Question about Flex Fuel / E85 Tuning

[ddtech]

After setting up everything normally following a stock GM holden cal, which spark table do we actual use for Flex fuel timing?

"flex fuel spark" or alcohal tab under AFR correction? I've already setup multi vs comp table but wondering which is the correct table to add to.

[GHuggins]

Flex fuel spark...

[ddtech]

I figured as much just wanted to confirm - I've been doing alot of research and seeing people doing alot of different stuff, just wanted to confirm my thoughts, thankyou.

What about a good bases to start from? Should i start with adding 4-5 degrees and go from there?

[07GTS]

i just changed to flex also but ive been running E85 for a while now so i just found an old timing table for when i was on petrol and copied that to the main spark table then done a compare to my E85 table and copied over the added difference to the flex spark table, i havent tuned my spark for best hp/torque yet but it was mostly around 4-5 in the mid to mid boost areas and couple up top but ive prob still got room to go further when i get some dyno time

[schpenxel]

You can always do a paste special-->add or subtract to add/subtract from your main timing table. I usually take the flex fuel spark table, copy it, paste special (add) to high octane table just to see what it'll look like. Then when you're done you can paste special (subtract) to pull that timing back out. It's easier to see what you're going to end up with that way.

[dreksnot]

Question concerning the flex fuel Multi vs. Composition table. Seems it's either 0 or 100% no matter what's put into the table for different alcohol compositions. It that just an anomaly? Say I want only 50% timing add and put 0.50 in the table, I still get 100% timing add (or multiplier of 1.0) - e.g., from the alcohol PE table.

[ddtech]

My Multi vs comp
0 0.25 0.850 0.925 1.000

[dreksnot]

Question concerning the flex fuel Multi vs. Composition table. Seems it's either 0 or 100% no matter what's put into the table for different alcohol compositions. It that just an anomaly? Say I want only 50% timing add and put 0.50 in the table, I still get 100% timing add (or multiplier of 1.0) - e.g., from the alcohol PE table.

I should have been more clear. When data logging and I get into PE, I see the "PE Advance" as a full 6*, which is the full value in my table even when my Multi vs. Composition table says it's suppose to be two-thirds that (e.g., for 50-60% alcohol it's set to 0.667). Logging shows I get the full 6* instead of the expected 4* (6* x 0.667). The Multi tables seems to be a all or nothing result - are you seeing that too?

[GHuggins]

Question concerning the flex fuel Multi vs. Composition table. Seems it's either 0 or 100% no matter what's put into the table for different alcohol compositions. It that just an anomaly? Say I want only 50% timing add and put 0.50 in the table, I still get 100% timing add (or multiplier of 1.0) - e.g., from the alcohol PE table.

Alcohol PE table? Assume that your referring to the composition table? Just wanted to make sure. I haven't seen this before if you are.

[GHuggins]

I should have been more clear. When data logging and I get into PE, I see the "PE Advance" as a full 6*, which is the full value in my table even when my Multi vs. Composition table says it's suppose to be two-thirds that (e.g., for 50-60% alcohol it's set to 0.667). Logging shows I get the full 6* instead of the expected 4* (6* x 0.667). The Multi tables seems to be a all or nothing result - are you seeing that too?

Never mind my questions. Have you verified with delivered timing that your actually getting the full 6 degrees?

[dreksnot]

Alcohol PE table? Assume that your referring to the composition table? Just wanted to make sure. I haven't seen this before if you are.

Spark > Advance > Spark Correction > AFR Correction > Alcohol -- PE/COT Advance Correction (Alcohol vs. RPM vs EQ Ratio)

My latest runs with E85 (sensor reading 69.8%) and had the logged PE/COT Advance reading the full 6* (which is what I have in that table). I'm getting the full amount versus a percentage (expected 6* x 0.667 = 4* but I'm logging 6*).

Multi vs. Composition table:
% 0 25 50 75 100 %
Interpolation Factor 0 0 0.67 1 1

[GHuggins]

That's why your having problems - your using the wrong spark table - the one your using will only add what you put into it, which is why it's not recommended to use

The one you need to use should be under misc - flex fuel spark... This is the one that the composition table will divide up...

[dreksnot]

That's why your having problems - your using the wrong spark table - the one your using will only add what you put into it, which is why it's not recommended to use

The one you need to use should be under misc - flex fuel spark... This is the one that the composition table will divide up...

Ok, thanks. I suppose you can't always believe the description for the tables at the bottom of the tab page when hovering the mouse over it, which states "The multiplier is used to modify the PE/COT Spark and Flex Fuel Spark...," which is why I thought it was okay to use for various (percentage) grades of E85. I've transitioned over to the Flex Fuel Spark table - looks to be much more versatile, and zeroed out the PE/COT Spark table.

[ddtech]

After some research and some helpful understanding from @Ghuggins, Yea, the box, "AFR correction" is spark for only AFR correction, the actual table you use is FLEX fuel spark.

[ddtech]

I also want to add, from what i've learned thank to others, that make sure your 93 table is tuned fully - people see huge gains because most of the time their tables aren't fully tuned and are just blah.. Take the time to make sure everything is in good, working order.

[DSteck]

The composition table absolutely applies to the Gas vs. Alcohol PE adder tables.

Typically, if you're really going to invest a ton of time into optimizing it, you'll work through both the PE adder and the global table for the ethanol spark adders.

[Jay@HAP]

FWIW, I had a 06 Vette that we put a D1SC, flex fuel sensor, E85, etc, etc.

When adding the additional timing for the E85 in the "Flex Fuel spark table" it would show the timing in the log but I believe it wasn't actually adding it.

The reason I say this is if I put the added timing in the high octane table I would see an increase in power, if I add it in the flex fuel spark table(and take it out of the high octane table" I'd loose a bunch of power.

Was I adding it in the wrong table?

[schpenxel]

I had mine do what felt like weird things like that before--extra timing showed up in total timing and showed up as ethanol advance as if it was being added, but after adding the flex fuel values to the high octane table and zeroing out the flex fuel table it felt like a different car. Didn't have it on a dyno but it was an obvious difference. I always just assumed it was mental but who knows.

Curious to see if anyone else has had this issue

[Jay@HAP]

I had mine do what felt like weird things like that before--extra timing showed up in total timing and showed up as ethanol advance as if it was being added, but after adding the flex fuel values to the high octane table and zeroing out the flex fuel table it felt like a different car. Didn't have it on a dyno but it was an obvious difference. I always just assumed it was mental but who knows.

Curious to see if anyone else has had this issue

EXACTLY! This car was on our dyno and can promise it wasn't mental. I didn't know if was due to it being a bastard 05-06 E40 ECU or if this carried over to other PCM's.

[schpenxel]

I've used that table on E38's before and it worked as expected (that one was on the dyno so I'm sure of it)

Might be a weird E40 thing since no E40 came with flex fuel from the factory?