Flex fuel sensor on 94 LT1 EE possible?

[Fastmax32168]

I think my title probably explains my question pretty well. When I built my 94 LT1 based 383 I had easy access to race gas, and I built it with 12.5 to 1 compression. Now that access has dried up and I have to back the timing off substantially in order to run it on 93 octane, leaving lots of power on the table. I have tried a snow methanol injection system with limited success in controlling the detonation. I do have an E85 station only a few miles from me, so I am wondering if it is possible to set up an EE based system to understand a flex fuel sensor so that I could convert over to running E85? Thanks.

[steveo]

reading the sensor is an easy thing
the hard part is you would want two timing tables and two stoich constants and blend between them
would require some serious assembly code
we haven't even figured out EE with two timing tables yet as thats a huge table and there's no free space for another one

[steveo]

of course if you ran only e85 you don't need a flex fuel sensor...

[Fastmax32168]

Steveo, Only running E85 would be my plan, however from everything I have researched the level of ethanol in E85 is not consistent, you can have 80% in one batch the gas station gets, and 65% in the next batch. No problem if you have a sensor that can read it and make the adjustment, but a problem if I need to tune it every time I get another tank of gas....or alcohol...or whatever.

[Pulse_GTO]

Thought of changing to an LS1 computer?

[Fastmax32168]

I have not investigated what it would take to change to an LS style ECM. I just thought of the whole E85 solution recently, up until now I have been considering changing to a head with a larger chamber, but converting to E85 seemed quite a bit easier and cheaper if it would work, and I did not know what sort of capability EE had or didnt have until today.

[LeMarky Dissod]

Steveo, Only running E85 would be my plan, however from everything I have researched the level of ethanol in E85 is not consistent, you can have 80% in one batch the gas station gets, and 65% in the next batch.
No problem if you have a sensor that can read it and make the adjustment, but a problem if I need to tune it every time I get another tank of gas ... or alcohol ... or whatever.

This, exactly.
Even if you get lucky and tune for E50 (the minimum), that just means you need another tune for E83, then maybe another tune for E72, and another for E61 ...
A 12200411 pcm (or its close relative) with far better flex fuel capability built in would be an easier solution, at least in terms of tuning.

[Tom H]

Looking through the 1997 LT1 code, it seems that there is a provision for low octane gas. Changes all sorts of tables centered around knock retard. I have yet to determine just how the code detects low octane. I wonder why the earlier LT1s didn't have this code (?) May have been a change when OBDII came in.

-Tom

[steveo]

I wonder why the earlier LT1s didn't have this code (?) May have been a change when OBDII came in.

EE does have low octane compensation tables and logic as well. it's probably the same code.

I have yet to determine just how the code detects low octane.

the logic is likely the same as most low octane compensation systems, if there are a lot of knock events within a certain timeframe, then it adds in more low octane compensation. the attack/decay is tunable.

that isn't really going to help this guys ethanol situation since spark is the not the biggest concern. if you don't have consistent ethanol levels, the difference between 50% and 85% ethanol is massive with regards to AFR.

[NomakeWan]

Steveo, Only running E85 would be my plan, however from everything I have researched the level of ethanol in E85 is not consistent, you can have 80% in one batch the gas station gets, and 65% in the next batch. No problem if you have a sensor that can read it and make the adjustment, but a problem if I need to tune it every time I get another tank of gas....or alcohol...or whatever.

Where are you located? This is true in places with no regulation defining “E85.” In places like California that get their E85 from Pearson Fuels, however, your ethanol content is guaranteed to be between 83% and 85% ethanol. 2% isn’t going to matter and is well within the correction range for closed loop operation.

Just putting that out there. While an ethanol content sensor and logic to support it would of course be the best, sourcing quality fuel and just using a static map will work too.