Timing

Oct 12, 2006
141
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16
Chicago, IL
whitemike;1623703 said:
I wouldn't run less than 91 on a FI vehicle, I don't know why you guys think $3/tank is a lot extra to put premium fuel in.

Is there a reason you wouldn't run less than 91 in a fuel injected vehicle? And some of us are pretty strapped for cash and don't spend moeny on higher octane when its not needed.
 

plyhard13

New Member
Nov 17, 2010
55
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0
Springfield, IL
I was searching for the correct timing and ran across this thread. I know it's been a while but I think its necessary to respond to the last post.

If you are running the correct timing and putting anything higher than 87 octane in your 7MGE, you are throwing money away. The reason for higher octane fuel is that it has a higher combustion temperature. When you are running high compression pistons or boosting, higher octane is needed because the extra compression creates higher temperatures. If you want to do your engine a service, use TopTier fuel(Shell, QT, Chevron, etc.) The extra detergents really do make a difference. That's what cleans your intake valves when the fuel washes over them into the combustion chamber.

To summarize, octane rating does not equal extra power all by itself. It just equals higher combustion temperature. Higher timing or higher pressure equals higher temperatures. Therefore, higher octane MIGHT be necessary.
 

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
12,568
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Fullerton,CA
Higher octane gas has a lesser chance of detonation. Which could happen to any one with a bad batch of gas or a shitty gas station owner.

Money has nothing to do with it. Its 3$ were talking about here. You could get that in less than an a hour on a freeway off ramp with a sign. Ive been broke with zero money and i still put 91 in my car.

You can tell the kind of owner by the gas they put in.
 

plyhard13

New Member
Nov 17, 2010
55
0
0
Springfield, IL
I hate to sound argumentative, but the idea of "bad gas" is basically an old wives tale. If you buy fuel from any reputable retailer, you will almost definitely go your entire life without ever encountering a batch of "bad gas". I'm sure there's someone on this forum who's received poor quality gas, but I'm also sure there's someone on this board who's won the lottery. That doesn't mean I'm going to run out and buy a ticket. On the wildly off chance that it happens, reputable gas stations have insurance policies to protect against this. Kind of like you have insurance in case you damage someone's car. However, that is not really the point.

Detonation, or premature combustion (insert pun here), is caused by one thing...combustion chamber temperature exceeding the flash point of the air/fuel mixture before spark is introduced. If you notice detonation (and I would venture a guess that the vast majority of people wouldn't know the sound) in your 7MGE, it is most likely caused by a timing issue. If you're purposely running crazy timing, higher octane fuel might be needed. Another possible cause of detonation is a burr somewhere in the combustion chamber. This, however, would likely only present itself in a new engine that wasn't prepped properly.

Are you doing any damage if you use fuel with an octane rating higher that what is required? Absolutely not. You're just feeding extra profit to an extremely greedy industry that preys on ignorance.
 

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
12,568
1
0
Fullerton,CA
Or carbon build up creating a glow plug.

Ive had bad gas and it wasnt just once it was all the time from 1 certain gas station, but it was either a lil from there or run out of gas. You put gas in and in less than 20 miles your out gas. odd. Thats also why i didnt just say bad gas.

Detonation can and does happen.