Timing Question: Stock vs. Thrasher 92...Diacom...

[brn agn]

I use Diacom Plus for a scan tool on my TTA. I was looking at some runs I had recorded today with the stock chip. At WOT, the timing (listed as Spark Advance on Diacom) ranged from 20-23 degrees. It is my understanding that this is correct for a stock chip. I then looked at some runs that I did last year at this time with a Thrasher 92 and it shows the spark advance as 32 degrees at WOT! There was no significant amounts of knock on any of these runs. This seems extremely high to me...what am I missing? Could Diacom be interpreting the timing incorrectly? One difference is that last year I was having a fuel mixture problem and my BLM's were maxed out during the run...that has since been corrected. Could this cause a difference in timing? Thanks!

 

[RobR]

Thrashers don't display the correct timing. It does display knock retard correctly though. Keep an eye on that and you should be fine. The Thrasher is a low timing chip ~17-18 degrees.

Its a very good chip, at least it was in my TTA

 

[brn agn]

Thanks for the info...that would explain the difference! Now that my BLM problem is corrected, I may have to try the Thrasher again.

 

[Swede2]

whats BLM ? BLock mode learn ? I know that its like 128 on my TTA all the time.

Is this correct or shall the value differ ?

Daniel

 

[brn agn]

BLM=Block Learn Multiplier. It is an indication if the ECM is adding or subtracting fuel to obtain the optimum fuel mixture. 128 is nominal and is what you want to shoot for. If it is higher than 128, the ECM is adding fuel, if it is lower than 128, it is subtracting fuel. I think it ranges from approximately 90-150.

Just as an example, my BLM's were maxed out at 150 last year and the car was running considerably rich (black smoke out the exhaust). I discovered that I had a small exhaust leak before the O2 Sensor. The leak was actually introducing more oxygen into the exhaust stream. This caused the O2 sensor to interpret that the fuel mixture was lean, so it was dumping fuel into the engine, although it really didn't need to. Once the exhaust leak was fixed, the BLM's dropped back to 128. That is my minimal knowledge of what BLM is. HTH.

 

[dennisL]

I then looked at some runs that I did last year at this time with a Thrasher 92 and it shows the spark advance as 32 degrees at WOT!

If you're using a scan tool with a Thrasher chip, subtract 15 degrees from the displayed spark advance. This will get you very close. So your 32 degrees is really 17.

 

[brn agn]

Thanks! The 15 degree shift makes sense. I do not get much knock with the Thrasher compared to the stock chip.