2 bar E38 issues

[XLR8NSS]

Ok, I recently installed a magnacharger on my '07 GMC Sierra. I installed a 2 bar MAP sensor and properly scaled it in the computer. I also used the 2 bar Virtual VE(VVE) to update the coefficients. The MAF was also left installed.

The issue I am seeing with this setup is that the truck will not go over .8 g/cyl until 4000 rpm. It starts out lean13:1 and gets leaner14:1 as rpms increase until 4000 rpm also. This is all at WOT. Once it passes the 4000 rpm mark the g/cyl jump to 1.10 and the AFR goes down to 11.5 or so. The jump to 1.10 g/cyl is very obvious. I am not sure what happens at 4000 rpm but, the "high speed mode rpm"(B8024) is set to 4000 rpm so I have a feeling that has something to do with it. PE was set to .80 and 40% throttle. I also tried adjusting the VVE table with no effect.

I have went back to the stock 1 bar/MAF setup and am using PE for fueling over 40% TPS. The .8 g/cyl limit is not present with this setup. I can go WOT from a stop and almost instantly be over 1.00 g/cyl as boost rises.

Anyone have any ideas what is up with the 2 bar setup?

Here is the stock .tun file from the truck.

[swingtan]

First observation is that 4,000 RPM is the default "High Speed Mode" setting for air flow measurements. I believe that this is where the MAF is used solely for air flow measurements. Below this RPM, the MAF is used in conjunction with the VVE table to determine the air flow. Do you have any log files showing problem?

Simon

[XLR8NSS]

The attatched log file shows a few different WOT blast where this happens. I know the fuel trims are wacked out but, am almost positive that it's a MAF placement/orientation issue. The MAF was located very close to a bend in the blower intake tube. I relocated it temporarily inline with the TB and it seems to work much better. Anyone else ran into these MAFs being sensitive to placement?

Anyway, the log file below has a couple good instances of my described issue.

One quick question. Do you have to do a FULL flash of the OS and Cal or just a Cal flash when you use the VVET to update the coefficients. I don't remember reading that in the instructions.

Also, a couple of observations you might notice. INJPDELTA_DMA would not read below 400 kPa and E38.AFRATIO_DMA reads 0 all the time. Could it be a crazy OS causing these issues?

Thanks

[GMPX]

Cal flash only to update the VVE.

Can you please list a couple of frame numbers in that log where your problem shows.

Cheers,
Ross

[dc_justin]

This is very similar issue as trying to run MAF with a COS3 2 bar tune. Airmass calcs are limited to the 105kPa column when in boost, ignoring both the MAF and boost VE at that point til MAF is used exclusively.

[XLR8NSS]

Hey Ross

Sorry not to list some frames, I am used to looking at my own files and know what to look for. :D Below are some frames range that have WOT blast with the problem. I have AFR logged over the serial connection.

3944-3975

4262-4318

11637-11682

19375-19417

Thanks

[XLR8NSS]

3375-3440 has a pretty good shot too. That is from a stop rolling into it a bit then going WOT.

[GMPX]

What you could do is this.

Put the 2bar MAP back on, rescale to suit.
Force the MAF to fail (whilst leaving it in place) by setting C0301 to 1500 Hz and C0303 to 10.
Fix the Virtual VE table for 2bar, because in stock form it's horrid. Also, you will need to make some changes to fix a bug in GM's VE lookup code see this thread -
http://forum.efilive.com/showthread.php?t=8888

Now you will be in SD mode you should be able to tune the VVE table as requried without MAF influence.
If the problem goes away then the problem lies with running the MAF, maybe it's where it's located? I don't know, majority of the shops here is Aus doing 2bar E38 tuning are doing it Mafless.

Also, before you get too far reshaping the VVE tables, consider bumping up the MAP Boundary 5 column in B8021 to maybe 130 KPa, it will help you shape the table in boost. I say do this before you make too many changes to the VVE table as it will alter quite a number of things once you make the change.

Cheers,
Ross

[XLR8NSS]

Ross I will give that a shot but, probably won't be until this weekend. I'll report back

Thanks

[MN C5]

Let us know what you find out... My motor is coming out tomorrow...

[XLR8NSS]

It's supposed to rain tomorrow pretty hard most of the day so it'll probably be Sunday before I try this. I'll let you know D

[XLR8NSS]

Truck won't even stay started without the MAF hooked up. Here is a log where I tried starting it a few times. It runs for a second or two and then dies.

[MN C5]

We switched to IMac's at home hopefully 7.54 will work well with windows running as boot camp. I've very interested to see whats going on..

[Highlander]

Do you have the part number for the map sensor 2 bar?

Than ks

[arubenstein]

Ok, I recently installed a magnacharger on my '07 GMC Sierra. I installed a 2 bar MAP sensor and properly scaled it in the computer. I also used the 2 bar Virtual VE(VVE) to update the coefficients. The MAF was also left installed.

Just curious --- I recently put a MagnaCharger in a 08 Sub with a L76. Running a 1 bar MAP and the Magna tune, things are running pretty well (scanning reveals over 500 ft-lbs of torque).

Any reason why you want to run the 2 bar MAP? Do you think the Magna tune is no good?

Also, did you end up putting in the MagnaVolt?

[XLR8NSS]

Nah, I just wanted to use the 2 bar map sensor as a "boost gauge". I did not realize that 2 bar and MAF don't get along for some reason.

The Magnacharger 1 bar tune is working just fine now.

I have the magnavolt sitting here but, have not installed it. It'll be installed this weekend probably because I want to get some tuning time in before a track meet on the 16th.

[arubenstein]

I have beed doing dome research on the need for the magnavolt.

As you may be aware, EFILive scanning has the ability to tell you what the Fuel Rail Pressure is. I have been logging that vs. grams/cylinder, and I have found that even under the heaviest loads with PE kicking in, fuel pressure is A-OK and the O2 sensors indicate that things are running rich.

There is further thoery that even if you use the MagnaVolt on vehicles with the FSCM, the FCSM regulates the voltage the fuel pump anyway.

YMMV, but I don't think I will be putting mine in.

Which charger did you get? I had a fitment problem in my 08, so I ended up changing to a more recent version.

I can post some pics if interested.

[Highlander]

why is the 2 bar map not compatible with maf?

[Highlander]

Can anyone confirm 213-796 as a 2bar map sensor?

[XLR8NSS]

why is the 2 bar map not compatible with maf?

DC_Justin explained what was happening with my setup in post #5.

[Redline Motorsports]

Hey guys,

Any further updates on this issue???

Howard

[Redline Motorsports]

Bump for an update!

[hymey]

The MAF should work fine with the 2 bar sensor, once the 2 bar vve is correct plug the maf back in and scale it, My guess is u had the bug issue or simply needs to be calibrated correctly before the maf goes back on. Also please try setting high speed airflow to 300rpm. This will use the maf solely and u can check the tune to see how it looks MAF wise.

If you want to use a MAF without upgrading the 1 bar sensor you will need to lower the high speed airflow settings from 4000 down to around 2000rpm so that the MAF is taking over before the engine hits full boost,other wise you will be over 105kpa. The MAF predominately does all the work before hand anyway which is why many guys set low speed air below 500 rpm and just forget about the vve.

If its your own vehicle I would spend the extra time and go full SD as the drivability is a little smoother.

cheers