102 - Advanced Tuning Of A Delco ECM with $12P

[v6bucket]

Great work
You list "Injector Battery Offset" above, what does it alter?

[VL400]

The fuel delivery will vary with battery voltage, so there are a couple of tables to correct for this...
"Injector - Injector Bias vs ADINJ" is to correct the opening and closing time of the injector with respect to battery voltage.
"Voltage compensation vs Battery voltage" is to allow for the fuel pump speed variation with respect to battery voltage.

[Holden202T]

so this is an offset in mS. Theres part of the injector opening time when it will not flow fuel but this is part of the mS pulse, so different injectors or the lower the battery voltage usually means this time is increased .... long story short, in my case I replaced 19lb stock injectors with 80lb garden hose fittings and this table is up to shit!

you can usually find a graph or similar from manufacturers showing the voltage offsets to put into this table, and at worst case scenario you need to do a bit of fiddling in a spreadsheet to get the numbers that line up with the scale in the delco table ....

that said if you alternator is ALWAYS charging at 14.2v for example and you tune it there it should always be right ... this issue only comes into play mainly when you have a dodgy regulator or heat soak etc (which is probably more than likely regulator anyways) but issues aside, its like everything else, you want to have the right numbers in there to stop having anything being fudged because we all know the more you fudge the more you get dodgy results!

here is an example of the stock $12P table (the bottom one and red on the graph) compared to the info I got from Siemens for my injectors.
(Incorrect information removed and re-posted below)
its fairly clear that theres a huge difference in injector flows at different voltage and the fact that at 14.4v theres nearly double the mS difference, that's huge!

its worth noting that this difference is not necessarily about the flow of the injectors its more about their design and efficiency.

[vlad01]

Can you explain the AFR table and how that is tuned.

So far I understand the importance of spark and VE and what they do plus other parameters, but how is the AFR table determined in the first place? Like how do you tune the AFR table to suit a specific engine?

[v6bucket]

I'll have to track down some info for the Siemens 60lb units that we are using in the Dato.
Could this have an effect on cold start? (as the starter is sucking up lots of power.)

[charlay86]

I'll have to track down some info for the Siemens 60lb units that we are using in the Dato.
Could this have an effect on cold start? (as the starter is sucking up lots of power.)

Yep certainly will have some effect, they are large injectors so it only takes a small change in PW to have a large effect on the fuel delivery

[v6bucket]

It starts good once it's warmed up, but needs some assistance(squirt of petrol) when cold.

[Holden202T]

I don't think you'll get away from the cold start issues on methanol, that's just its feature but that said, once mine starts it runs perfectly like a petrol car even cold!

i'll have a look, I think I have some 60lb info!

[charlay86]

yeah methanol's latent heat of vaporization is about double that of petrol which is why it has such a nice cooling effect on the intake charge.
once you have the injector settings correct, you might need to fiddle with the cranking pulsewidths, the low velocity of air that occurs while cranking doesn't do much to help the fuel evaporate either unfortunately

[Holden202T]

I would like to correct the previous post above with the injector offsets, they are not quite correct, so I have listed below what I believe to be the correct ones for both 60 and 80lb seimens dekas!

battery injector bias table comparison.jpg (120.28 KiB) Viewed 25794 times

Edit by Antus: The first table pictured is "Injector - Injector Bias vs Battery Voltage" and the second "Injector - Injector bias add-on vs Injector pulse width". Also note Holden202T has configured the tables to display the other way around, make the values on the left hand side line up when using this information.

please note, these are the two tables in $12P ... other code bases might have different labels or such.

Now as far as working out the AFR table goes, mostly what I work with is factory from holden with the only exceptions being a few cars I have tuned with way to big of a cam for the street, and they would surge at light throttle and low rpms, so to fix this and to stop it going into closed loop in these cases I have changed the AFR table from 14.7's to 14.4's and in one case 14.2's .... this was required till approx. 2000rpm, but is also depending on the cam size etc.

now in a normal practical example where the cam isn't too big you should be able to leave pretty much all the settings as per Holden, but you might want to change some areas, so for my car with methanol I found 5.2 AFR at WOT was the most suitable, but then when I tuned a V6 sprint car we got the WOT AFR's to 5.2 (by tuning the VE table) then we experimented with 5, 4.8 and 4.6 AFR's and the end result for them was 4.8 made more power. the added advantage of this is the cooling effect and the fact that your running the car really rich so its safe!

BUT, there are other factors, for a drag car you probably want to get the best power AFR because you really aren't getting it hot enough to hurt anything, but then if it was a track car or like a speedway car that might do 50 laps on the loud pedal the whole time, then you obviously want to make it a bit richer and maybe sacrifice 2hp to get a motor that lasts to the end without hurting anything or overheating!

The long and the short of it, the AFR table is a pretty good and probably safe starting point and you don't really need to touch it, but if you want to experiment with different numbers you might find you can gain some power or economy, because obviously too rich chews the fuel so for a street car you don't want to run it at 12.4 AFR you might be better off with 12.8 or even 13 in some motors.

also a lot of more so new cars do things like stupidly richening the WOT fuel to safe guard the motor and also to make it kill off a bit of power ... just simply changing this stuff can see a marked improvement in economy if your seeing power enrichment a lot!

and lastly, I thought i'd take a video to show you v6bucket how my car starts on a 15 degree day on methanol like I said struggles to get going but once it does runs smooth as a babys bottom!

[youtube]http://www.youtube.com/watch?v=qdlhAClR7dE[/youtube]