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Just want to see if anyone here can confirm this:

Got a fella who has a L67 he has put into a VR using what he believed to be a VS ECU & matching wiring harness.
The ECU is correct, but tne wiring harness has purple covers on the two plugs where they are normally pink in colour. The wiring pin outs appear to be in the correct order he said, although the alignment runners on the purple plugs are not. While trying to work it out another punter has said the harness is from a police spec model which had an ecu with metal connection points & not plastic like the standard variety. Said it had something to do with RF reception or interference.

Can anyone confirm this ?

Not sure on the VS but the VRV8 RFI ECU has a different plug socket as in your pic and the ECU socket is alloy not plastic. Don't know what they were thinking when they made them.

Charlescrown wrote:Not sure on the VS but the VRV8 RFI ECU has a different plug socket as in your pic and the ECU socket is alloy not plastic. Don't know what they were thinking when they made them.

Thanks for that info.

That is correct. the police radios transmit high power which can get in to the efi electronics. That is why grounded metal connector. Because its different, different keyway and colour connectors. But because its a phisical difference only, same pinouts.

Heres some pics of one in my pcm collection. Service number 16208257 and "3.8L RFI PCM" where RFI is "Radio Frequency Interference"

You can chop the keyway pins off and plug a standard pcm in and it'll be fine.

Its weird considering the plugs and harness are not shielded, only the sockets are.

Proper design would have all metal plugs and sockets with foil/braid shielded harness with all interconnecting grounds. Seems like they got the ECU design done and then went "yeah nah, that'll do" "purple is a fruit!" on the harness.

Well in RF design physical measurements are based on wavelength. If they know what frequency they are transmitting on (of course they do) they can calculate the wavelength, and its possible the opening was the size where bad things happened and with the metal parts the gap is a different physical size where RF ingress is not a problem at their frequency. It could also be to do with impedance filtering on the wire. You'd need to talk to an RF engineer to know if this stands up. Ive found most the stuff in the OEM world that does not make sense up front does when you learn more about the hows any why. That said, sometimes its still just marketing.

good point, but in my experience with this design aspect back in my diploma days most interference came from exposed wiring regardless of frequency as many common wavelengths often corresponded to the common wiring lengths. Emergency services including police run around the 160-165Mhz range which has 1st order wavelengths around 1.9m, inconveniently typical harness wire lengths.

shielding of plugs in my research back in the day only offered some reduction in noise but good wire shielding, grounds and decoupling circuits did wonders. Often just the wire shielding was all that was needed as it was more than often the root cause other that PSU noise.

This design seems really odd considering what I know and had experience with. I am willing to put my finger on that it was initially designed and implemented for the ECUs but field tests maybe showed it was not necessary and they probably continued with more standard harnesses.

All very interesting, thanks guys.

@vlad, We'd need to find the original designers or test with the actual radios in the car, but for the record I do know they have/had (pre GRN) UHF frequencies in addition to the VHF. (GRN is UHF too, but that didnt exist in the vs commodore days).