Dyno Tuning

Dynamometers, or "dynos" have become an integral part of reputable workshops and tune shops, and help the dyno operator diagnose and tune bikes and cars to their full potential.

Dynos are more typically used to improve performance on bikes, cars, trucks etc., but for the purpose of this article we will stick to bikes. Using a dyno to tune and diagnose most problems, be they chassis, electronic, engine or fuel, will require the use of a load controlled or brake dyno, the most common being the
Eddy Current Load Absorption Unit.

Without being able to apply the correct load to a certain rev range and/or throttle position (TP), it is almost impossible to simulate road conditions in order to identify problems.  Simple inertia dynos are great for providing horsepower and torque data, but leave little available for use as a tuning tool.

Dynojet’s model 200i

Modern motorcycles incorporate an ever growing list of technologies. It is important to understand what engine management and electronic systems a particular bike uses. For example, ride by wire, traction control, rider modes etc. Using a load controlled dyno enables the operator to quickly diagnose problems and perfectly tune such high tech motorcycles.

Dynojet’s Model 250i

Understanding the motorcycle before tuning.

There are a couple of things about the bike  you have to know and understand before tuning. Its general  condition,  current state of tune and whether the bike has a problem or not. I have  seen dyno operators spend hours trying to tune a bike when a problem existed that they were not aware of, either on the bike itself or a problem  with the equipment used.

Nowadays there are many tuning modules and methods that can be used to tune fuel injection systems, some more preferred than others. In this article we will discuss fuel injection adjustment units (Power Commander™) and ECU tuning (flashing).

 Before tuning you should have a firm grasp of Volumetric Efficiency (VE).  VE is the efficiency with which air (actually air plus fuel or charge) is moved into and out of cylinders.  This is dependent on various things, such as barometric pressure (density of the air), air filter resistance and air box volume, velocity stacks, forced induction or naturally aspirated, camshaft profile, exhaust system etc. Keeping this in mind is extremely important as it will have an effect on the end result, again lots of time can be lost and damage done to the bike as well as your equipment.

Now that we have some of that out of the way we can actually talk about tuning a bike. We will start with Power Commander™ which is my personal preference as it offers the best balance between ease of use, money spent and results achieved. Power Commander first came onto the market in the late nineties and was very high tech at the time, looking back now the first version  seems a bit archaic. Power Commander II worked on the basis of sensor offset, very similar to the GSXR 750WW stock FI system. Sensor offset, in short, affects the voltage seen by the ECU from the various sensors. From this "picture"  the ECU will calculate and output data to the injectors.

The current Power Commander V (PCV),  is however a really nice piece of kit which is almost infinitely  upgradable. This unit uses direct driver technology, in other words the PCV plugs in line with the injectors and modifies the signal from the ECU to the injectors giving the tuner full control of the injector duty cycle.  Also worth mentioning is that the PCV uses original equipment connectors so no cutting or splicing of the wiring harness is required. Installation is usually straightforward  and removal is simple, returning the bike to factory spec immediately.

Now that you understand how a Power Commander works, I am going to explain how a bike should be tuned. In order to do this job properly you have to have the right equipment (as discussed earlier), knowledge and experience.

Installation of a PCV is pretty simple on most bikes (unless it is a Ducati, some of them take around three hours to install). Knowing what air/fuel ratio (AFR) targets certain bikes will require makes the job easier, but also comes with some experience. In my opinion there is only one way to map a bike kitted with a Power Commander and that is on a dyno using Dynojet’s “Tuning Link” software.

The software takes control of the dyno and the Power Commander at the same time allowing REAL TIME tuning. It is up to the tuner to determine and choose the correct dyno load in order to get  the desired AFR, and this can only be learned with experience. Too much or too little load will result in a badly tuned bike which is either going to be too rich or too lean or a combination of both.

Everything about a tune is of extreme importance and requires accuracy and finesse. For example, at what point in the exhaust the AFR is measured and how many litres of air per min is sampled by the vacuum pump for small opening throttle position areas. Many tuners and riders are too concerned with peak horsepower and torque figures, but in the real world it is all about feel and rideablilty. In other words, connectivity between the throttle and the rear wheel. This is not to say that peak horsepower is not important, but concentrating on only that takes your focus off your goal.

A Dynojet dynamometer, “Tuning Link” and  Power Commander are, in my opinion,  the ingredients for a perfect tune. I know this is starting to sound like a Dynojet advert, but I'm afraid this is a fact.  Over the last eighteen years I have used many tuning modules but they have always fallen short in some way or other. 

Another brilliant product is the Autotune for PCV, this thing fitted to your bike is like dragging me and my dyno behind your bike, constantly keeping the AFR in check.

What I am going to say next  is where lots of people in the industry will disagree with me. (Again!)
In  my opinion, an  Autotune works best and most accurately with a custom map specifically mapped and configured for a specific bike on the dyno. Using a zero or downloaded (canned) fuel map and then waiting for the Autotune to correct each offset would take forever for it to become perfect. Let's imagine a line (pictured below) which is your target AFR at thirteen parts of air to one part of fuel (13.0 AFR).  On the first peak the bike's current AFR is 14.5 and the first valley it's 11.8 and this is all happening at say 15% TP throughout the RPM range. The Autotune now has to work within wide parameters in order to get that TP and RPM range to the correct AFR.

Let's also just throw in some more factors which must be considered. Let’s say on the first day of riding the conditions are 1029 Mbar air pressure, humidity of 40% and temperature  22°C and you have ridden the bike for a hundred kilometres. Lets also say on day one the bike was ridden pretty aggressively (heavier load) with X fuel quality (and we all know the variants of fuel we get in S.A).

On the next day of riding which could be a week later, the conditions are 1005 Mbar air pressure (which relates back to volumetric efficiency being less because of lower barometric pressure), humidity of 23%, temperature 30°C, and the bike is ridden more sedately with Y fuel quality of a different brand. Now the Autotune has to work with these very different parameters and as you can imagine it would take quite some time and kilometres to build a decent  map.

Imagine now that the bike is mapped on the dyno and all the target air fuel AFR’s are perfect. On the road, in real world conditions, this perfect map could be out by a small percentage. Look at the lower  line at 13.0, on the first shorter peak the AFR is closer at 13.2 and the first shallower  valley at 12.8. this means the Autotune has to work within a much smaller range to keep the AFR in check.

ECU tuning (flashing).

With technology growing by the hour and more becoming available to tuning shops, ECU tuning (flashing or reprogramming) has become very popular. In 2007 I got my grubby paws on an interface and software which gave me access to Suzuki ECUs and was beaming with excitement, anticipating that I had everything the factory had put into this thing at my disposal for editing the ECU default settings. I could now turn off the factory limiters, disable lambda sensors and PAIR valves, enable quick shifters and so on. This was great until I got to the tuning bit, I soon realised that this was not going to be easy and was going to take lots of hours if not days.

For example, a K7/8 GSXR1000 has 1150 fuelling cells in the throttle position (TP) table that need to be adjusted if necessary, and I have found that most of the time they do need adjusting. In the inlet air pressure (IAP) table there are 1000 fuelling cells that have to be looked at as well. Now you can imagine how long this would take an experienced tuner, and we haven’t even looked at ignition timing maps yet.

Because the tuning is not happening in real time it means it is less accurate and it takes a patient and knowledgeable tuner to get a perfect tune. Products like Woolich are brilliant for ECU editing and functionality adjustments and I believe that if it is your choice, it has to be used with a logger. A logger will collect AFR data as you are riding and the AFR trims have to then be written to the ECU, much like an Autotune. Again, you have to consider that it will take some time for the map to be perfected.

I trust this has been helpful and informative.

Julian Neethling.