EvilAreXeven

iTrader: (20)

Sorry to pose you all with yet another problem. My car recently made 326 whp after being tuned. For boost, we relied on two gauges: A prosport (verified inaccurate) and a VDO mech(read dead accurate for years).

The Prosport gauge read ~ 15 psi
The VDO gauge read ~13 psi

Given my mods, 13 psi and 326 lbs on sequential twins is presumably the most accurate, we also weren't able to get the car to hold anymore boost than 13 psi, per the VDO gauge.

I just noticed today that my PFC commander is reading 1.6 Kg/Cm2, which translates to ~22 psi.

Relevant mods:
Gm 3 bar map
99 spec twins sequential
m2 CAI
SMIC/greddy elbow/BOV
hks twinpower/ngk 9's
550/1300 injectors
supra pump
3 inch turbo-back
Water injection @ 315cc

Initially, I figured the PFC must be the most accurate. But 22 psi on the twins doesn't seem possible, and 326 whp doesn't seem like an accurate translation of 22 psi.

My thoughts were that the map was reading 22 psi, and somewhere between there and my gauge,I was losing 9psi. But that doesn't explain the 326 whp?

I'm stumped.....

What could be the cause of this disparity?

arghx

iTrader: (3)

We need to know the scale and offset setting for your MAP sensor. A MAP sensor works like this:



A MAP sensor calibration is a linear function of voltage vs pressure, where the scale = slope of the line and the offset is the Y intercept. FYI, a MAF sensor calibration is usually a logarithmic/exponential function so that there is increased resolution under lower loads. The MAF sensor based PFC's (SR20, RB, 4G63, EJ20, etc) also have a calibration screen and different options for MAF sensors.

Anyway, under settings --> PIM volt, which option is selected? PIM stands for "Pressure Intake Manifold" which is engineering notation used in Denso-based fuel injection systems. The Commander won't show you the calibration (scale and offset) but normally "Option 2" would be selected if the GM MAP sensor is installed. And then in the Datalogit software it needs to have been configured properly. Here is the Commander screen:



Here is how a system properly set for a GM MAP sensor would look in the Datalogit Software:



There are a couple calibration settings that people have been using for the GM MAP sensor, but almost all use an offset of 0. The calibration itself does not directly compensate for changes in altitude. A Power FC does not have an on-board barometric pressure sensor like the factory ECU and most other OEM speed density systems.

EvilAreXeven

iTrader: (20)

I seriously feel like every one of your posts should be a sticky. I don't have a dataloggit to see those values, however, off the top of my head from poking around in the commander yesterday, "option 4" was selected. I could definitely double check, though.

DaleClark

iTrader: (55)

First off, there's absolutely no good reason to run the GM 3 bar MAP with the twins. The stock MAP sensor will read to 17psi, and if you exceed that on the twins you're blowing them up.

The calibration of the MAP sensor is what is wrong.

Personally I'd go back to stock unless you're planning on going single turbo and big boost in the very near future. Stock MAP sensor works great, lasts forever, and is dirt cheap to buy one used if necessary.

Dale

EvilAreXeven

iTrader: (20)

Ok, assuming I'd like to switch back to my OEM map sensor, would this be as simple as switching back to the "NORMAL" setting for PIM voltages in the PFC commander?

ttmott

iTrader: (1)

It seems to me that whom ever set it up had to tailor the fuel and spark maps to be compatible with Option 4, whatevery option 4 is, otherwise it would run very rich in the higher PIM areas; at least based upon your comparative measurements. Without having access to a better data input and logging device (Datalogit) I think you would be guessing....

arghx

iTrader: (3)

I'm not getting the warm and fuzzies about your tuner