TripleZee Cycles

Because we Tune for Best Power not an AFR number

We dont subscribe to the theory that Tuning to an AFR is the best way.

If its the only tool you have then fair enough, its better than nothing.

But a lot of tuners have trouble with this concept, believing you must know what the AFR is

"If you dont tune to an AFR how do you know the mixture is right?"

"Well it must be right if the engine is putting out Best Power"

"But what is the AFR?"

"I dont know"

"But......."

Indicated AFR is an Indication, a Clue as to

whats going on. It is useful information but it isn't the

Be All and End All of Tuning

A WBO2 detects Residual Oxygen levels in the exhaust.
The Assumption that Residual O2 is an accurate indication of Optimum AFR is FALSE
Many Abnormal Combustion Events result in an increased levels of Residual O2 and it doesnt neccessarily mean the mixture is lean

A lean mixture results in excess Residual Oxygen..........TRUE

Excess Residual Oxygen means a Lean Mixture..............SOMETIMES

Its a bit like going outside when it's raining, you get wet.

But going outside and getting wet doesnt neccesarily mean its raining.

The Assumption that an engine has one Optimum AFR is FALSE

Optimum AFR is essentially LOAD and RPM dependant.

Using the same AFR through different rpm and throttle ranges is Lazy Tuning

NO-ONE KNOWS what the Optimum AFR is for any particular engine combination. You find out AFTER you have tuned the engine.

Different operating conditions, fuel, air quality, climate, etc, require different AFR’s 
The WBO2 AFR modules are approximately +/- 5% accurate. eg tune for 13.5 means you will be in the range of 13 to 14 
So we have a 95% accurate AFR meter and we have to make an educated guess at the AFR

THE TWO MAIN PROBLEMS WHEN TUNING TO AN AFR WITH A WBO2

1. You don’t know what the AFR should be
2. The WBO2 is only about 95% accurate

 
Two Wrongs Don’t make it Right
 They just make it Twice as Wrong!!!

Problem..........Excess oxygen could be a symptom of some problem, eg ignition timing, cylinder stagger, heat. Adjusting the fueling to get your desired AFR is masking the real problem by "fixing" a symptom. Especially if the power goes down as you approach the ideal AFR

A WBO2 is a good bit of kit but it wasn’t designed to be a primary tuning device. WBO2 AFR tuning gets you close but that’s it.
The normal procedure when tuning to an AFR is after getting the AFR curve looking good, do a Power Run. Go back and retune to a different AFR and do another Power Run. Do this a few times to find the AFR that gives Max HP. VERY TIME CONSUMING (even when using TuneLink or AutoLink) and leads to unnecessary stress and wear and tear on the motor. 

PROBLEM...................there will likely be only be one place on the Power Curve (at Max HP) where the AFR will be at its Optimum
Everywhere else on that curve, in all likelihood, the AFR will not be Optimum, meaning Less Power.
The situation is much worse when part throttle tuning because of the larger variations in Optimum AFR at smaller throttle openings.
(unless a lot of time is spent adjusting individual cells. Which negates the Auto-Tuning to an AFR concept anyway)

Somtimes a Problem when Tuning to an AFR on a Hybrid Inertia/Brake Dyno

Generally speaking you set your AFR parameters up and run through the tuning procedure in "Brake mode". Then do a Power Curve run in "Inertia mode"

Change the AFR parameters and do it all again, when you have the best power curve you are done. Are you? maybe. The potential problem here with tuning under Brake Load and testing under Inertia Load is that the fuel requirements under acceleration(inertia) and steady state(brake) are different.

By adjusting the AFR to get a good Inertia result you are using the base map to get the acceleration map right. Of course what this does is screw up the base map.  Which was probably wrong anyway if you "tuned to an AFR"
Some bikes it won’t make much difference to, others it makes a lot. Result is a lot of bikes will run a bit (or a lot) rich after tuning, especially at cruise or steady speeds.

You can use the optional Torque Cell, tune for max torque and use this AFR as a basis for tuning. Problem is this may not yeild the best power curve when you do an Inertia run. SO adjust the acceleration compensation map to get a good inertia result and alls sweet! Which is the same as Tuning for Best Power!!
What we do is use a our Low Inertia Brake Dyno, Use Steady State testing to tune the base map, and then check the acceleration map/offset/correction by doing a Controlled Acceleration Sweep Test. If the Acceleration map needs tuning we tune the acceleration map. 

This is why 99% of the time we will find extra power when retuning bikes that have been tuned to an AFR, especially if they have been “Auto-Tuned”

WHEN DO WE DO USE A WBO2?
Once the engine has been tuned, we can then use a WBO2 to monitor the AFR at various points of interest. This way the tune can be monitored in different conditions, eg weather, fuel etc.
We can then make changes to get back to the optimum tune without another Dyno Session.

WE KNOW WHAT THE OPTIMUM AFR IS BECAUSE WE TUNED FOR BEST POWER FIRST and THEN USED THE WBO2 TO GET THE AFR

This is actually how they were designed to be used and when used as a monitor they work extremely well..

WHY USE A WBO2 AND TUNE TO AN AFR ?
Cheap and Easy.
“OK” result. Within 95% correct 
Easily integrated into an automatic tuning system which aims for a number.
Automatic Tuning for Best Power is a bit more complex ($$$$$$) so generally speaking Best Power Tuning requires more input from the Dyno Operator/Tuner, a higher spec Dyno than what is commonly available, more training, more knowledge, which still equals more $$$$$$ 

Is 95% Good Enough for you???

IF TUNING FOR BEST POWER IS SO GOOD WHY DOESN’T EVERYONE DO IT ?????
Everyone did it this way before the advent of cheap computers and electronics.
Remember changing a main jet and then seeing how fast the bike goes?
Bit harder to do that on a modern sportbike, much easier and safer on a Dyno
Computers, cheap O2 sensors, etc, have made the job easier for the Dyno Operator.
At the end of the day

***************

Tuning to an AFR is easier than Tuning to Best Power

But like a lot of things, the easy way rarely gives the best results

***************

If our engines were 100% efficient at converting 14.7 lb of air and 1 lb of fuel into horsepower, I would say we could use a WBO2 to set the AFR and it would be right.

But they aren't 100% efficient, they dont mix all the fuel and all the air, they dont burn everything that is in the chamber, combustion efficiency varies cycle to cycle, cylinder to cylinder, So aiming for an Air Fuel number as your final tuning goal isn't the greatest idea.

Of course maybe you do want a number, in that case go for your life!

HOW MANY AFR'S ARE THERE ?

THE AFR MEASURED AT THE EXHAUST?………right? wrong? who knows? who cares?

THE AFR THAT PASSED THROUGH THE INTAKE SYSTEM?……..again, who knows? who cares?

THE AFR THAT WAS BURNT IN THE COMUBUSTION CHAMBER?......THE ONLY ONE THAT MATTERS

SIMPLY PUT, THE CORRECT COMBUSTION CHAMBER AFR GIVES THE BEST POWER. 

SO WHEN YOU HAVE BEST POWER YOU MUST HAVE THE CORRECT AFR

UNFORTUNATELY

THIS MAY NOT BE THE SAME AS THE AFR YOU

MEASURE AT THE EXHAUST

TUNE TO A NUMBER BASED ON SO-SO INFORMATION?

OR TUNE FOR BEST POWER?

SHOULD BE A NO-BRAINER