GX460 KCLV for premium vs regular gas

[tingc222]

So - in my pursuit of trying to figure out regular vs. premium gas use for my GX460, I got myself deep into the rabbit hole that is the Toyota/Lexus ECU mapping for injection timing in trucks, how Toyota engines calculate injection timing, and how the knock feedback works.

I can’t find any info out there on reported KFB (Knock Feedback Value) and KCLV (Knock Correction Learned Value) values for the 1URFE engine, especially in the context of different fuel use - 87 vs 91. There is also zero info out there on ECU ignition tuning of the GX460 1URFE versus Toyota implementations of the 1URFE.

From what I suspect, the only POTENTIAL reason for Lexus to require premium gas in our GXs is due to a different ECU tune than Toyota (would be nice to see someone map the factory tune of a GX460 and compare against a Toyota 1URFE)

I know that the community is either for or against regular fuel use in the GX460. Maybe these numbers will help us figure it out?

for premium and regular gas GX460 users - can you post your type of gas and your KCLV and KFB values? It’s helpful to record changes to these values over a modest drive, to report a range of numbers (hypothetical example: KCLV 20-22, but dips to 16 under heavy engine load, KFB stays at -3.0)

From what I’ve come to understand, KCLV is an automated adjustment value to optimize injection timing as part of the knock feedback. On ECU reset it defaults, then over time advances the timing to improve performance until knocks are detected. Eventually this feedback loop arrives at an optimized value. This should mean that KCLV and/or KFB values would differ for different gas types…on my OBDLink it comes out of the Toyota/Lexus/Scion PID “Knock Correction Learning Value” and “Knock Feedback Value”.

From FJ forums:

Desired Spark Advance (SA) = Base SA + KCLV + KFB + Compensations

Toyota specific PIDs

Hi, all! Does anyone have a list of specific PIDs that can be used with Torque or similar app? I have a Car Scanner Pro set up on my phone with various useful info, but I want more. Specifically what I want to see is: -KCLV (Knock Correction Learn Value) -KFV (Knock Feedback Value) -O2FT B1...

www.fjcruiserforums.com

I just had a ECU reset, so will run through a few more tanks before I post mine.

Please educate me if I’m thinking about this incorrectly! I’m technically minded but not an engineer.

 

[r2m]

Personally, I just bite the bullet and run premium all the time. Although, when we did our road trip to Maine last year, once we got over the Continental Divide, I noticed that premium gas octane went up a couple of points and so did my MPG! So I run premium for a little better gas mileage and to ensure I get over half a million miles off my engine.

 

[Acrad]

Just a short drive and couldn't remember the other parameter at the time but my KCLV seemed to stay between 27 and 27.88

I always run Premium

 

[tingc222]

I'm pretty sure that the dealer fueled me up with regular 87 gas

My KCLV hovers around 21, and KFB largely stays put at -3

So perhaps this means that the GX460 is, in fact, using a knock-feedback to "compensate" for 87 octane use?? Which means it "learns" how to not knock with 87 gas...which in turn means that 87 gas is, in fact, safe to use (please tell me if I'm wrong in my logic here).

Consensus out there says that lower KCLV decreases performance. However, retarded ignition timing doesn't generally affect low-end rpm performance (such as in torque-y truck engines), so for general driving, it's very possible that 87 octane does not significantly decrease engine performance.

Again...someone tell me I'm wrong here?

I will see how my next fill-up (which will be premium) will change this.

Edit: Interesting read here on a 2GR-FKS : Knock Correction Learned Value - vF Tuner Forums - https://forum.vftuner.com/forum/toyota-3-5l-2grfks-development/2069-knock-correction-learned-value

 

[GrizzlyClint]

Personally, I just bite the bullet and run premium all the time. Although, when we did our road trip to Maine last year, once we got over the Continental Divide, I noticed that premium gas octane went up a couple of points and so did my MPG! So I run premium for a little better gas mileage and to ensure I get over half a million miles off my engine.

On our long road trip I absolutely noticed not only fuel economy but a performance difference between 87 and 91. I’m happy to put 93 down here in Texas to ensure the most out of it. It isn’t that much more $$ in the grand scheme of things to matter about the price increase. Was hugely disappointed to see only 91 up north. WTF was up with that?

 

[tingc222]

On our long road trip I absolutely noticed not only fuel economy but a performance difference between 87 and 91. I’m happy to put 93 down here in Texas to ensure the most out of it. It isn’t that much more $$ in the grand scheme of things to matter about the price increase. Was hugely disappointed to see only 91 up north. WTF was up with that?

There is definitely a performance advantage to ignition timing advance.

If only...around here I'm expected to pay $4 for a gallon of premium, versus $3.30 for regular. That's the only reason why I'm reading so much into this. I don't even like to read

 

[GrizzlyClint]

There is definitely a performance advantage to ignition timing advance.

If only...around here I'm expected to pay $4 for a gallon of premium, versus $3.30 for regular. That's the only reason why I'm reading so much into this. I don't even like to read

Understandable.

 

[r2m]

On our long road trip I absolutely noticed not only fuel economy but a performance difference between 87 and 91. I’m happy to put 93 down here in Texas to ensure the most out of it. It isn’t that much more $$ in the grand scheme of things to matter about the price increase. Was hugely disappointed to see only 91 up north. WTF was up with that?

The whole west coast only gets 91 octane. There are a few gas stations that sell (I think) 100 octane race fuel, but very expensive.

 

[GrizzlyClint]

The whole west coast only gets 91 octane. There are a few gas stations that sell (I think) 100 octane race fuel, but very expensive.

Ugh, that sucks. I like 93 octane

 

[Rednexus]

FWIW (GX470) I finally stopped running 91 octane when gas got expensive and switched to 87. The 1UR was also used in the Tundra where it required 87 octane and made more power than the GX460 application, both using 10.2:1 compression, so it seems that the only difference is the GX vs. Tundra tune. I see very, very little time at WOT in my GX, so I see virtually no performance difference on 87 vs. 91, and it performed flawlessly and had plenty of power when we drove it up to nearly 12k ft in CO this summer. Of course it's a different engine, but I've found the benefits of premium not to be worth the cost.

 

[Acrad]

According to the brochures…in Eurasian markets the 4.6L in GX puts out 292 hp / 323 lb⋅ft versus our 301 hp / 329 lb⋅ft.

Could this lower rating be an assumption that one is generally using questionable and perhaps more often than not lower octane fuels in many other areas of the world?

 

[Rednexus]

According to the brochures…in Eurasian markets the 4.6L in GX puts out 292 hp / 323 lb⋅ft versus our 301 hp / 329 lb⋅ft.

Could this lower rating be an assumption that one is generally using questionable and perhaps more often than not lower octane fuels in many other areas of the world?

It could also be emissions standards. Perhaps that is also the difference between GX and Tundra power ratings.

If someone is interested in quantifying this perhaps they could do a series of 0-60 runs on 87 octane (after the ECU has had time to "learn" on 87) and on 91/93 octane (after disconnecting the battery and allowing the ECU to re-learn it's 91/93 tune). 0-60 runs can be logged pretty easy in Torque Pro and probably other ODBII apps. Maybe I'll do this on my 470 sometime.

 

[Acrad]

It could be emissions related but there are also Eurasian configurations that don't have an EGR valve either.

 

[GrizzlyClint]

It could also be emissions standards. Perhaps that is also the difference between GX and Tundra power ratings.

If someone is interested in quantifying this perhaps they could do a series of 0-60 runs on 87 octane (after the ECU has had time to "learn" on 87) and on 91/93 octane (after disconnecting the battery and allowing the ECU to re-learn it's 91/93 tune). 0-60 runs can be logged pretty easy in Torque Pro and probably other ODBII apps. Maybe I'll do this on my 470 sometime.

The solution would be tuning software logger like others get from Diablo Sport and etc. Actually log the vehicle while driving then drive with both under varying throttle %’s then compare. Follow that up with a few fill ups with one octane a full reset between octane change then a dyno All of that should definitively tell us if octane really matters.

 

[Acrad]

I saw a little bit of variation with KFB today.. it mostly stayed at -3.0 but getting on it up a hill with a trailer brought it down to around -2 a few times.

KCLV only dipped down to 25 a few times

Not a heavy tow.. just my old '85 Honda TRX 250

 

[Acrad]

-

 

[tingc222]

I saw a little bit of variation with KFB today.. it mostly stayed at -3.0 but getting on it up a hill with a trailer brought it down to around -2 a few times.

KCLV only dipped down to 25 a few times

Not a heavy tow.. just my old '85 Honda TRX 250

That does make sense - since the ECU retards timings with higher engine load.

It could also be emissions standards. Perhaps that is also the difference between GX and Tundra power ratings.

If someone is interested in quantifying this perhaps they could do a series of 0-60 runs on 87 octane (after the ECU has had time to "learn" on 87) and on 91/93 octane (after disconnecting the battery and allowing the ECU to re-learn it's 91/93 tune). 0-60 runs can be logged pretty easy in Torque Pro and probably other ODBII apps. Maybe I'll do this on my 470 sometime.

I will fill up on premium after the truck gets back from the shop and report back.

 

[BigSwede]

The general theory is that higher octane will allow the ECU to advance the timing for more power.

But there was a recent episode of Engine Masters on Motor Trend network. They ran the same LS3 on a variety of octanes from 87 to 110. They played with ignition timing and fuel/air mixtures to see if they could achieve a power difference. The bottom line was, with all of the octanes the optimal fuel/air mixture and ignition timing and resulting horsepower was effectively identical.

Their conclusion was that the only reason to run higher octane gasoline is to prevent pre-ignition (pinging). So I am really curious if the GX can control pinging with 87 octane. The 50 cent/gallon difference really adds up on a long trip.

 

[tingc222]

You know I’ve read many reports of that too - that so long as it doesn’t knock, there is no harm using 87 whatsoever.

We probably can’t assume the LS3 and the 1URFE behave similarly when using different octanes, however.

which raises 2 questions:

1. I assume by the way Toyota designed the ignition timing/spark advance algorithm, that since it works at least in part by knock FEEDBACK, that a few occasional engine knocks are normal? Otherwise, KCLV would be static (from what I read and understand, KCLV is never a static value; it’s designed to slowly advance until knocks are detected, even without a ECU reset. For instance, switching from 87 to 91 gas alone would cause the KCLV to slowly increase over time)

2. by the above logic, even 91 gas would knock a little once in a while when the KCLV constantly establishes and re-establishes it’s “learned” threshold.

would all of this reaffirm BigSwede’s point above, for the GX?

 

[tingc222]

…and to the issue of power - check out post #72 at this link - example is from testing KCLV vs dyno results for the 2UR-GSE in the Lexus ISF.

Data-Logging The 2GR-FE ECU

This may be of very limited interest because if you can't tune it then why would you want to log it and those who are capable of tuning this ECU probably have no need for this but here goes anyway. I take that back there may be some interest in using this for making a semi-accurate evaluation...

www.mr2oc.com

If KCLV makes a difference in power, that would likely explain the improvement in power (and maybe mpg?) going from 87 to 91 octane.

Whether or not this power difference is big enough to be noticeable, is up for debate.