PowerFC values for GM 3-Bar MAP? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

productions14 · 08-25-2007, 03:05 PM

My car's at a tuner right now and he's having trouble getting the PFC to read correctly with the GM 3-Bar MAP sensor I've been using. On the previous tune it was running 18-20psi on a GT28R and now I have an SC61 (basically turbo setup is all that has changed) and it breaks up after 14 psi (sort of acting like a 2-Bar MAP). If anybody knows an easy fix for this, as the car has had (apparently) 37 dyno pulls (which tells me I run good oil and did a good job building the motor ha), and the tuner has thus far been unable to get it to read correctly above 14psi. He said its the MAP Sensor 'scaling.'

Anybody?

sean350z · 08-26-2007, 12:37 PM

The larger the bar sensor the less resolution on your maps you are going to get. I would stick with a smaller resolution unless you want to run 30+psi. The 2 bar should be fine for your application and shouldn't break up at 1 bar unless that wasn't scaled right (ie - engine hitting 1 bar and pfc thinking it's a 2 bar). Just a thought...

Scaling example that you need to perform
(taken from datalogit usergroup) -

"This is the scale and offset I ended up with. Scale = 41900
Offset = 200 These are the actual readout results with this scale/offset set
up on my car. * 28psi = 4.85vlts = 1.97kgcm *0 psi =1.7vlts = 0 kgcm *16inHG
= 406mmHG and 23inHG = 584mmHG The psi and inHG readouts are from
vacum/boost gauge and the kgcm and mmHG readout is from the hand commander.
Looks pretty close to perfect to me now with everything matching up as it
should"

Like anything else you are probably going to need to tweak the offset for your specific application.

I run L-jetro but this is from the datalogit group and should be correct.

productions14 · 08-27-2007, 09:59 AM

Thanks for the input, I'm aware at 13psi I would be within the range for a 2-Bar sensor, but I was intending on running 20+ psi. What I'm confused about is why the values would need to be changed, as it was reading correctly on the GT28R up to 22psi.

So far the tuner has gone ahead (kinda without my 'ok') and installed an A'pexi 3bar sensor... hopefully this will fix the problem and then I guess I'll be selling the GM 3-Bar.

I guess the question I want to ask now is - Has anybody had similar trouble using a GM 3-Bar sensor with FC Datalogit?

08-25-2007, 03:05 PM	#1
productions14 Join Date: Sep 2005 Location: Arlington Posts: 9 Trader Rating: (0) Feedback Score: 0 reviews	PowerFC values for GM 3-Bar MAP? My car's at a tuner right now and he's having trouble getting the PFC to read correctly with the GM 3-Bar MAP sensor I've been using. On the previous tune it was running 18-20psi on a GT28R and now I have an SC61 (basically turbo setup is all that has changed) and it breaks up after 14 psi (sort of acting like a 2-Bar MAP). If anybody knows an easy fix for this, as the car has had (apparently) 37 dyno pulls (which tells me I run good oil and did a good job building the motor ha), and the tuner has thus far been unable to get it to read correctly above 14psi. He said its the MAP Sensor 'scaling.' Anybody?

08-26-2007, 12:37 PM	#2
sean350z Zilvia Addict Join Date: Nov 2005 Location: Downingtown, PA Posts: 890 Trader Rating: (5) Rides Gallery: sean350z Feedback Score: 5 reviews	The larger the bar sensor the less resolution on your maps you are going to get. I would stick with a smaller resolution unless you want to run 30+psi. The 2 bar should be fine for your application and shouldn't break up at 1 bar unless that wasn't scaled right (ie - engine hitting 1 bar and pfc thinking it's a 2 bar). Just a thought... Scaling example that you need to perform (taken from datalogit usergroup) - "This is the scale and offset I ended up with. Scale = 41900 Offset = 200 These are the actual readout results with this scale/offset set up on my car. * 28psi = 4.85vlts = 1.97kgcm 0 psi =1.7vlts = 0 kgcm 16inHG = 406mmHG and 23inHG = 584mmHG The psi and inHG readouts are from vacum/boost gauge and the kgcm and mmHG readout is from the hand commander. Looks pretty close to perfect to me now with everything matching up as it should" Like anything else you are probably going to need to tweak the offset for your specific application. I run L-jetro but this is from the datalogit group and should be correct. __________________

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08-27-2007, 09:59 AM	#3
productions14 Join Date: Sep 2005 Location: Arlington Posts: 9 Trader Rating: (0) Feedback Score: 0 reviews	Thanks for the input, I'm aware at 13psi I would be within the range for a 2-Bar sensor, but I was intending on running 20+ psi. What I'm confused about is why the values would need to be changed, as it was reading correctly on the GT28R up to 22psi. So far the tuner has gone ahead (kinda without my 'ok') and installed an A'pexi 3bar sensor... hopefully this will fix the problem and then I guess I'll be selling the GM 3-Bar. I guess the question I want to ask now is - Has anybody had similar trouble using a GM 3-Bar sensor with FC Datalogit?