what octane?

[hks308]

i got a 02 400ex that is stock other than the tires and i was wondering what octane gas should i run? 87, 89, 91,92,93,94? what is the best for my quad??

thanks

[gotwarrior]

One of the guys I ride with runs 91 octane in his stock 400ex

91 pump gas is recomended. You could get away with the cheepest stuff though cause its low compression.

[John Pennella]

93 is fine. I never really noticed a difference when i would put 89 for riding at my house then putting 93 when I go riding in Massachusetts, and mine's stock too. Only time i would notice that the machine is running really strong is when it's a nice cool fall day outside.

[hks308]

alright. guess i will just get the highest octance. its only like a 20 cents difference.

[rooster300ex]

You should be fine. I've ran 87 with 11:1 before and had no det. I would just put the highest available pump gas as possible.

[billawright]

Just like the others say 87 is fine but I run 93 in mine at all times. Once I get mine jetted im going to run mix 110/93 in it.

[400eXr1d3rZ]

Originally posted by billawright
Just like the others say 87 is fine but I run 93 in mine at all times. Once I get mine jetted im going to run mix 110/93 in it.

Why not just straight 110?

[billawright]

Originally posted by 400eXr1d3rZ
Why not just straight 110? Well unless the motor is built for just straight race gas its not good for it from what i've been told and im going to be running mix for the added performance but without harming it.

[GPracer2500]

There's not necessarily any added performance to using a race fuel with a high octane rating--be it straight or mixed. Octane rating is a measure of detonation resistance and that's it. If your engine does not detonate on pump fuel (or whatever fuel) than addtional octane rating will do nothing. Nothing!

Now, a racing fuel can offer a performance advantage independent of octane rating. But then you're not looking at octane rating; you're looking at other specifications of the fuel (or you should be if you're trying to predict the performance of some specific fuel choice).

[onesexyrider609]

I got my 400 in July, and the first tank I ran was 93. After I finished it, I accidentally put in my dad's 87 for his welder. And on a hot summer day, you can definitely tell the engine didn't run as well. Now with fall, he just got me 7 gallons of 105 and I'm running with it some 93 and I'm pretty sure I feel a difference.

[400exrider707]

Originally posted by onesexyrider609
I'm pretty sure I feel a difference.


Its amazing what your mind can "make" you feel:rolleyes:

[onesexyrider609]

Yeah. I don't know, like I said, I'm pretty sure I felt one, I'm only 130 lbs and along with colder air now and a little higher octane gas, she seemed like she pulled a bit harder. Maybe its just me.:ermm:

[John Pennella]

Ya but there isn't a quad out there that is going to run good on a hot summer day cus the air is humid and dry and basically crappy for motors which all love cool air and a hot combustion and sense it's air cooled, cool air will keep the motor cool and not really hot.

[svahle]

Others will correct me if I'm wrong (it won't be the first time) but I thought higher octane gas burned cooler. If this is true, I would think higher octane would be better for the engine. Just a thought.

I have a 416ex with 11:1 compression. It runs fine on 91.

Not to open another can of worms, but I also sometimes mix 91 with 110. Some say they don't mix well, others say this works fine. My experience is that I can't really tell much difference in 91 vs. mix of 91 and 110.

[ilpadrino113]

It doesn't burn cooler, the higher octane requires more heat to combust. 87 octane might ignite itself in a high compression engine, where as a higher octane would resist the detonation. The actual brnin temps aren't different

[GPracer2500]

Originally posted by ilpadrino113
It doesn't burn cooler, the higher octane requires more heat to combust. 87 octane might ignite itself in a high compression engine, where as a higher octane would resist the detonation. The actual brnin temps aren't different

Correct.

The temperature, speed, and general characteristics of deflagration has nothing to do with octane rating. Deflagration is the normal kind of combustion that happens inside our engines. A high octane rating just means that the fuel can withstand higher temperatures and pressures before it begins to break down into chemicals that will auto-ignite (i.e. detonation). Deflagration and detonation are two different types of combustion. Octane rating has nothing to do with deflagration and that's the type of combustion our engines normally use.

This point is central to what octane rating means. Octane rating says nothing about how a fuel will perform when everything is combusting the way it's suppose to (deflagration). Other fuel specifications (that most folks never pay attention to) determine that. All octane rating tells us is where the threashold is between normal combustion (deflagration) and abnormal combustion (detonation).

[wombatz400]

My 03 runs noticeably crappier if i go below 93 octane the engine is all stock

[krt400ex]

well if u ride in really hot weather, i might make some sense because with an engine running hotter the gas gets to tis flashpoint easier, thus if the engine gets too hot, then the gas will reach its flashpoint and ingine prematurely (detoe). it will also reach the flashpoint easier if u r running higher compression, because the friction from the air/fuel molecules rubbing together will get a bit hotter than a lower comp motor. that is where ppl hear that high octane will keep an engine cooler. higher octane gas has a higher flashpoint, and can handle higher running temps, and higher compression...

[yellow400ex05]

I started to run 89 octane in my quad till i read the manual and it said 91 or higher. And after i burned up all the 89 octane gas i put in 93 and my quad ran much better. I can definaltley tell a difference to how my quad ran with 93 that it did with 89 octane gas. I guess different quads are more sensitive to minor changes than others.

[GearHeadz400ex]

I've always put in the highest octane at the pump in all my wheelers... When I got my 400ex last spring I looked through the book to see what they suggested. I believe it was 91 or higher like yellow400ex05 said.

[bah1491]

I run straight 110 turbo blue, my family has built engines for years, and has a lot of experience on dyno testing with diff. fuels. running a higher octane will not hurt a stock engine, if anything it will help it last a little longer, althought, whether its a HUGE power differece, i cant be the judge of that, take it to the dyno

www.barthartman.com

[GearHeadz400ex]

I've always put in the highest octane at the pump in all my wheelers... When I got my 400ex last spring I looked through the book to see what they suggested. I believe it was 91 or higher like yellow400ex05 said. so i'd say just go with the highest or close to it, hell its only what 20 or 30 cents more...,