Question About Ecu Pin Out For Rb20 & Rb25

[604cefiro]

I'm just wondering if anyone knows if an RB25DET ecu can plug into the wiring harness of an RB20DET.

I know it's different, rb25 has vtc etc, but all i really want to know if the 25 ecu can plug into the rb20 harness.

THanks guys!

[paulr33]

technically it can yes, the rb20 ap engineering powerfc is an rb25 ecu with two injector wires flipped around to work. wether this is a good idea or not, is another story

[whiter31gxe]

if thats the case, if you were to buy a rb25det powerfc, which is cheaper, and just modify the rb20 loom to swap the wires over, would it work?

[paulr33]

read the powerfc faq (in my sig), its covered in there.

it lists the steps to do it. people have done it, im not sure how "safe" it is however, it shoufd be ok. not sure what happens when it can't detect the vct

[604cefiro]

Thanks for answering!

The reason I am asking is because of my current engine setup.

1989 R32 GTS-T Chassis

Motor - RB25DET

Wiring Harness - RB20DET

ECU / Management Being used right now - Z32 Mines + SAFC2 + AVCR

Currently VTC is not hooked up because RB20 harness never had vtc.

I'm told I could hook it up using a 'vtec' switch to activate vtc during certain rpms.

SO, if I decide to go with POWER FC management, I could in theory get the RB25DET version, and wire up the VTC correct???

[funkymonkey]

wtf? "VTEC yo" in a skyline?

VCT (variable cam timing) is slightly different to VTEC (which is more an on/off thing depending on what RPM you're at).

If you were to properly do it, you'd want a circuit that feeds an emulated VCT signal to the ECU. I'm assuming the PFC dosen't work with 1993 R33 ECU's then as the RB25's in the initial batch didn't have VCT.

[paulr33]

in theory yes you could, the powerfc faq has a diagram that cubes did to identify the wiring differences between rb20 and and rb25 so if you could just make those changes, it should be fine

[604cefiro]

Sorry, what i meant was to wire up vtc using an rpm switch (ie// like how ppl wire up vtec with an rpm switch).

my mind thinks differently from my fingers lol.

wtf? "VTEC yo" in a skyline?

VCT (variable cam timing) is slightly different to VTEC (which is more an on/off thing depending on what RPM you're at).

If you were to properly do it, you'd want a circuit that feeds an emulated VCT signal to the ECU. I'm assuming the PFC dosen't work with 1993 R33 ECU's then as the RB25's in the initial batch didn't have VCT.