Dudes. I drove 18 hrs yesterday to get o Denver. Now my truck is DOG slow

[jeremyc74]

I've pulled Floyd Hill in my 84 4Runner with a 22RE and 40" Iroks once! Right lane, 25-30 mph all the way up! Never doing that again! Remember [MENTION=67615]Dirtco[/MENTION]

I crossed the divide in an RV with a 22RE in it 7 times in four months at various places. People hated me. I put went from Key West to Port Angeles, WA (with detours through VA and TX, and all sorts of other places. Total trip was 16k miles, and I passed THREE vehicles on the interstate the entire time. Two of them were beat up old farm trucks, and the other was a VW bus. I could see him off in the distance coming across New Mexico and spent nearly an hour trying to catch him! :car:

It was three hippies and as I went by (slowly) they were laughing and rocking forward like they were trying to help it get some speed. :whip2:

 

[amalik]

From an anti-knock perspective, which is all the Octane rating is, yes.

Knocking, pre-ignition, auto-ignition, self-ignition, pinging, are all names for what is essentially an uncontrolled explosion in the combustion chamber.

The Octane rating is not an indicator of the energy content in the fuel. It is only a measure of the fuels tendency to burn in a controlled fashion, instead of exploding in an uncontrolled fashion.

I've been measuring this on my last 4-5 fills based on what you said.

1. More 85 fits in the tank than 87 (a little over 1 gallon)

2. 87 gets me a bit better MPG than a tank of 85

 

[jeremyc74]

I've been measuring this on my last 4-5 fills based on what you said.

1. More 85 fits in the tank than 87 (a little over 1 gallon)

That is physically impossible. The octane rating doesn't change the volume of a gallon of gas. :

 

[JayRolla]

I've been measuring this on my last 4-5 fills based on what you said.

1. More 85 fits in the tank than 87 (a little over 1 gallon)

2. 87 gets me a bit better MPG than a tank of 85

LMAO, you do relize all pumps are different and not calibrated perfect. Like he said physically impossible to fit more in the tank due to octane rating. I just had a good laugh, nice start to the work day.

 

[amalik]

LMAO, you do relize all pumps are different and not calibrated perfect. Like he said physically impossible to fit more in the tank due to octane rating. I just had a good laugh, nice start to the work day.

# of gallons isn't as important. Ignore #1.

The 87 consistently gives better MPG, which he said shouldn't be the case.

 

[jeremyc74]

# of gallons isn't as important. Ignore #1.

The 87 consistently gives better MPG, which he said shouldn't be the case.

The number of gallons is important, because it changes the mileage calculation.

It's not impossible your truck is getting better mileage on 87 compared to 85, but it's not likely. If it is, it's because the ECU is pulling timing to avoid knock on the 85 and not running right, but generally you'd get a code for that. It's also possible that the 85 has higher ethanol content, which has lower energy.

The really test this you would need to do an average of several tanks with each fuel, filling up at the same station each time. Otherwise, when you're just talking about a small MPG difference there are just too many variables.

 

[JayRolla]

# of gallons isn't as important. Ignore #1.

The 87 consistently gives better MPG, which he said shouldn't be the case.

It shouldnt be the case. In this altitude running 85 octane will not cause any knock or detonation. Meaning no timing pull, no change in anything so same fuel mileage.

 

[steezemcqueen]

I can see 87 octane giving a little better MPG and slightly more power. The ECU on these does constantly adjust the timing and hold it at the knock threshold. Now it only listens to the knock sensors above 3000 rpm and then calculates timing for under 3000 rpm based on load, throttle position, and the timing data from above 3000 rpm.

This is why many people will still get low rpm ping when they install a supercharger. It doesnt know its pinging because its not doing it at a higher RPM and its not checking for it at a lower RPM. Now averaging out over a few hundred miles, you could see an increase in timing with higher octane which would give you a slight bump in power and MPG.

I just recently switched to some larger injectors and E85 for my setup and purposely didnt touch my timing map. After a few hundred miles, i'm seeing almost 10 degrees of increase in timing as reported by the ECU.

 

[jeremyc74]

I just recently switched to some larger injectors and E85 for my setup and purposely didnt touch my timing map. After a few hundred miles, i'm seeing almost 10 degrees of increase in timing as reported by the ECU.

How are you seeing the ECU timing? Can you see it with a scangauge or other OBDII reader?

 

[steezemcqueen]

How are you seeing the ECU timing? Can you see it with a scangauge or other OBDII reader?

UltraGauge

 

[JayRolla]

I can see 87 octane giving a little better MPG and slightly more power. The ECU on these does constantly adjust the timing and hold it at the knock threshold.

Now it only listens to the knock sensors above 3000 rpm and then calculates timing for under 3000 rpm based on load, throttle position, and the timing data from above 3000 rpm.

This is why many people will still get low rpm ping when they install a supercharger. It doesnt know its pinging because its not doing it at a higher RPM and its not checking for it at a lower RPM.

Now averaging out over a few hundred miles, you could see an increase in timing with higher octane which would give you a slight bump in power and MPG.

I just recently switched to some larger injectors and E85 for my setup and purposely didnt touch my timing map. After a few hundred miles, i'm seeing almost 10 degrees of increase in timing as reported by the ECU.

So your saying on a stock motor, your will get more timing because you can have detonation under 3000rpms? I dont see that happening at all. With 85 or 87, under 3000rpms you will get no knock, meaning both fuels will gate same timing advance.

E85 is some magic juice. In my DSM I was able to get 22* max timing advance that would start around 12* lowest drop at onset of boost. This was running a small turbo past its efficiency range peaking at 34psi and dropping too around 28psi by redline. Granted low compression 8.5:1 pistons for boost but stock oem pistons. All this and never a blip of detonation.

 

[shootmymime]

UltraGauge

What's the value? I want to look for mine.

 

[steezemcqueen]

So your saying on a stock motor, your will get more timing because you can have detonation under 3000rpms? I dont see that happening at all. With 85 or 87, under 3000rpms you will get no knock, meaning both fuels will gate same timing advance.

E85 is some magic juice. In my DSM I was able to get 22* max timing advance that would start around 12* lowest drop at onset of boost. This was running a small turbo past its efficiency range peaking at 34psi and dropping too around 28psi by redline. Granted low compression 8.5:1 pistons for boost but stock oem pistons. All this and never a blip of detonation.

I'm saying that over 3000rpm (where the ECU listens to the knock sensors) It can possibly increase timing further with higher octane since its holding it at the knock threshold. Not saying yes you will definitely see more timing but it is possible. Less likely with a stock motor but not impossible.

And since it uses the higher RPM data to calculate the lower RPM data, that can change as well.

 

[jeremyc74]

What's the value? I want to look for mine.

Same here, just for curiosities sake. I'm so used to being able to see all the data on my car (and keeping a constant eye on it) that I have a hard time just accepting that everything is OK and the ECU is doing what it's supposed to and not worrying about it. :bash::thanks:

 

[steezemcqueen]

What's the value? I want to look for mine.

Same here, just for curiosities sake. I'm so used to being able to see all the data on my car (and keeping a constant eye on it) that I have a hard time just accepting that everything is OK and the ECU is doing what it's supposed to and not worrying about it. :bash::thanks:

The gauge name is timing advance. Mine bounces between 15-30 degrees of advance usually but my truck isn't exactly typical......

 

[shootmymime]

Ok I'll go look

 

[shootmymime]

Legit got it all set up

 

[amalik]

I can see 87 octane giving a little better MPG and slightly more power. The ECU on these does constantly adjust the timing and hold it at the knock threshold. Now it only listens to the knock sensors above 3000 rpm and then calculates timing for under 3000 rpm based on load, throttle position, and the timing data from above 3000 rpm.

This is why many people will still get low rpm ping when they install a supercharger. It doesnt know its pinging because its not doing it at a higher RPM and its not checking for it at a lower RPM. Now averaging out over a few hundred miles, you could see an increase in timing with higher octane which would give you a slight bump in power and MPG.

I just recently switched to some larger injectors and E85 for my setup and purposely didnt touch my timing map. After a few hundred miles, i'm seeing almost 10 degrees of increase in timing as reported by the ECU.

Great info Dylan. Thx.

 

[Supermoney]

How to tow with the 4Runner through rocky mountains:

1. Stock tire size
2. Supercharger
3. Transmission cooler

 

[02SE]

I've been measuring this on my last 4-5 fills based on what you said.

1. More 85 fits in the tank than 87 (a little over 1 gallon)

2. 87 gets me a bit better MPG than a tank of 85

Read this.

The number of gallons is important, because it changes the mileage calculation.

It's not impossible your truck is getting better mileage on 87 compared to 85, but it's not likely. If it is, it's because the ECU is pulling timing to avoid knock on the 85 and not running right, but generally you'd get a code for that. It's also possible that the 85 has higher ethanol content, which has lower energy.

The really test this you would need to do an average of several tanks with each fuel, filling up at the same station each time. Otherwise, when you're just talking about a small MPG difference there are just too many variables.

As stated in this quote, there are sooo many variables, that it would be impossible for me to pinpoint your results over the internet.

Did the 85 you used have a higher Ethanol content, than the 87, thus reducing the energy content of the 85? We don't know without testing each sample.

Did you drive the exact same route, in the exact same manner, with all atmospheric conditions identical for each tank?

Only one tank of each Octane could easily give erroneous results. I wouldn't make any judgement for one octane over another, on any test that wasn't averaged over at least 5 tanks of each.

We also have no idea if the gas pump for the 85 and the 87 were calibrated the same. Most likely there is some difference.

Then there's also the fact that summer blend Gasoline is being phased back in this time of year. That could account for the difference.

Does your 4Runner have deposit build-up in the combustion chambers, creating potential hot spots, and/or slightly higher compression, which could result in the ECU detecting knock, and retarding timing. Again, I can't tell you without inspecting your combustion chambers.

The bottom line is if your truck is designed to run on 85, and it doesn't experience knock while doing so, AND the energy content of the gas is the same for both the 85 and 87, the 87 won't make a difference at high altitude.