This is a discussion on Aftermarket ecu within the Monkey Talk forums, part of the Honda Monkey 125 Forums category; Originally Posted by Wibbly the stock o2 sensor cannot report that AFR yuminashi is likely just loading an open loop map in these ECUs, hence ...
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The sensor cannot report 13.2. It can only change state (voltage) between low and high. It doesn't sit at a voltage at stoich it switches. There's a very narrow window there hence the name of the sensor.
I believe that the Hoedar stand-alone ecu is able to use the stock o2 sensor, how would that be any different to this?
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A narrowband o2 sensor cannot report actual afrs.
If you offset the voltages that does not give you actual afrs, it gives you a "richer than stoich" or "leaner than stoich". Not actual.
This is why companies use wideband sensors. They can tune to actual values.
Without proper feedback, a control loop cannot match the output to the setpoint.
The feedback from the narrowband is two values very near stoich. One above and one below. By fueling such that time spent above equals time spent below, then averaging the output, the computer can figure out what value produces stoich.
If the feedback to the ecm does not indicate actual AFR, then the system cannot output to actual AFR.
The factory ECU is "self learning" just as much as these yuminashi ones. In fact I doubt they changed the open loop fuel maping and even if they did, there would be a very small chance that it would be the correct map for the exact modifications that have been done to one's bike. I think the term "self learning" is a bit vague.
-TST fender Eliminator / Tail Light
-Two Brothers Tarmac Exhaust
-Kitaco Type 2 cam
Awesome info. Thanks, now I understand a little more. I was drawn to dynojet, but it seems Aracer is the choice of the super high performance guys. I said seems, I know some of the heavy hitters use dynojet. The local dyno is dynojet, but I am going to get the RC1, their AF1 autotune, and the iMode. Should I install the 181 neo first? Problem is, I want my bbk afr to be correct from day one so I might want the aftermarket ecu to be up n running. Btw, I am looking for contrary opinions. I like the Pod 300.
I've been riding around all day running errands and the engine revs a freer at high rpms, likely because it's getting more fuel at high rpms. Overall the throttle is more crisp and responsive even at low rpms, probably from the different ignition timing curve. The bike keeps up with traffic easier without having to wring out the engine. Comparing the Yuminashi to the stock ECU, it seemed to have been holding back the engine at high rpms. It took a few cold starts and about 60 miles of riding for it to dial itself in. During that time the engine ran weak, but that quickly passed. I'm quite pleased with how this is working out. Still running the modified stock exhaust on it for this week to log some gas mileage. It makes a nice compact little package tucked under the engine with nothing sticking out anywhere. I like it.
After that I'll put the TOCE exhaust back on to see what happens with it.
Last edited by tooter; 04-01-2019 at 07:49 PM.
2018 GROM: Modified for reliability longevity gas mileage... and fun.
Thanks for posting. How much re-pinning was involved? I am tempted, but then I am planning on going to an Aracer in a few months. I have an aftermarket pipe and the chimera intake. I am running 16f and 32r sprockets. And a lot of expensive stuff that doesnâ€™t make it faster.