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Thread: Usage of MAP and MAF on the '99 G20, why?

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Posts: 1-4 of 4
2013-12-04 22:48:59
#1
Usage of MAP and MAF on the '99 G20, why?
It is uncommon for engine management to use both MAF and MAP sensing. Anyone know why the "99 G20 does?

My G's engine management is still completely stock and well maintained. It's the smoothest running sr I've had so far and I wonder if the extra control systems are there for that purpose.
2013-12-04 23:43:56
#2
You got a special car, maybe one of a kind, because every other 99 G20 and factory Nissan fuel injected cars are maf based.

Do you have a picture of the so called MAP sensor?
2013-12-04 23:52:12
#3
Originally Posted by 5speed
You got a special car, maybe one of a kind, because every other 99 G20 and factory Nissan fuel injected cars are maf based.

Do you have a picture of the so called MAP sensor?


They use the MAF as the primary, more accurate at lower power and engine speed. The absolute pressure sensor (MAP) and intake temp sensor are part of the MAP system, most likely used for EGR to sense positive pressure while it is working.

Seems so smooth, wondered if MAP was used for anything else other than testing EGR.
2013-12-13 17:23:05
#4
It is not "directly" used to manipulate the ecu fuel map, and is referred to as an ABSOLUTE PRESSURE SENSOR in the FSM.

http://www.nicoclub.com/FSM/G20/1999_G20/1999_G20/ec.pdf (go to ec125).

The MAP/absolute pressure sensor detects variance between atmospheric pressure and intake manifold pressure to ensure the emissions system for the EVAP/EGR is ready to be turned on/off. That's the purpose it is serving on these cars with a stock ECU.

Now, OBD G20/Sentra SR20 ECUs utilizing a daughterboard and with options for an input signal can utilize these senors with some pretty simple wiring to detect the exact point in time when boost hits. It will not detect how "much" boost because these stock sensors only detect vacuum, but give a tuner a perfect point in time and on their tune when to start adding more fuel for efficiency. No extra wiring needed for someone who knows what they're doing.

But to answer your question, it is not using a MAP/Absolute Pressure sensor to control fuel delivery.
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