MAP sensor?

[VIN CODE 6]

So I'm poking around under the hood of my 98' LGT and notice what looks to be a map sensor on the right side strut tower. I do a little research and confirm this. So my question is why is there a MAF sensor and a MAP sensor, I thought normally you had 1 or the other? My other question is the factory manual calls it a boost sensor so can this be used for a mild (5-6psi) turbo application and the ECU might hopefully compinsate?

[VIN CODE 6]

So I did a little digging and found an article on The End Wrench. Apparently this thing is a pressure sensor for the evap system however it seems to function basically the same as a MAP sensor.

"The pressure sensor functions to monitor manifold and
atmospheric pressure. PSSS position determines the pressure
source. Changes in pressure (positive or negative) produce
a changing reference voltage signal. Reference voltage
signal changes are used by the ECM to determine optimum
ignition timing and injection duration."

The last sentence is what sparks my interest. Could a mild 5-6psi sensed through this sensor tell the ECU to adjust accordingly. I do realize that a piggback or standalone is the best way to go but curiousity has the best of me right now. The Raptor kit puts out 5.2 psi in basic form and the kits are all for MAP based cars right now. I'm wondering if the combination of a MAF sensor and this pressure sensor would be enough to keep the engine from blowing itself apart. Any Scooby guru's out there wanna shoot this down? Also I have no idea if the MAP based cars use this sensor or not.

[rougeben83]

MAP and MAF are related to how the ECU measures the air coming into the engine. You can have other pressure sensors on your engine, but they don't relate specifically to that purpose.

Technically, you can run any F/I kit on any engine as long as you have the engine management to adjust the fuel mix tables. You can put the raptor kit on your car, but you need an engine management that can use the MAF system (emanage piggyback will work for both MAF and MAP cars).

[VIN CODE 6]

I realize all this but just bare with me, consider this more of a hypothetical type question. I know that you can't have a reliable turbo setup without proper engine management. What I'm pondering is sense this pressure sensor is triggered to see manifold pressure every 30 min or so, not all the time, if you put a tee in so that the sensor would measure manifold pressure all the time and you ran a very small amount of boost could the stock computer have enough range to compensate for it? The sensor range is 0-5V and measures negative and positive pressure changes so "theoretically" if you could keep the values in this range the ECU would adjust timing and fuel accordingly. I know this is not ideal but after figuring out what this thing does and what it affects the light bulb went off. Maybe I'm just looking for someone to say they tried it and no way in Hell does this work! Either way it makes an interesting discussion. Maybe if I decide on the Raptor I will give it a try!

[jey]

I am running a light turbo setup on my stock ECU. But I also have an EJ257 shortblock to lower the compression ratio and an S-AFC to help the fuel delivery. So yes, there is enough range to use those stock MAF/MAP sensors and ECU in certain situations - I've been doing it for 40k miles now. I would not dare try it in an unmodified NA motor though - I don't think the ECU has enough range in ignition control to do it safely in a higher compression situation.

I am also convinced that the MAP sensor is not designed for boost. I experienced a MAP sensor AND purge control solenoid valve failure - which I have never heard happen before to a "normal" car :lol:

[VIN CODE 6]

Very interesting, how much boost are you running?

[rougeben83]

yup from my understanding the MAP based systems are easier to setup, but they don't respond as quickly to changes in air flow to compensate with fuel. That is why WRX's and STi's and a lot of modern F/I cars use a MAF based fuel-control system, even though MAF tends to be more fragile and with less room for error in tuning.

[jey]

Very interesting, how much boost are you running?

Wastegate pressure on the TD04.