neutron82

no reason to be sorry, I think this is all relevant to the topic at hand... I'm no expert but from what I understand ethanol is very hygroscopic and who knows how long it sits in the tanks before someone pumps it out into their gas tank, add a humid climate to the situation and it will probably get worse... it might be ok for these daily driver flex fuel cars that are just trying to get to and from work but with a high hp car surely it can cause problems when making a wot pull and I agree with you, I'd rather not find out... in my opinion it's just too easy to test to not do it and this is something we can actually control to an extent, I am not aware of any way to easily test the octane rating of regular pump gas so there is no way to know if you get a bad batch until you start getting knock

Detoxx03

Allan Futral at Futral Motorsports

Chiselchst

Both would be expensive. MON is very expensive, i.e., requires a special engine to get numbers. RON cheaper (sometimes NIR testing can do it), but likely cost prohibitive for consumers (Refiners online analyzers for stream blending are NIR and very accurate).

Perhaps IF the content of E could be determined accurately, an estimate of AKI could be deduced (at least a minimum?). Not sure what "hydrocarbon" blending component they use to make E85, but I'd bet it's something such as hydrobate (low octane straight run naphtha i.e., cheap low value blending component). The E provides the octane, and the HC is only needed to make spec (RVP, etc). The E content of E85 can be much lower in colder climates...

This is making me more curious. It's interesting. Gosta learn more.

lt1z

Yes I have built quite a few over that level but I still maintain that if you are not willing to break it you need to stop pushing it in the mid 700s. On the other side of the coin I have seen poorly built and tuned LS3s expire in the 600s so YMMV.

It isn't all in the tune either. The LS3 block starts to distort above 800 or so which leads to issues as well. You will always have guys who have engines last better then most. I have a customer with a stock long block LS2 and a cam that has been running a max effort D1 setup for years racing all the time and hasn't hurt it yet. That is more of an exception then the norm though.

ChrisG23

E85 burns cooler than 91/93, so meth isnt always neccessary. IMO most guys blowing up E85 cars do so because of poor tuning. With 91/93 you add timing until you see knock. E85 is quite knock resistant, so novice tuners keep adding timing until they see knock, which is very bad. With ethanol, you add timing until you stop seeing HP gains, then stop.

Now I dont know much about the tuning software support (yet) for GM vehicles, but the advantages of running flex fuel are obvious. I dont understand why someone would bother upgrading their fuel system for E85 and not go flex.

schpenxel

It takes talent to screw up an E85 tune so bad that it blows a motor, but I shouldn't be surprised that it happens all the time

Chiselchst

Some standards (areas) allow E85 to contain as low as 51% E (or 40% in AZ?). Wonder what that octane is...

schpenxel

True... no clue though. I guess it'd be pretty dependent on what that other 50% actually is.. I'm not sure what they blend in with E50'ish. Local pumps here are consistently right at E80 so I haven't really researched it much

Chiselchst

I don't know much about E85, trying to learn more. It's confusing, need a law degree almost.
The HC (hydrocarbon) added to E85 is always going to be a crappy, straight-run low octane hydrobate with an appropriate VP (vapor pressure - measurement of volatility) for the region the fuel is headed. Warmer climates can get by with a lower the VP for starting engine. Colder/winter blends require a higher VP for engine starting. Brazil uses almost pure E due to their climate.
They also talk much about "octane giveaway", so E85 definitely won't be using a higher octane product like a reformed component (reformate) or an alkylate. Those are high value blending components reserved to boost HC octane blend pools that need higher octane (not E85).

It also appears that the US 49 states (Non-CA), CA and Europe are all using different specs. If everyone was to follow ASTM D5798-09b, then the E content is guaranteed to be a min of 70%. It would range from 70-79% minimum. A benefit I would assume for tuners, as the fuel octane/mixture would be more predictable?

But the following snips make this confusing. One says US E85 blends allow the E content to drop to a 51% minimum, while ASTM D5798-09b (which is cited often) keeps the E range from 70-79%. That would be better for tuning, as it dictates a minimum octane and HC content. That would at least allow a MIN octane based on the 70% E.
And one cite refers to CA having - or planning to create their own E85 specs!
Point is, the HC blended to any E85 is NOT a octane quality product. It will be an extremely low value un-reformed hydrobate/pentane straight run product. Those are normally about 60 octane, or less.

Unreal also talks about AZ changing their specs allowing the E content to drop to 40% E.