cbr125 forum

Thought I would make up a quick post about the electrical side of things on our test bike. It's a lot different then a stock bike as we're running;

-Rear USB Charger
-Front USB Charger
-Nitrous Oxide (requires a relay)
-Wide Band 02 (requires a relay)
-OE Electric Fuel Pump (now requires a relay)
and several more switches (Nitrous arming switch/Quick Shifter inputs/Launch Control Inputs)
and probably a few more I've missed

This all started innocently enough. Originally I needed fused circuits for the two USB chargers. To that end, I picked up an inexpensive auxiliary fuse panel.


This, of course, wiped out the location for the tool kit. Not necessarily a bad thing, it weighs quite a bit.

But then, the obvious thing is that you don't want that panel being powered when the bike is off - it needs to be switched on only when the ignition is on. So....we added a relay....



Fair enough. This worked out really well. But then, when I added Nitrous into the equation, well, I needed another relay. So I added one in, and all was well. Thing is, there's only space for so many relays on the bike..... at this point, there were two.

But then, I added in a wide band Oxygen sensor. Problem is, it has a heater and you don't want that heater running when the ignition is on and the bike is not running. This will shorten the lifespan of the 02 sensor. So, we needed yet another relay (that's three now).



Problem is, in order to trigger that relay you need an input that tells it when the bike is running. The easiest input for that is output from the ECU's Fuel Pump line. The ECU will fire up the fuel pump for two seconds when the ignition key is turned on and then shut it off. This is to purge air and send a priming pulse of fuel into the engine. (On our ECU this is configurable - the stock ECU does the same thing).

So I triggered the Wide Band 02 Heater off that output from the ECU...but a funny thing happened. Every once in a while, when the engine was shut off, the headlight would stay on along with the center light and the tail light. After a LOT of diagnosis it was determined that intermittently, when the engine was shut off, and the fuel pump was spinning down (remember, it's electric) the fuel pump would generate power and send some of the power back up the line and hold the relay open. This power then back-fed through the rest of the harness and kept the light on

So...what was the answer? The answer was to split the wide band 02 heater and the fuel pump off of the same relay. Which means, of course, adding in yet another (!) relay. That brings us up to 4 (!!) relays with the idea that I might want one more for a second Nitrous solenoid for a staged Nitrous double shot......(one size Nitrous shot for low RPM and a larger Nitrous shot added in at high RPM)

As you can imagine, with 4 relays stuck on the back of the bike on the sides of the fender it was starting to get pretty crowded and there were wires going willy-nilly across the back of the bike. Reliability? No problem. Appearance? Ugly stick.

The answer is a new auxiliary fuse panel complete with micro relays. That's what I'm installing now and it's been quite the process. There are some out there for bikes but they are way too limiting and pretty costly too. None of them would accomplish what is needed here especially since most only have one (!!!!) relay and more cannot be added. In the end I came up with a custom system that has a 5 relay capacity along with 10 separate fused circuits.

Sounds simple right? In a way, it is. It took no less then 4 hours to determine which box to use, what relays, terminals, connectors and insulators were required and of course, to measure out the entire apparatus using the manufacturer's blue prints to see if it could be made to fit. That's 4 hours of research before I could even order up all the disparate parts required to make it work. It is after all, custom, and represents the ideal motorcycle auxiliary panel.

Good news - it's ideal. It's also IP66 rated waterproof which means I can still maintain the dream of riding around on a lake bottom Thing is, as we all know, the trunk of the 125 (and probably most bikes) is not 100% water-proof. Usually there is still a small amount of water that gets in. IP66 is very water-proof though, to the extent I was thinking of re-claiming trunk space by mounting the entire panel on the bottom of the fender directly in the water spray from the rear tire But that would be ugly.

Anyway, here's a shot of the wiring in progress. The idea is to shift over from functional but ugly to functional and clean and logical and 100% reliable. Ie, we never have to revisit it again and have two spare relays for future use along with +/- 5 fused circuits. In other words, room for the second Nitrous solenoid plus one more relay switched item and the corresponding circuits.

For instance, wouldn't it be nice to be able to have the ignition key on but the headlights and tail light off when the engine is not actually running? That is possible but it would require...another relay! With two spares that is possible. But there's another side to this that relates to 'thinking like an OEM'. What happens if the relay for the wideband 02 packs it in on the road? It's not the end of the world (in our case due to the custom ECU) but if the fuel pump relay packed it in...we would not be moving forward. On the other hand, we have two spare relays sitting in the panel so it's just a matter of swapping one for the other Lift the trunk, remove the panel cover, swap the relays, back on the road

It's a bit complex right now but the overall goal here is to Keep It Simple Stupid



What you don't see is how tightly the clearances are between the truck latch mechanism and the trunk's lock cylinder - among other things. It's very nearly a perfect fit. I'll post up some completed photos when it's done and all cleaned up.

BTW, that box hanging off the side is the custom ECU along with it's wiring harness (prototype version on the harness - the production harness will be 100% clean).

_________________
Best & Thanks!
Marvin Miller
cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...

Being that the other two relays (Wide Band 02 and Fuel Pump) are both ground switched at the relay I thought I would keep the same theme through the entire panel. Unfortunately, I was switching the Nitrous Solenoid with power. That means I need to go in further and replace the lines closer to the solenoid (due to custom line lengths that are now not long enough).

I've got to say, doing this piece-meal one addition at a time was more fun then revamping the entire wiring as I'm doing now. I've been chipping away at this over the last couple of days because I really didn't have the heart to sit down and nail it all in one shot

_________________
Best & Thanks!
Marvin Miller
cbr125world Store

...because every day is MotoGP day when you own a CBR 125r...