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I have a R32 with an RB20DET in it and was tinkering around with things under the dash and pulled my ECU out. Its got RB25DET written on the side of it!

So I'm wondering if its possible to run an RB20DET with a standard RB25DET ecu?

I haven't owned the car too long and I'm hoping its the cause of a few of my running issues at the moment. miss on idle, goes nowhere above about 4,500-5000 to red line fair bit of black smoke. Thought maybe it could be a quick and asy fix with the ecu. Otherwise I'm going to spend some quality time with my coil packs cleaning them up.

Edited by Jinman
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Problems you explained are what I'd expect running an rb25 ecu on an rb20.

The ecu's are virtually interchangeable except for the VVT, but the tune will be vastly different, hence you car running like shit.

Just go get the ecu its supposed to have, as the previous owner most probably had an aftermarket ecu, which he kept and put in the closest thing that worked(or didn't).

does it have an safc?

rb25det ecu's are tuned for 370cc injectors, so unless its got different injectors or an SAFC it will be running lean as

if it has an safc, adjusting the mixture ~ 37% to get it to run, it would probably make it rich and retard off sfa power :)

the engines are very similar, as far as cams etc are concerned, and with a plain rb20 long motor on an rb25det ecu with all the rb25det sensors and electrics, you'd find it would run pretty well (should be fine on boost). But with the rb20 sensors and all the other crap along with it, it makes sense it would be pretty average. VCT shouldn't be a big deal, as unplugged on an rb25det it still runs fine...

So more info, what turbo do you have? what injectors? any piggyback devices? fuel pressure regulator?

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