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 :D


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 :shock:

Cheers,
Ross

[Earl H]

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
Should all the values in the coolant spark multiplier have a value of 1 or just those at the tail end of the table (i.e. 4000rpm)?

[Delco]

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
Should all the values in the coolant spark multiplier have a value of 1 or just those at the tail end of the table (i.e. 4000rpm)?

Depends on how you want to setup your spark retarders , there is a 1000 ways to skin the same cat , even the factory cals do it in different ways for different models.

There is no 100% CORRECT way to go about all the adders etc.

What you need to remember when I used to work in R&D for engine control and tuning if I had a problem where I needed a extra table to do THIS in the event of THAT we just asked the programmers to add some extra code routines to cover that eventuallity , later down the track that table might become obsolete and be factored out but it is still in the cal if required.

Same thing here , we have asked GMPX to add extra tables to cover a issue but it doesnt mean it has to be used just that if required it can be used to get better control

[Earl H]

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
Should all the values in the coolant spark multiplier have a value of 1 or just those at the tail end of the table (i.e. 4000rpm)?

Depends on how you want to setup your spark retarders , there is a 1000 ways to skin the same cat , even the factory cals do it in different ways for different models.

There is no 100% CORRECT way to go about all the adders etc.

What you need to remember when I used to work in R&D for engine control and tuning if I had a problem where I needed a extra table to do THIS in the event of THAT we just asked the programmers to add some extra code routines to cover that eventuallity , later down the track that table might become obsolete and be factored out but it is still in the cal if required.

Same thing here , we have asked GMPX to add extra tables to cover a issue but it doesnt mean it has to be used just that if required it can be used to get better control

So your example is a real one. If I set the final column of the coolant spark table table to 1 and set the boot spark table to 5, it will retard the values by 5*1 for the asociated cell?

[GMPX]

That's right Earl, always think of multipliers as exactly what the name implies and nothing more.
You multiply a value by 1 then you end up with the same value, you multiply it by 0.5, you get half, multiply it by zero, you get zero.
How the GM engineers designed them is so certain tables have less impact based on whatever the multiplier is using.
For example if you look at an IAT spark table {B5911}.
Somewhere like 122°F & 0.60g/cyl I see a value of -3.0
So, then you need to look at the IAT multiplier table {B5943}, actually there is two, but we will just look at the impact of one for now.
At 800 RPM that table has a value of 1.00
So -3.0 x 1.00 = -3.0
At 4000 RPM that table has a value of 0.78
So -3.0 x 0.78 = -2.34
At 7200 RPM that table has a value of 0.63
So -3.0 x 0.78 = -1.89

As you can see, using the multiplier you can alter the final value from the main IAT spark table based on the RPM.

Cheers,
Ross

[hquick]

I know really, REALLY old thread.
I'm wondering why the description of A0010 hasn't been changed as per this thread?
As you can all see....I'm searching through 'everything'. :D