I Don't HaveTime to Research This (Warning - Octane Related!)

[FinallyGotOne!]

Pulling the pin on the hand grenade and tossing it.....

Anyone here heard of KCLV? I've got an IS F and I read about KCLV on an IS F forum. Lots of talk about it there, where you find many guys dragging and racing their IS Fs and looking for max performance. For those of you who haven't heard of it, KCLV stands for "Knock Correction Learn Value." On the IS F, it is simply a long term ignition correction factor. After you flash your car or reset your ECU, the KCLV goes to 15. Once you start driving the car, particularly doing long pulls at high load, the ECU starts bumping the KCLV up in small incremental steps until some knock is detected. It then backs it off, and leaves you with optimally-advanced ignition timing.

The value is apparently continually adjusted, based on octane, driving style (engine load and RPM) and other factors. It also appears that the IS F guys use Techstream to flash (reset) their ECUs when they think they've lost a high KCLV and/or are going to the track. Rather than using Techstream, some guys disconnect the battery, and some just go blasting around at WOT for a while to ease it back up.

For some reason KCLV popped into my head this morning as a possible partial answer to a number of questions often raised in this forum, e.g "Why does the LX require 93 octane and the LC doesn't?", "Why is the LX spec'ed at 1 more HP than the LC?", and the big one: "Why buy premium???"

Many have answered these questions with some variation of "It doesn't matter, the ECU will accommodate the variation in octane so don't worry about knocking. We have a modern engine."

All that said, has anyone noticed KCLV in Techstream or on an OBD2 dump? I won't have time for researching this any time soon, but I wonder if the LC/LX uses KCLV, I wonder if we really will realize some degree of increased performance if KCLV is increased (regardless of how), and I wonder if the true answer to the octane question is "Yes, you will eventually achieve slightly better performance if you keep using premium, and yes, we told you LX owners you could make more horsepower if you kept buying premium, but so will the LC owners."

I also wonder how around town driving vs highway towing affects KCLV and overall engine performance. Lots of evidence in the IS F forum clearly shows stop and go, easy around town driving results in a reduced KCLV and reduced engine output, therefore the reflashing before racing.

So, there's the grenade. Nothing really earth-shattering, but I know how we all love/hate to talk octane. At the very least, this might be an interesting topic for discussion.

Your thoughts?

 

[Narkhelek]

Max timing advance is going to depend on a number of factors besides the fuel octane rating with engine compression and air density being the two most important factors that define the timing advance limit. The higher the engine compression and/or air density the more probable it is for the fuel to pre-ignite. That is why high performance (high compression) engines tend to require higher octane fuel and why high elevation mountain states regular gasoline is 85 octane. In the first case the engine needs higher octane (ignites at higher pressure) fuel to avoid pre-ignition and in the latter case the lower air density will allow one to get away with lower octane fuel (ignites at lower pressure). This is a good time to point out that octane in fuel in no way equates to amount of stored energy. Timing advance allows an engine to increase RPMs faster so it's desirable to have the engine advance it's timing when trying to achieve max acceleration.

Our engine is continuously doing what you describe above as far as advancing timing until it detects pre-ignition and backing off, it just does it a lot more conservatively than someone who races would desire. So yes you could probably squeak out a little bit more performance if you can get the ECU to more aggressively advance timing. Higher octane fuel could also squeak out a bit more performance especially if you are advancing the timing as much as possible. However, I believe the performance gain would be marginal. The 3UR-FE is just not designed to be a high performance racing motor. To get real performance gains you have to ram more air/fuel into the engine than is possible with natural aspiration.

 

[PhillipPinot]

@FinallyGotOne! - completely unrelated, but my next purchase will be an IS-F. Know of any particular year to go for or stay away from?

 

[FinallyGotOne!]

Our engine is continuously doing what you describe above as far as advancing timing until it detects pre-ignition and backing off, it just does it a lot more conservatively than someone who races would desire. So yes you could probably squeak out a little bit more performance if you can get the ECU to more aggressively advance timing. Higher octane fuel could also squeak out a bit more performance especially if you are advancing the timing as much as possible. However, I believe the performance gain would be marginal. The 3UR-FE is just not designed to be a high performance racing motor. To get real performance gains you have to ram more air/fuel into the engine than is possible with natural aspiration.

Very well stated and I completely agree!

 

[FinallyGotOne!]

@FinallyGotOne! - completely unrelated, but my next purchase will be an IS-F. Know of any particular year to go for or stay away from?

No. They are truly amazing vehicles. High reliability. Monster power. And they don't attract police. I have had an '08 and an '09 and loved both. They do have a harsh ride...this is not a typical Lexus. Some of that was fixed in '11 when they slightly modified the suspension to get a smoother ride. I'd recommend an '11 and newer because of that, but I have put ~50K miles on my two and I don't mind the suspension at all. They can be loud inside, especially if modified with fresh air induction.

08-09 have an electronic limited slip differenatial, mechanically it's an open diff.

2009: interior trim on doors, center console, nav changed from silver to black
2010: updated nav (gen 6), new style wheels
2011: Torsen limited slip diff, suspension updates, new style headlights (no longer adaptive), alcantara leather, updated gauge cluster, updated steering wheel
2012: more suspension updates?, Newest style wheels
2013: minor nav updates
2014: minor nav updates, carbon fiber rear spoiler, F embossed headrests & maybe a couple other minor interior updates?

Reliability is high for all year models. The only mechanical flaw is leaking water pumps for early model years 08-09 and maybe 2010. Most of those will have had the water pump replaced by now

 

[steenh]

I had an '08 ISF for a few years and can vouch for them... one a few cars I've sold over the years that I regret selling. I only drove it to 60k miles but in that time I had zero issues and more than a few track and spirited mountain drives. As mentioned above, the ride is harsh compared to any other Lexus but it never really bothered me either. The amazing thing with all that power is that I averaged 28 MPG at highway speeds.

 

[TeCKis300]

Absolutely the LC/LX, and every modern vehicle since the advent of ECUs, have KCLV, or an equivalent implementation of the concept. It's as much a power thing as it is efficiency (mpg). The key to this is to ride the threshold before knock, but also to keep the engine safe from incidental situations or bad fuel.

So while any modern motor can use lower octane fuels, it's certainly not optimal. Manufactures design engine parameters (including software) to get the most out of target fuels. Meaning if they specify 91, they certainly will be calibrating the ECU for that target. But of course with fail-safes for those that think they know better.

I've tuned many lexus cars for turbo kits, including my own supra twin turbo swapped IS300. And I've tuned my own Porsche for bigger turbos and injectors, where 1 degree of advance can equal something like 15hp. It's eye opening the extent of parameters that the OEMs use to get optimal power/safety/emissions.

 

[PhillipPinot]

No. They are truly amazing vehicles. High reliability. Monster power. And they don't attract police. I have had an '08 and an '09 and loved both. They do have a harsh ride...this is not a typical Lexus. Some of that was fixed in '11 when they slightly modified the suspension to get a smoother ride. I'd recommend an '11 and newer because of that, but I have put ~50K miles on my two and I don't mind the suspension at all. They can be loud inside, especially if modified with fresh air induction.

08-09 have an electronic limited slip differenatial, mechanically it's an open diff.

2009: interior trim on doors, center console, nav changed from silver to black
2010: updated nav (gen 6), new style wheels
2011: Torsen limited slip diff, suspension updates, new style headlights (no longer adaptive), alcantara leather, updated gauge cluster, updated steering wheel
2012: more suspension updates?, Newest style wheels
2013: minor nav updates
2014: minor nav updates, carbon fiber rear spoiler, F embossed headrests & maybe a couple other minor interior updates?

Reliability is high for all year models. The only mechanical flaw is leaking water pumps for early model years 08-09 and maybe 2010. Most of those will have had the water pump replaced by now

Wow!!! This was much more than anticipated! Thanks! '11+ it is!!!!!

 

[linuxgod]

Reviving this thread. I’m wondering if some folks would report their knock correction values reported from OBD Fusion for both LC and LX.

I’ll start. 2013 LC. Currently towing 6000# trailer in 5th gear, roughly 70 mph, 4.88 gears. 87 Octane. (No I’m not texting while driving, my wife is driving). Two screenshots, lower value is under load while ascending a small hill in Minnesota. Second is after cresting and going easy on the throttle

 

[TLC2013]

Reviving this thread. I’m wondering if some folks would report their knock correction values reported from OBD Fusion for both LC and LX.

I’ll start. 2013 LC. Currently towing 6000# trailer in 5th gear, roughly 70 mph, 4.88 gears. 87 Octane. (No I’m not texting while driving, my wife is driving). Two screenshots, lower value is under load while ascending a small hill in Minnesota. Second is after cresting and going easy on the throttle

View attachment 2719693
View attachment 2719694

I Start looking for those PIDs in the fusion app and will report back. For some reason I have one heck of time searching and locating specific PIDs. Are there Specific keys words or areas to look to locate those in the app?

 

[linuxgod]

I Start looking for those PIDs in the fusion app and will report back. For some reason I have one heck of time searching and locating specific PIDs. Are there Specific keys words or areas to look to locate those in the app?

“Knock” should work for this one. You have to be in the right category for the search to find it. It’s “knock correction learning value” under “Toyota, Lexus, scion”

 

[TLC2013]

“Knock” should work for this one. You have to be in the right category for the search to find it. It’s “knock correction learning value” under “Toyota, Lexus, scion”

Thanks. I'll start digging into this over the weeknd.

 

[radman]

I’m wondering if some folks would report their knock correction values reported from OBD Fusion for both LC and LX.

I just downloaded the app and took a spin around the block. Last 100gallons or so were 87 octane
2015 LX

 

[linuxgod]

I just downloaded the app and took a spin around the block. Last 100gallons or so were 87 octane
2015 LX

View attachment 2719856

View attachment 2719858

Thanks

I don’t have a non-towing baseline, but I can definitely tell the ignition timing is being retarded right now as even with ECT PWR enabled I fell like to have to get down on the skinny pedal, at which point the truck keeps wanting to downshift. Wasn’t driving like that last night

I may run a few tanks of premium to see if it improves

 

[NYC570]

Remember that there are two KCLV values. One below a certain RPM and another above. In the ISF the threshold is around 3k RPM. I'm not sure if the threshold is the same in the LX/LC.

 

[linuxgod]

Remember that there are two KCLV values. One below a certain RPM and another above. In the ISF the threshold is around 3k RPM. I'm not sure if the threshold is the same in the LX/LC.

I was not aware of that

I have not been watching the values closely but I have found on two tanks of premium that the engine doesn’t feel like it’s bogging down. Right now knock correction is floating around 16-17 though also not driving it quite as hard as I’m off highway

 

[TLC2013]

Here are three examples of what i saw this night while driving on the highway. Outside temps between 80-90F with 87 octane. Fwiw i have no idea what these readings translate to lol. I tried to capture various throttle positions.

 

[linuxgod]

Thanks. I’m still trying to understand what’s normal. I’ve seen anywhere from 10.8 to 17+ deg kclv so far :-/

 

[TLC2013]

I’ll keep an eye on the KCLV and report back any updates. So far I haven’t seen it deviate from between 11.0-11.6. I have absolutely no idea what’s considered normal or good lol. I am a bit intrigued that you have seen as high as 17 degrees.

I would speculate that with the turd fuel I have in CA that its playing role in these readings… not sure how it impacts knock if at all on the 5.7 but I’d imagine it’s Most prevalent under WOT.

Having had my sports car on the dyno and using HP tuners to adjust timing and A/F I was told some horsepower would need to be left on the table to ensure safe operating conditions with CA fuel.

 

[NYC570]

I’ll keep an eye on the KCLV and report back any updates. So far I haven’t seen it deviate from between 11.0-11.6. I have absolutely no idea what’s considered normal or good lol. I am a bit intrigued that you have seen as high as 17 degrees.

I would speculate that with the turd fuel I have in CA that its playing role in these readings… not sure how it impacts knock if at all on the 5.7 but I’d imagine it’s Most prevalent under WOT.

Having had my sports car on the dyno and using HP tuners to adjust timing and A/F I was told some horsepower would need to be left on the table to ensure safe operating conditions with CA fuel.

I'm not sure what's normal for this engine, but this would be terrible for an isf. Try to do some full throttle pulls and if your engine is healthy, it should go up. You can also try upping your octane if you're not at high altitude.