Video shows that octane doesn't make power.

Depending on the vehicle, you'll see a 10-20% gain in fuel efficiency. So depending on how much more the ethanol free cost it could be worth it.

 

Well efi engines do care when it comes to running moonshine....they just won't run on it. A carb type engine will.

 

Isn’t the lead in the av gas going to kill your catalytic converter at some point?

 

Only thing better is slightly better fuel mileage but usually the cost per gallon makes it not worth it.

 

That's impossible. 85% e loses about 30% fuel mileage so going from 10% e to non e will not gain 10-20% fuel mileage.

 

Octane doesn't 'make' power, it reduces the detonation point, allowing engines to run more advanced timing without knocking, which makes for more thorough overall burn before exhaust valves start to open. That can lead to more power.

However, if the engine/fuel/spark isn't tuned specifically for high octane, you're not going to get a difference in power. Though you might run more efficiently and see a very small increased in your MPG over time.

Unless you're running a factory tuned sports model(that specifically states 98+ octane only!), vehicles aren't going to come from the factory tuned for the higher octane. Too many people would run regular gas and end up bringing them in for 'warranty repairs' for knocking and pinging.

 

Exactly. That's why even 91-93 tuned cars have a low octane map just for that reason. But they do drastically lose power when you run low octane. You can see a 10-15* timing drop in the low octane map.

Oh and side note for anyone that reads this since I've seen it said. STOP CALLING DETONATION PRE-IGNITION. THEY ARE TWO SEPARATE THINGS.

 

Toyota being Toyota, I doubt they would allow that to happen. It might retard timing, but it won’t advance it to make more power than the OEM spec.

 

I love that show on Motor Trend on Demand

Freiburger , Dulcich and Brule are awesome !! I've had my Camaro there awhile back on their chassis dyno

 

Higher octane gas is actually less volatile than lower octane gas. Thats why higher octane gas is used to avoid detonation. The pcm doesn't know what gas you put in so there isn't different fuel maps for different octanes. The pcm is simply looking at the knock sensors and will back off timing when knock is detected. 99% of driving conditions will not lead to knocking on regular gas. A turbo car on the other hand, you will definitely feel the difference between high and low octane gas because it will ping and the pcm will back off timing creating the lack of power feeling.

 

I’ll just continue to call it “spark knock” like i’ve done the last 45 years lol

 

It doesn't have different afr maps unless flex fuel but most cars do have a low octane timing map. It will switch to this map after multiple runs of detonation.

 

That engine clearly can run a lower octane fuel. However, what is not discussed is it is an aluminum head engine. You can run more compression with aluminum heads because the shed heat more efficiently and are less prone to uncontrolled ignition. Also, while the static CR is 10:1, we don’t know what the actual cylinder pressure is. That will vary depending on cam design. We also don’t know what heat range plug is being run. Al of these factors can affect octane requirements.

I would bet that engine is specifically built to run on pump gas. This would be a different outcome if we were talking about an iron head, 10:1 engine, or a higher compression engine. This engine meets its potential on pump gas, because it was designed for such. There isn’t any more power available with a higher octane fuel because the engine doesn’t need any more timing and we are not talking about a boosted application where more boost might be available.

Modern engines are more tolerant of lower octane and some can adjust for a tank or 87 vs 91. If you ran that test on a classic, high compression, iron, muscle car engine, or one designed for 100+ octane, it would be a different outcome.

As it’s been said before, there is no more power available in higher octane fuel, just more resistance to ignite which is needed for high cylinder pressure, more timing, iron heads, et. al. That higher octane rating allows an engine to run within the parameters (cylinder pressure, timing, heat saturation, it was designed around.

 

That's not really how the ECU logic works, at least in the Denso stuff that Toyota and Subaru use, and the GM stuff I've played with. Each load/rpm lookup will have stored fuel trim and knock feedback data, in addition to base and advance timing data. Based on torque demand, the cells used for ignition timing will be selected by using whatever conditions are met by all of the other lookup variables and it will then use that timing value. So it can be using one map and switch to another for the next lookup, happening multiple times a second.

 

Well I've been tuning GMs for a bit and it actually has low octane timing maps. Once I hit knock in about 3 WOTs in a row it literally reverts to the low timing map. The ecu will get stuck in this map sometimes so I have to disable it. I run e85 so not worried about low octane.

 

WOT? Never been there. My foot is allergic to the floor. If I need more acceleration I use a lower gear and still don’t floor it.

 

Pretty sure that was a joke. Nobody is that dumb AND going to such lengths at the same time, lol.

and as for your later post on cam design affecting compression ratios, I don’t see how. Did you mean to write piston design? Because that is how you change compression ratios.

 

Actually compression ratio can be change by the amount of the cylinder head volume to.

 

There's two different compression ratios. Static and dynamic. Static is just that... fixed and the one you're used to hearing. Dynamic can vary a lot and is impacted by the cam and it's timing.

It's actually how our engines simulate the Atkinson cycle. It leaves the intake valve open during the beginning of the compression stroke. This effectively lowers the compression ratio by shortening the compression stroke.

 

I've read the 2GR-FKS is like 11.8:1.