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Question on Honda ECU operation once a piggyback fuel computer is added


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Not sure if anyone can answer this question or not, but I would be interested to know if anyone does know the answer.

When connecting any sort of fuel computer to the VFR ECU, we remove the O2 sensors, which is meant to cause the Honda ECU to then recognise that the O2 sensors are there, but somehow make the Honda ECU stay with a constant fuel map that doesn't change or try to go into closed loop when cruising to get better fuel economy with a AFR of around 14.6 to 1.

With a standard ECU and the O2 sensors connected etc. The bike then can go into closed loop, but also, from my understanding, the ECU will also make adjustments to the fueling according to air temperature and height about sea level etc etc. I believe the ECU does adjust fuel according to air temp as I noticed in winter, the bike uses more fuel (open highway cruising) than it does in summer.... its very noticeable just how much extra in fact..

 

So my question is this...

With the O2 sensors removed and replaced with the resistors and then installing a piggyback ecu such as the PCv or Bazzaz Zfi, does the standard Honda ECU still make adjustments to the fueling when it senses a change in air temperature or air pressure - being height above sea level?  Or does the map just stay the same all the time, no matter what the conditions are..  If it doesn't make any adjustments, it seems - to my way of thinking then, that installing a PCV or Zfi and doing a dyno tune, basically negates the advantages of the honda ECU, whilst gaining small amounts in power/torque and rideability.  Kinda making the fuel injection act like carbies - which are non-adjustable once tuned correctly with the right jets etc.

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Everything I've read about using O2 eliminator resistors is for the purpose you describe.  A fixed map module cannot "know" what do if the ECU is constantly changing its outputs based on what it's getting from sensors.  Holding the ECU output constant gives a known result from a fixed map.  You might also want to check out Rapid Bike.  If you get the My Tuning Bike module, the wideband O2 sensor allows it to tune itself to a desired AFR target continuously on the fly.  Power Commander can not do that even with its Autotune module - it only offers a fixed map that you can analyze later and change if desired, but it remains a fixed map.  I just got my RB Racing and MTB modules set up - it's very impressive. You can watch it dial in the parameters on your laptop.   It's a bit more expensive than PC w Autotune, but way ahead and like anything you get what you pay for.  It could end up being cheaper than PC if you factor in a dyno session which likely would not be needed with RB.  I don't know if there's an Australian distributor for RB - there is one in the US. 

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The ECU uses the MAF to adjust for temperature and altitude...the O2 sensors only seem to come into play for closed loop mode.  But...

 

My 2002 still dialed back mixture at steady cruise between 4K and 7K RPM even with O2 eliminators.  The ECU definitely has logic in it to do so regardless of whether it has them installed or not.

 

My RapidBike fixes it with real time adjustments and pre-empting the ECU with its own map to the harness, but you can also get around it for free. Someone on VFRW figured out a trick: switch the bike on, kill switch on.  Let the whine noise (fuel pump priming) and dash sequence complete.  Then turn key off.  Now, turn key on and hit the starter quickly, before the boot sequence (whining noise and dash sequence) completes.  
 

For whatever reason...if the ECU doesn't complete its boot sequence it doesn't go into closed loop control.  Works well enough and obviously enough that whenever I forgot to do it I was 🤦‍♂️on the highway until I got somewhere I could restart again.


That being said, as happy as I was with the key-switch method, the Rapid Bike makes the bike overall better in too many ways.  Go for it if you can!

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To answer OP's question, YES, ECU still adjusts for air-density and temperature. It's built-in function of MAF when it measures air-flow. This data is then used by ECU to calculate injector pulsewidth. This is initial process always.

 

Then, if you've got RB installed, it intercepts this injector pulsewidth and applies its own adjustment-map on top. It can be zero adjustments and original ECU's maps goes through unchanged. And it can also use wideband-O2 to sample exhaust and adjust as necessary to hit your desired AFR. This function of RB is lightyears ahead of PC.

 

Factory O2-sensor is used only after everything has occurred. If left connected, ECU will use that data to try and adjust mixtures back to OEM maps. Over time, it'll make opposite adjustments to RB/PC. Thus why factory O2 needs to be disconnected.

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I discovered when one of my resistors failed that the fault code thrown u was a failure of the sensors heater. All the resistor does is stops the ecu light flashing a fault that does not affect the running of the bike.

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yup, you can just disconnect O2-sensor and ECU operates in open-loop mode just fine. It'll just throw error-code. Resistors connect heater circuit and tricks ECU into thinking. O2-sensor is still there.

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Thanks Everyone.

 

My bike came with a Bazzaz Zfi fitted.  But only had the Bazzaz standard map in it.  I bought a Autotune module for it.

 

Debating if i just sell off the Bazzaz system and go with Rapid Bike.  I can buy it from the distributor in Australia.

 

I've yet to get to a dyno tune place to have the bike tuned properly.. and no one it seems on the forum is using a bazzaz as i've had no replies regarding a map, in my other post.

 

But thanks for clearing up my questions, as I was also considering a ECU re-flash.

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