Hi guys, man have I been off this forum for a while!

I know my initial timing is set at 6 *. In DataMaster, where it says spark advance is at 33 * WOT and 36 * cruising.

Is spark advance the amount of timing added to initial timing?

I mean does that mean my car is at 39 * (6 + 33) at WOT and 42 * (6 + 36) while cruising?

If so, maybe this is one of the reasons my car is detonating and pulling 7 * of timing at WOT due to knock. I don't believe it to be false knock cuz when it was on a dyno I could hear it detonating and the dyno operator said it sounded like a can of rocks.

 

Since the ECM doesn't know what is current base timing, I suspect it simply looks up timing advance from tables in the EPROM. In which case your readings would be minus whatever base timing you have set.

Does your timing light have a dial on it? If so use it to get total timing with the EST connector made and compare with DataMaster readings.

What is your O2 sensor reading at WOT?
If the dyno operator used a WB O2 sensor, what was the A/F?

What are BLM values at say idle and while cruzin?

What coolant temp are you running?

Is the EGR system in tact?

 

i thought it threw timing in Till it read's knock and backs off ???

 

So basically my total timing is whatever datamaster says my spark advance is? I get my work done at my mechanics and it will be a few months until I get it out again, so I am not sure about his timing device.

My O2 readings if I remember were around the 875-900 range at WOT but they seem to fluctuate a bit and jump around.

I always try to play with my AFPR to get around a 128 at idle, but whenever I can do that, at cruise it's off, so I can never get it set just right. I am going off memory here as I don't recall exactly what it is reading.

My coolant temps are 175-180 highway and 180-192 town driving.

My EGR system is still intact I believe.

Again, my mechanic does the work, I drive it, lol.

I did buy a Pocket Programmer 2, but haven't yanked my chip out yet to see what 's going on at that end.

 

Sorry, what i meant was that I don't believe the ECM has any of knowing total timing advance. So your readings would be the timing advance above base.

Those O2 values at WOT don't sound bad, so I don't think a lean mix is causing ping. Mine start out around 920-930 and drop off a little just before the 1-2 shift, due to the ram air intake.

You really only need to tune fuel flow for WOT and then check that BLM & Int are within +/-6 counts of 128.

I assume you were running 93 octane fuel during the dyno pulls.

 

OK, thanks for clarifying the timing issue. I believe it to be too much timing programmed into the chip. I think 39 * @ WOT is too much, don't you? If I ever learn how to use that Pocket Programmer I'm gonna try taking out 4 * timing all the way across the board and see if it helps any.

Here's a copy and paste of a previous post I had made last year.

This was done on a WOT run.

*PASTE*
Target AFR 11.2 - 11.5 ( dips to a fat 9.94 - 9.60 - 10.14 - 10.92 - 11.11 - 10.64 - 10.73 - 11.09 - 11.18 - 11.28 - 11.32 - 11.46 - 11.52 at 5575 RPM then 14.5 on shift all within a span of 3.6 seconds)
*/PASTE*
This is referring to the Target AFR cell in my version of DataMaster. I believe the O2 was around 875-900 at that time. It does seem to be a bit jumpy though.

Not much was done on the dyno pulls cuz the operator said he didn't want to damage my engine, so these results are mostly all from me with my laptop and DataMaster runs.

I tried to tune it for cruise to get 128 +/- since that's where it is at most of the time until I can get the chip done properly.

I can only get 91 octane gas around here.

Last year I tried an experiment with having about 50 L of 91 gas and 15 L of 114 race gas in order to give me around a 95-96 octane rating. I did this to see if it would still knock and detonate and pull timing. It still pulled that much timing out but the car did smell really cool ( reminded me of the drag strip with all the cars running the high test gas), but not worth the $3/L of the 114 gas.

 

I had this same question a while ago...

Basically your total timing (as viewed by datamaster and the ECM) is set in the Spark advance table in the ECM. A "BASE TIMING" table is used only as a reference to the computer to tell it what the distributor is actually set at. In this way, you can trick the ECM to add or subtract timing by lying to it and saying that there is more/less BASE timing than the distributor is set at. It's just a value though- the timing is derived from the Spark Advance table that you see in tunercat, tunerpro, etc.

you can also set the MAX Total timing allowed in the ECM by saying I don't want my advance to be over... X value.

One minor caveat: There is also a table in the code that is HIGHWAY SPARK - this increases your total timing by values specified in that table while driving under certain conditions that mimic highway driving/speeds.
These values can and will exceed not only your WOT values, but the "MAX Timing" specified, because they are literally added on to the Spark Advance tables/values that are used for WOT and part throttle advance. This is done for fuel economy, and explains why you can have ~40* to 50* advance or more while cruising.

Makes sense, huh?