To 91 or Not to 91 Fuel Octane

[johnyrocket]

ethanol

I recently read an article on marine 2 stroke engines; they tested various 2 stroke engines on e15. Some engines did not even finish the test do to melt down. I know we only have e10 here in co, but if you use an alcohol based boost witch most are you will be around e12 or so. Now to the point ethanol does make a difference on 2 stroke motors if you don’t take some precautions like don’t use alcohol based boost do use something like startron to keep water separation down. You should not have any problems. As far as octain goes both my sleds are ported and moded I do see a difference even above 10k feet if I use boost on 91.

 

[WyoBoy1000]

I recently read an article on marine 2 stroke engines; they tested various 2 stroke engines on e15. Some engines did not even finish the test do to melt down. I know we only have e10 here in co, but if you use an alcohol based boost witch most are you will be around e12 or so. Now to the point ethanol does make a difference on 2 stroke motors if you don’t take some precautions like don’t use alcohol based boost do use something like startron to keep water separation down. You should not have any problems. As far as octain goes both my sleds are ported and moded I do see a difference even above 10k feet if I use boost on 91.

If tuned right any 2 stroke can last with e, your comparison doesn't take that into factors. I don't know what sleds you have but I really doubt you need more than 91 octane, sometimes stuff like startron enzyme helps on how smooth it runs because it stabilizes the fuel but not really upping the octane.

 

[johnyrocket]

I use startron only to stabeliz fuel. I have a ve700 with port job and slp pipe and can that run just a little better with lucas boost. I also have a m1000 full race port and bmp head speedworx pipe and can that performs a little better with 91 and 100 mixed 50/50. Or atleast I think they do

 

[aksnopro]

run the octane the sleds designed/fuel mapped for. it wants a little slower burn with the 91, give it to it. its how its designed. you can put 100 octane in it and you will lose performance, you can put 87 and you will lose performance, its designed for 91. put 91 in it.


any additives always are questionable very few are true octane boosters, most just do the same thing that a higher octane does (accomplishes a slower burn)

so your really not increasing the octane with most these boosters. and your throwing random junk through your motor.


stick with premium!

-Aksnopro

 

[Dam Dave]

the 91 octane requirement for the 2010/2011 HO M8 is only for low elevation, like sea level

 

[backcountryislife]

run the octane the sleds designed/fuel mapped for. it wants a little slower burn with the 91, give it to it. its how its designed. you can put 100 octane in it and you will lose performance, you can put 87 and you will lose performance, its designed for 91. put 91 in it.

as DD said, that is what it needs at sea level.

octane needs change with compression, and elevation/ air density changes compression. If you're saying that a sled designed for 91 requires the same octane at ANY elevation... you're simply wrong. Do some research, you'll find out what we're talking about.

Think of changes in elevation (in the postive) as if they're just adding a low compression head, which decreases in compression as you go up. Just like how adding a high comp head requires MORE octane, altitude requires less.

Now, do we know EXACTLY how much (IE: 1 less point octane/ 500 feet elevation)??? No. I don't anyhow, that's why I run a lower octane till I hit the octn code, then I know to step it up a small notch & go from there.

 

[WyoBoy1000]

or ...
High elevation means less hp, less hp means a slower rate of compression thus lowering the octane requirement.

 

[joel97mustang]

Rebuilds?


Because of lack of oil?


Because of lack of octane?


WHERE, WHEN? Show me ONE person who has actually had an M8 go down due to det.

As to oil... the issue is a linkage that can fail, and that 100:1 will let your sled blow just like no oil at all will.


Sorry, but I'm just blown away at the fear-mongering that some of you guys buy into.

As to limp mode, I'm not suggesting that someone run too low an octane every day, simply that it's not hard to figure out since the det sensor protects you from damage. One day to see what you really need.

It's NOT the $$. You will run the strongest with the least octane you can safely run, running more just costs you HP. (the dollar a tank is a non issue, we're not talking about running 116 here!)


Lankford, I've seen a number of people on ACchat who have mentioned never having any problems with the 90 in AK, some were pretty worried about it, but they found it worked fine.

I wasn't sure what I was looking for when I started this post but some interesting ideas/facts have come out. I am not specifically trying to be cheap and save 10 cents per gallon but really interested in whether or not 91 is a must based on real world use not just AC mfg specs which is sometimes suspect.

I like the fact chevron provides non ethanol fuel, I will be shopping there from now on.

 

[joel97mustang]

So if I am riding between 2-8,000 ft I should stick with 91 or would 89 be applicable? Mostly ride Whistler, Pemberton, Kelowna and sometimes Stevens.

Appreciate all the good advice. Thanks

 

[Dam Dave]

So if I am riding between 2-8,000 ft I should stick with 91 or would 89 be applicable? Mostly ride Whistler, Pemberton, Kelowna and sometimes Stevens.

Appreciate all the good advice. Thanks

you will know if you are having issues, "Octane" will flash on dash and sled will lose power if det sensor picks up any knock, it will protect it self, it works

if sled runs strong on 89 you dont need 91

 

[ullose272]

so what if its got an slp pipe, bdx airbox, pcv with racin station map? 91 or less? 4500ft and up

 

[Mjunkie]

I once owned a '02 800 RMK, that had 2 "on" positions on the key. One was "on" and the other was "premium fuel". The premium fuel setting advanced the timing slightly and thus required more octane. I ride from about 7000 ft and above and not once did I run it in the "on" position and I always ran 85 octane fuel without ever a problem. This was before ethanol but still like everyone else has said, the higher octane is only needed at low altitudes on a stock sled, so don't waste your money buying premium fuel only to get less performance.