93 Octane - Timing Advance by 20-30 Degrees

Last fill up was with 93 octane shell v-power, and tracked the cylinder 1 timing advance reading anywhere from 20-30 degrees.

I assume if I use lower octane it will start dropping negative, or am I completely off here?

 

Short: Theoretically, yes.

Long: You're covering a range with a 50% spread saying 20-30deg. To see the exact difference you'll want to try and match rpm and engine load (throttle more or less). There's other variables too, but if you can match conditions as much as possible you should see the timing drop. So for example, I would do a few tests and see the truck REPEATABLY hits like 23deg, and then change octane and give it some time (or unplug the battery to reset the computer) and then repeat those conditions and again see if you can repeatably get a new timing value. Then you'll know how much the timing is getting pulled at that point.

 

I wasn’t able to find it in a quick search, but it’s posted somewhere this site by one of the vendors that tunes these trucks. They have done testing on the dyno and shown that even on a completely stock truck, the ECU will advance timing with higher octane.

Now it is still up for debate if that makes the added cost of premium worth it. The MPG improvement (if any) doesn’t offset the cost, but there are other factors to consider. Regardless of what you do long term, your truck will be fine running 87, as the ECU compensates for it.


EDIT:
Found it. Post #7 in this thread.
https://www.tundras.com/threads/octane-rating-advice.110726/#post-2857684

 

I see almost 40 degrees advanced on 87 octane. I don’t think it pulls timing until knock is detected.

 

The PCM will globally advance or retard timing via KCLV and Knock Feedback in real time. You can watch those two PID's to get an idea of the general amount of change provided between fuel grades.

Im not really sure how useful it would be to monitor the absolute timing angle because there are so many variables that will change it. Engine load, RPM, IAT's, coolant temp, fuel grade and quality, etc. Im not really sure how you could be certain how much of the timing was from any one variable. My F150 Ecoboost would fully utilize 96 octane in the summer but in the cold winter air on 91 octane it would run into the MBT and cylinder pressure limit tables before the fuel octane limited timing, so you couldnt even compare it in absolute terms. It was running more advanced timing in the winter on 91 than in the summer on 96.

 

You bring up many good points, the impact of those other variables is why I run premium. To me it gives the ECU a better chance of maximizing performance under any given circumstances, even if those gains are small on the 3UR compared to the FI engines out there.

 

Do you guys see any advantage of running Ethanol Free 90 Octane? My 21 has about 14K on her and I feel the E free is helps keep everthing clean and not gummed up.
Thought?

 

I would run it in everything all the time if it were available in my area, more BTUs per quantity. It can give a tangible increase in MPG, but not enough to offset the price difference.

 

I thought the 3UR did not adjust timing for differences in octane while the Lexus version does - is this wrong?

I had an Acura that did adjust and it was very noticeable and got about 10% better fuel efficiency - does anyone's 3UR get improved mileage from higher octane?

 

I get an extra 1-1.5mpg on premium - doesn’t cover the cost.

 

My fuel economy is more affected by ethanol content than by octane.

 

From master yota techs mouth they run fine on 87, if your towing or in desert your maf/knock sensors will retard timing. Min of 91 was recomended.

 

They all adjust timing. How far it can go might be a different story.

 

Is this a mpg upgrade or a power upgrade.... Both ?

If so how much power ?

 

No. But kind of. I'm trying to find the thread with timing advance vs octane vs RPM (might be on a different forum) but basically higher octane fuel will allow more timing advance at lower RPM, but top end timing advance isn't much affected. The end result: you make more power under the curve, but the same peak power on the top end, resulting in a smoother driving experience but no real change in peak numbers.

Learning more about about how modern fuels are formulated, I wouldn't run regular in any vehicle if one can afford it. The higher octane won't pay for itself in the MPG department or HP department, but whenever I've switched, general drivability and engine smoothness is noticeably improved - enough that I could tell immediately when that my wife had accidentally filled up with 87 when I drover her sequoia the other day. And according to Lake Speed Jr and his testing, premium fuels can contribute to motor longevity and reliability same as quality oils and timely oil changes.

 

I have always been in the opinion that if the engine was made to run on xx octane then run it. I have tried the whole power/MPG thing and it's not there for the price difference. And we aren't talking 10HP and 5 MPG either, more like 1 and 1. I have also read that on low compression engines, higher octane doesn't get a full burn, there for more raw fuel out the exhaust to clog your cats up. Fuel is fuel, doesn't matter the octane, they all have the same BTU(power). Octane is just a measure of a fuel's ability to resist knock. I have also tried the non ethanol and still the same crap. Waste of money. Fortunately for me, I now get to run 93 all the time and enjoy a lot of more HP/TQ.

 

Octane is the ability of the fuel to resist detonation. You want it to detonate, but you want the spark to trigger that detonation, not the increase in heat and pressure within the cylinder. Low compression engines don't need higher octane usually, higher compression engines benefit from it. Knock = pre-detonation, or fuel igniting before the spark plug fires. Knock can damage engines and reduce power. The engine will pull timing if it detects knock, reducing your power. All commercial gasoline grades (non-ethanol) contain the same amount of energy, so premium and regular make the same amount of power. High octane does not equal high power fuel. High octane may allow a higher compression engine to create more power without pre-detonating the fuel.