so i guess the big question is: Is it worth the insane price HPtuners charges for the 2bar upgrade?

 

To convert to 2bar, you need a GM 2 bar MAP sensor. The one I used was GM part 12580698 (AC Delco #213-1631). It snaps right in in place of the stock 1 bar map on the truck manifold. What the 2bar tune lets you do is keep your vacuum settings and your boost settings. You can do it in a standard 1 bar tune, just by adjusting the MAP calibration (and from then on you double whatever map value you see -- e.g. 20kpa == 40kpa in reality). The interpolation built in to the GM OS takes care of potential resolution problems. You can do the same trick as above (i.e. calibrate the MAP to get a more lopsided postive vs negative pressure) to get more boost into the MAP.

Theoretically you can do the same thing with a 3bar map but the conversion gets messier and I can't speak to how well the interpolation works at that resolution.

What you get from this is more columns to control fueling at boost. With the 1 bar MAP in stock configuration, you are mostly running out of 1 or 2 columns (or rows I guess) in each table for all your boost -- the exact opposite of the problem I talked about above with zeroing out the vacuum. That means you're running richer than necessary (since you have to make one column rich enough for max boost) and sacrificing power -- although the 'scarifice' is minor compared to the power you get from the boost itself. Basically, you add the ability to fine tune for different boost levels.

I can't answer about the HPT 2bar tune -- it seemed pretty expensive to me, especially when I added in the $150 for the EIO cable and another license I needed, so I sold my HPT and bought EFI Live Commerical -- which will let me run dual spark tables, valet switch, etc., and has lifetime upgrades.


Okay, here's the translation

I was wrong I thought the MAP offset would let us slide the readable range around, but the GM MAP is mechanically limited to 110kpa max pressure, so while you slide the bottom of the scale up, you don't get to read any significant boost.


info:
1 bar = 100 kpa = 14.5 psi *total pressure*
2 bar = 200 kpa = 29 psi *total pressure*
3 bar = 300 kpa = 43.5 psi *total pressure*

sensor range
1 bar 0 bar - 1 bar **0 psi boost, -14.5 psi vacuum**
2 bar 0 bar - 2 bar **14.5 psi boost, -14.5psi vacuum**

 

Thanks, know I understand appreciate the lesson!

 

A 2BAR map will show about 7 1/2lbs of boost max,that's 7lbs normal atmosphric pressure plus 7 1/2lbs of boost to equal 2BAR or 14.7lbs atmosphric pressure.I do use 2BAR tuning on my truck.

 

Only if you're giving *more than* 14.5psi to vacuum ( scale: -14.5 .. 14.5 ).

How was the MAP scale calibrated? EFI or HPT? What kpa (or psi) does your map read at idle?

 

I show about 35kpa at idle 105kpa is zero vacuum and the 2bar map maxes at 210kpa. The tuning is recalibrated with HPT.

 

Ah -- I'm using EFI, so I'm not sure if you can shift yours, but theoretically you should be able to -- it depends on whether HPT exposes the MAP offset PID or not. This pid is added to the MAP voltage conversion to get you the "MAP value" the PCM uses. There is also a MAP scale PID which converts the MAP sensor voltage into kpa -- this is the one you use to presto chango convert the GM 2 bar map into a GM 1 bar MAP inside the PCM.

In my case, the PCM still thinks I have a 1bar MAP -- it sees 0 kpa to 105 kpa, with the actual kpa = read kpa * 2. With a 1 bar MAP, there is a +10 kpa offset to the MAP signal (and that's currently what my 'drive to work tune' uses). I've played around with shifting this down to -20 kpa (which means 50kpa in the old version would be 20kpa in the new -- 50 - 10 - 20) and as long as you adjust all the MAP dependent pids, it works great -- shifts the whole scale towards 0.

Ideally, I need to do some more playing around, recording in Hg. Then I can take the lowest Hg reading and make that 0. The really frustrating part is the silly scanners... One I have shows MAP as negative psi, one shows positive only (kpa or in Hg), one shows -psi to +psi

Note that the available range for this PID is -105 to 105 kpa / -14.5 - +14.5 psi, which means you could do all kinds of mischief...

 

damn, it's going well over my head now......but I'm trying

 

Sanity check...

Say the Baro drops from 80kpa to 75kpa. What's going to happen to the vacuum? Is it a 1:1 (ie vacuum will also drop 5kpa?)

Whitt do you know if baro learning is disabled in the HPT version?

 

I don't think the baro is diasbled.My readings up to 105kpa are exactly the same as with a 1bar MAP so the baro has to be compensating for changes in pressure.I am running speed density tuning with a 90mm throttlebody so both the MAP and Baro readings are more important without a MAF.