoline isn’t a carcinogen? Or that your car is capable of getting cancer?

you’ll get more power on 93

It was a figure of speech. Ethanol is a contaminate. It has its uses, sure. But it properly belongs outlawed, and civilization spared its costs.

 

[shogun32]

-Yes the car can suss out how much E is in the fuel.-

The op point was he isn't racing and he's driving normally. Qed, the last but of timing is irrelevant as is attaining max theoretical power.

 

[engineermike]

I will give you that. Can anyone provide dyno results that conclusively show that Gen 6 Mustangs produce more power using 93 vs. 91? I would be interested in seeing if the system can tell the difference and advance timing to do so. I am not disagreeing with you. I am more interested in if the car is smart enough.

The gen3 coyote does not have octane learning activated from the factory. The way the algorithm works is it initially commands “borderline” spark timing (where it expects to see knock on 87 octane) and then starts adding “knock advance” until it hits either a spark limit, MBT (maximum brake torque timing), or senses knock. I can share some actual numbers if you like. Ford even goes as far as to predict the torque output as a function of actual air density, cam timing, lambda, and how far below MBT the timing is.

I have done quite a bit of tuning and have found that a stock gen3 will not reach MBT on any sort of pump gasoline, but rather will be limited to around 23 deg, 24 max. MBT is upper 20’s, so even on 93 e10 a stock coyote needs 4-5 deg more timing before it will make max power. 91 e0 will be a bit worse. On 87 they typically are stuck in the teens. Each degree of timing is worth roughly 5-6 hp NA, but that depends on how far from MBT you are and it’s a bit of an S
-shaped torque ratio curve.

That said, I really don’t think anyone would bother to dyno the difference between 91 and 93 because the difference isn’t worth the cost of the dyno time.

 

[GregO]

It was a figure of speech. Ethanol is a contaminate. It has its uses, sure. But it properly belongs outlawed, and civilization spared its costs.

Aldehyde tailpipe emissions. That’s the dirty secret suppressed by the Corn growers lobby and a few other alphabet soup agencies.

 

[engineermike]

Yes the car can suss out how much E is in the fuel.

FYI the coyote is tuned from the factory to run 87 e10 and does not “learn” the octane or ethanol content. The f-150 coyote will learn ethanol but not octane, and it won’t learn all the way down to e0, as the learning range is actually e10 - e77.5. There really isn’t enough difference between e10 and e0 for it to matter from a calibration standpoint, as the octane difference will be handled by the knock algorithm and the fueling difference will be handled by adaptive fueling (trims).

 

[GregO]

Reid Vapor Pressure is often over looked when caught up debating octane ratings.
It’s a rabbit hole but fuel free radicals are a thing.

 

[Paul McWhiskey]

Mike,

Does the Gen 2 Coyote have any learning ability? If it does, does it also limit MBT?

 

[engineermike]

Does the Gen 2 Coyote have any learning ability?

Looks like the gen2 mustang does use Octane learning and can add up to 4 deg borderline timing in the midrange and 2 deg up top. But it still has the ability to add another 10 on top of that in knock advance, but that happens regardless of the learning.

If it does, does it also limit MBT?

In the gen2, MBT is a function of cam timing, load, rpm, and lambda. The gen3 adds ethanol content and ethanol lambda to that list. However, octane doesn't affect MBT which is why it isn't affected by it. This is why timing is calculated 4 or 5 different ways and a low-select is done; because each way is a function of differing things.

 

[markmurfie]

What happens at WOT isn't necessarily representative of the engine conditions seen during normal everyday use of the engine.

The car is perfectly capable of running 87 octane and not being at any risk, as at loads less than 50% it's still using base(MBT) or calibrated borderline values have only just slightly gone below base values and the knock adder can very easily add it back to obtain the base spark timing. It isn't until above 70% load where you might actually be detonation limited.

Of course you can keep RPM low and lig the engine and find a detonation limited area, but most people or automatic shift schedules are not going to do that.

Run what ever is cheaper if you want to. There are benefits from the higher octane, but you don't NEED them for every day normal use of the car.
IMO E0 gasoline is too costly to run in a vehicle that was designed to handle ethanol perfectly fine. Ethanol is the better fuel source to use.

 

[GregO]

Again, how long the fuel has been sitting in the storage tank would be the deciding factor for retail pump fuel.

 

[WildHorse]

Ethanol is the better fuel source to use.

100%. Too many people are living in the pre August 2005 world.


Carb rebuild kit suppliers use ethanol compatible

Again, how long the fuel has been sitting in the storage tank would be the deciding factor for retail pump fuel.

Not a concern for me, I buy it by the barrel.

 

[GregO]

Not a concern for me, I buy it by the barrel.

The light ends still disappear and RVP drop.
If you’re a barrel purchaser then check this out.

https://www.drumpreserve.com/default.asp?m=0

 

[WildHorse]

The light ends still disappear and RVP drop.

Pass.

 

[K4fxd]

There is no way to make a small engine carb alcohol safe. Thats why hardware stores sell E0 in a can.

We should not be using food crops to use as motor fuels. Ethanol is at best net zero as far as energy to produce and energy returned.

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