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Octane & Tune

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67hat34c

Active Member
Most of our EFI bikes require 91 Octane.

Question is that would the engine perform worse with 100 Octane? The 100 will burn slower so in theory it should produce lower power in an engine with NO Knock sensor.

Now the second question is: would the engine produce more power with 100 if you re tune and advance the timing even more?
 
What compression is your motor? Does it have O2 sensors? These need to be answered as compression less than 11 to 1 wil see no benefits from the 100 octane, also most fuel around 100 octane has some type of additive usually lead which will screw up your O2 sesors. Lastly if you tune it with 100 octane and go crazy advancing your timing you are going to have to run 100 octane all the time, it's pretty hard to find it at least in my part of the country.
 
The engine can only use so much octane and giving it more than it needs will be a waste of good fuel and possibly end up damaging the engine to boot. If the engine isn't set up to run the 100 octane, you can do more harm than good.
 
I am asking for info only. I read on other forums that guys in foreign countries are using 100. They say engine runs quieter when they use it.
I replied that is becuse of slower burn and less power.

I was only wondering if someone was to use 100 and then advance the timing if it would work. Would never consider it myself.
 
That may be true.

Still wonder if my theory would work though.

On a side note, I posted that My engine was making a belt squeel/tin sound that did not appear to be engine ping but still could not rule that out. Sound shows up when engine oil temp is north of 180 and you accelerate hard.

I changed from BP to Chevron just incase the BP gas was lacking for some reason. This did not make an immediate change. I filled up again at chevron and added 2 oz of MMO. No immediate change but after riding a couple of times it seems the sound has gone away. Still need to give it another workout this weekend to verify.
 
That is what I was thinking. I will run it hard this weekend in the heat here in orlando and see if I can confirm a cure.
 
Glider, Read the tip using water.


Funny story, In my boating days someone told me about this process but did not explain how to do it. Well I dumped way too much water down the throat of the Onan Gen and blew a head gasket and also burned a set of points. I also tried it on both 454's and did not hurt anything but did get water in float bowl throught he Horn on the q jet. Casuse engine to run very rich.

Due to that experience i did not want to try it again on anything else. However using spray bottle and and limiting the amount to 4oz or so i think i would feel safe.
 
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