Question about Speed Density and dual spark map

[agreif]

I'm on the verge of ordering the personal version of EFI. I still have a question on the speed density and dual spark map. The speed density allows me to take the MAF out of the equation and use the MAP sensor instead. My questions comes into play with the spark map. If I'm not running boost(no need for the 2 bar), does the personal version allow me to run a speed density tune and run full adaptive spark, both high and low octane? If I want to take full advantage of 93 octane and will only be filling up with that (unless I can only find 91), do I even need the full adaptive control in the high octane spark table? I'm not sure what is considered "high octane", 93, racing fuel, etc?

Thanks ahead of time, just trying to get my head around this,
Andrew

[caver]

SD and Dual spark map are only available in the Efi Live custom operating system.
This is not available in the personal version.
You can still run in SD mode but without the spark scaler.

[ringram]

Or if someone you know has the commercial or workshop version and can update your pcm you can use your personal version to tune it.
You just cant do full OS updates, just calibrations. You can update calibrations for any OS including the custom ones.

[agreif]

You can still run in SD mode but without the spark scaler.
I can't find an explanation of adaptive/dual/scaler spark. Here is a portion of what Paul has told me. I guess I'm curious why the adaptive spark would be needed . In copying the high octane into the low, you are basically telling the PCM you will be using high octane right, so what's the adaptive portion?

" PCM will default to the low octane spark table. In the past, tuners would copy the high octane spark table values to the low octane spark table to control the spark. However, that leaves the PCM no room for adjusting the adaptive spark."

Sorry for all the questions,
Andrew

[Tordne]

So this is basically what happens on the Stock PCM Operating System:

When the system s running in Speed Density mode (MAFless) the PCM considers that a critical component (the MAF) has failed and goes into a self preservation mode for want of a better description. It therefore forces the spark timing to be derived from the low octane table ONLY.

This is where you need to copy/alter your timing in the low octane tables when running Speed Density on a stock OS.

With the Custom OS you can retain/use both the high and low octane tables, as the factory intended. There is a scalar that balances between the two tables. For example:

- If the scalar is 100% then the timing is coming from ONLY the high octane table.
- If the scalar is 0% then timing is coming only from low octane.
- If it was 50% then it is averaging between both high and low equally.

The scalar starts out at 100% and as you get KR degrades. As you drive with the absence of KR the scalar increments back towards 100% again.

I hope that help, and is answer what you actually wanted to know :)

Cheers,

[agreif]

My only question is still around the high/low octane tables. From what you are saying there is a high and low octane table in the stock PCM. I understand your explanation of only using the low table without the MAF, but I still don't understand what the high octane is for. Is it really for higher octane fuel, or is it a more aggressive spark table that is used unless a problem is detected? If i can adjust the low, I am just trying to understand what the high does. If there is a tutorial on this table stuff, I would love to read that instead of pestering you guys. I just wasn't able to find that in the tutorials, stickies or in a search.

I hate being a pain when people have already given good anwers. I just have a gap in my knowledge here. Thanks for your patience.

[GMPX]

Basically there is two spark tables, the High Octane generally has higher timing values for situations where you are running with good fuel and the engines propensity to knock is not as great as when running with a lower octane fuel. The Low Octane map will contain spark timing values that are still 'safe' when running lower octane fuel.
The system normally works by scaling between the High and Low Octane table values depending on knock activity.
When you go MAFless, without running custom O.S of some sort the PCM will ignore the High Octane table totally and just use the values in the Low Octane table. Of course you could increase those values but you leave no 'safety' factor.
If you do a search on here for "Octane Scaler' there is bound to be a few good threads.

Cheers,
Ross

[dfe1]

If i can adjust the low, I am just trying to understand what the high does. If there is a tutorial on this table stuff, I would love to read that instead of pestering you guys. I just wasn't able to find that in the tutorials, stickies or in a search.

I hate being a pain when people have already given good anwers. I just have a gap in my knowledge here. Thanks for your patience.
The original system is designed to allow an engine to operate on a wide range of fuels. Actual spark timing is determined by "blending" the settings in the high and low octane tables. If little or no knock is present, timing is biased towards values in the high octane table. As the amount of knock detected increases, spark timing is biased more towards the values in the low octane table. Keep in mind that this system is designed to be applied to a variety of vehicles, some of which are driven by people wo don't have enough sense to come in out of the rain, let alone back off the gas pedal if they hear knock.

In the "old days" PCMs/ECMs had only one spark table and knock retard was used to control detonation. Dual spark tables were developed as a means of improving "customer satisfaction", which is GM's way of saying "we have a system that allows brainless drivers and cheapskates to drive high performance vehicles on low octane fuel without causing engine damage".

On my personal vehicles, I always use the same values in both the high and low octane tables, use gas (petrol) of the appropriate octane and listen for knock if I'm not data logging. If you're tuning someone else's vehicle, it's always a good idea to tune for a wider degree of "driver indescretion". Hope this helps.

[agreif]

Ahhhh. Ok, that makes sense now. Those last two responses turned the light bulb on. (Reading Tordne's again made it clearer too). Thanks for bearing with me guys.

Andrew

[Tordne]

No problem at all. There is a lot of "stuff" in the PCM and a lot of people on here that can help you understand a good deal of it :)