I am confused whether to add PE spark into my main timing table and zero out the PE table like in super AUJP. Or to leave the PE spark in the PE spark table. I want some of your opinions on this. Also if you zero out your PE table and add the advance into your spark table do you only add the spark to the 90 and 100 KPA column of the spark table?

EDIT: I am running a 730 ECM with $8d calibration

 

I just zero'd mine out (and eventually elimiated it altogether) and used the main table. You could add the timing in to the higher columns and smooth the rest of the table out so it blends together nicely.

Although, the PE spark does make sense in its own way. Ive noticed that upon TC lockup or throttle opening, the MAP will go up to around 90-100 kpa momentarily without the ecm entering PE. Having the extra timing without being in PE could cause detonation.

 

That's why there's the TCC lockup SA table . Although I've yet to use it, I guess having a "healthy" motor doesn't see the tcc lockup as much of a load, 3.73's in the rear also help.

I've also zerod out my PE adder only because my motor almost never see's 90+kpa under closed loop driving unless I'm at LOW RPM, like idle (stupid large TBI open a crack and it flows a tone of air). If I had a smaller TBI or normal gears in the rear I might use 2-3 degrees in PE. Some guys here have noticed that they can run more spark with richer AFRs. I haven't noticed this but it's not to say I've done enough testing... so might be work trying.

 

I can't find the spark advance TCC lockup table in the $8d (which is what I am using) am I missing something?

 

$8D doesn't have the code to do it, just the TBI code. Seems as if GM didn't think it was necessary , wonder why.

 

If you are using features such as Highway Mode, then you will want to use a separate PE Spark Table. You want you Main Spark as a good base and then add according to the PE.

If you are not using Highway Mode, then the separate PE Table becomes less important and a single table can work just fine. But I personally prefer to use both tables because I want the extra spark in the PE Table to coincide with the extra fuel in the PE table. Using one table, either you aren't running enough spark in the main table because you don't have PE fuel or risking detonation until the PE fuel kicks in. That is my reason for using two tables.

As for the example where the MAP value shoots up to 90-100 on lockup, it will not cause detonation unless your high (100) MAP values have a higher spark advance than lower MAP values. This is because you typically have less spark advance in high MAP/load values because the engine is filling the cylinder more and the mixture is more volatile.

And you run higher spark advance as the MAP value decreases from 100 kpa because the cylinder is filling less and can handle (and needs) more spark to make up for the thinner air.

This is based on extensive testing in high elevations in mountainous British Columbia.

 

<Looking at tuning notes>
Yep, there it is, I stopped using the PE spark adder in 1997.

I'm now using a VSS spark retard table.

But, I just got one of em lil V6's.

One spark table is fine.

 

My example there was to illustrate that the MAP can rise substantially for a short period of time without the motor entering PE. With one table with timing optimized for peak WOT performance, it may mean too much timing in closed loop with the afrs around stoich. Yes, it was a bad example as there is a table to retard the timing based on MAP and rpm when the TCC is engaged.

 

My experience is that the stock PE enable tps % values allow plenty of high loading in closed loop, before PE mode, more so with manual transmisions. One could either find out the TPS% needed for whatever was deemed a safe closed loop load (80kpa maybe) then change the enable throttle positions to those values. Or cals with a MAP treshold for PE table wouldn't have this problem. I will say that my SA adder vs rpm for TCC lock table has only a degree or two removed, and only at high load from like 800-1200rpm. On my 9C1 calibration, the TCC won't even lock until like 43mph, which is like 1300rpm. So that table isn't even really used, from stock. I have it lock now at about 38mph, though.

Either way, I think there is a PE SA adder for stock engines for a reason, as some have mentioned.

Another thing is, stock engines (at least in my experience) don't seem to mind high loading at stoich AFRs. It's those hot modified engines that really seem to have a problem with them.

So, I think the answer to the question is: it depends (on your engine).

 

Over the years I have learnt that tuning an eprom is a lot like climbing a mountain; at the bottom there are many paths leading to the top with some paths easier than others. But, if you comfortable with a particular path, use it (even if it is not necessarily the easiest path to take...it's your path).

I believe the key to whether you use one spark table or multiple spark tables, is whether you are also using a separate PE fuel table. And, this may be dictated whether it is a MAP based system or a MAF system (with the MAF sensor being maxed and you need to use the PE fuel table to compensate).

A MAP based car tuned to run in open-loop (with a WB) makes using a single table for both fuel and spark easy (and possible the best way to tune a MAP car). It has the advantage of letting you clearly see both your TOTAL spark and TOTAL fuel needs. Other than tuning the pump shot, the "single table method" greatly simplifies tuning. And, I have always found "simpler is usually better". As the old say goes..."Keep It Simple...".

But, if you DO need to use a separate PE Table (such as a MAF car that's maxing the MAF), then you want the two events (spark and fuel) timed together. You don't want the spark occuring before you have the fuel, as this can cause problems. And having the fuel occur before the spark will make the engine doggy.

To me, you need to syncronize the spark event with the fueling event. If you can handle all your fueling with only one table (whether it's the VE Table or MAF Tables), then you can try and use the single Main Spark Table. But, if you MUST have a separate PE fuel table for whatever reason, then you are probably better off with a separate PE Spark Table because you don't want the spark kicking in unless you have the fuel for it (and vice versa).