Please explain CO levels

But it does not go to the 'correct' F/A ratio, it just adjusts relative to altitude from baseline.

So if it starts lean, it still is lean; but not more lean, when you go up in altitude.



Got it...the FI tool adjusts the baseline.  Thanks.

Not to try to hijack this post, but I am following it with great interest.  I have tuned many carb and early injected cars back in the day with the co meters.  It was a necessary tool back then and kinda fallen by the wayside now,  We used to shoot for 1 to 3% co at idle, and usually 3-5% above that with carbs.  Early injected cars sound similar to the bikes now, where you set the base co at idle and the map pretty much dictated the rest.  Good rule of thumb was to shoot for lowest HC.


Is there an 02 sensor?  I suspect not or it could be mapped for optimal mixture automatically.  I am also assumming it is a MAP system due to the presence of an air temp sensor to calculate air mass. I am very interested in the inner workings if anyone knows?  2D or 3D mapping?  Adaptions?  TPS


Thanks in advance if anyone is able to educate this poor old fool.

Is there an 02 sensor?


No, but the O₂ sensor never has anything to do with altitude or temperature adaptation, anyway.  They provide the method by which true "closed loop" operation is achieved, and in spite of advances in their response speed, they are not particularly useful for the sort of performance required of an off-road machine.


It is true, as I pointed out earlier, that while the system does compensate for air density and temp, it still has it's original fuel and timing algorithm as the base it is compensating to, so if it's set up as a low emissions engine, it will run like one anywhere you take it until that gets "corrected".  The thing that causes a lot of debate and such is the question of whether the system is capable of and set up to update for density and temp "on the fly", or only once per ignition cycle, usually at start up.  Again, that sort of thing is deep in the firmware, and can be difficult, if not impossible, to change.

It sounds similar to the early Honds car PGMFI system that was a MAP controlled throttle body FI, but of course in the car thay would go closed loop once warmed up.


I would suspect that they do indeed adjust on the fly, although probably much slower than a controlled emmisions vehicle.  It would be easy enough to determine by fooling the MAP values while running to see if it alters the fuel map.


Honda has a lot of FI experience in their automotive division that I am sure trickled down.  It would not surprise me to see a certain amount of adaption also. 


Is Honda completely tight lipped about their systems?  Seems counterproductive on a performance machine.

The temp/density correction is typically programmed in one of 3 ways; system checks and corrects on startup, system checks and corrects at preset time intervals; system maintains "corrected" state in real time.  The second setup is almost as simple to do as the first.

Got it...the FI tool adjusts the baseline.  Thanks.


Since this FI system cannot check it's output (O2 sensor capable), it cannot change F/A ratio to the 'golden' Stoichiometric ratio.

It can only compensate relative to the baseline F/A and Inition curves,  in the provided programming. 


This is the biggest confusion over 'auto compensating' FI systems on 'green sticker' dirtbikes: they do not and cannot 'fix' a lean A/F ratio, as they are not designed to do so.

They are designed to stay in the one ratio, regardless of altitude or air density, with compensations in ignition map retarding for additional compensation for leanness.

To change this, you must 'unlock' the ECU, if possible, or change it to a competition model (GYTR). Then you can change the A/F and igniton curves  base on multiple rpms and TPS.

So setting the CO sets the A/F ratio at a fixed value and follows a predetermined non adjustable map.  That much I understand fully.  You need a programmer to modify the map values.  This I also understand.


My guess question is does the system adapt CO to altitude as you ride?


I suspect it probably does as it can easily calculate air density from MAP and air temp values and keep the CO value level within the predetermined computer map.  I suspect timing alterations are based more on engine temp than any other value as it has no other way of knowing leanness without an O2 or EGT.


Forgive me if I am asking questions that have been answered and I am too dense to grasp.  I knew nothing of this system till now, and really do want to wrap my mind around it. 

So setting the CO sets the A/F ratio at a fixed value and follows a predetermined non adjustable map.  That much I understand fully.  You need a programmer to modify the map values.  This I also understand.


My guess question is does the system adapt CO to altitude as you ride?



OK, one more time... The CO adjustment being referenced covers ONLY the idle fuel/air mixture, whether the ECU is the factory "smog" unit or the competition ECU from GYT-R.  In either case, once it is set, it will compensate for temp and density, but in so doing, it is only trying to maintain the A/F settings that are programmed into it.  The only setting that can be altered on the OEM unit is the idle CO.  The rest of the mapping is locked in, and only the technician's ECU scanner can reset the the idle mixture on either the factory one or the comp ECU.


The system clearly adapts, but what we aren't entirely certain of is whether the unit adapts to altitude and temperature changes "as you ride", or only at startup.  If it's the latter, then you could conceivably start at the bottom of a mountain somewhere and climb 7-8000 feet without the unit compensating for the change, if the whole trip was made without shutting down the engine anywhere along the way.  In that case, you'd shut the bike off and restart it to "correct" the mixture. 



I kinda expected more from Honda than that though.  It sounds almost exactly like early D-Jetronic Bosch systems like on the '67 Volkswagen Squareback.

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