downside of E85 blends

[krazy86t]

i don't know if it is $%&!Y gas for the winter blend, but car has a fair amount of knock retard for a couple months - sometimes as much as 7-9 degrees.

i could be dreaming, but seemed to happen around the time when i expect the pump gas to get cold weather formulation from the refineries.

without any other changes to the set-up, mixing in E85 seems to help a lot. the pump gas could be 10% EtOH, so with 5 gallons of E85 and the rest 91 pump gas i guess i'm running E30. Is there any downside for fuel system components running this fuel? i've heard that the E85 guys have to make some changes so the fuel does not destroy things.

i have a TT 91 chip, 42.5lb inj, cold air, 160 stat, 3"DP, adj fuel pressure, walbro240 and hotwire.

 

[novaderrik]

i've heard from people that have actually used it- including myself- that E85 does nothing to harm the fuel system.

 

[jasjamz]

Maybe you need to check your fuel pump. It could be getting weak. Posting the location or tempature helps too. Cooler weather makes the air charge denser and the boost could be creeping up on you. Adding fuel through the chip may help or lower the boost. The E85 you mixed in won't hurt anything but is in my opinion a band aid to mask a real problem. Kinda like mixing in race fuel to make the knock go away.

 

[krazy86t]

Denver, CO area. I have heard that the winter fuel blend/additives are changed in this area. I don't know details. even on warm fall days (T =60's) i'm getting KR readings. i'm working through the long list of things to check because it might not be a fuel problem. last time it was the ICM failing, so that part is only 6 months old.

This link explains one important aspects of the difference between summer/winter gasoline formulations. Increased butane in winter blend due to relaxed VOC requirements in colder weather. butane is a low molecular weight, and therefore low vapor pressure, hydrocarbon and has a very low ingition temp.

 

[Red C5]

Are you asking if there are things you should do so you can run E85?
Our gas in CA is crap too.

 

[krazy86t]

sorry for the confusion. really two questions: 1) anyone notice that winter gas formulations cause KR issues, 2) is there any truth to what i've heard regarding E85 degrading fuel system components (thanks for the reply Novaderrik).

winter gas can have higher vapor pressure at std temp/pressure. This equates to higher concentration of lower molecular mass hydrocarbons, which can mean lower flash points. however, (R+M)/2 octane ratings are the same. but knock (pre-ignition or detonation) is a complex process that is further complicated by boost pressure and fuel formulation changes.