Table Indexes

[Fingers]

Reading through the tables, everything is mm3 against RPM. However some should be ECT or IAT or whatever. Is this a feature or a bug? For instance B0930 should have a temperature component as an input. Am I wrong?

[GMPX]

Well, here's how I see it, and this is from looking at the flow of the code in the ECM.
I am certain the A, B & C maps you refer to are selected from either Baro or MAF, GM have this usually set to Baro.
So now lets assume it is looking at Map B, Map B also has a multiplier that is based on the actual intake temp, that is the temp component.
Having said that, the multipliers for those tables have only just been added, that's whay you can't see what I'm talking aboutm they will be released very soon.

Cheers,
Ross

[Fingers]

I see some of the multipliers. Just didn't make sense to simply stack tables without bringing in another variable as part of the stacking. I will stare at it some more, but I am now getting a feel for why there are so many quirks to tuning these beasts. I don't see things working well by simply scaling values.

I would have added the extra dimension to the tables if it was me, but it is what it is. But what do I know....

[GMPX]

I don't see things working well by simply scaling values.

Well, without starting an argument this a pretty good way of doing things when you are limited in flash space.
Think of it like this, looking at table {B0932} you can see that between 50mm3 to 90mm3 and 1400RPM to 3200RPM they have added 4degrees of timing. But looking at the multiplier for that table {B0935}, those numbers are only fully utilized when the IAT is below -18°F, once the IAT is above 61°F then the engine no longer needs the extra timing so it is multiplied out by having it set to 0.
Now having that multiplier basically gives you 31 IAT timing maps depending on how things are scaled, or I should say, you get 31 options to scale that 4degrees between 0 and 4.
When a table has a multiplier associated with it assume the values in the table are 'worst case' or 'maximum' and then work back from there.

Cheers,
Ross

[Fingers]

Is there a shortage of memory? Provided what you want to do scales correctly, yes, it is a viable solution and saves memory. The A, B, and so on maps are really just 3 Dim maps themselves.

I'm always cycle conscience. Floating point multiplies, additions and memory lookups VS just memory lookup.

No argument, it is a solution when memory is tight.

[GMPX]

Actually, the code is certainly not written for maximum throughput on these things, it's pretty 'loose' compared to the LS1 that needs to run spark and fuel up to 8000RPM using the same CPU.

Cheers,
Ross

[bobo]

When I am logging charts, things seem to be coming out real close to the set points. I have seen duration and timing match to a tee.

[killerbee]

Think of it like this, looking at table {B0932} you can see that between 50mm3 to 90mm3 and 1400RPM to 3200RPM they have added 4degrees of timing. But looking at the multiplier for that table {B0935}, those numbers are only fully utilized when the IAT is below -18°F, once the IAT is above 61°F then the engine no longer needs the extra timing so it is multiplied out by having it set to 0.
Now having that multiplier basically gives you 31 IAT timing maps depending on how things are scaled, or I should say, you get 31 options to scale that 4degrees between 0 and 4.
When a table has a multiplier associated with it assume the values in the table are 'worst case' or 'maximum' and then work back from there.

Cheers,
Ross

Help me out here Ross or anyone. I am highlighting your passage rather than starting a new thread. I have been looking for timing anomolies and stumbled across something in the endeavor. But a little background:

One of the vehicles worst features thermally speaking, is the out of control IAT when under load. The vehicle is designed such that, increasing load leads to increasing IAT, a thermal feedback loop that deteriorates performance until the cycle is broken. The offender is the turbo and CAC. The heat dissipated in the CAC (in the form of over 260 degree ambient temps) is fed into the intake air box, where IAT is measured.

Now back to my query.

1st: B0935 is a multiplier for IAT (so titled). Yet the scale displays ECT (SAE.ECT) ???? I observe this on all 3 IAT multiplier tables I can tell you IAT and ECT are not interchangeable.

2nd: B0935 (BARO MAP C IAT multiplier), on all the stock tuns I have looked at: It is opposite to what the BARO MAP B and A multipliers do. See B0933 and B0934. This makes no sense, and I wonder if I have stumbled onto stock tuning anomolies, or if EFI is illustrating incorrectly.

With a thermally unstable IAT, you might see where this is going to be very important to how we look for improvements to things like overheat cures.

Definately looking forward to this discussion.

[killerbee]

I also just went to look at an LB7 stock tun (LB7's are less prone to OH). It has one (instead of 3) IAT timing multiplier table, correctly uses SAE.IAT, and it is set to all zeros.

[GMPX]

1st answer -
The 'link' is wrong, the link reference is only used to link the scantool data back into the map, the table is IAT Degrees. (I'll fix that up now).

2nd answer - What GM are doing is at high altiltudes they give you more timing and the intake is hotter and low altitude they give you none.

Cheers,
Ross