Basically this.

The ECU is generally always trying to get to max desired spark advance. Without access to the maps, we can all guess how it works, but generally speaking it's always trying to get to a certain advance at a certain load. Though there's usually several tables that further modify that, intake air temps, coolant temps, open loop vs closed loop, etc.

The ONLY place I'm curious if it can gain a degree or so of advance, is because it can handle some Ethanol. For those that have never run E85 and had access to a tune, you can dial in a lot more advance on E85 (generally speaking). Of course, the difference would be almost impossible to notice, but I am curious if running E0 91/93 would get you the same advance as running say 87 E10.

Tossed some pics from HP Tuners from my old LSJ for the OEM Stage 2 tune, my 100 Octane tune and the IAT modifier table. It can get really interwoven depending on the OEM's approach.

Attached Images

     

I just commented on another thread about this.

A few years ago I posted about how my truck bogged down drastically when city driving in 90+ degree temps. I could almost put the peddle to the floor and it seemed to take several seconds to get any type of response.

Someone here suggested running a higher octane. I've been doing it ever since when temps get high.

The 4runner scoots around like it should, no bogging. When the temps cool off I go back to regular.

The explanation was the timing adjusted with the increased octane. I don't know if this is true but my problem was solved.

It's a pretty immediate effect. It's very noticeable to me too, I certainly would not be spending the extra money if not.

If I didn't have full time 4WD (Limited), I'd volunteer as tribute.

Until then, it's really just lots of testimonies, supposed to's, and I read somewhere about something. Oh well, still fun to discuss.

And btw, I mainly run 91 in mine too lol.

I think - just guessing - that it needs to run very lean at idle to meet emissions targets. Running lean at idle is hard to manage is my guess. Also that engine is 11.8:1 compression ratio - to it's a good bit higher than the 1GR. But... the 2GR FKS has variable compression via the extended valve timing. So it may run at 8:1 or something during idle.

Maybe useless info, but do you live in an area affected by different seasonal blends?

i kinda feel that way too.. i leave the house in the early morning and my 4runner definitely has more pep? As mid day comes along and temps rise to triple digits it drags like a slug. A/C on or off, sometimes i just drive windows down in 100+ weather for fun... AC kicks on when my kids are with me..

could be the same idea with cold air intakes and the colder air in the morning yadi yadi la bla bla

Not sure what the numbers mean on that map but being in Dallas I'm in either the pink or brown area.

it's pretty consistent, the closer we get to 100 degrees, the more heat soaked the engine gets and she bogs down. Put in 93 and she bogs no more.

I will note this is for big city driving, lots of stop and go in the sweltering Texas heat. Highway or small town driving probably isn't as noticeable.

I'd be curious to see if you find a change putting in the higher octane.

Not sure if humidity makes a difference though, looks like you are in Nevada. Here it's 97 degrees with 80% humidity sometimes.

What's likely here is that your engine was pinging when the temp got hot. You won't hear it, the ECU will detect it long before it's audible to your ears. The ECU detected pinging and retarded the timing. When you put higher octane in, the ECU could return the timing to the proper advance.

The stock ECU maps are typically pretty conservative. It's one of the main ways tuners extract more power with "chips" (Chips are no longer used, the ECU can be reprogrammed through the diagnostic port. But people still use the word chips or chipped.).

The new maps will have more advance at any given spot on the map. This will get you more power, but at the risk of pinging. Increasing octane can reduce the pinging.

Wikipedia used to say it makes 278 hp and 290ft lbs with premium fuel but that part has since been removed.

Wow, that is deadly stuff right there. In the east/northeast when that happens people die. It’s not talked about a lot, and it seems to be better than it used to be, but when it gets that hot in big northeastern cities the elderly actually die from the heat. Others, too, from working outside, getting stranded, etc. Dangerous stuff.

We call it a typical summer day in South Louisiana. It was 95F in the shade, 110F everywhere else, with 85% humidity and a dew point of 77 yesterday. You MUST hydrate and adapt to it. I went to Navy boot camp in Florida in the summer (forever ago), the guys from up North were having trouble...I thought it was nice to not have such thick humid air and it was cooler there than my hometown.

Engine management will adapt and advance timing based on ambient conditions and new sensor data from the change in octane. Adaptation will happen faster when driven in a more aggressive manner. Especially WOT events.

On daily drives I run Nuvu's 88 Octane Regular. On days when I run the Silver Lake Sand Dunes I dump in a can of Royal Purple MaxBoost once I'm at a half full tank then I fuel up with 93 octane. On Dune days when I can fuel up from a quarter tank I fill up with 93 and I skip the booster. Quick numbers puts those mixes just under 92 octane. I live roughly 90 miles from Silver Lake. I can usually feel difference in acceleration halfway through the trip there. When I stop before the entrance to put my flag on I can feel and hear the difference in the engine idle. On rare Dune days when I fuel up with the low-fuel light on, I fill up with 90 octane Rec Gas. Call me crazy, the butt-dyno says the Rec Gas is the best performance of all.

So everyone is getting tunes now??