As posted earlier, there are basically two methods (well three if you combine the two) to achieve a good running engine. The one we will be using is the Narrowband method. This method uses the narrowband O2 sensors that come installed on your motorcycle. These sensors are critical to maintaining a well running engine over the life of the engine, usually regardless of gasoline quality, altitude, engine condition (air intake leaks, etc). It is also critical to proper catalytic converter operation and meeting EPA requirements.
My personal believe and the way I ran my motorcycle, is to use the narrowband sensors to monitor your engine. This keeps the engine always in a safe region. A well tuned motorcycle will run cooler, even though the AFR target is still 14.7:1 due to not having to hunt for the target. The ECU will have a better beginning fuel tables to hit this target closer right away. Unless you are drag racing, there is little value in setting a richer AFR for idle through cruise range of the engine.
This blog will therefore only present the narrowband method as well as supply equations that will tune using narrowband sensors only.
Our goal will be to set a wide engine operating range to 14.7:1, thus putting that region into "closed-loop" operation. We will then record data logs of critical operating parameters.i.e Short Term Fuel Trims and Long Term Fuel Trims as well as timing retard due to knock. With this data, we can then tune the fuel tables in the ECU to optimal values for your engine. Once we have completed this tuning, the Target AFR table will be placed back to reasonable values.
The equation(s) that Chafik, I, and Dynojet have wrote have been developed over the last 3 to 4 years. This has been through extensive testing and tuning many engines. The narrowband equation is very sophisticated and is applicable for tuning TS111/TS116, Scouts, and FTR-1200 engines. It has been optimized to require very few tuning cycles to achieve a well tuned engine result.
We are freely giving this and other equations out to the public domain. The intent is for the owner/hobbyist and not for commercial use; hence the removal of the wideband portion. The first equation can be downloaded from this blog.
One of the major features of this tuning tutorial is tuning without the use of a dyno. There is a lot of misinformation about this subject. Some will say you can only tune with a dyno and/or with wideband sensors. Let's discuss this. A dyno places a load on the engine typically through a rolling drum that is a known mass. This known mass and RPM of the drum is important for measuring the Torque and then calculating the Horse Power that the engine is producing. That in itself is not very useful for tuning the motorcycle except for wide-open-throttle operation. I have never been one to care about dyno charts. They are excellent as a tool for the operator of the dyno to see the progress of the tune, but in general are pretty useless except for bragging rights. When I see numbers that are far better then all others I've seen, I am usually suspicious of that dyno or dyno operator. There are happy dynos and corrupt operators out there.
As far as with wideband sensor only tuning, while optimal when in open-loop, not so when keeping the engine in closed-loop. The narrowband sensors when coupled to an ECU that tracks fuel delivery accuracy, we can obtain excellent results with them only. In fact, when tuning my bike, I had both installed in my exhaust. I always used the narrowband sensor when in the closed-loop operating range and then the widebands when in the powerband range. Since our goal is to produce a well behaved engine that is smooth and fun to ride, the narrowband OEM sensors are sufficient (and preferred).
A dyno with a dynamic load brake is very useful in tuning an engine (DJ250i for an example). With that type of dyno, a good operator can hold RPM and load at all the operating conditions of the engine and tune each of these points very accurately. Unfortunately there are not many dyno operators with the knowledge to tune Indian motorcycles.
Fortunately for us, we have a natural dyno, which is the road! Look at the the road as a reversal of the dyno. The bike is the rotating mass, the road is providing the load (as well as the wind and bike's brake). If we are careful with our driving while recording data, we can hit a tremendous amount of fuel cells that we can then tune to perfection. The other cells that are normally reached by a dyno are then either interpolated or ignored. We can usually ignore them as we are not able to hit those cells even when driving in extreme manners. Just like a dyno tune, it takes several cycles to tune in the engine. In our case, I have found about 10 cycles. You can also just record and ride normally or a little aggressive if that suits you and you will still have a good running engine as the end result as well.
Point being, you are in control of the tuning process as well as the range of tune that is done.
The next post will go though the Dynojet Power Core installation as well as a discussion on the PV3 flash unit.