Compression of our motor and octane

In this thread...

 

Yes. Direct Injection allows us to run regular fuel with this CR.

 

Or because the dirt bike engine is air cooled, running at a higher temperature

 

Said this a hundred times already, compression does not necessitate higher octane.

Compression increases the rate at which a mixture burns. This must be adjusted for which can be done by (1) increasing the octane since 93 burns slower than 87/89, or (2) running less timing which ignites the spark later in the cycle so the burn peaks at the right spot in the crank rotation. Both have a functionally identical outcome when it comes to ignition.

The only reason 93 is of any benefit is if you live in Satan's Backyard, AZ and your truck is pulling timing to compensate for knock under extreme conditions (e.g. 120* out while towing at capacity). In that case it will allow for your truck to run factory timing spec. Otherwise, you're wasting money and probably hurting performance because your mixture is going bang later than Toyota intended it to.

All that matters is that you [probably] aren't a Toyota engineer and you don't know better than the Toyota engineers who coded the ECU. This isn't a Mustang designed to run on both, these trucks have a single tune and it's for Regular.

 

More like a dirtbike doesn't have to worry about emissions. You could tune these trucks to run on 110 if you wanted to, you just can't do it on the street.

 

Heat does affect detonation, but it is mainly that in a DI motor, the incoming charge is pure air. The fuel is injected just before ignition, so there is no chance for detonation.

That said, on this motor, we do have multiport injection also which is great for keeping the intake valves clean. That has its own voodo.

 

I own a saab don't worry they break down just as much anyway.

 

You’re wasting your breath. People are stuck on the “Premium” label and think it is somehow better.

You can explain it to them a thousand different times and ways, you can use sock puppets to demonstrate or bring Einstein back from the dead to explain the physics. They will never accept that it is does absolutely nothing but eat up your money quicker because they “feel” it.

I guarantee you that if the marketing geniuses had named it “Slow Fuel” instead of “Premium” to describe its burn rate, people wouldn’t touch it and we wouldn’t be having this discussion. But hey they are a lot of fun. Much like oil threads.

Let the show go on...

 

My previous trucks manual said designed for 87 only, i put in 91 one time, before i read my manual and it ran like shit.

My toyotas manual states select octane rating 87 or higher. Feels like it drives better with 91. Maybe its in my head or maybe because it has no ethanol.

Why the fuck they are confusing us?

 

Sorry, I wasn't trying to start an internet fight. But do some reading on the subject, you'll learn a lot

 

OK, have you ever monitored the PIDS associated with ignition timing/knock correction on the 2GR-FKS in real time? See what happens when fuel of various octanes are used? Log that shit so you can actually compare? Some in this thread did, have posted as such, and STILL get dismissed.

 

Lol, oh boy...

 

I had an air cooled bike that ran hotter than probably any one out there. I monitored CHTs and saw temps well over 400F. I ran 87 with no fuel related problems. Of course, the CR was low. I get the relation between temp and detonation. You might be missing the relationship between CR and DI?

 

I have, absolutely zero effect either way. My Indian motorcycle, has a high compression air cooled engine that requires HO. That you will notice if you try to use low octane fuel.

 

Premium makes my wallet lighter which makes me lighter which makes my truck lighter which makes it feel faster which makes it feel like it has .5 more horsepower

 

Mechanical compression ratio is one of several factors that determine what octane is best. What is needed is even another conversation .

I run 87 exclusively and am quite satisfied with power and fuel economy.

 

the Atkins Cycle engine holds the intake valve open at the beginning of the compression stroke, that has to effect the compression some how.

 

They sure do have to worry about emssions. That's why they stopped selling 2 strokes and also why bike and atv's are always tuned to run lean from the factory for emissions purposes.

 

@TacoMamba35

Nice catch! I forgot about that. From the Tacoma Engine document, it says that Atkinson is used in lower load areas and heavy load goes toward Otto cycle. So, the CR under high load would be similar to Otto cycles with no charge getting pushed backing out where ignition advance might be a problem.

On the OVT side, I'm running the FOB 87 octane tune where most all of the Atkinson cycle is backed out. My preference is for 87 octane.