skibum

I will be using nothing less than 94 octane.(New York )
Will I have more power or does the car need to be tuned to take full advantage of 94? How much gain should I expect from 94?
If I add octane booster will that help too? (Will I get more buzz from a high octane cocktail?)
Does the car automatically take advantage of higher octane?
Where is the point of diminishing returns on octane numbers?
There is much discussion about it but, what are the facts?
I would like to hear from tuners so I know they have at least some credentials.
Thanx in advance

poknatcha

I have the exact same questions. The highest rated gasoline in my area is 100 octane. So far I've only been putting 91 octane in my evo. I won't be driving my car on a daily basis so keeping 100 octane in it all the time will be an option for me.

Can someone help us out?

EvoDaWayToGo

iTrader: (8)

You guys are lucky... I live in CALI, and the highest I can put in any of my cars is 91 octane, unless I was too goto a special fueling location where I might be able to find 103 octane at about 5 dollars a gallon.... You guys are lucky, go with the 100 octane, your Evo will run muchhh better...

trigeek37

100 octane may be WAY too high of an octane with the mapping that the evo comes with from the factory. I am coming from the RX7 world - so I might be way off, but I know that with anything over 94 octane in an fd you better start thinking about different ECU settings or you are actually going to be taking a performance hit. I am sure that someone could come up with some proper maps for the evo to run well on 100 octane, but that is probably going to be prohibitively expensive, expect on track days & such - then you will need to Ecu settings.

I'm hardly an expert, but I would do some research before filling up on 100....

JeffGST

The EVO has a knock sensor which listens for detonation. Whenever the it senses knock, the ECU will retard timing until the knock disappears. Retarding timing will result in a loss of power.

The knock sensor works in the opposite way also. If the sensor hears no knock, it will then advance timing until a tiny bit of knock is developed. A power increase will be felt.

If you put 94 octane in the tank, the knock sensor will advance timing to the optimum point. As long as you continue to use this octane, you will maintain the same power. But if you suddenly add 87 to the tank, the engine will quickly back off the timing as you drive out of the gas station.

100 octane is the highest octane available in unleaded gas. The ECU will advance timing even more because the high octane suppresses detonation.

As for octane boosters, they are not effective because of price and the amount added to the gas tank. On the bottle, they usually say that it will add 7 to 9 points to a full tank of gas. THIS DOES NOT MEAN 91 WILL TURN INTO 98 OCTANE!!!!!!!

What it really means is that 91 will turn into 91.7 octane.
The amount that they provide in the bottle is insignificant to affect the octane rating.

skibum

Thanks for the info.

JeffGST ,I did not know that 7 points was .7
I would need a case of that stuff!
It does say on the bottle "do not over treat"?!?!??

Fortunately my company pays for my fuel.