Boost with a 1bar map sensor

[franckrem]

Hi I'm really new to the GM stuff (in my shop we mostly do mustang and honda) so please don't fame me I'm a real newbie. I have done a lot of reading but its not all clear.

We started experimenting on a trailblaser ss E67 with a magnacharger on it and I would like to ask some question

How come on a GM there is several tune for blowers application that dosent require a 2bar map sensor?

How can you adjust the VE table If you only half of it?

Is this the Maf that do the work at wot ?

Is there a way to use only the maf and no map like on a ford ?

Why dose the maf is separate between low and hi? How do the computer know want to change?

[ScarabEpic22]

Use the 2 Bar VVE instead of the 1 Bar VVE.

Dont know about the MAF, usually with FI a lot of people remove it and go SD. You can run OL-MAF, but you probably will not be able to get it as driveable as you'd like.

Using a 2Bar MAP is a good idea, I would recommend one for your TBSS.

Read the VVE Tutorial included with the EFILive download (in Tune or Scan click Help->Tutorials then click Virtual VE Tutorial.pdf.

[franckrem]

But why is it an option to use a 2bar sensor?

How can the computer know if he is in boost if you only have a 1bar sensor on the motor?

[ScarabEpic22]

You are just rescaling the VVE table to have good values past 1Bar, the ECM can do up to 3Bar from the factory. The ECM will know its in boost once it sees airflow values over 14.7psi aka 1Bar, no way a regular NA motor can push more than barometric pressure, it would defy physics.

It is an option in the E67 to use a 2 Bar sensor because cars like the supercharged Caddy CTS-V use it to control the s/c.

[joecar]

Hi franckrem, welcome to the forum...:cheers:

It may be optional to use a 2 bar or 3 bar sensor... but it is the "right" thing to do.

Each E38/E67 file can have the virtual VE table be configured to be either 1, 2, or 3 bar... you have the whole VVE table as long as you configured the right one and use the matching MAP sensor.

It looks to me like the low and high MAF tables don't overlap, the low table max Hz is the high table min Hz (i.e. the same value)... this is the ECM's Hz threshold between the 2 tables.

I don't know with E38/E67 if the ECM can run MAF-only...?

Like Erik said, the E38/E67 PCM's are very smart.

Did you find the VVE tutorial that Erik mentioned...?

[franckrem]

Yes I found the tables but do I need to tell the computer witch table to use or it will chose it on is own?

[joecar]

There are 4 operating situations:
- IMTV open (no AFM),
- IMTV closed (no AFM),
- IMTV open with AFM;
- IMTV closed with AFM,

In each of those there is:
- one table of VE polynomial coeeficients (the real VE table, but in mathematical form)...
- three virtual VE (VVE) tables (1, 2, 3 bar);

whichever VVE table you manipulate is how the real VE polynomial table gets configured.

If you have no IMTV and no AFM, then the default is the first of the operating situations listed above.

This is my understanding of it.

More info: showthread.php?t=8961 (http://forum.efilive.com/showthread.php?t=8961)

[franckrem]

I dield in the fuel injectors today and it seems not that far off... the bigest problem I have is that the transmision dosent want to cooperate it seems to fall in neutral at 5500 rpm from 1st to 2nd

it was working fine before the blower

do you guys have any clues?

[ScarabEpic22]

Have you pulled the TCM file and have played with shift times and line pressures? Is the trans built? If not, I wouldnt expect it to last more than a month tops with the Maggie on there.

I havent heard of a trans simply dropping into neutral unless there's a physical problem...

[franckrem]

It seems to drop in neutral but as soon let off the throttle it shift in 2nd
almost like its stuck in 1rst...

should I pull the tcm out even if I dont care about the shift point and firmness?

would it help to make it last longer?

[ScarabEpic22]

You really need to tune the TCM, leaving it stock and making lots more power is a recipe for disaster. I havent tuned a blown truck yet, but I imagine you're going to want to raise the line pressures and make sure it doesnt hit the rev limiter before shifting (what it sounds like its doing now).

If the trans isnt fully built (billet input/output shaft, upgraded clutches, shift kit, etc), it will help but its going to need a built trans asap. The 4L70Es the TBSS comes with is worthless in the trucks, they blow up behind bone stock trucks. Add an extra 100hp = very short life span. The trans is the weak spot, 2WD trucks are better off because they can break the rear tires loose with excessive power, AWD trucks (like mine) are pretty much screwed when it comes to this because all the power just keeps it internal to the car. Weak point is the trans, so thats what goes first.

[franckrem]

ok my truck is almost all tune now but I found out that I was not having a transmissin problem... The problem is that when I'm at full throttle the truck is pulling real hard until 4500 to 5500rpm and than stop... the fuel injectors just shut down from 15ms pulse to only 2-3ms and the engine stay at that rpm until I let off the throttle. I disabled the TCS completely and it dosent work ether... It seam like en engine protection of some kind I also upped the MAF Flow vs RPM and vs volt of about 20% and it dident do anything...

I have tried every thing I know I dont know what to do whit this...

any one have an idea?

[MN C5]

I had some trans issues with mine until I went Mafless. Seemed to cure all of my shifting woes.

I also had the TB slamming shut under high boost too, so you may want to check that. I switched to a Corvette TB and haven't had it happen again.

Good luck