2/3 Bar Tuning: Boost Timing Table ?

[Earl H]

I am starting to read up on the 2/3 Bar Tuning.

I'm a little confused on the Boost Timing Table {A0010}. The .pdf manual says the value will be subtracted from the final timing table value.

This calibration works in conjunction with {B5956} Coolant Temp Spark Multiplier wihich must have a value of 1 whenever you want boost retard active.

Could someone please explain the relationship between the Boost Timing Table and the Coolanat Spart Multplier? Also can anyone confirm that the final timing table value are in the {B5913} Spark High-Octane Table and that those values will be retarded by the Boost Timing Table values based on airflow? Thanks in advance.

[Delco]

Earl we only normally use the boost timing table IF we max out the normal spark airflow tables , it was a way of taking extra timing out on big cube motors where we were using more than 1.2g/cyl of air and we had run of the standard igh octane table.

the value of A0010 is multiplied by B5956 and that final amount is taken of the main spark table

[kbracing96]

I'm wanting a little more info on this as well. I'll wait and see how this thread goes, and if my question get ansewerd. If not, I will start a new thread as to not highjack this one :wink: .

[GMPX]

Delco is correct in what he said.

Why does the boost timing table depend on the coolant spark table?.
You have to remember, we are not GM, we don't actually fully re write the O.S, instead, we 'patch' into it extra features.
So, for the boost timing table that was added into the coolant temp spark routine, this means that the coolant spark multiplier must have a value of 1.0 or the boost spark table will be ignored.

For example, if you has 5 degrees everywhere n {A0010}.
The maths is like so -
5 x {B5956} = Final boost retard value....or
5 x 1.0 = 5
5 x 0.5 = 2.5
5 x 0.25 = 1.25

Cheers,
Ross

[Earl H]

I'm confused, which is pretty common these days


The explanation in tune says:
{AOO10}
Once the MAP is above the maximum value allowed in {B0101} "Main VE Table", the PCM will subtract this amount of timing from the final spark advance.


So, I get that {A0010} is the amount of retard from the final spark advance, assuming the coolant spark value is at 1. What I don't get is what table is the final spark advance found in. Is it {B5913} Spark High-Octane Table or ....

[mistermike]

Yes, it's going to be the last column in your high octane spark table.

[mistermike]

Yes, it's going to be the last column in your high octane spark table.

[GMPX]

The explanation in tune says:
{AOO10}
Once the MAP is above the maximum value allowed in {B0101} "Main VE Table", the PCM will subtract this amount of timing from the final spark advance.

That is wrong :oops: :oops:

It should say "once the calculated airflow goes above 1.2g/cyl (the limit in tables {B5913} & {B5914}), then this table can be used to subtract timing further once high boost levels are reached" or something along those lines.

Better fix that up :cry:

Also, a new set of V3 O.S's should be getting uploaded today, these all included the IAT VE Multiplier, you will need to download both the tun file and the cal files (which will have that description fixed). Thanks for getting totally confused Earl :wink:

Cheers,
Ross

[Delco]

Yes, it's going to be the last column in your high octane spark table.

You wont always use your hi octane spark fully , depending on whow you have your VE and injector scaling you dont always max out the spark airflow ( well I try not to anyway ).

GMPX can verify this but even if you are at 0.8 g/cyl and tyhe boost timing tables are set for 4 deg at this point it will sum all the timing amounts THEN take 4 deg off this figure for the final figure.

I try and map all the timing table slowly bringing the boost up on each consecutive dyno run till the spark table airflow is maxed out THEN use the boost timing tables for any extra correction I need to get the final spark in the right place.

[GMPX]

Delco you are correct, it appears to be my mission today to confuse the s*** out of everyone.

I better describe it's operation like this.

Once MAP goes above 105kPa then this table can be used to reduce timing beyond what the main spark tables define, regardless of the g/cyl.
Depending on how you have scaled the injectors and the VE table numbers you may not actually hit 1.2g/cyl (the end of the main spark tables) until say 170kPa, in which case you would still have full control over the timing using the main tables, if however you were reading 1.2g/cyl at 140kPa but planned on running boost all the way up to 230kPa then you have 'some' control over the timing even though the main tables are at the limit.

O.K, I've re-read that and I think that is as clear as I can be

Cheers,
Ross