Tuning 101

[Syler]

There are a lot of threads about various tuning devices so I figured I would start one on the basics of how an internal combustion motor is tuned. Please note this is about basic tuning. If others would like to chime in with specific details about the devices available, please feel free to do so.

The two key elements of a good tune are the air fuel ratio (AF) and timing. Both of these elements must be correct for the circumstances the engine is under at all points in time. These generally include RPM and "load." Load is how far the throttle is open. There is another important factor called volumetric efficiency (VE). VE is how much your cylinders fill with air and is given in percent.

AF Ratio:

The stoichiometric point for gas and air is 14.7:1. This means that the fuel molecules and O2 molecules are in perfect balance. There will be times when a richer AF ratio is required (heavy load and high VE) and times when a lean AF is used to save gas (light cruising). If the AF is too lean under heavy load - especially where VE is highest, detonation can occur. On the other hand if the AF is too rich, the fuel will not burn properly and power will be lost. The rule of thumb is that the most HP can be produced at 12.5:1. This is where timing can be advanced the most without detonation.

We hear a lot of talk about creating a lean condition by adding aftermarket parts. In fact, this may be a lean condition or may be a change in VE causing slight detonation due to increased compression. Either way it must be corrected and that is where these tuning devices come into play.

Timing:

Timing plays a crucial role in achieving power. The object is to advance your timing as much as possible without causing detonation. Things to take into account are AF ratio, because a lean mixture will burn faster than a rich one, and VE because the higher your engine compression, the faster combustion will occur. Increasing air flow of a motor means you are increasing VE which affects the amount of timing you can run at a given RPM and load range.

VE, RPM & Load:

The VE of a motor changes greatly depending on RPM and load. ECU software generally has tables with RPM on one axis and load on the other. Each cell represents a given RPM and load. And for each cell, there will be a given VE. These three things must be taken into account when determining what the AF should be at that point as well as timing. Getting this all perfect is the goal of tuning and is best done on a dyno.

Auto Tune:

Most cars have auto tune. In cars, this is called "open loop." Generally, the ECU gets info from sensors such as an AF sensor and sometimes a knock sensor. Over time these ECUs "learn" and tweek the tuning for the conditions and driving habits. Generally, open loop is used to reduce fuel consumption and emissions. Under heavy load, a car motor will enter "closed loop." In closed loop, the ECU drops the info from the sensors (not knock sesnor) and uses the information stored in the tables. Generally, open loop is not considered adequate for high load WOT conditions and therefore not used as a tuning mechanism. One reason micht be because regardless of how many times your ECU samples a wide band O2 sensor, the sensor can only measure at a given rate and it probably isn't anywhere near fast enough to acturatly assign values all along the RPM and load range.

So, if you are just wanting to maintain a decent AF ratio (assuming that is your problem) and auto tune device may work. But the proper way to tune a motor is to buy a device that controlls AF and timing, put the bike on a dyno and have it properly tuned.

By the way, pretty much all tuning problems can be masked by running a rich AF ratio. But that may come at the expense of lost power. Never assume that because adding fuel made your bike "run right" you have properly tuned your bike.

Octane:

Like a richer AF ratio, high octane ratings slow the rate of combustion. So, the higher your RON, the more timing and the leaner AF ratio you can run at a given RPM / load. This translates into more power. Also, combustion of lean AF mixtures can actually release more energy where as rich mixtures can result in unburned components and lost power.

Bottom line:

If you want to make your bike run ok after putting on a cool sounding pipe, an auto-tuning device that enriches your AF will work. But, if you want a proper tune that will result in more power, get a device that controls both fuel and spark and have your bike properly dyno tuned.

Well, that is a start. Gotta get to work. I hope people find this useful.

[Canadian]

Good thread and good start to the thread. I’ll share some of my experiences… might be some overlap.

I spent 10 years modding my Talons for the track. I started stock knowing nothing. I then moved to some simple things like upping the boost and improving the airflow.

Then I got into the tweaks to the existing system starting as simply as putting a potentiometer into the barometric sensor circuit to fool the computer into thinking it was colder out so it would be more aggressive when looking at it's closed loop maps for timing and fuel. I also modified my MAF sensor to trick it into thinking less air was entering than there really was.

The next major step was getting a piggy back computer (AFC) to hack some of the other inputs to the computer to further confuse it into being more aggressive and with more precision. It also allowed me to introduce offsets for things like larger injectors.

All of this was just hacking the existing system. It allowed for some great strides but it had it's limits as did the system itself. One big limit to the system was the narrow band o2 sensor. The narrow band sensors don't accurately tell you the current A/F ratio... they merely let the system know if the a/f is above or below stoich. So when the car is in closed loop cruise mode the computer looks at the narrow band sensor and when the A/F goes above stoich it adjusts it richer slightly causing the a/f to go below stoich... creating a compensating cycle above and below stoich. That is what the narrow band o2 sensor is there for. It's cheap, it sucks but it does that job well enough for the system to work.

The stock computer never looks at the narrow band o2 sensor at WOT (wide open throttle). The designers of these system know better than that. As stated above it looks at other sensors including actual airflow (MAF or MAS sensor), air temp, barometric pressure (sometimes gears i.e. TRE) and goes off to it's maps and comes back with a timing advance value and a ‘time to leave injector on’ value (how much fuel to add).

In addition the stock computer is listening to the knock sensor all the time. If you start knocking the computer starts scaling everything back. When there is no knock it scales everything forward again up to the max ‘everything is great’ map values. So I had a knock light on my car that told me when the ECU was scaling things back. Actual knock events are too quick to see with and LED so there is no point hooking up and LED to the sensor line itself.

That brings up my point about octane. If your car is stock it likely tuned well to be pretty close to the point of knocking but not knocking when using the recommended octane gas. So if you are NOT knocking on 91 octane gas your computer will be using max map values. If you then put in 94 octane your car will still NOT be knocking and so the computer will use those same max map values. There is no improvement to be had here if you are not knocking. In fact you will actually LOSE performance. This is due to the fact that higher octane gas burns slower. So the point of peak pressure of the combustion is later. Delaying the point of peak pressure is in fact delaying your actual timing. So you are losing performance in this case. You would HAVE to advance your timing somehow to compensate.

The only time higher octane gas makes sense is when you are free to advance your timing and lean out you’re a/f ratio. Or if you need to compensate for a lean condition you have created with mods. Otherwise it’s going to slow you down. I have seen it time and time again when a guy rolls up with his stock car to the ¼ mile and runs slower on high octane gas vs. the gas he drove in with.

So back to my story… eventually I learned enough to take the big leap. I ditched the stock system entirely and went with a standalone engine management computer (AEM). The major upgrades I had were being held back by the stock system even with the hacks. This was a hell of a learning process but I eventually was running my own maps I built from scratch on the road (daily driver) and at the track (500+ hp out of a 2.0L 4 cyl). Fun stuff. The main accessory that was required was a real o2 sensor… a wide band o2 sensor. This made WOT tuning possible. I could graph out all of the major considerations during a run (including knock) and make adjustments for the next run. It even had a closed loop system that looked at the accurate reading of the wide band o2 sensor and made slight adjustments keeping it to the target a/f I set for that range of settings during cruise.

So that bring us to now. I don’t know bikes yet. I assume my 109 has a similar system where the computer listens to knock, looks at air flow, air temp, throttle position etc and looks to a narrow band… going open loop for cruise and closed loop (go to the maps) for off-cruise. I need to learn. Any 109 info you have to offer about the system I am all ears.

I haven’t had a look at each of the tuner options available. I am not sure which are tweakers or what they tweak in each case and which are legitimate systems yet. A system that claims to be an auto-tuner without a wideband o2 sensor scares the sh#t out of me. Obviously the TRE is a simple tweak… fooling the ECU as to which gear it is in to eliminate the pull back scalars it uses for gears 1-3.

Keep in mind that the maps are designed for limits to each variable that the bike would normally see under stock conditions. You can very easily fall off this map when you start modifying your bike. So there can be conditions where you really need more fuel but the max map position the stock computer has to reference is actually lower than needed… causing a lean condition. I do not know any of the limits for the 109 yet so can’t offer any advice.

Anyway… that’s my tuning story and hopefully some useful information. I look forward to the next chapter as I get into the world of bike modifications (when money allows).

[TRod]

Just a point of correction. Closed loop is when the sensors are providing feedback. Open loop is when they are not.

[Wjduke]

There's usually a challenge to something by now...I think everyone is impressed!

[Canadian]

Just a point of correction. Closed loop is when the sensors are providing feedback. Open loop is when they are not.

I beleive you are correct. Been out of the game a few years now. Feeling a bit rusty getting into it on the bike side of things so I am going to take my time.

So let's start with the basics for the M109R system. What sensors do you know about? Please keep in mind I am coming from the world of cars so I am very ignorant about bikes. I also know nothing about the world of carbs and distributors so don't go there.

How much is the ECU monitoring...

Airflow? Is there a sensor that accurately measures the amount of air entering the system? What type is it (Karman vortex or hot wire or other?)? Where is it located exactly?

Knock sensor?

Air temperature?

Barometric pressure?

Gear sensor? Yes it seems since the TRE hacks this.

RPM? Yes

Any help you can offer would be appreciated. I'll try and dig up what I can online and from the service manual.

[Zoom]

I beleive you are correct. Been out of the game a few years now. Feeling a bit rusty getting into it on the bike side of things so I am going to take my time.

So let's start with the basics for the M109R system. What sensors do you know about? Please keep in mind I am coming from the world of cars so I am very ignorant about bikes. I also know nothing about the world of carbs and distributors so don't go there.

How much is the ECU monitoring...

Airflow? Is there a sensor that accurately measures the amount of air entering the system? What type is it (Karman vortex or hot wire or other?)? Where is it located exactly?

Knock sensor?

Air temperature?

Barometric pressure?

Gear sensor? Yes it seems since the TRE hacks this.

RPM? Yes

Any help you can offer would be appreciated. I'll try and dig up what I can online and from the service manual.

It monitors engine temperature, air temperature, barometric pressure, throttle position, gear position and rpm. I can't think of anything else it looks at to set engine tune parameters. Definitely nothing that measures actual air flow, such as a MAF or MAP system.

No knock sensor, and only European bikes have O2 sensors.

[TRod]

I beleive you are correct. Been out of the game a few years now. Feeling a bit rusty getting into it on the bike side of things so I am going to take my time.

So let's start with the basics for the M109R system. What sensors do you know about? Please keep in mind I am coming from the world of cars so I am very ignorant about bikes. I also know nothing about the world of carbs and distributors so don't go there.

How much is the ECU monitoring...

Airflow? Is there a sensor that accurately measures the amount of air entering the system? What type is it (Karman vortex or hot wire or other?)? Where is it located exactly?

Knock sensor?

Air temperature?

Barometric pressure?

Gear sensor? Yes it seems since the TRE hacks this.

RPM? Yes

Any help you can offer would be appreciated. I'll try and dig up what I can online and from the service manual.

A peak at the service manual will reveal all the feedback to the ECU from various sensors.

[Canadian]

A peak at the service manual will reveal all the feedback to the ECU from various sensors.

Indeed. So far from a quick look the basics seem to be...

It looks like the main FI maps use:

• Intake Air Pressure Sensor [IAP]
• Crankshaft Position Sensor [CPS] (engine speed)
• Throttle Position Sensor [TP]
• Secondary Throttle Position Sensor? [STP]

Then there are some further compensation adjustments based on:

• Engine Coolant Temp Sensor [ECT]
• Intake Air Temp Sensor [IAT]
• Battery Voltage
• Engine RPM Signal
• Starting Signal
• Acceleration/Deceleration Signals
• Tip-Over Signal (Cut)
• Over-Rev Limiter Signal (Cut)
• Gear Position Signal

[Syler]

Did I have my loops backwards. Been a long time.

I'm gathering the 109 uses a speed density system? That makes sense cuz a MAF system shouldn't need a tune just from changing your intake and exhaust. I think some of the auto-tune deals like the Cobra do use a wide band O2 sensor. But still, I know car tuners don't rely on even WBO2 sensor feedback for WOT, high RMP map areas. It just isn't considered Kosher. Keep in mind, a WB is measuring the exhaust gas. Things in the motor are happening much faster than that process can take place. If you hit a lean condition at the wrong point in the map your motor would blow long before it even reaches your WB. Bottom line, auto-tune devices are mainly for small fuel adjustments and are not really a proper way to tune. I think we can all agree on that.

As far as knock sensors, my understanding is that they still aren't perfected and not all motors have them. Not imporatant for us though. We want to get in there and push things up past where the stock map might max out. Anyway, the Power Commander V will add timing up to 20 deg.

As far as octane - of course the idea is to run more timing or leaner AF ratio. Not much point otherwise although a hotter plug might make a difference. It isn't really the "burn" that is slowed; that is just a simlified explanation. It actually raises the energy of activation point. That means you need more initial energy to get the combustion reaction started. But yes, timing is so subtle that I could see how that would have the same effect as retarding your timing.

Anyway, it's great to start a discussion on the 109 system. I would like to know if devices such as the PCV are piggy back systems or what. I'm curious as to how a plug and play device can add 20 deg of timing on its own. Anyway, my plan is certainly to get my setup together and then have my bike dyno tuned. The PCV even has a dual map with a switch.

Now, if I did one tune for race gas and one for a wet nitrous system, could I use the nitrous tune for pump gas? I've never tuned for nitrous but my understanding is that it is just a less radical tune. Race gas really isn't all that rare here in the greater Detroit area. Also, I've heard you can add some toluene to your gas to bump up the RON. Anyone do this?

[Syler]

Well, I just found a guy down the street who sells 110 RON $7.99 per gallon. So, it looks like a good dyno tune is in my future. It will be interesting to see how much more power I can make with an intake, pipe and tune for 110 RON. I bet I get a good 15HP maybe more.

[Canadian]

Let us know how it goes.

I started looking into the Cobra FI2000 and Power Pro. Both tap into the injector duty cycle wire to each injector and modify that signal.

Pretty standard stuff. The ECU figures out how long to leave the injector on and sends that signal to the injector. The singal is basically an on/off square wave. It cycles high for the time that the injector should be firing and then off. How much fuel gets into each cyclinder for each combustion is determined by how long its injector is on turned on by the ECU.

So these tuners are' piggy back' or 'hyjacking' tools. They intercept the signal coming from the ECU and modify it. So they modify the signal to leave the injectors on longer to add more fuel than the ECU knows is being added. In this way you can offset for the extra air entering the system without the knowlege of the ECU from say an aftermarket exhaust or intakes or other mods.

You might not be able to perfectly compensate with the base model but you can ballpark once you learn how to properly use the 3 pot settings. Fortunately the units come preset for different bikes and shouldn't be too far off out of the box. You can also check with the community here to find similar mods and see if you can find settings that work best. Of course a dyno tune would be great but not everyone can afford that.

The Power Pro Auto-Tuner does the tuning differently... at least the on throttle tuning. Usually auto tuners look to a wide band o2 sensor reading to see what the a/f ratio actually is an adjust from there. The Power Pro does NOT do this however. The Power Pro uses a method where it just looks at the crank sensor. The crank sensor tells the PP how fast the engine is turning. If it makes a change and the engine turns even faster then it made a power improvement. During acceleration the Power Pro makes minor adjustments to the fuel on the fly and checks if the rate of acceleration improves or gets worse. If adding fuel improves the rate of acceleration it adds some more and checks again. It continues these adjustments until it does not see improvements. It does this many times a second.

I am not sure if it keeps any memory of what it has learned or if it just stays in a constant state of adjusting based on a default value. I will try to dig into it more. It is clear that it never stops tuning though.

Interesting idea.

But again it only adjust the amount of fuel and has no direct impact on timing.

For most modest modifications tweaks to the fuel are probably good enough for the masses.

The only concern I have is that an engine will perform it's best just before it blows up. So with no o2 sensor to check and no knock sensor how does the Power Pro stop from going too lean? I mean they must have thought of that, they don't want the liability of blowup up everyone's motorcycles. I am just curious how they achieve the best performance without going too far.

Also this is not one of those mods you can do by simply adding a resistance to the wires. You need circuitry that can modify the duty cycle wave intelligently. This is not a DIY project for anyone but an EE or a good Tech.