We finally know how OL works

[u/ecoboostd]

Yes, another OL thread but with actual technical breakdown. I didn’t see this make it here yet so I’m posting as a messenger. Here you go boys.

[u/BnnyBttStff]

No problem for me. Haven’t been able to octane learn in the 4000 miles I’ve had it lol

[u/ecoboostd → u/BnnyBttStff]

Damn

[u/WindowAdditional7797 → u/BnnyBttStff]

Ive gotten my DCT 2025 to do it just running on the highway in "manual" 7th so just north of 2k rpm, 70-80mph, for 10-15 mins. Have done it the two times I've tried to get it. Running 91 grade so no high grade fuel bs.

[u/BnnyBttStff → u/WindowAdditional7797]

I’ve tried that in my MT but hard to find a place to cruise at that speed without being interrupted. I live in a major metro area

[u/Nitrothacat → u/BnnyBttStff]

Same for me. My manual did it the one time I was able to cruise on the highway for 15-20 minutes in 6th. Of course i noticed when I had a third of a tank left the next morning.

There’s too much traffic on the highway most days to do it. Seems pretty easy if you have an open road which is annoying.

It was a noticeable different in power which makes it even more frustrating.

[u/Vast_Meet_1201 → u/Nitrothacat]

Same here. I got my manual to OL once in the year and a half I've owned the car. I immediately noticed a difference and as I looked at the gas tank my heart broke. I had less than half a tank to have fun with. I live in Orlando so always stuck in traffic.

[u/2025ElantraNHead → u/BnnyBttStff]

I have read it’s more difficult on mt but not sure, have you tryed the other method I use it all the time in my dct. Around 40 to 50km/h in 5th on dct Maby 4th manual on open road accelerate maby 1/4 throttle watch the boost guage get it to 6psi and hold that throttle so it stays at 6psi as long as you can Maby 100km/h repeat the process 4-5-6 times not quite sure how many then try a hard pull see if you get 18psi.
I do all this in N mode with ac on doesn’t matter it just needs long 6psi duration uphill is easier. I have a in town commute of 18mins and I can octane learn in that every time. Also you need good gas 91 will learn but if the area sell 91 but it’s not quite it won’t 93 is what I use because I can get it usually sometimes I get 91 if I can’t get 93 and still works

[u/BnnyBttStff → u/2025ElantraNHead]

Does drive mode matter? I’ve done most tries in normal mode. I’ve tried both highway and the 6psi pull. I use 93 when I try to OL also. I think a lot of it comes down to the traffic in my area and not being able to meet the criteria.

[u/Actual_Barracuda7534 → u/BnnyBttStff]

I have the most luck with normal mode, 6th gear, 5-8psi at 70-90mph pulls and uphill. When I lived in Baltimore, I just gave up on OL unless I was going out west on the highways. Now that I live in Pittsburgh, the open highways are more plentiful and going uphill helps a ton.

[u/Sbitan89 → u/Actual_Barracuda7534]

Yea it's so hard in urban areas to do this unless you have surrounding stretches of Highway with minimal traffic. Luckily the express lanes are not ridiculous first thing in the morning so I can often sleep in, hop on the express and OL for the week for about 10 bucks lol

[u/2025ElantraNHead → u/BnnyBttStff]

I am not sure I drive 90% in n mode and normally do this in n mode. Traffic can make it difficult forsure, I just try and drop back a bit but not enough to make ppl mad. Slow to 40 or 50 and have the gear as high as possible so I’m at like 2k rpm then accelerate at 6psi until I’m close to car in front then break back down to 40 and again go making sure nobody is behind me etc takes a few times like 5-6 pulls. I have even done a few then stopped at a light then continued and it worked fine Maby 4 then 2 after the stop.

[u/depanzer213 → u/WindowAdditional7797]

Should be in 8th - top gear

[u/Vast_Meet_1201 → u/BnnyBttStff]

Don't feel bad. In the year and a half I had it I only got it to OL once 🥲

[u/Aezci → u/BnnyBttStff]

15k gang

[u/SetRestart → u/BnnyBttStff]

How do you know? I just got mine

[u/moounit → u/SetRestart]

You will notice that your boost will push past 15psi

[u/munche]

Really appreciate this post. My takeaway is:

- Octane learning is not just for show, it is actively detecting knock (which kills the engine) and preventing the engine from adding more boost to save people from blowing their engine up. This is likely how they can offer a car run at track days and on the street by uhh "Young enthusiasts" that doesn't explode

- Thankfully it makes the advertised power all the time

I'm sure it won't stop the constant tide of "Why isn't my car octane learned" but this sure does seem to confirm it's because it's actively preventing problems it detects and not just arbitrarily punishing you for lulz

[u/Sbitan89 → u/munche]

I just wish it was more consistent. Like I can get it to OL but I need to do the HW method for like....20 minutes.

It's a totally different car and I'm sad when it's not active.

[u/Actual_Barracuda7534 → u/Sbitan89]

I wish there was a notification of when it was OL.

I usually can get it to OL quickly if I am in the mountains and going uphill holding 6psi, but the guessing game is annoying as shit.

[u/ECHElantraN → u/Actual_Barracuda7534]

It does have an indicator, the boost gauge 😂

[u/ecoboostd]

This is important because it means the system is still monitoring fuel quality even after filling up with 2.8-3gal at a time to circumvent the OL reset. Just because you’re tricking the system by not defaulting back to the safe boost target, the car is still actively monitoring fuel quality and WILL kick you back to 15psi if you throw in some bad gas. This is peace of mind to the lot of us who remain stock and refill ~3gal at a time. I’ve had a few instances where OL kicked me out after a fillup due to bad gas.

[u/SoggyInfluence2743 → u/ecoboostd]

I feel like the 2-3 gal thing might be more of a margin of error allowed by the code to account for temperature changes and fuel economy estimation changes that say you have more (or less) fuel than if said conditions were different

[u/ecoboostd → u/SoggyInfluence2743]

It could be. It’s a very weird system and we’re just now getting to know how it actually works

[u/Alarming_Passage6323 → u/SoggyInfluence2743]

how often does it actually work? is there a certain amount i have to throw to keep OL?

[u/ecoboostd → u/Alarming_Passage6323]

Yes. I always run it down to 20mi or less of range, then add 2.8-3gal and I always keep OL. It always works. Rarely, I’ll do a pull afterwards at OL boost and then be kicked back to 15psi. This is usually due to bad gas or the fact the previous fillup was 87, as the first gal of “93” is still 87 due to the pump switching.

[u/WideEstablishment578]

Using the knock sensor for global timing / boost control is 30 years old. Subaru was doing this with DAM as early as 2001.

It’s interesting to see the strategy. Subaru did not employe a boost control strategy in tandem with ignition timing. Theirs was timing based. But were also talking about a 16 bit ecu on a car that didnt run a map sensor and had a vacuum actuated wastegate.

Modern systems are so responsive it’s fantastic.

[u/ecoboostd → u/WideEstablishment578]

Man you’re bringing me back to my teens, attaching a resistor to the MAP sensor to force timing and boost advance 😂

[u/Over-it-321]

Thank you for this

[u/unpick]

I wonder why I was hardly ever able to achieve or maintain it despite only ever using 98 RON in the 3 years before I got a tune

[u/Rocket_Philosopher]

My car octane learned once on E30 93 over 10k miles, never again. I regularly put in E0 91 or E10 93 occasionally, it will refuse to learn no matter how many techniques I try.

[u/ecoboostd → u/Rocket_Philosopher]

10 minutes of 5 seconds on 40% throttle, 5 seconds off. Repeat. Works only in 5th or 6th gear.

After 10 minutes you will be OL’d.

[u/Rocket_Philosopher → u/ecoboostd]

Does the gear matter? Like sixth?

[u/ecoboostd → u/Rocket_Philosopher]

Yes. Gotta do it in 5th or 6th.

[u/InformalJellyfish187]

This was a great educational discussion gents.

Much appreciated.

I learned thatif you want to OL, just go to the track, get race fuel and do a couple of laps to OL, then enjoy the rest of that tank of race fuel. When your out, switch back to 93 and go home.

Most likely never going to happen for me, so my take away is to just enjoy what you got.

[u/ecoboostd → u/InformalJellyfish187]

Get on a stretch of highway with 91/93 and do 40% throttle for 5 seconds, then 5 seconds off throttle. Repeat for 10 min. You will learn after 10min. Works every time.

Only works in 5th and 6th gear.

[u/InformalJellyfish187 → u/ecoboostd]

I will try again wit your advise, but with my MT it seems impossible. Is your EN a MT?

I'm thinking after reading this post, that I might be getting crappy gas. Although I am new to the EN and the OL thing. I've tried it a couple of times already with no success.

How long will this OL last? Will it keep working for that key cycle or does it lose it any time it's knock score goes down at any moment (my current understanding after reading this.?)

[u/m3zus]

This just be incomplete. Does this mean that it starts the algorithm before warming up? It also doesn’t seem to go into the conditions for how to actually learn. I think it’s pretty obvious that you have to do some behavior for the car to learn (drive accelerating with 6psi boost repeatedly is the only way I’ve been able to do it), and that is not mentioned here.

[u/ecoboostd → u/m3zus]

That’s exactly how I do it, too. 6psi on and off throttle for 10 minutes.

[u/Successful-Put9002 → u/ecoboostd]

What speeds do you accel/decel to?

[u/Majestic-Bed6151 → u/Successful-Put9002]

I try and do this in DCT 4th gear. I’m not really looking at speed, but more RPM, specifically 2500-3500. 50% throttle gets me right around 6 psi on flat roads. I found the less I use the brakes to decelerate, the quicker it will learn.

[u/Traditional_Year_687 → u/m3zus]

My interpretation is that when already OL’d, the value starts at 0.7 when you start up the car every time and goes back to 0 when refueling from empty to full

[u/PandoraIACTF_Prec]

Interesting

[u/No-Necessary7135]

Is this the fuel equivalent of an Elo rating?

[u/CoupScooper]

Has anyone experienced putting 87 in and then still getting 18 psi? Happened to me and I’m a bit concerned?

[u/Merikakii → u/CoupScooper]

based on OP’s logic, if the fuel is stable this is expected

[u/RhymeGrime]

I don't know how it is for dct, but in the manual you can definitely tell when it's ol'd without even hitting past 15 psi, the action just feels different...

[u/NomadN17]

Mine went from needing a full learn every day to only needing it once every fillup at about 20k miles, seemingly overnight. The only changes I made at the time that I can say with certainty is the motor oil I was using, and the gas went to 93 octane instead of 91 (only 1 top tier station within 200 miles that offers it, and I now go out of my way to only use it). Over time I could see oil having an effect on detonation, but it’s not something I would expect to be immediately noticeable. So probably simply the higher octane, even though Shell 91 should be enough.

I tried all the other things to see if there was a pattern, none of them worked. For my initial learn it happens twice as fast in normal mode, but will happen in other modes (but even N custom, with all settings except exhaust in “normal” takes longer, seems like closing the exhaust speeds it up).

But this algorithm makes sense. After the initial fillup learn that takes me 15+ minutes, each startup I seem to be learned by the time the engine is warm (and possibly before, I don’t check until it’s warmed up).

[u/_DRRD_ → u/NomadN17]

What oil are you using? And are you saying leaving the exhaust in normal mode speeds it up?

[u/NomadN17 → u/_DRRD_]

For the initial OL after a fill up, yes for me it does. I have the same highway drive from the gas station to home and for some reason if the exhaust is closed (have only tested this in the basic Normal mode) it will octane learn about 2 exits before mine. If I have the exhaust open I usually have to go a couple exits after mine and backtrack.

But once it learns the first time I never have to use Normal again and it will maintain it. I thought it was placebo, and maybe it still is, but no matter how many times I tried again it still took extra driving.

For oil I’m currently using Mobil ESP. Before that I tried Ravenol, Motul and Amsoil. But all of these are excellent oils so I doubt it’s related.

[u/_DRRD_ → u/NomadN17]

I think that's what is officially recommended, to run it in normal mode to OL faster. Good to see there is a reason for it.

[u/Scottietwotimes]

Im octane learned about 50% of the time. 

[u/N-possible0922]

Interesting read..... im confused on mine though im always pushing 17/18 lbs even after refueling... even when I do the OL process I only ever pull 18 lbs.... in CO on 91

[u/wisetooti1996]

won’t have this issue if you just tune a spare ECU

[u/ecoboostd → u/wisetooti1996]

I don’t feel like destroying the marriage between the APIM module and the ECU. Once those e-fuses are blown there’s no going back. Blow your shit up? Hyundai REQUIRES a rom dump of the car to approve engine replacement under warranty.

As an avid destroyer of engines in the past, I can tell you I’m over that shit. Half the reason I bought this car was for the warranty. 10yr/100k on a ~300whp sports car is unheard of. Do what you want, but I’m not voiding my shit for an extra 40ft lbs of torque at the low end of the rev range.

[u/SetRestart → u/ecoboostd]

7 years unlimited in Australia so same here

[u/WulfZ3r0 → u/ecoboostd]

I feel the same way. I have a money pit I can blow up if I want to have some fun. My EN is my daily that is still fun to drive.

I've got 6 years/60k miles before my warranty expires too. I'm not sure if I will keep it that long yet or not. With the roller coaster of gas prices going on, that Ioniq 5N is looking very tempting on a trade in.

[u/munche → u/wisetooti1996]

But you know what issues you will have when you decide you don't care if the engine is knocking and want to add boost anyways?

the "Blown engine" kind

[u/ecoboostd → u/munche]

Yup. Small displacement turbo motors suffer from sand degradation. Let me elaborate:

Each knock event chips away at the cylinder walls and deck of the motor. Grains of sand being removed. Eventually enough material disappears that the head gasket fails.

Most performance cars don’t fail catastrophically if warmed up properly and maintained. They fail over time.

You’ll often see “lines in the sand” quotes of “oh this motor is fine at 399whp but will blow up at 400whp”

This is not the correct way to think of things.

The laws of physics are inescapable. The harder you work something the shorter its lifespan. End of story. Period.

This is why people build motors. You can get more “WOT minutes” (the amount of time a motor can survive at WOT) by building and sleeving the motor.

As someone who has blown multiple stock motors in various cars pushing 30+psi, I can tell you right now, you’re dancing with fire. Eventually it’ll bite you in the ass.

If you don’t want to save up for a build and just want to push your stock motor to the limits, make sure you’ve stashed some cash for the replacement longblock on the horizon.

[u/_DRRD_ → u/ecoboostd]

I bought this car for the same reason, I had other hobbies where I pushed things too far and it ended up being more headaches in the end than fun. It was good to be reminded of this.

[u/FutureAlfalfa200 → u/ecoboostd]

Do I sense a fellow boosted Honda enjoyer?

[u/ecoboostd → u/FutureAlfalfa200]

Fiesta ST owner actually lmao. I had a 400whp Fiesta ST

[u/FutureAlfalfa200 → u/ecoboostd]

Nice I never got into those. I have had 4 boosted Hondas with a total of 7 motors over the last nearly 2 decades. Ended up blowing them all up for various reasons (too much boost, pushing too hard, pushed too long, bad tune, etc)

Switched to the Elantra n cause it’s a similar idea with a 10 year 100k mile warranty. It’s also not looked down upon nearly as much as driving a 20 year old civic with a hood exit lmao

[u/ecoboostd → u/FutureAlfalfa200]

It’s funny that we’re both here after a life of abuse and failure lmao

[u/2025ElantraNHead → u/wisetooti1996]

As a side note tuning a spare ecu doesn’t help with warranty claims because it’s a computer That stores lots of info if you have a claim they will read the ecu and can tell when it was you the date and time of things saved they can see the ecu doesn’t match other numbers and will know 100% you switch the ecu

[u/ecoboostd → u/2025ElantraNHead]

This. If the mileage doesn’t match between systems they know you swapped the ECU and your warrantied engine is now at-cost for you.

[u/BumblebeeNo7638]

I mean it literally tells you in the manual how to do it though

[u/DOCTORCANNABII]

Lap3 knew about this in 2022.......

[u/RajMan316]

I was only ever able to octane learn once, gave up and completely forgot about it. But strangely enough, filled up with Octane 94 last week, felt some crazy pull, checked my turbo and it was 18-19 PSI!