What Is The Max Afm Voltage The Rb20-25det Stock Ecu Will Allow Before The Fuel Cut?

[DennisRB30]

What is the max AFM voltage the RB20-25DET stock ECU will allow before the fuel cut is initiated, and is this value dependent on RPM as well?

Thanks.

[R31Nismoid]

5.1v

[DennisRB30]

5.1v

Thanks. 5.1 is the max resolution of the AFM isn't it? What is the max voltage the ECU sees before it hits the fuel cut? Sorry for the confusion.

[R31Nismoid]

They are all 5.1v far as i know (including Q45, Z32 and so on)

So that would be the max one assumes that the ECU can see.

Being the resolution of the others is the difference, the peak is still the same for all of them

[DennisRB30]

They are all 5.1v far as i know (including Q45, Z32 and so on)

So that would be the max one assumes that the ECU can see.

Being the resolution of the others is the difference, the peak is still the same for all of them

Yeah but isn't there some sort of fuel cut built into the ECU that prevents too much boost being run? I would expect that value to be reached before the absolute output limit of the AFM. For example the JZ MAP sensor reads up to 5V, but the ECU hits fuel cut at 4.3V.

Edited May 13, 2009 by DennisRB30

[R31Nismoid]

There is no such 'cut'

It simply sense's the AFM flow has reached its threashold (which i believe is less than the max of 5.1v), and puts the ECU into the rich/retard mode, not a cut.

It might be more than just AFM dependant as you see some guys running 11psi no problems, others run 11psi and have issues. So no doubt its probably a "range".

Someone else will know more.

End result is the same though, the mid range is heavily penalised

[paulr33]

its a ramp that increases over the RPM range

so it 3000rpm it could be 3.1v and at say 5500rpm it could be 4.1v

who knows, but its a linear ramp - why do you care?

get a real ecu or piggyback or remap or keep turn boost down until you avoid it