Hondata

Hi There,

My EG's fuel pump wiring is toasted, and I'm planning to add a dedicated circuit and relay to directly drive the pump on a new relay.

I see one oddity I look at the wiring diagram here: https://www.hondata.com/tech-k20-swap-wiring

E1 is a sink, and apparently provides ground to control the pump. The diagram shows it running to the 86 pin of a relay, though, which seems a little odd to me. Best practice for compatibility with diode-protected relays, as I understand it, suggests that the greater voltage potential should go to the 86 pin and 85 should go to ground.

I just wanted to confirm my understanding of the pin above is correct, and that a combination of 12v and the E1 pin connected properly with te 85/86 pins on my relay will control the pump as per the KManager setting (2 second prime, etc.). Am I understanding this correctly?

--Matt

Yes, for a diode protected relay 85 and 86 should be switched.

Perfect, thank you!

Are there any known limits on the size of the relay the ECU can drive for fans, fuel, and the O2 heater? Can I safely put a pair of relays that draw 100mA in these ground triggers?

Unknown. 100 mA is a lot for a relay by itself.

Hondata wrote: Fri Jan 12, 2024 8:20 am Unknown. 100 mA is a lot for a relay by itself.

Is it? As far as I can tell the coil current requirement for the stock EG fan relay is also ~100 mA. It seems like 100-150 mA is typical for smaller (<40a) relays and up to 250 mA is common for bigger ones. 🤷

I'm just using Picker PC785 relays. Their specs seem comparable to others with similar capabilities, though.

Honda relays should be 120 ohm coil resistance. So more than 100 mA I guess but not by much.

So far so good with 2 relays. The IC controlling the relay sink looks to support up to 1A and has over-current protection, so it seems like it should be fine for the long haul.