Gasoline

[zoltan57]

i just recently moved from colorado back to florida... in colorado i ran 85 octane gas which my bike rode great on... since i moved to florida i been using 87 octane and was told they use alot of ethonal in the gas down here.. i wrote a topic a month ago since i moved here when i start the bike  at a cold start  white smoke puffs out.. and told it was normal?  and notice my gas mileage is off as well... i changed my plugs as per caution and still the same symptoms.. will my bike run better if i go higher octane other than 87 and will it affect my plugs and performance. i also have two brothers exhaust pipe 3 on each side and notice a different sound to them since i moved to florida.. is it because of the altitude change or air difference?
thanks,

emrik   

[Brewer]

Humidity, elevation (air pressure) and fuel can play a part. I am not a carb expert but understand the topic.
Rough air pressure in Denver 12.5 psi, sea level is 14.7, you might need to adjust the carbs or even rejet for your new local conditions.

[zoltan57]

thanks for the input.. i bought the bike in 2000 in colorado and moved to florida in 2004 thru 2007 and had no problems with the transition then.. it ran great and now moving back i  noticed the change... the only thing i changed when i moved here 2 months ago was i  had to adjust my idle from 1000 to 800... now if i do need a carb or rejet adjustment wondering how much would that cost?...

[JC]

I see a 10% drop in MPG when using ethanol gas. I'd guess the altitude difference will affect the sound slightly.

[F6Dave]

It irritates me that in high altitude states, you have to pay for mid-grade to get 87 octane, while in the lowlands the regular is 87.  But there is a good reason for what they do.  With the 'thinner' air at these altitudes there is actually less effective compression, since there are fewer molecules that get compressed.  So an engine that needs 87 octane at sea level will usually run fine on 85 here on Colorado.

Also keep in mind than higher octane fuel has slightly less energy, so if an engine tolerates regular just fine, a higher grade can actually reduce the power and economy slightly.

[BF]

It's the heat and humidity.  It makes me sluggish too.  

On a cool day with very low (for around here anyway) humidity, my Valk will run alot ......snappy'er....for lack of a better word. 

[F6Dave]

Got a blizzard outside today so I'm spending more time here on the board than I have for a long time.  Here's a little more on octane.  The reason for higher octane fuels is to resist detonation (or knocking or pinging) in the combustion chamber, which can cause major engine damage.  The downside is that to accomplish this, higher octane fuels actually have a bit lower flash point and less energy content.  So not only does more octane cost more, it also returns slightly lower mileage.  In fact, a simple engine that can tolerate a lower octane fuel will generate less power with more octane because there are less BTUs in a given amount of fuel.  I say a simple engine because those with engine management computers detect knocking and optimize ignition advance accordingly.

My '98 Tourer runs fine even on the crappy 85 octane gas they sell here at high altitudes.  My '99 IS, however, pings under full throttle on hot days, so I usually run mid grade (which is only 87 octane here) in the summer.  This could be due to the advanced ignition curve on the IS.  It also may have a trigger wheel installed.  I bought it used and have not yet looked under the timing cover.