DYNCYLAIR_DMA reading low on boosted application

[KAZ MotorSports]

OK guys,

My nightmare continues with this 1998 Tahoe that I upgraded the PCM to a 411. Way smoother idle, better throttle response, better HP and torque numbers. I am running COS3 on the Express van OS. It has a 2bar MAP in it, Whipple at 5.5-6.0 psi_g of boost at 6000' elevation, 8.8:1 w/forged internals. She is ready to run with plenty of fuel from the Walbro 255 HP pump and FPR.

The problem I am having is DYNCYLAIR is the axis the spark table is looking at to map the spark curve. I do not see anything recorded higher than 0.80 at 108kPa and it looks like from the log it is actually reading the 0.40 area of the map. Commanded spark at 0.80 = 21.5*....actual in the log is showing 30* at the same RPM and that is what is commanded in the 0.40 cell at RPM. All of the spark corrections, multipliers, etc have been zero'd or set to 1.0 to try and track why it is doing this and pin-point which cell it is truely getting the commanded spark value from.

Any insight? I did read Howard's post which was similar to this back in 2006, but there was no real resolution explained or posted from what I read.

Thanks all!
-Kenny

ps...attached is the tune and log file.

[Doc]

Kenny,
Looks like the Optimal Spark table could be contributing. Fuel Mixture spark correction looks like it is playing a role as well.

Doc

[KAZ MotorSports]

Hey Doc,

Why would Optimal Spark be referenced for actual spark curve? As stated in the discription "This table is used as a reference for what would be best timing, which is then used for various torque calculations."

I have never seen any setup I have tuned ever give me more or less timing than what I have commanded in the High Octane Spark curve when adders, multipliers, etc are zero'd. Am I missing something?

Thanks,
-Kenny

[KAZ MotorSports]

Hey Doc,

I zero'd the FMSC and now my commanded spark is being shown proper through the pull. If I calculated the cell it was in for High Octane Spark, cross to the FMSC, (which was 1.5) and used that as a multiplier (1.5*21.5=32.5) that was where the actual spark was being shown as a higher value hense my timing issue.

I am still wondering why this only reads up to 0.80 DYNCYLAIR, and it is not maxing out like I have seen on other COS3 setups I have done.

Thanks for your help Doc!!!!
-Kenny

[JezzaB]

Check your injector flow rates. Looks like it is set to 23lb/h @ 58psi, which looks really really low. Putting in a lower flow rate than what the inj really flow will lower the VE numbers and lower the g/cyl.

It is sometimes done to try and pull the timing back within the 1.20g/cyl boundry if its running off the scale. But you can just use A0010 to control it.

Jez