What happens when you go into boost?

[hpcubed]

I know you go real fast :wink: But really, if you have some type of forced induction, what does the computer use for a spark table at that stage? The spark table stops at 105kPa and I don't see any other provisions such as spark v. rpm at WOT as in the PE table. So does the computer send the same timing number that it was using for 105kPa at a given RPM for anything above 105kPa? Or do you have to revert to other methods to scale everything down? In other words: How the h*** do you tune for force induction without that two bar map support :D

[Delco]

2 bar map support does not affect the spark table in any operating system.

Spark is calculated from dynamic airflow not map values

[hpcubed]

2 bar map support does not affect the spark table in any operating system.

Spark is calculated from dynamic airflow not map values

Woops, your right, got my y axis confused. :oops: Thanks. But let's say that you do not run a maf and run speed density. The VE table stops at 105kpa. Where would the computer get its values at that point. On the other hand, if you did run a maf and it maxes under boost, where do the values come from?

[Delco]

2 bar map support does not affect the spark table in any operating system.

Spark is calculated from dynamic airflow not map values

Woops, your right, got my y axis confused. :oops: Thanks. But let's say that you do not run a maf and run speed density. The VE table stops at 105kpa. Where would the computer get its values at that point. On the other hand, if you did run a maf and it maxes under boost, where do the values come from?

Thats where a proffesional tuner comes in that recalibrates and modifies the system to run a 2 bar map sensor.

The ametuer can do it as well - just be prepared to have the possibility of wearing out or breaking the first few engines getting a base tune setup.
You would experience the same problem if you started from scratch with the stock GM code and didnt have any values in all the tables , that sort of data takes months to years to get right on a dyno.

As a experiment , go into flashscan and zero all the spark tables , zero the maf and IFR tables as well as the VE table. At this point you still have a big advantage in you know roughly what shape and order of magnitude all those tables should be. Now start tuning the stock vehicle without doing any copy and pasting from from another calibration.
Thats sort of what its like but you are only doing 4 tables - now go and do all the other 2000+ engine calibration variables and bring them into line - not a easy or quick job.

The first part of the experiment is exactly what happens when you purchase a code modified calibration ( from any company ) to run 2 or 3 bar.

If you are going to keep the maf then things become a lot easier as 98% of the work is already done for you as the MAf does not look at VE

[deezel]

I think, when a MAF maxes out, the PCM goes to a dynamic airflow calculation based on the maxed MAF values and the VE table.... ?

The open loop PE vs RPM table can also be used to add more fuel when the MAF maxes out.

[hpcubed]

I think, when a MAF maxes out, the PCM goes to a dynamic airflow calculation based on the maxed MAF values and the VE table.... ?

The open loop PE vs RPM table can also be used to add more fuel when the MAF maxes out.

Yes I do not see the fueling as a problem. I just don't see how to compensate for the spark if the maf maxes out.

[Ira]

Seems to me if you replace the stock MAP sensor with a 2 bar sensor you essentially need to take all of the tables that refer to MAP and delete every other row and copy the last row into the now empty half of the table. That should make it close to working with the new sensor. I know that's not quite exactly correct, but it ought to be a reasonable place to start. I'd surely do that test before the blower was installed as small mistakes at that point are much less damaging.

Or am I missing something really big?

Ira

[GMPX]

If you put a 2bar sensor on, the PCM will assume at key on (100kPa) that it is in fact about 35 - 40 kPa. The easiest thing to do is adjust the MAP scaler {C6301} to make the value 50kPa at key on (Off the top of my head the number is about 130, up from 94 for a 1bar).
Then you just have to think in your head to double the actual MAP values.
So you would see 70kPa in the scan tool, but in reality it would be 140kPa.
You cannot adjust the scaler so the 2bar reads 100kPa because as soon as you go into boost the PCM has hardcoded limiters to 105kPa.

You also need to disable the Barometric updates {B0301} or the PCM will adjust the fueling thinking atmosphere is 50kPa!!.

NOTE: This works on MAF Less setups, not sure about a MAF car.

Cheers,
Ross

[hpcubed]

Excellent information - thanks . I have a thought, when the maf maxes out, maybe the computer reverts to engine protection mode? There is a spark vs rpm table for engine protection mode.

[hpcubed]

If you put a 2bar sensor on, the PCM will assume at key on (100kPa) that it is in fact about 35 - 40 kPa. The easiest thing to do is adjust the MAP scaler {C6301} to make the value 50kPa at key on (Off the top of my head the number is about 130, up from 94 for a 1bar).
Then you just have to think in your head to double the actual MAP values.
So you would see 70kPa in the scan tool, but in reality it would be 140kPa.
You cannot adjust the scaler so the 2bar reads 100kPa because as soon as you go into boost the PCM has hardcoded limiters to 105kPa.

You also need to disable the Barometric updates {B0301} or the PCM will adjust the fueling thinking atmosphere is 50kPa!!.

NOTE: This works on MAF Less setups, not sure about a MAF car.



Cheers,
Ross

Ross - Are these the only things that we have to change - every table with map as an axis, map scalar - anything else?

I think it is a good idea as suggested by Ira to tune the car with the two bar map sensor before adding the turbos. I think I will install the 60 lb injectors as well, get everything running right NA and then add the turbos and finish the tuning.

[GMPX]

Excellent information - thanks . I have a thought, when the maf maxes out, maybe the computer reverts to engine protection mode? There is a spark vs rpm table for engine protection mode.

Engine protection is an overtemp handler.

Cheers,
Ross

[GMPX]

Ross - Are these the only things that we have to change - every table with map as an axis, map scalar - anything else?


Arrgghhh, just spent 25mins typing a reply, I hit send and page not found error :x

I might have to start a 2bar thread to answer all the questions.

Cheers,
Ross

[hpcubed]

Ross - Are these the only things that we have to change - every table with map as an axis, map scalar - anything else?


Arrgghhh, just spent 25mins typing a reply, I hit send and page not found error :x

I might have to start a 2bar thread to answer all the questions.

Cheers,
Ross

Please start this thread. I would greatly appreciate it and I think others would as well.

Thanks

[joecar]

Arrgghhh, just spent 25mins typing a reply, I hit send and page not found error
Aren't computers fun...

[Blacky]

Ross - Are these the only things that we have to change - every table with map as an axis, map scalar - anything else?


Arrgghhh, just spent 25mins typing a reply, I hit send and page not found error :x

I might have to start a 2bar thread to answer all the questions.

Cheers,
Ross

When filling out web pages with more than a few lines of text, I always do a select all and then a Ctrl+C, just so I have a copy of the text in case things go wrong. Been burnt too many times.
If I'm really paranoid (and my computer keeps rebooting for no apparent reason - you know what I mean Ross) then I also paste it into notepad and save it to disk - just in case.

Hehe! just did a select all and Ctrl+C before posting...

Paul

[hpcubed]

Ok, when the maf maxes out, it is still outputting the max freq. so the spark will be determined by that max value. Anyone disagree?

If going with just a speed density tune and rescaling all the tables by 1/2 then initially we need to know how VE is related to boost, ie. for 1 lb of boost how much does the volumetric efficiency increase per given RPM. I wonder if there are any formulas out there?

I assume that the PE modifier will modify the A/F using the VE table for air calculation when in speed density mode?

If this is the case then you have a bit of a dangerous situation for initial wot tuning. I guess you could set the PE really rich to start until you get the VE close.

So the VE table above atmospheric is the place we would need a "base tune" to start with which I hear will be released soon.

[Delco]

Ok, when the maf maxes out, it is still outputting the max freq. so the spark will be determined by that max value. Anyone disagree?

If going with just a speed density tune and rescaling all the tables by 1/2 then initially we need to know how VE is related to boost, ie. for 1 lb of boost how much does the volumetric efficiency increase per given RPM. I wonder if there are any formulas out there?

I assume that the PE modifier will modify the A/F using the VE table for air calculation when in speed density mode?

If this is the case then you have a bit of a dangerous situation for initial wot tuning. I guess you could set the PE really rich to start until you start to get the VE close.

Other way around , set the PE to what you want to achieve , run the VE rich and bring it back to it matches the desired AFR's.

Boost is easy , 55kpa is now what used to be 100kpa , 100kpa is now 200kpa or 14psi of boost , its very easy to do as you are watching the scanner and it shows you where in the VE table you are accessing 8) .

Anytime you run a new combo it is a dangerous tuning situation , the only time its not is when doing a stocky as GM have done most of the work for you. get a agressive 402 with a big cam and its a guessing game getting a baseline done - thats where experience can save your butt

[hpcubed]

edit

[hpcubed]

Other way around , set the PE to what you want to achieve , run the VE rich and bring it back to it matches the desired AFR's.

Boost is easy , 55kpa is now what used to be 100kpa , 100kpa is now 200kpa or 14psi of boost , its very easy to do as you are watching the scanner and it shows you where in the VE table you are accessing 8) .

Anytime you run a new combo it is a dangerous tuning situation , the only time its not is when doing a stocky as GM have done most of the work for you. get a agressive 402 with a big cam and its a guessing game getting a baseline done - thats where experience can save your butt


Good points. Needless to say, definitely have to have a wideband on board. It would be nice to have access to a forced induction ve table before I start. It would also be nice to have a list of all tables that reference map so that I don't miss anything.