If it is true that Ethanol provides a higher octane rating than premuim gasoline, then how can ethanol be run in 4 and 6 cylinder engines? Will they have lower octane ratings available for these engines? And if so, won't those be slightly higher than the gasoline counterparts?

This is probably a stupid question, but I don't care.

 

Not sure what you're asking, but I don't believe a higher octane will hurt a 4 or 6 cyl. Only problem w/ octane that I'm aware of is too low an octane in a higher compression engine could expose it to detonation.

 

I guess that 4 and 6 cyl engines dont use high octane gas? News to me.
I wonder what kind of effect E85 gas will have with a direct injected motor like the 2.0T in the Kappa's?

 

If I put 91 in my car, it would run like ****, like most other v6 and 4 cylinders that require 87 or 89. It's like you guys running low octane, we can't run higher.

 

Um, yes you can? If you run a low grade octane gas in a high compression engine, you will develop detonation, but I have never heard of any problems if you run high octage in a low compression engine. You need AT LEAST that rating of octane, not that EXACT rating.

 

Maybe it's the quality of gas you're getting, not the octane. I got Racetrack one time....neeeever again! It knocked like hell running super in my old Formula. At least it was trying to before the computer dumbed down the timing to account for it. Terrible quality stuff, thats probably why it was so cheap

 

I had a 2001 Z24 Cavalier and it could run on any of the 3 octanes. Had more power with 89 and 93 but got better mpg with 87. Odd to say the least. It was running 10:1 compression stock.

 

Well I'm quite confused. I've always been told you can't run premium in most V6's unless it says to.

Well, needless to say, I don''t think my 3.4 will run any better with 89 or 91.

Sorry for the waste of a thread, lol. I'm just excited about ethanol.

 

the number of pistons has nothing to do with the required octane rating. what matters is compression, whether it is by the natural compression ratio made by the shape/position of the pistons and volume of the head or if it is caused by some form of boost, you only need higher octane with higher compression. it also allows for more spark advance.

if the engine is not meant to run on the higher grades then use the lower ones. it isnt a quality thing. your engine should run best at the point where anything lower will hurt it.

 

Understand that a higher octane rating actually means that the fuel burns slower and therefore allows higher compression and more aggressive timing...and therefore more power.

You'll actually get higher dyno numbers with lower octane fuels...but in the real world, detonation is your enemy and bigger, more powerful engines need the protection offered by higher octane fuels.

Normal 4 & 6 cylinder engines are programmed to use a lower octane rating because they are meant to be workhorse, economy motors. Using high octane fuels is just a waste..but I doubt that they actually run worse...it's just that you were probably expecting more.

 

Why?

Other than the fact it takes about twice the ethanol to do what gasoline does....I don't see what the party is about.

Bring me biodiesel anyday...

 

It's not that high octane fuel burns slower; it's that it is harder to ignite and therefore more resistant to pre-ignition and knock. That is what allows for higher compression / more aggressive timing.

Higher octane does actually burn slightly slower and some people claim this as a reason not to use higher octane in an engine not designed for it. But in the real world its slightly slower burn rate is a non-issue.

 

Putting premium in a car designed for regular causes carbon build up though... While it may not make an immediate noticeable difference, its not good for the engine.

Im sure someone could find a work around of what you are talking about if it is a legitimate concern.

I can imagine the outrage when people are given the choice between $2.00 E60 for their Civic and $1.25 E85 for a Z/28

 

Vehicles designed for use with E85 adjust the fuel AND timing accordingly; therefore, if the manufacturer says that a vehicle can run E85, it can. I don't understand the mystery here.

The reason that few smaller engines have been equipped to run E85 is because the whole reason behind flex-fuel vehicles is to gain a CAFE break (there's a HUGE bump in the economy figures that are used for the fleet average calculation), and that's why the attention is being put on getting larger vehicles to be compatable with ethanol.

 

The 3.5L OHV V6 in the Impala can run on Ethanol.

As long as the engine is tuned fo E85 there are no problems. Ford sells 1.6L FlexFuel cars in Brazil.