There’s a lot that can lead to discouragement when you’re looking at the overbearing task of transforming your project into your street or track dream. Money, resources, worrying about being thorough and doing the job right, time, tools; there are dozens of things that actively pressure us to prevent the projects from moving forward. Some of these things we can’t really change. After purchasing my most recent project, it sat through the winter because I wouldn’t spend the money to purchase space heaters in the garage, saying I would hit it hard when it got warm. Then in February, I got called out to work out of state for what ended up being the better part of two months, completely unable to keep working even if I had all of the time and energy ready to go. I flew back on some weekends, but the compressor seal went on my daily driver, so my weekends were mostly devoted to pulling all the intercooler piping, cleaning everything that was now slobbered in oil, and rebuilding the blower, all so I’d have something I’d be able to drive again once I would be working back in my home state.

There can be a lot of things that push our projects further and further on the back burner that happen out of pure circumstance. This is in a large part why you see so many unfinished projects for sale. The sheer, undeniable gravity of forging ahead when coupled with circumstance and real life can ultimately question what was once your passion and almost nearly turn it into a burden; so you slap a For Sale sign on it, and move on with your life.

However, I feel that more often than not, these barriers we set up for ourselves can be easy to overcome with the right motivation. Even after years of being involved in modifying cars for the street and track, there are times when I feel downright overwhelmed with the projects I undertake. I spend time several nights a week, just staring at the project I purchased over the winter, dumbfounded by the amount of effort and time that must be left to feel any pride or adrenaline out of it. So I say ‘tomorrow‘, close the door, and wait for the right motivation to keep pressing on. For me, surrounding myself with similar-minded people has always been a fuel to my motivation. Friends from out of town coming to visit? Better get the timing right or button up the exhaust so I can fire it up for them. Being in the garage with a handful of beers and similar-minded friends can make even the most insurmountable tasks seem minuscule, leaving to ask yourself ‘Why didn’t I do this three weeks ago?’. Regardless of how inexperienced you may be, don’t let your projects overwhelm you, no matter what it is or what you need to do. Go for it. If you’re nervous, or inexperienced, take the time to learn about what you’re trying to do. More often than not, people have done what you’re trying to do before, and have some form of guidance to help you on your way. Even if your project really is one-of-a-kind, the root principles in building cars still all apply. Learn from your mistakes. You’re bound to make them. Don’t let them discourage you, these things can and will happen. It’s important to realize that some of the reasons you’re not progressing on your projects can be preventable. Just remember, the only failure is inaction. Everything else is trial and error.

Link to ’25 Things Every Young Professional Should Know by Age 25′: http://www.huffingtonpost.com/danny-rubin/25-things-every-young-pro_b_3272145.html

Without further ado I give you my newest project: 2000 Ducati Monster 900

This project has been an idea I have had for a while now. I have always loved the Monster design; there is something about that naked trellis frame that i love. Back 3-4 months ago I was helping a friend look for a Monster and had come across an early 2000 Monster 900 Dark. bike was is good condition and I like fell in love with the matte black color of the 900 Dark and that was when i decided i wanted to build a Cafe Racer styled Monster. I didn’t really have any specific idea of what I wanted to do from a design/modification/fabrication standpoint, but I knew i wanted a Monster 900 as the base of the project. The day I went to buy it for my friend/as my project bike (those details were to be hammered out later) I got a call from the owner that it was sold earlier that day. Looking back at that bike I am glad it sold before I bought it. Realistically it wasn’t a project bike plus the asking price was double what I paid for the current project bike.

Last week I finally found the bike I was looking for: a 2000 Ducati Monster 900 with a ton of miles on the frame and a good chunk on the replacement engine. The bike was painted by a previous owner therefore making it much easier to justify repainting everything and tearing the whole bike down to do so. (If you can’t do it right it isn’t worth doing) So keep an eye out for updates regarding the new Cafe Racer styled Monster 900. I have no idea how often I will be posting updates but i can’t wait to start tearing into this project.

One last note regarding projects. Don’t pick up the first one you find unless you know it is the one. Realistically that 900 Dark would have been nice to have, but it was already a complete 100% ready to go bike. This new one is much more of a project bike. I won’t need to justify anything I decide i want to change since it has already been painted and isn’t in perfect shape. Remember good things come to those who wait.

Hopefully I’ll get some pictures up by the end of the week. Here is the photo from the Craigslist add

However, there is another, much more sinister potential for failure that is much harder to catch, and typically much more devastating. In almost every case it is caused by the same thing: overthinking the problem – typically caused by trying to be “clever.”

When this is the case, the following will always be true:

The equation utilizes the rule of pi (the fact that for any project the amount of time, effort and money required will always be 3.14159 times your initial expectations, while payoff will 3.14159 time less, with the chance of failure being 3.14159/amount of sleep in the past 24 hours) and a few constants and functions relating mostly to attempts to be clever.

Note that as time thinking increases, you reach an inversion point where the likelihood of failure increases and, initially, begins to oscillate randomly. This corresponds to that point in any project when we begin to rethink our design and try to be “clever.” Note that the chances of failure momentarily reach a negative failure. This is the epiphany moment. Every project has one, though it is brief and 99% of the time we will pass through this moment and never realize it until it’s too late.

As an engineer I have been on the wrong side of this graph on a few occasions, and typically there was a disastrous consequence (though following proper procedure, designs were tested in safe and reliable manners before they were implemented, saving any real harm other than lost time, material and much frustration.). I almost every case the same underlying theme was there: we tried to be clever. In an attempt to save weight, gain power, improve packaging   or similar goals (typically combining a few of these) there would be an overly complicated solution to what is typically an simple problem.

In every case there was an exhaustive list of issues that could have caused the failure. Though as a design becomes more complex and more time is spent on the thought process items which may have been a minor issue and have been easily remedied or diagnosed are now part of a complex system and easy to overlook.

Chances are, it will happen to you at some point. And yes, it will suck. I feel your pain. But take that moment to learn a lesson. And next time keep it simple!

In conclusion, I leave you with the wise words of Pat Clarke: “The trick is, There is no trick!”

http://www.tuneddesign.com/Seminars/Sus_101.ppt

I still find that I struggle to succinctly describe suspension design and theory. It is such a broad topic, and requires a in depth discussion of the physics of vehicle dynamics which tends to either bore or confuse/scare most. I’ve been working with vehicle dynamics for 5-6 years now and still find myself reaching for reference material on a regular basis.

With my current round of Engine tuning articles wrapped up (though I am far from done with this topic!) I am going to focus on the same approach for suspension. I still believe I can use the same approach and break it down into the basics with out requiring a PhD. in advanced mathematics to understand. Maybe I can keep fooling you guys into believing I know more than I do. At least I can still stall and sound like I know what I am talking about until I figure it out.

The physics

Knock and pre-ignition are phenomena that describe improper or uncontrollable combustion, and both lead to reduced performance and drivability and can even cause catastrophic engine damage. Understanding what these terms describe, the physics behind the phenomenon, why they occur and how to prevent them is the most critical aspect of tuning your engine, as a mistake here will essentially guarantee eventual engine failure.

Ignition

To fully understand the phenomena we must first discuss and understand the basic ignition process itself. Recall that an engine is essentially an air pump and relies on changes on pressure to move air in and out of the engine. Ignition of the air/fuel mixture is initiated by the spark plug when either the ECU or distributor signals the ignition coil to fire. This causes expansion of the previously compressed gas mixture.

Proper timing to ensure maximum power requires ignition of the mixture at the peak pressure in the cylinder. However, since ignition is not an instantaneous event and the flame front propagates through the combustion chamber. This requires the initial spark event to occur Before Top Dead Center (BTDC) and is always measured in degrees of rotation in reference to top dead center. When tuning ignition timing in an ECU map it is these values that are being modified. Typically positive values indicate degrees BTDC while negative values are ATDC.

Timing the spark event to ensure full ignition of the mixture always occurs at peak cylinder pressure will create the most torque from the engine being tuned. The key is to have as little timing advance as possible, while still maintaining this pressure – this is a torque limited ignition mapping method and the value may be referred to as the Mean Best Torque Spark Advance and should always be the target when not limited by engine behavior such as knock or pre-ignition. This is precisely why monitoring and controlling knock is so important.

Knock

Knock, pinging and detonation describe improper propagation of the flame front – in other words, the air/fuel mixture is burning in an inconsistent and unpredictable rate. This causes the final ignition event to occur at a time other than peak cylinder pressure and a decrease in pressure. This can be caused by many issues, including incorrect spark timing, failure of the fuel to atomize, or local hotspots in the combustion chamber. This will cause multiple areas of ignition not in the same location as the flame front. This can be basically described as the ignition force “jumping” around the combustion chamber, rather than coming from one location.
The result is each of these ignition events producing its own pressure or shockwave. These waves propagate from the local ignition point, and run into each other within the cylinder. The result is a combined shockwave resonating at a different frequency than normal combustion and even creates an audible metallic knock or pinging noise, hence the name of this phenomenon. This can case holes in engine components and small indents on the piston face as well as very rapid wear and stress on all engine components.

If knock occurs at an ignition timing value less advanced then that for best torque, the engine is said to be knock limited, as ignition timing is tuned to prevent knock at this map location rather than for maximum torque. This is often the case in higher compression and force induction engines, where pressure and temperature in the cylinder can be very high. The key is to request as much spark advance as possible while avoiding knock during any engine operations and parameters.

Pre-Ignition

Pre-Ignition is a very separate and differing phenomenon than knock. Pre-Ignition occurs when the mixture is caused by a means other than the timed spark event, often significantly before the intended timing. This causes massive stresses on the rotational components of the engine, as full ignition occurs before peak cylinder pressure and far before TDC. The premature ignition attempts to push the piston backwards against the rotational inertia and can often lead to broken connecting rods, wrist pins and other component failure.

Pre-ignition is often caused by excessive temperatures in the combustion chamber from high intake temperature, high compressions, high levels of boost (which cause high intake air temperatures), physical hot spots due to piston imperfections or damage, or low-grade gasoline (lower octane gasoline is easier to ignite.) Prevention of pre-ignition is achieved largely through proper selection of parts, operating parameters (boost, fuel used, etc) and engine building. Pre-ignition is usually an indication of a larger scale problem with the engine of vehicle. Pre-ignition can also be avoided by using items such as water/methanol injection or an intercooler to lower intake temperatures or methods to increase the effective octane rating of the air/fuel mixture.

Tools of the Trade

Thankfully there are many tools for detecting, predicting and controlling knock. The cost of these tools range from under $25 to a $1000 or more – The simpler tools will allow the user to determine when the engine is knocking, while the more sophisticated tools will use assumptions and prior data to predict and prevent knock before it becomes severe. Understanding how each tool works, what the information means and how they are applied is critical to deciding which tools are required for your tuning strategy.

• “Det” Can
  A detonation, or “det” can is essentially a stethoscope for an engine and allows the tuner to physically listen to the internal heart beat of the combustion process. It is the simplest and cheapest tool for detecting knock yet is still a very reliable means of detecting knock – and the good news is you can build one yourself for $25 with parts from your local hardware store. The det can is basically an amplifier for the vibrations of your engine. It attaches a cylinder to the block that will vibrate and create a pressure wave inside the cylinder, and then connects this cylinder via an air hose to a headset or another can to allow the user to listen to the noise. This works on the same principle as homemade “two cans on a string” trick.
  During normal operation the noise generated in the det can will resemble normal engine noise and have the same frequency. If knock were to occur, however, there would be a different and very distinct noise heard. By listening for these events you can determine when your engine is knocking, and tune accordingly.
• Knock Sensor 
  There are 2 common types of sensors that may be used to detect knock. The first and more common type – which will typically referred to as a knock sensor, is the microphone type. The second is an in-cylinder pressure sensor. Both are discussed and have distinct applications and advantages.
• Microphone Knock Sensor
  The microphone style sensor is the most common knock sensor used, and is even commonly found on most OEM vehicles with a closed loop knock system. Many aftermarket knock lights, knock monitoring systems, and standalone engine management systems also heavily rely on this style sensor as the backbone of their system. This common sensor is really just a microphone in the most basic sense. The sensor is attached solidly to the engine block, and detects engine noise the using the method any common microphone uses. This sensor, however, is calibrated to listen and detect very distinct frequency ranges.As discussed earlier, knock will create a pressure wave in the combustion chamber that will vibrate at a frequency easily differentiable from background engine noise. The microphone knock sensor has to be calibrated to determine the normal frequency range of the engine, and will filter this noise from the output. When any noise outside of this frequency is detected, the knock system will pass this information to the ECU or to the indication system being used (I.e. knock light). By tying this information with other data in the ECU, such as AFR, RPM, Load, Spark Advance, etc the tuner can determine the location in which knock is occurring and change the tune accordingly.

  There are a few drawbacks of this sensor, however. The largest is it susceptibility to noise. While most engine noise can be filtered, there are cases were excessive background and engine noise will prevent the sensor from providing a reliable and accurate signal. The opposed Subaru engine is a common culprit – the OEM knock detection system will actually operate in open loop and ignore the sensor in the upper rpm ranges due to this issue. More sophisticated systems may provide better filtering and sensitivity to prevent this issue, but care should always be taken when determining a mounting location for a knock sensor of this type.

  Since this sensor works by detecting vibrations transmitted through the block from the combustion chamber it is really detecting the symptoms of knock, and not knock itself. Due to this, it is especially critical that the sensor be bolted to the block itself, and as close to the combustion chamber as possible. Problems arise if there are differing materials or gaskets/seals between the material the sensor is bolted to and the cylinder. This method of measuring also means that knock must first occur before the system can detect it, making prediction of the onset of knock difficult and based on assumptions and historic data rather than real time measurements.

• Pressure Sensor
  Utilizing a pressure transducer the actual pressure in the combustion chamber can be measured. Since knock creates a pressure spike and fluctuations within the combustion chamber, this is a very accurate way of detecting and measuring the severity of knock. The sensor can also measure real time propagation of the flame front as pressure will rise as the ignition event occurs.Since the pressure sensor will detect very small changes in cylinder pressure the tuner can see fluctuations or inconsistencies which may indicate the onset of knock. This additional resolution and foresight allows the tune to be more aggressive with less risk of potential performance degrading situations or harmful engine conditions. Additionally, this sensor allows the tuner to accurately determine the point of maximum cylinder pressure and provide another useful tool for determining optimal ignition timing.

  This method is not without drawback however. The sensor is typically more expensive than other methods of knock detection. Mounting requirements can also increase the cost of the engine if installed in an OEM system. Additionally, mounting of such a sensor, if not originally equipped, can be extremely difficult, if not nearly impossible without modification to the engine block itself. One solution to such a problem is incorporating the sensor into the spark plug. A piezoelectric pressure transducer is fitted onto the spark plug, and then the spark plug is installed as normal (albeit with an additional wire lead for the new sensor.) This is a very simple and elegant solution to the problem – however it does significantly increase the price of the spark plug as well as the consequences for damaging or fouling plugs.

  The application of these types of spark plugs is still fairly narrow, and it may not be possible to purchase such an off the shelf solution for many cars at the present time. It is however possible for the electronic savvy individuals to fabricate their own plugs with such a solution, though care should be taken not to disrupt the behavior of the spark plug or influence the combustion process with placement of this sensor. Also note that many sensors may be negatively influenced by the electrical activity during a spark event or the heat of the combustion process. These areas will require special attention if constructing a homemade sensor. Only the most experienced and knowledgeable tuners and engine specialists should attempt such a sensor, as the consequences of a mistake and failure during operation can and will cause dangerous conditions and can lead to catastrophic engine damage.

Controlling the Chaos

Ignition is the last of the critical steps in the combustion process. Ignition and timing is what extracts the energy stored in the compressed air fuel mixture. Without the spark AND the correct timing any engine will never achieve maximum performance. The most common shortcoming of many tunes and tuners is the timing setting and a lack understanding of the physics of combustion and timing.

Understanding combustion, the effects of timing and causes of knock is critical to extracting the most from your engine. This begins with being able to accurately detect and measure knock. Determining when and why knock occurs will give you the edge in building not only a high power and efficient engine and control system, but also a safe one. Less money spent fixing broken parts is more to spend on the parts to go even faster.

This article appeared in Juiced Custom Automotive Magazine

Copyright © Brian Barnhill 2011
Cannot be used or reprinted without permission.

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The FT-86: If you haven’t heard of this yet you have been living  under a rock (or hiding from tuner fan boys)

The resurrection of the drifting cult hero car – the new hachi has certainly generated excitement and possibly a few wet dreams in the import tuner crowd. With its Subaru based 200hp in a ~2600 lb chassis, rwd, LSD on manual cars and a wide array of the toys that make us giggle like school boys finding our dad’s “ahem “special magazine collection” – it’s no surpise,

Can this car deliver on the hype though? So far Toyota has been mum on official specs and details. The specs that have been circulating the internet as the official numbers come from a leaked training manual in Japanese. If the car delivers, and at the price being rumored of around $20k, it will be quite the contender. I can’t help think that there might be some disappointed young men re-watching their Initial D collection to cope when this car hits the showroom. Anyone remember the Hyundai Genesis? Hype.

I will be writing a little more on this soon and will be watching the developments as this car makes it’s way to the showroom. For now what are your thoughts? Will the car be all it’s hyped up to be? Discuss.

A proper launch is key to success in any level racing. Eliminating wheel spin and wheel hop, maximizing traction, weight transfer and power off the line, and in forced induction car, to build boost before launch are all critical components in the launch of any vehicle. The ability to do all of these consistently and in a controlled fashion with as little impact to the vehicle as practical is key to success in any level of racing. Sophisticated traction control systems can aid in the traction and wheel spin areas, but work by limiting your power. This can seem counterintuitive when you “want to go fast.” In addition, true traction control systems sophisticated enough for racing applications are available only in a handful of exotic cars with a price tag much out of the traditional “tuners” budget. The solution for all of these problems, however, is quite simple: Launch Control.
What is launch control, and how does it work?

Launch control (sometimes known as a stutter-box or 2 step rev limiter) are fairly simple, yet effective in ensuring consistent reliable launches at the track, strip or even on the street. The user defines a “launch rpm” that, when launch control is activated, the vehicle will maintain. This allows the user to hold the car at full throttle while still maintaining a suitable RPM for launch, based on vehicle capabilities, traction, wheel hop, etc. Turbocharged cars see an additional benefit in the ability to build boost before the vehicle leaves the line. These capabilities lead to smoother, consistent and reliable launches with maximum power from the moment you leave the line. This will help lower your 60ft times and/or help you be the first into the corner.

In turbocharged vehicles, additional boost can be gained using Gizzmo Electronics LI2 ignition retard feature. Retarding the ignition from the default setting increases load, which in turn will cause the turbo to spool, thus creating more boost for launch. Each vehicle will have unique requirements to achieve maximum, yet safe, consistent and reliable power during a launch event. The ability to control the amount of timing retard only when launch control is activated allows the user to custom program the LI2 to their particular vehicle setup and requirements. When adjusting these parameters it is also suggested that Exhaust Gas Temperatures are monitored to ensure EGT levels remain in a safe range as retarding ignition can increase EGTs in such conditions.

Note that launch control is not to be confused with Anti-lag, which is another method to aid in launch and off throttle boost. Anti-lag essentially creates an explosion inside the turbo to maintain boost, even when the driver is off throttle or at a stop. Anti-lag is commonly used on rally cars and other turbo-charged race cars. It is VERY hard on the turbo and should not be run by anyone with a budget less than that of a race team as it will lead to premature failure of your turbocharger. Sometimes these terms are used interchangeably – however typically Anti-Lag Systems refer to a system that functions AT SPEED (i.e. while the vehicle is in motion and in gear) with the throttle closed. This is sometime refereed to as Rally-Anti-Lag, due to it’s common use in Rally Racing vehicles. The intention is to keep boost pressure even when the drive is off throttle while cornering, etc.

An anti-lag system will retard timing, bypass the throttle plate (i.e. injector more air into the exhaust stream, creating a VERY lean mixture) and sometimes will influence fueling. The idea is to create a lean, dense mixture in the exhaust stream and keep the turbo spooled at all times. As the mixture is so lean, it will ignite in the turbo/exhaust stream. This is much more violent than that of WOT style launch control and hence the additional danger to turbos and other vehicle components. Creating boost with the throttle closed also poses additional threats to the turbo due to the additional pressure on the compressor housing (think surge!) Many turbo manufacturers will not warranty damage caused due to use of this Rally-Style Anti-Lag system. As mentioned in the article, unless you have the budget of a rally team, or a large supply of turbos, it is NOT recommended to use Rally Style Anti-Lag for street vehicles.

Hopefully this clarifies the difference between the two systems and terms which are commonly interchanged. For the purpose of all my articles, unless otherwise specified, “Anti-Lag” will refer to at speed Rally style ALS and Launch-Control to WOT Standstill/Shifting boosting systems.

Launch control units work by intentionally creating a misfire event in random cylinders when launch control is activated (commonly activated through the use of a clutch switch and/or speed sensor signal.) The launch control interface intercepts the spark trigger from the ECU (note this is NOT the high voltage spark signal!) and modifies/interrupts the signal to create the misfire event to hold the vehicle at the desired launch rpm. In a turbo application, having the throttle open while inducing misfire will increase the velocity and density of exhaust gases, which will lead to turbo spool and generating boost with load. This results in boost being generated before launching and therefore allowing a vehicle to launch with considerably more power. In addition to control at launch, controllers which use a clutch activated reed switch, such as the Gizzmo Launch Interface, also can serve as a controller for flat shifting (no lift to shift) where the driver keeps the accelerator floored during a shift and simply presses the clutch to activate the second stage rev limiter. Similar to a launch event, this will cut ignition and timing to the desired rpm, preventing over-revving during the shift event. This allows the user to make quicker shifts and maintain boost while shifting.
Do I need it?

• Do you want consistent launches, without wheel spin or wheel hop in your boosted or naturally aspirated car?
• Do you have a boosted car and wish to build boost before you leave the line for more powerful launches?
• Do you want every advantage you can get to win races, run better times and/or just get the most out of your vehicle?

If so, then a launch control interface may be a serious consideration for your vehicle.

Keep in mind that the harder you launch the vehicle, the more stress you will put on your drivetrain. Axles, driveshaft, clutche, etc must all be capable of transferring the power you’re now applying to the wheels. With sticky tires such as drag radials, these forces are only magnified. Before launching your vehicle aggressively you will want to make certain that all these components are capable of handling the higher loads.

NOTE: in some vehicles an aftermarket launch interface may not be compatible with the ignition system in all cars. Vehicles which use a “smart” off board igniter where the ECU communicates with the igniter (rather than just triggers a spark) may not function properly, since the launch interfaces interrupts this signal. In addition, cars with misfire detection as a hard fault, or where the ECU receives a receipt of the spark.  A little research into your vehicles ignition system and coil setup will determine if launch control is possible with your vehicle.

This article appeared in Juiced Custom Automotive Magazine, Issue #4 May 2011

Copyright © Brian Barnhill 2011
Cannot be used or reprinted without permission.

The Ratio
We begin by first understanding exactly what we are tuning and why. The topic of interest here is the Air to Fuel Ratio (AFR) which is, as may be self-explanatory, the ratio of air to fuel in the combustion chamber. This ratio influences the behavior of the combustion process and will make the difference between maximum (and safe) power and/or torque and potential catastrophic engine failure. Because just a small difference in ratio can dramatically change the reaction, it is critical to understand not only the how, but the why when tuning fuel mix based on AFR.

It must once again be stressed that we should treat the engine as essentially a large air pump. At this point, however, you should have a strong grasp on the how, what and whys of the air flow in an engine and have maximized these aspects before moving on to tuning air fuel ratios. At this point we will first determine the theoretical air fuel ratio based on desired performance, and then begin manipulating the amount of ratio and adjusting the mixture from our theoretical baseline to account for dynamic engine conditions, additional engine modifications, drivability and other variables which influence combustion and an engines air consumption.

A reaction in which all components are completely consumed is considered to be stoichiometric (stoich). For gasoline/petrol this mixture is approximately 14.7 parts air, to 1 part fuel (14.7:1) for E85 this ratio is approximately 9.7:1 (note these ratios are approximate based on theoretical data assuming perfect laboratory samples, these ratios may vary slightly due to variations in regional and seasonal blends of fuel.) A ratio which has more fuel left over (ratios lower than stoich) are referred to as rich, while those higher, and thus having excess air, are lean. In all but very specific and extreme cases rich ratios should be the goal, this is due to combustion and flame behavior as well as safety reasons and avoiding accidental ignition of the mixture as leaner mixtures are easier to ignite.

 
AFR influence on Engine Behavior (Gasoline/Petrol)

AFR                 Lambda (λ)
14.7:1              1                                 Stochiometric
12.8:1              0.87                 Lean Best Torque (LBT)
12.2:1              0.83                 Mean Best Torque (MBT)
11.76:1            0.8                   Rich Best Torque (RBT)
11.01:1            0.75                 Flame speed fastest in cylinder

 
The table gives a basic overview of AFRs influence over engine behavior and dynamics and should serve as a general guide when determining air fuel ratios at full power/Wide-open-throttle. Assuming knock is not a limiting factor, Mean Best Torque should serve as a general starting point (if knock is a factor, more fuel, less spark advance, or less boot/compression will generally be required.) Note that best torque does not occur and the fastest flame speed. Any ratios richer than 11.01:1 should be avoided, as there is a very sharp and rapid decrease in torque at ratios richer than this point. Worth mentioning is also the fact that we may often see ratios leaner than 12.8:1, which is where lean best torque occurs. While this may sacrifice a small amount of torque the fuel economy and emissions at peak power can be improve which may be desirable (and necessary) on many street/pollution controlled vehicles.

This chart should be used as a guide; there are many other factors which will also influence your tuning and target air fuel ratio. Smooth idle, throttle response, fuel economy, emissions and general drivability. Typically target ratios should increase fuel (become more rich) as load and RPMs increase and approach the peak torque power band.
Note about Lambda vs AFR
You may have noticed in the table that Air-Fuel Ratio has an equivalent value called Lambda (λ). Lambda is representative of the stoichiometric ratio where a λ=1 will always be stoichiometric, regardless of the fuel in use. Other ratios are simply defined as a ratio in relation to stoich. For example, a ratio of 11.76:1 would be: 11.76/14.7 = 0.8. This simplified measurement is very useful, in fact, most oxygen sensors actually read in values of lambda, as they are actually measuring the ratio of free air in the gas mixture, and thus the ratio in regards to stoich. This simple process allows vehicles to also quickly adjust to differing fuel types. Most modern flex fuel vehicles that run on both E85 and petrol/gasoline have done away with the expensive alcohol sensors and rely on the oxygen sensor to determine what the mixture of fuel is and reference the appropriate map accordingly.

Measuring up
Knowing the exact ratio at any given moment is critical to tweaking the recipe to achieve the desired performance and engine goals. Thankfully there are tools which easily allow us access to this data, and at the heart of any of these tools is the oxygen sensor. An oxygen sensor basically works by reacting to unburned oxygen in the exhaust stream via a chemical reaction between this free oxygen, and the material in the tip of the sensor. This reaction causes the sensor to emit a voltage, which is then read by the controller and/or ecu to determine air/fuel ratio. There are variations in types of controllers, sensors and settings for oxygen sensors, understanding which one is right for each situation is an important step in tuning your engine.

Closed or Open loop?
These terms refer to the control method being used by the engine management system and determine how any information received from the oxygen monitoring sensors is used and applied. The loop refers to the path of data. In a closed loop system, data from the oxygen sensor is relayed to the engine management system. The control system will then use this information to determine if the engine is operating at the desired ratio, based on the programmed tables in the tune, and then adjusts fueling as necessary. This allows the engine to more accurately maintain the requested air to fuel ratio. Note, however, that if the base tune in inaccurate this method will cause the system to “seek” and constantly add or subtract fuel as it tries to maintain control. This will appear as the AFR fluctuating around the desired value. This can cause degraded performance, hinder tuning efforts, and even cause harmful engine damage.

Additional closed loop control is possible in systems using fuel trims. Fuel trims are a representation of the amount the control system is altering the fueling tables to achieve the requested AFR. Short term fuel trims are the instantaneous adjustments made by the control system and can be used by a tuner to monitor, log and apply the changes the system is making during closed loop to help tune the engine. In more complex control system long term fuel trims are used to apply changes to the base tune. The long term trim will average changes made in each site over a pre-determined time period. Once the time period or number of data points have been met, it will change the base tune by a calculated value to help dial in the base tune and correct for changes in the engine or permanent operating conditions.

The equation to determine % change of the injected value of V.E. based on AFR is: % Change = Actual AFR/Desired AFR *100%

Open loop systems do not use this data to make on the fly changes. This mode is desired in operations where rapidly changing engine conditions may make closed loop control difficult or dangerous. Wide open throttle and very heavy loads are examples of such conditions. Since conditions change faster than the sensor is capable of reading and the changing the mixture, closed loop control may allow for very rich or lean conditions at precisely the moment they would be the most dangerous. Again, having an accurate and complete tune is critical in these conditions to maximize performance and engine longevity.

Wideband vs Narrowband
There are two main differences when speaking about types of controllers and methods of measuring air fuel ratios: Narrowband and Wideband. Both are very useful tools in tuning and deserve a thorough discussion and understanding. Understanding how they work and when to use each method will simplify your tuning efforts and increase the quality and accuracy of the tuning and control strategy.

Narrowband
The oxygen sensors traditionally used by most OEM manufacturers are a Narrowband type sensor. These sensors are used to measure AFR in a very narrow range (thus the name) and are only accurate within this narrow area. The sensor will normally have a 0-1 voltage output and will be most accurate around a lambda of 1 (stoichiometric). The intent of these sensors, as equipped by the factory, is to control the vehicle in controlled loop operations, such as cruising on the highway as well as monitoring to pollution control systems of the vehicle. These operations are critical for maintain proper emissions and maximizing fuel economy and performance.

The drawback of these sensors comes precisely from this narrow accuracy band. Outside of this range, which is approximately 14.2 to 15.0, the sensor cannot be accurately relied upon for any changes, and it thus ignored. This prevents their use in applications such as wide open throttle or heavier load, where the conditions are too fast or ratios out of these ranges are desired. Recall from the table earlier in this article that for maximum power and torque the ratios are far outside this range. This limits the use of a Narrowband sensor to cruising and light load use only. It is, however, much more accurate than a wideband sensor in this range and is still a vital tuning in properly tuning a well rounded street vehicle.

Wideband
Wideband sensors, on the other hand, have a 0-5v output and a much wider accuracy range (The Innovate Motorsports sensor is accurate from ratios of 7.35 to 22.39 for example.) This increased range allows the sensor to measure the ratio accurately in all engine conditions. This information is critical when tuning your engine, as most of your tuning will focus on areas other than light load and cruising. Additionally, depending on the speed of the sensor and ability of the engine management system, can be used to create a closed loop control system in conditions other than just cruising. This control allows the engine to automatically adapt to changing conditions and correct for inaccuracies in the tune (as previously mentioned, and worth repeating however – closed loop, should NEVER be used as a “band-aid” for an incomplete tune.)

The Final Product
The air to fuel ratio is simply a representation of the most basic ingredients of combustion. Understanding how this ratio influences engine behavior is critical to controlling and tuning your engine and will be where most tuning efforts will begin. The main tool for monitoring this ratio is the oxygen sensors and controller and they are an integral part of modern vehicle control systems. In controls systems both open and closed loop controls will be necessary to ensure safe and controlled operation – and through the use of narrowband and wideband controllers it is possible to tune your vehicle for maximum performance, while also maximizing fuel economy, emissions and drivability – all of which are critical for a modern street vehicle.

This article appeared in Juiced Custom Automotive Magazine, Issue #5 June 2011

Copyright © Brian Barnhill 2011
Cannot be used or reprinted without permission.

This picture makes every part of my brain scream and my body automatically flinch. This is just a horrendous accident to come across. The rider keeps his cool and manages to avoid getting tangled up in the flying mess. Original rider escaped serious injury, few minor injuries (broken toes/foot) caused by riders struck by the rotating bike.

See the whole video here

THAT is calm under fire. Yeah. motorcyclists aren’t like the rest of the general population.