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Improving Knock Learning and Power on Lexus ECU’s

I just thought I would share with you some of our experience with KCLV and some ideas of how to improve it.  For those of you who haven’t heard of it, KCLV stands for “Knock Correction Learn Value.” 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.

We have tuned quite a number of ISFs, and generally find them to be very consistent in their response to tuning, but occasionally, there are what I call “KCLV challenged” cars that tend to run lower KCLV with the tune, and without the tune, even those running 93 octane.

So recently, we purchased a 24,000 mile 2014 IS350 F-sport for the purpose of developing a Supercharger Kit, and upon initial tuning, we discovered that this was one of those “KCLV challenged” cars. Even on stock tune, KCLV was at about 15-17, whereas a normally healthy stock tune car typically runs
20+.  We are fairly certain the car was run very easy, probably with a lot of city driving, and maybe even on 87 octane for a while. Pulling the plugs and inspecting the pistons showed a bit of excessive carbon buildup.

So we did the following:

(1) Added 1 bottle of Royal Purple Injector cleaner
(2) 1 bottle of Sea Foam intake treatment (and created lots of big smoke clouds). I recommend spraying it all in on a warm engine, then letting it soak for 15min or so.

After running through the tank of gas this way, KCLV would immediately shoot to 22! Initially I thought that the bottle of injector treatment improved the fuel quality, but even on successive fill-ups, the KCLV shoots right back up after reset.

So the bottom line is that if you have a higher mileage car, or the background of your car is unknown, this procedure is probably a good thing to do. I was even surprised with the results.

We haven’t tried it on an ISF yet, but I don’t see why it wouldn’t be effective, as carbon buildup affects most engines similarly (see the photo below of an ISF engine with heavy carbon buildup), and causes increased knock correction.

I would recommend doing the Sea Foam treatment before changing oil, as some of the solvent may make its way to the oil.

-Rafi

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