Spark Bias

[Razor]

Anyone explain the main spark bias and coolant compensation spark bias tables???

Is the coolant compensation spark bias correllate with the zero'd out locations for IAT timing adjustments? And how do they interact.

 

[Eric Stage I]

Razor,

The "coolant advance correction table" and the "coolant advance correction table bias" work together. The values in the table will add to timing, the bias will subtract from timing.

The main spark bias is actually mis-named. It is actually the "airtemp spark correction table bias", which works with the "airtemp spark correction table".

For example, you can only add timing in the "airtemp spark correction table". But, if you add, say 15 degrees to the entire table, then put 15 degrees in the "airtemp spark table bias", you are back at zero. That enables you to remove timing from the table if you desire.

So, to sum up, you have a table and its bias, and they work together to give you the final result.

Regards,
Eric

 

[WSLN 6]

Not trying to hijack the thread at all..............
Eric, does your chip subtract timing if the coolant temp is below 160 degrees?
Do you need the air temp sensor to be in the airpath, or is just under the hood good enough?

 

[Eric Stage I]

Sean,
The way your chip is set up, it will add about .4 degrees of timing as the coolant drops below 160F. The way the stock chip is set up, it would add almost 2 degrees as you get below 160F. I don't feel comfortable adding that much timing based on coolant temp alone, so I reduce the correction so its very low.

Which brings up a good point. Many people run faster times when they get their coolant down in the 150-160F range. If their chip has the stock coolant advance correction table, then they're getting almost 2 degrees more timing than at 185F. So it most likely will be faster, but not necessarily because the engine is cooler, but because timing has been added.

On the airtemp sensor, its best to leave it in the airstream near the sensor. The stock MAF has to have temperature compensation to remain accurate. Most likely its only going to be a few % here and there. However, if you leave it hanging in the engine compartment where the temp can get 150-200 degrees, then it will start correcting a LOT (like 10-15%), causing the mixture to go rich (at least until the MAF pegs at 255).

The maf correction table can also be zeroed out if someone should so desire.


Eric

 

[WSLN 6]

Thanks Eric!
That makes more sense.
I guess I should put that air temp sensor back in the airstream.
Probably would make it leaner off the bottom end.....

 

[turbotwister]

hmmmmmmmmmmmm.sounds like this guy knows what he's talking about.go figure

 

[boostcreep]

While we're on the subject of spark stuff, does anyone know what the BKR active time is ($317A)? And what the heck is time domain correction to spark ($3164)? Thanks

Nick

 

[dennisL]

BKR Active Time
First, BKR stands for Burst Knock Retard. The "Burst" refers to the sudden in-rush of air when you stomp on the gas pedal. I'm gonna guess you know what Knock Retard is.

When you punch it, a bunch of air comes rushing in. There is a time lag (delay) between when the throttle opens and the MAF sensor responds. So, the intake manifold empties, the airflow reading is too low which makes the injector pw too small, and the engine knocks. Fortunately, the MAF lag is short but still, the spark advance must be reduced until the MAF sensor can "catch up". That's where BKR comes in. [insert drum roll here] The BKR Active Time (100 msec) is the amount of time to apply the spark retard (14 degrees) to prevent "burst knocking".

Time Domain Correction to Spark
Explaining this one is much more difficult, but I'll try ...

It is derived from a combination of Quantum Physics and a quirk that Albert Einstein discovered. Uncle Albert discovered that as something travels faster, time slows down. Well, the spark travels at 186,281 miles per second! Time at that speed is very, very slow. The "domain" in this case, refers to the ECM which is what the ESC module logs onto when you start the car. So, the Time Domain Correction to Spark" takes something that travels at the speed of light and corrects it down to something acceptible for an NHRA racetrack.

 

[boostcreep]

BKR Active Time
Ahhh....I see how this works. Thanks.


Time Domain Correction to Spark
I found some notes that I thought I lost, and it had the explaination I was looking for. Thanks again.

Nick

 

[dennisL]

Time Domain Correction to Spark
I found some notes that I thought I lost, and it had the explaination I was looking for. Thanks again.

That's great Nick. I was just messing with you on this answer because I don't know what it does. Its used in a portion of the code that I don't spend much time in. Can you post the real answer?