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What Are These Boost / Map Sensors For? R34 Gtt

BlackBox

By BlackBox,
in Engines & Forced Induction

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BlackBox Rising Star

BlackBox

Posted
Posted

trying to tidy up some wiring and unused components in my engine bay while its all apart.

got these 4 sensors going directly to the intake manifold on my r34 gtt.

can somebody please explain the function of each?

im assuming there is 1 for boost gauge, 1 for apexi pfc boost controller and 1 for ecu reference, what is the other one?

i am replacing the standard boost gauge so would like to remove the old sensor & plug.

also getting the apexi replaced with haltec platinum pro so will the haltec utilize the wiring ran for the pfc or can i remove/hide that?

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GTSBoy Grand Master

GTSBoy

Posted
Posted

The first one is the ECU's boost sensor, used for calling off the fun when the boost is too high.

The second one could be for just about anything, but not factory.

The third one is not a sensor, it appears to be a solenoid. It is probably the solenoid that regulates the application of vacuum to the charcoal canister.

The fourth one is like the second one - could be anything but wasn't put there by Mr Nissan.

The OEM dash MAP sensor is on the firewall near the brake booster.

Kinks Grand Master

Kinks

Posted
Posted

the r34 uses map VE aswell for some calculations

It does, but the factory MAP sensor is plumbed in pre-TB (and hence pre-manifold). They seem to use some sort of pre-TB-MAP+TPS to calculate transient fuel requirements.

I moved my factory MAP sensor post-TB (now measuring manifold pressure) and the car totally died every time I changed the throttle position. After about 2 seconds it magically came back to normal. So I can say the stock ECU uses AFM for steady state airflow metering and pre-TB-MAP+TPS for transients.

Reason why I moved the MAP sensor was fitting an Adaptronic. Had to swap the stock ECU back in temporarily and it didn't like it! (Probably should have just unplugged the MAP sensor).

No idea why they fitted it pre-TB. You'd think post-TB would make more sense. Oh well.

GTSBoy Grand Master

GTSBoy

Posted
Posted

The VE map is referenced off of things other than the boost sensor. The boost sensor is essentially just the fun police. It's never meant to see vacuum either (because of where it is) which is a good reason why poo poo happens when you move it behind the TB.

  • Like 1
Kinks Grand Master

Kinks

Posted
Posted

Nothing to do with overboost I was nowhere near positive manifold pressure.

Has nothing to do with fun police or poo poo or any other vague suggestions like that. The sensor simply expects to see pre-TB MAP to do transient fuel estimates and the ECU doesn't cope when you show it a vacuum reading. Likewise if you just left it sensing atmospheric pressure it would still be a pile of shit on transient throttle as well (and leaving it atmospheric would defeat the fun police...)

The very same MAP sensor is now running my Adaptronic just dandy. Sensor doesn't care. Just the ECU is expecting pre-TB MAP.

  • Like 1
STATUS Grand Master

STATUS

Posted
Posted

use the

It does, but the factory MAP sensor is plumbed in pre-TB (and hence pre-manifold). They seem to use some sort of pre-TB-MAP+TPS to calculate transient fuel requirements.

I moved my factory MAP sensor post-TB (now measuring manifold pressure) and the car totally died every time I changed the throttle position. After about 2 seconds it magically came back to normal. So I can say the stock ECU uses AFM for steady state airflow metering and pre-TB-MAP+TPS for transients.

Reason why I moved the MAP sensor was fitting an Adaptronic. Had to swap the stock ECU back in temporarily and it didn't like it! (Probably should have just unplugged the MAP sensor).

No idea why they fitted it pre-TB. You'd think post-TB would make more sense. Oh well.

correct its not the main load source only auxiliary.

GTSBoy Grand Master

GTSBoy

Posted
Posted

Has nothing to do with fun police or poo poo or any other vague suggestions like that. The sensor simply expects to see pre-TB MAP to do transient fuel estimates and the ECU doesn't cope when you show it a vacuum reading.

Yes well that's the poo poo of which I spoke. Would have thought that was pretty obvious. Fun police not real vague either in a discussion that had already mentioned boost cuts.

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