GREGGPENN

On the ARAP bin (similar to the AYPY bin), the PE table shows a big jump -- with a 9-degree bump in timing at 3200 rpms. If you look at the spark table, you can see a signficant drop in the table SOMEWHAT corresponding to that bump.

If you add 9-deg from 3200 up to the 4800 row, the results wouldn't be very linear. In fact, they'd be too severe. Maybe it's graduated from one row [up] to the next?

It seems clear that PE spark only applies to the right-most 2 or 3 columns.

But if you at 9-deg to the 208 load column at 3200 rpms, it would jump from 23 to 32-deg going from 2800-3200 rpms. Plus, you'd have 40-deg in the 4400 row.

Since the spark tables SEEM somewhat irradic, and the PE spark doesn't seem straightforward, I think the notion of simply adding PE to the spark table leaves out something we're (or at least I'm) missing.

Got any idea what it is? (IOW, how it works?)

bjankuski

Greg, The power enrich table can be eliminated and all the timing can be added main spark advance table. Smooth out your main spark table to eliminate the jumps in timing. The power enrich spark table is used on pick-up trucks that have a time delay at WOT before they go to power enrich fuel. When the trucks are at WOT for 15 seconds they still operate at closed loop and then they use less timing so they do not ping, after they final go to power enrich fuel they add in the extra timing for additional power.

Unless you are lugging your vette in closed loop at WOT you can eliminate the power enrich timing and add it to the main timing table.

Caboboy

This is how I've done it & that makes it easier to add and subtract timing (for me at least)

dan_t

The ECM will calculate between the values set in the tables. While at 2000rpm it will be adding the specified 1.05 and at 3200rpm 9.14 - for RPM's in between those two it will calculate the average (interpolate).


Something like -
2000rpm = 1.05
3200rpm = 9.14
= difference of 8.04 / rpm difference (1200rpm)
= 0.67 per 100rpm

The curve for 3200 to would be more gradual at .50 per 100rpm giving you around 33* at 4400rpm

nearly all of the tables work like this its just that the main spark tables etc are more closely grouped so you see a closer representation of the value inputted.

dan_t

Just to add -

I too like to go down the route of having all my spark in the main table. I think that the way the PE was setup was to give that impression of "Punch" as you nail the gas. It flicks the power on like a switch. Gives people that instant kick that some look for.

I think it makes it harder to modulate the power in a real driving situation though. Who wants to be on the limit of grip feathering the throttle around a bend while having 10* of timing kicking in and out as you drop in and out of PE.

If all your timing is in the main table your FOOT dictates the timing much more closely.

GREGGPENN

Thanks guys...esp Dan. Brian gets the credit for my initial tutoring and led me to setup my bin as described above. But, the curious "boy" in me has always seen that disconnect that Dan finally explained.

I knew (from simple addition of the two tables that the factory curve made no sense -- if done that way. I "played" for months with different section of my table...testing, burning, testing, and burning. As such, I'm sure I burned over 200 bins in the process of tweaking mine the best I could.

But, I have it out again for a heater core project. And, there are still one/two "idiosynchrocies" I wanted to work out. Heat at idle was one of them. Another is the warm-up grid. Overall, I looked back and still had that nagging question -- about PE averaging that made me wonder if there was something else worth knowing.

Not necessarily that it would make my table jump in performance...just that I'd left no stone uncovered. Besides that, it never hurts to play.

The tables in post#1 were ARAP. FWIW, this is what I've been running for the past 18mos....


Visually, it looks like this. (Notice the subtle dip at 1600rpm that put in to negate a mild resonance of the headers.)



Because of the heat at a [hot summer] idle, I recently considered taking a bit of timing out low...like this:


Which will look like this....



Because of a link (by Cliff) in the last scan/tune thread we had, the other thing I'm going to try is reducing the O2 Error Reduction Gain in the lower rpms. The original goes down to a minimum of 78. Mine will drop to 68 with the change.


Thoughts?

GREGGPENN

I agree. I always felt a bit of "jagged" transition even with normal driving (with the OEM 350). Once I learned about PE, it was instantlly clear what I had been feeling all those years. And, I didn't like it.