Why no O2 sensor?

Why dont the EFI bikes use an O2 sensor, EGT sensor, or anything of that nature??

Because they are not a closed loop system. I don't own a newer YZ with FI, but I don't think they have a Manifold Absolute pressure sensor either which means they are probably a modified Alpha-N type system that meters fuel on throttle opening and RPM only. If they do have a MAP, them they would be a speed density system (uses MAP sensor). Mass airflow systems use a mass airflow sensor (not ware of these being used on any bikes). All of these can be open or closed loop, although Alpha-N systems are normally open loop.

A lot of it has to do with not needing to meet emissions regulations, although I do have a street bike that is FI and has to meet emission regs, and has no O2 sensors (open loop). My other two, do have O2 sensors and cats (FZ1 and BMW R1200R) They are all speed desity systems with MAP sensors.

Edited by YamaJet
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Because it's a race bike. O2 sensors don't respond fast enough to be used at full throttle, and are only useful in trimming AF mixtures during cruising situations. Systems that have O2 sensors typically go into "open loop" operation at heavy throttle loads anyway, so there would be no point in having one on a YZF.

Some of the latest and most sophisticated automotive systems are set up so that the base map is edited by the system itself during closed loop, but these are expensive and complicated, and the YZF would spend so little in closed loop anyway that it just wouldn't be practical with current technology.

Then what about an EGT sensor?

The 2010 does have a map sensor on the throttle body.

Then what about an EGT sensor?

Those are for diesels. Besides, an O2 sensor is almost the same thing.

Not to mention that the leaded race fuels that many people like to run can screw up O2 sensors.

Not to mention that the leaded race fuels that many people like to run can screw up O2 sensors.

Leaded fuel will kill an oxygen sensor in a matter of seconds. Especially race gas.

Many many snowmobilers with mod engines use EGT gauges as a tool for precise jetting/efi settings. And EGT sensors are safe with leaded gas. Does the MAP sensor on the 450 allow the bike to calibrate itself for elevation and temp changes?

Does the MAP sensor on the 450 allow the bike to calibrate itself for elevation and temp changes?
the system has both a MAP (manifold air pressure) and BARO (barometric pressure) sensor, as well as ECT and IAT (engine coolant and intake air temp) sensors, and is completely capable of compensating for that sort of thing. There does appear to be a low temperature limit to the amount of fuel the system will deliver and the lack of a thermostat makes it run rich in colder temperatures, but in reasonably normal weather, it works fine.
Those are for diesels. Besides, an O2 sensor is almost the same thing.

how are those 2 sensors "almost the same" when they do 2 specifically different jobs?

Leaded fuel will kill an oxygen sensor in a matter of seconds. Especially race gas.

Incorrect. I run an EGT on my shifter kart to monitor jetting. 12,500 sustained rpms, running CAM II and 24:1 premix. No issues. Racers have been doing this for years.

Leaded fuel will kill an oxygen sensor in a matter of seconds. Especially race gas.

Incorrect. I run an EGT on my shifter kart to monitor jetting. 12,500 sustained rpms, running CAM II and 24:1 premix. No issues. Racers have been doing this for years.

So tell me how what you said makes what he said wrong....

An EGT is not an O2 sensor.

So tell me how what you said makes what he said wrong....

An EGT is not an O2 sensor.

Never mind, my contacs are dirty, I had "EGT sensor" stuck in my mind. Disreguard my post !

All good points guys. So it sounds like a speed density system (map and baro sensor). Leaded fuel, no need for part throttle fuel trimming, O2 sensor response, lack of emissions req, all good reasons for no O2. Since O2's are only used in closed loop mode, I don't think that off road bikes ever have a throttle setting stable enough for any type of closed loop system to work. We are constantly accelerating or decelerating or at a throttle setting where closed loop systems are not in closed loop mode anyway.

As far as EGT goes, Ive seen a lot of EGT monitoring, but is anybody controlling the fuel closed loop with them? Not sure about their response time either. Iv'e heard of them being used on a dyno to get the fuel map or carb set up.

All that being said the open loop speed density FI system has worked fine for decades and apparently the gains, if any are not worth the added cost.

Good discussion.

well you can get the auto tune system for the PC5 with an a/f ratio sensor and it gives you real time fuel correction to create a map for a certain track or can be left in closed loop operation. Pretty much like having an on-board dyno.

It would be nice if the factory mapped the bike perfectly for 13.7 for the entire fuel map!. Out of the box this bike is off bigtime!

Why?????

the system has both a MAP (manifold air pressure) and BARO (barometric pressure) sensor, as well as ECT and IAT (engine coolant and intake air temp) sensors, and is completely capable of compensating for that sort of thing. There does appear to be a low temperature limit to the amount of fuel the system will deliver and the lack of a thermostat makes it run rich in colder temperatures, but in reasonably normal weather, it works fine.

Ohh thats cool. No need for an O2 sensor then. I was thinking an O2 sensor or EGT sensor would be usefull for self adjusting the a/f ratio but i guess it's already covered.

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