PCM Adjustment Time to Octane

[swamp2]

Also posted this in the Raptor section (my truck) but figured much more traffic here. Do they use the same PCM on 2.7 and 3.0?

I can only monitor some real basic stuff via my OBDII dongle and the Torque app. No tune yet. Does anyone have any actual data as to how quickly the factory PCM and tune can adjust to a significant octane change in the fuel? I'm experimenting with a roughly E48 blend or 96 octane. My guess was that the factory PCM might pull timing up to 95 octane. TIA.

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[Area51BS]

It’s very quick. Knock sensor.

 

[Ducati1098]

Also posted this in the Raptor section (my truck) but figured much more traffic here. Do they use the same PCM on 2.7 and 3.0?

I can only monitor some real basic stuff via my OBDII dongle and the Torque app. No tune yet. Does anyone have any actual data as to how quickly the factory PCM and tune can adjust to a significant octane change in the fuel? I'm experimenting with a roughly E48 blend or 96 octane. My guess was that the factory PCM might pull timing up to 95 octane. TIA.

Similar, but not the same part number.

It’s going to adjust within milliseconds of what the wide bands are seeing. So extremely fast

That being said, it’s going to take a few minutes for the mixture to reach the injectors if you just added some E, so that won’t happen right away.

E48 is probably going to be too much ethanol for the stock calibration to handle.

 

[BAUS67]

I currently have about 6K on my Bronco. I've ran 93 octane in it on every fill up. Except one. I started pumping gas and noticed I had hit the 87 button. I had just filled my truck the day before and without thinking hit the 87 button.


About a block away from the gas station. I thought to myself the same thing that you did, "How long will it take to figure out I put 87 in it". Well not long. It felt the same taking off from a stop sign, but seemed kind off sluggish.

I've driven the Bronco enough to get an idea of how much pedal I can feed it before I see boost. I have a Procharged Stang so I have trained myself to get fuel economy when I can, by staying out of the boost is the best way.

Anyhow, the next stop sign I pushed the gas like I have always done it, but this time I watched the boost gauge. Low and behold I had about 5lbs in second and third gear. Then the boost would tail off over the next few gears. Now the boost would always creep in when it got into the higher gears, even with the 93, but by then I was getting out of the gas because I was up to speed. It did the same with the 87.

I tried to give it less throttle but there would always be a few pounds of boost in those lower gears. Now I'm sure some of you will think this is crazy talk but these are just my observations.

The next tank of gas was back to 93. Although it did not "switch" instantly, it only took a few blocks to slowly take the boost away in the lower gears and return to running up to speed without boost. I gave her a few WOT shots to see if things were acting the same. That did not change, saw a steady 15 almost 16 lbs. with a flash on occasion to 17. It has done that since new so I concluded things are "normal".

In closing I know this sounds crazy but I could feel a difference between the two. It was most definitely a bit more sluggish with the 87 in it. Now it seems it needed the boost compensated for less octane, but it does "feel" different, to me anyways.

 

[swamp2]

Similar, but not the same part number.

It’s going to adjust within milliseconds of what the wide bands are seeing. So extremely fast

That being said, it’s going to take a few minutes for the mixture to reach the injectors if you just added some E, so that won’t happen right away.

E48 is probably going to be too much ethanol for the stock calibration to handle.

I think I've seen at least one Bronco model that states that specified power is only available with 93. Furthermore, we know the system can accommodate 87. My guess was it would adjust up to about 95, this just to be sure, I mixed to 96.

Is it your guess or knowledge that if can't adjust for xnd benefit up to 95?

Thanks!

 

[swamp2]

It’s very quick. Knock sensor.

So that sensor does more than just retard timing with low octane, if does the opposite?

Doesn't it also depend on the software that reads the sensor? Sure preventing pre-ignition needs to be very fast, pretty well real-time, but one could imagine that going the other way could be done more slowly.

 

[Ducati1098]

I think I've seen at least one Bronco model that states that specified power is only available with 93. Furthermore, we know the system can accommodate 87. My guess was it would adjust up to about 95, this just to be sure, I mixed to 96.

Is it your guess or knowledge that if can't adjust for xnd benefit up to 95?

Thanks!

I’m guessing you’re mixing E85 with 87 to get 96 octane at 48% ethanol? Because 93 mixed with E85 at 48% ethanol would be ~99 octane

The 96 octane isn’t the issue. It’s the 48% ethanol that’s the problem. I highly doubt the stock calibration can adjust for that much ethanol.

If you want to run 96 octane it needs to be E85 with 93 mixed to E30

 

[swamp2]

I’m guessing you’re mixing E85 with 87 to get 96 octane at 48% ethanol? Because 93 mixed with E85 at 48% ethanol would be ~99 octane

The 96 octane isn’t the issue. It’s the 48% ethanol that’s the problem. I highly doubt the stock calibration can adjust for that much ethanol.

If you want to run 96 octane it needs to be E85 with 93 mixed to E30

I'm mixing 91 octane pump gas (10% ethanol) with E85. Unfortunately, we can't get 93 here. That would be my every day fill if we could.

I'm using the following chart (source) along with E85cal app.

The app also said to get E48 it is very close to 50-50 ratio of 91 and E85. That checks out with a basic back of the envelope (BOE) calculation of pure ethanol at 100 octane and 91 octane averaging to 96.

(BOE - 1. Ignore the 10% ethanol for a quick BOE, 2. assume equal parts mixture, 3. result is 95.5, not 96.)

She is running good. My 0-60 (definitely not the best way to estimate power) improved from (a poor) 6.6 s down to a 6.3 s. My physics based full vehicle performance simulator calculated that this about a 25 hp gain (and used the same % gain for torque in the simulations).

Are you sure E48 is 99 octane? Are you sure E30 is 96 octane? Does not sound right.

Still not sure how magazines report running sub 6 in the Raptor...

 

[Ducati1098]

I'm mixing 91 octane pump gas (10% ethanol) with E85. Unfortunately, we can't get 93 here. That would be my every day fill if we could.

I'm using the following chart (source) along with E85cal app.

The app also said to get E48 it is very close to 50-50 ratio of 91 and E85. That checks out with a basic back of the envelope (BOE) calculation of pure ethanol at 100 octane and 91 octane averaging to 96.

(BOE - 1. Ignore the 10% ethanol for a quick BOE, 2. assume equal parts mixture, 3. result is 95.5, not 96.)

She is running good. My 0-60 (definitely not the best way to estimate power) improved from (a poor) 6.6 s down to a 6.3 s. My physics based full vehicle performance simulator calculated that this about a 25 hp gain (and used the same % gain for torque in the simulations).

Are you sure E48 is 99 octane? Are you sure E30 is 96 octane? Does not sound right.

Still not sure how magazines report running sub 6 in the Raptor...

I was just basing the octane rating off an online calculator I found. Certainly could be wrong, but here is what it shows with 91. Obviously this is assuming the pump gas is actually 10% and the pump E85 is actually 85%, which I'm sure is lower. So the octane probably isn't as high as this suggests.

 

[EvilJim1971]

The ECU won't read the ethanol percentage.
It will run is 93 octane tune unless it detects knock then will adjust down till the knock goes away.
Keep in mind, since you didn't have a fuel sensor and the ECU doesn't tune for E, it is shooting for E10 AFR with the E48 fuel.
I assume you know that goal AFR for gasoline and E are different.
Stoich for gas being 14.7:1, E85 being around 10:1, and your E48 mix being around 12-12.5:1.

 

[Brian_B]

In closing I know this sounds crazy but I could feel a difference between the two. It was most definitely a bit more sluggish with the 87 in it. Now it seems it needed the boost compensated for less octane, but it does "feel" different, to me anyways.

Exactly my experience. The turbo is pretty amazing that it can compensate for a lot of things (at the expense of drinking more fuel to do it)

 

[Aonarch]

The ECU will read the ethanol percentage.
It will run is 93 octane time unless it detects knock then will adjust down till the knock goes away.
Keep in mind, since you didn't have a fuel sensor and the ECU doesn't tune for E, it is shooting for E10 AFR with the E48 fuel.
I assume you know that goal AFR for gasoline and E are different.
Stoich for gas being 14.7:1, E85 being around 10:1, and your E48 mix being around 12-12.5:1.

I started a thread on E0 fuel and how I get worse fuel economy with it.

My results show that it does look like the ECU is tuned for E10 fuel.

 

[EvilJim1971]

I started a thread on E0 fuel and how I get worse fuel economy with it.

My results show that it does look like the ECU is tuned for E10 fuel.

Autocorrect got me.
ECU WON'T read the percentage of ethanol.
It will tune based on O2 sensors and knock sensors.
Since the AFR needed for E is different than gas, it's a roll of the dice on of it will run right.
One reason that flex fuel vehicles run the fuel sensor is to adjust for the increased fuel need and to scale for the AFR.

 

[BigMeatsBronco]

you can use forscan, and see the fuel trims, and a ton of other relative information...misfire numbers ect...

 

[swamp2]

The ECU won't read the ethanol percentage.
It will run is 93 octane tune unless it detects knock then will adjust down till the knock goes away.
Keep in mind, since you didn't have a fuel sensor and the ECU doesn't tune for E, it is shooting for E10 AFR with the E48 fuel.
I assume you know that goal AFR for gasoline and E are different.
Stoich for gas being 14.7:1, E85 being around 10:1, and your E48 mix being around 12-12.5:1.

I'm aware of the variance in AFR. There is no way it was running massively botched/lean AFR, it ran great, made about +25 hp and as expected, got crappy mpg, right about 20% worse.

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