To answer the original question: Higher octane lets you run a bit more timing. More timing typically results in more power. Also, you can run less gas and/or less air pressure to maintain the same highway speed - meaning better fuel ecconomy. The problem is that you're usually running 15-18in/Hg vacuum to move a Honda down the freeway @80mph, and it's already running very advanced timing.

Think of it this way: you would use much less [throwing] force to make a 1lb rock land 10ft away than you would to make a 1lb pillow go 10ft.

 

Thank you for your answer, that's just what I was looking for. So all octanes have the same, or very similar, energy content, even above 93, like 100 octane, or higher? The information came from a source that should be reliable, but my BS meter was twitching, so I had to question it. Thanks for the info though, and keep it coming!

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AutoEng2002Si &raquo;</TD></TR><TR><TD CLASS="quote">How would it be that you make more power on high octane gas then?</TD></TR></TABLE>

The power would come from the ability to run more timing without causing detonation. I'm not that dumb.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drdisco69 &raquo;</TD></TR><TR><TD CLASS="quote">Thank you for your answer, that's just what I was looking for. So all octanes have the same, or very similar, energy content, even above 93, like 100 octane, or higher? The information came from a source that should be reliable, but my BS meter was twitching, so I had to question it. Thanks for the info though, and keep it coming!</TD></TR></TABLE>

All commercial gasolines have approximately the same energy content. They do vary from batch to batch but pretty insignificantly. The main thing to watch out for is how much methenol or ethenol the fuel has been diluted with since alchohol only has about 9000 BTU's/lb.

This 20,000 BTU's does not include race fuel as its composition is completely different than the stuff you buy for the street. I couldn't find my information but I know I have some info. on ERC racing fuel around here somewhere.

Diesel fuel has about 22,000 BTU's/lb. and that combined with the ability to run higher compression ratios is what makes them more efficient. (I know nobody really cares about diesels on this board but I was trying to use it as an analogy to show that an increase in energy content will yield an increase in efficiency).


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drdisco69 &raquo;</TD></TR><TR><TD CLASS="quote">
The power would come from the ability to run more timing without causing detonation. I'm not that dumb. </TD></TR></TABLE>

Sorry, man. Wasn't trying to disrespect and never will.

 

As everybody is saying, it won't make a difference for a car desinged to run 87, but it will for a car desinged to run 91 (designing for higher octane allows you to squeeze more power out of an engine).

Just for your reference, on my jdm b16 crx I noticed a large and experimentally verifiable difference between running 91 octane and 94 Sunoco. They probably tune them for higher octane fuels used in japan.

 

expletive that **** it doesnt make a difference unless your car is supposed to have it if not your just waisting your money but i still have a 91 octane sticker i took off of the pump on the inside of my gas door i dont know why i guess its cus i saw other poeple do it but i think im going to go get a 87 one next time i get gas

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by another silver ej8 &raquo;</TD></TR><TR><TD CLASS="quote">expletive that **** it doesnt make a difference unless your car is supposed to have it if not your just waisting your money but i still have a 91 octane sticker i took off of the pump on the inside of my gas door i dont know why i guess its cus i saw other poeple do it but i think im going to go get a 87 one next time i get gas</TD></TR></TABLE>

I too was getting leary about the source of others here, until you posted. I can't tell you how much more intelligent I am for reading your reply...

 

im not 100% sure what you were saying with your post but i guess i shouldnt just post nonsense anymore.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lsos &raquo;</TD></TR><TR><TD CLASS="quote">As everybody is saying, it won't make a difference for a car desinged to run 87, but it will for a car desinged to run 91 (designing for higher octane allows you to squeeze more power out of an engine).

Just for your reference, on my jdm b16 crx I noticed a large and experimentally verifiable difference between running 91 octane and 94 Sunoco. They probably tune them for higher octane fuels used in japan.</TD></TR></TABLE>

Just out of curiosity, what killed your B16 CRX?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AutoEng2002Si &raquo;</TD></TR><TR><TD CLASS="quote">

Just out of curiosity, what killed your B16 CRX?</TD></TR></TABLE>

A 1992 Honda Accord. It decided to make that left turn at just the right time.
The engine was still good though and I passed it on to someone else: https://honda-tech.com/zerothread?id=387497

I'm kind of curious how it's doing now....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AutoEng2002Si &raquo;</TD></TR><TR><TD CLASS="quote">All commercial gasolines have approximately the same energy content. They do vary from batch to batch but pretty insignificantly. The main thing to watch out for is how much methenol or ethenol the fuel has been diluted with since alchohol only has about 9000 BTU's/lb.</TD></TR></TABLE>

Great, thanks. We were discussing/arguing the type of fuel for the Formula SAE car here at school. I said 100 because we can run higher compression to help with the restrictor, others said the lowest octane possible because "it will give more power". (BS meter rising...)

The fuel for the car will be supplied by SAE at the event, so I'm sure they get commercial stuff trucked in. We have a choice of 93, 100, or E85, with a penalty of a 19mm restrictor with E85 vs. the 20mm for the conventional fuels. No penalty is given for 100 octane.

And what I was trying to explain to them was that for most high compression engines (CBR600 F4i) , you reach the knock limit before you reach the amount of timing advance the engine can use without losing power. So finding that amount of advance then "going lower on octane till it knocks" like was suggested to me doesn't really work out. With 12+:1 compression, I'll get it to knock...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AutoEng2002Si &raquo;</TD></TR><TR><TD CLASS="quote">Sorry, man. Wasn't trying to disrespect and never will.</TD></TR></TABLE>

No offense taken at all. Just letting you know where I'm coming from.