FastBikes-USA Dyno Tuning & Tech Page
1) FastBikes-USA's Superflow SF-240 Dynamometer
In 1997 when we decided to purchase a Motorcycle Chassis Dynamometer we spent quite a bit of time weighing the options available in the market place. At the time there were three options available, Dynojet, Factory and Superflow. Dynojet had been making motorcycle chassis dyno's for a long time but did not offer an Eddy Current Controlled Load Braking option at the time. I'll get into the absolute necessity of Eddy Current Brake capability later. Factory did offer an Eddy Current Dyno but was not a major player in the market. Superflow had a long and respected reputation for laboratory quality engine and chassis dyno's in almost all areas of the market, NASCAR, Formula One, Drag Racing, Emissions, etc. and was just about to release their motorcycle chassis dyno. Based on Superflow's reputation, their Eddy Current option and their highly sophisticated software we decided to put a deposit on their soon to be released SF-240 chassis dyno.
Since 1998
The SF-240 is not just capable of measuring and plotting horsepower and torque, but also has a vast array of configurable digital and analog inputs for measuring data such as oil pressure, oil temp, exhaust temp, turbo boost, fuel and air consumption or any other parameter that can be measured via digital or analog inputs. The SF-240 automatically corrects all measured data to SAE standard sea level conditions based on atmospheric conditions, including air temp, barometric pressure, humidity and vapor pressure. The software doesn't just apply this data to the atmospheric horsepower calculations but even goes so far as to use the calculated air density to adjust the air drag losses of the dyno roll rotating through the air, applying plus or minus hundredths of a horsepower corrections for air drag on the roll to the already sophisticated SAE atmospheric correction. All this adds up to a truly astounding level of repeatability. We have proven that we can dyno test a bike on one day, then retest that same bike, days, weeks and sometimes even years later, under totally different weather conditions and receive exactly the same results. In fact the horsepower plots will virtually lay on top of each other if there have been no changes to the bike between tests. This gives us confidence that changes that show up on a dyno pull on a different day are valid and useful for diagnosing a loss in power or quantifying a gain made from modifications since the last dyno test day.
Complementing our SF-240 is a four gas digital Exhaust Gas Analyzer (EGA) and a Wide Band O2 sensor which reads and plots in real time. At Fastbikes-USA we rely on both 4 gas EGA and O2 for all carburetor tuning and fuel injection mapping. Most dyno tuning centers rely solely on wide band 02 because of its ultra fast response time but do not realize that O2 readings are virtually useless at some combinations of throttle position and RPM, especially when tuning for maximum power (rich side) or in situations with long duration performance camshafts.
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2) Why we do what we do- Coming Soon
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3) Dyno Tuning Basic Terminology
Disclaimer - The following terminology is specifically applied to motorcycle based dynamometer applications and to Alpha-N based fuel injection systems.
Chassis Dynamometer - A device for measuring horsepower produced by an engine by simultaneously measuring torque and rotational speed (rpm). A chassis dynamometer measures power at the rear wheel of the motorcycle eliminating the need to remove the engine from the chassis of the motorcycle.
Engine Dynamometer - A device for measuring horsepower produced by an engine by simultaneously measuring torque and rotational speed (rpm). An engine dynamometer measures power at the crankshaft of the engine which requires that the engine be removed from the motorcycle and mounted to a test fixture. The test fixture provides a rigid structure to restrain the engine during testing plus all electrical, fuel and ignitions requirements to operate the engine.
Dyno Roll - The large roll at the rear of a chassis dyno. The motorcycle engine transfers power through the drive chain, (or belt or drive shaft) to the rear tire, and then through the rear tire to the dyno roll. The dynamometer uses the inertial mass of the dyno roll and the rate of acceleration to calculate horsepower and torque.
Eddy Current Brake - A computer controlled electromagnetic braking system that allows the dynamometer to control the rate of acceleration or deceleration of the motorcycle during testing. An Eddy Current Brake can also be used to hold an engine at a steady rpm regardless of throttle setting. Although they are essential for carburetor tuning and fuel injection mapping not all dynamometers are equipped with Eddy Current Brakes.
Controlled RPM Test - A dynamometer test where the motorcycles engine speed is held at a constant rpm by a computer controlled Eddy Current Brake. The dynamometer operator sets the engine speed via the dynamometers controller. He is then able to test the bike at any throttle position while the dyno constantly varies the load applied to the dyno roll via the Eddy Current Brake to maintain a constant rpm. This type of test is essential for fuel injection mapping. Fuel injection maps are basically tables with throttle position divided up along the horizontal axis (columns), and rpm divided up along the vertical axis (rows). Each cell in the table is the intersection of a specific rpm and throttle position and contains a value which the engine's ECU uses to determine the proper amount of fuel to deliver to the engine at that specific rpm and throttle position. Through the use of an Exhaust Gas Analyzer to monitor fuel mixture in real time during this test, the dynamometer operator can check (and adjust if necessary) every cell in the fuel delivery map.
Inertia Acceleration Test - A simple dynamometer test in which the motorcycle is accelerated from a low rpm to a high rpm (typically redline) at a fixed throttle position (typically wide open). The dynamometer uses the inertial mass of the dyno roll and the rate of acceleration to calculate horsepower. This is the quickest and simplest dyno test for measuring horsepower.
Controlled Acceleration Test - A dynamometer test in which the motorcycle is accelerated from a low rpm to a high rpm (typically redline) at a fixed throttle position (typically wide open). During this test the dynamometer uses a computer controlled Eddy Current Brake to control the rate of acceleration during the test. The dynamometer uses the inertial mass of the dyno roll and the rate of acceleration to calculate the inertial component of the horsepower measurement, and then adds the power dissipated by the Eddy Current Brake during the test to calculate the total horsepower. This test is useful for testing high horsepower motorcycles which would otherwise accelerate to quickly during an "Inertia Acceleration Test" to properly load the engine.
Step Test - A dynamometer test in which the motorcycle is accelerated from a low rpm to a high rpm (typically redline) at a fixed throttle position. The dynamometer uses a computer controlled Eddy Current Brake to control acceleration in fixed rpm increments (steps). The dynamometer holds the rpm steady at each step for a fixed period of time before advancing to the next step. Both the rpm step increment and the step hold time are predetermined by the operator and entered into the dynamometers controller before the start of the test. A typical example would be an rpm increment of 1000rpm per step and a hold period of 5 seconds per step. Step testing is useful in conjunction with an Exhaust Gas Analyzer for testing air/fuel mixture since the pauses at each step allow the analyzer time to record a stable reading. Step tests also result in more accurate hp and torque measurements to due to increased loading of the engine and the elimination of engine and drive train inertial losses. Air/Fuel Ratio - The amount of air relative to the amount of fuel in the air/fuel mixture expressed as a ratio. Measured by mass (weight) not volume. ECU - Engine Control Unit. A computer controlled device which monitors and controls all electrical functions of an engine. Typical functions which an ECU controls include ignition timing and firing, fuel injector pulse width control and firing, cold start enrichment, idle speed, rev limiter, etc. Typical parameters which an ECU monitors include, engine rpm, crankshaft and cam shaft position, engine temperature, air temperature, barometric pressure and air box pressure. Fuel Injector - A device located in the intake tract of a fuel injected engine. A fuel injector is basically an electronic "on/off" valve for fuel. Pressurized fuel is plumbed to the injector inlet and the injector is cycled on for a short period of time during each engine intake cycle. The length of time the injector is held open is called the "injector pulse width" and determines the amount of fuel allowed to pass into the intake air stream. The injector sprays a very fine pattern of fuel to help ensure that the fuel is uniformly mixed with the incoming air. The injector is controlled by the ECU.
Dyno Test - To use a dynamometer to measure parameters such as horsepower, torque, fuel mixture, etc. Never tell a shop you want your bike dyno'ed, always use the terms "dyno tested" or "dyno tuned".
Dyno Tune - To use a dynamometer to adjust engine parameters to achieve maximum performance. Typical parameters include fuel mixture (carburetor jetting of fuel injection mapping), ignition timing, cam timing, and intake and exhaust modifications. Never tell a shop you want your bike dyno'ed, always use the terms "dyno tested" or "dyno tuned".
EGA - Exhaust Gas Analyzer. A device which samples the exhaust gasses produced by the motorcycle engine to determine the percentage levels of individual gasses in the exhaust stream. For high performance engine tuning the gasses of interest are O2, CO,CO2 and HC.
HP - Horsepower. A measure of work performed. When applied to an engine the formula is (Torque x rpm)/5252.
Injector Pulse Width - The length of time a fuel injector is held open per intake cycle expressed in milliseconds (ms). Injector pulse width is controlled by the ECU to ensure the proper amount of fuel is delivered during each engine intake cycle typically based on throttle position and rpm.
Lambda - Lambda is the measure of an air/fuel mixture as referenced to Stoichiometric. A Lambda value of 1.0 equals Stoichiometric (14.7/1 for gasoline engines), lambda values less than 1.0 represent rich mixtures, lambda values greater than 1.0 represent lean mixtures.
Lean Mixture - An air/fuel mixture that has too much air compared to the amount of fuel in the mixture, a lambda measurement greater than 1.0, an air fuel ratio greater than 14.7/1 for gasoline engines.
MAP - A table stored in the ECU (Engine Control Unit) of a fuel injected motorcycle. Fuel injection maps are basically tables with throttle position divided up along the horizontal axis (columns), and rpm divided up along the vertical axis (rows). Each cell in the table is the intersection of a specific rpm and throttle position and contains a value which the engine's ECU uses to determine the proper amount of fuel to deliver to the engine at that specific rpm and throttle position.
O2 Sensor - Oxygen Sensor, also called a Lambda Sensor. A sensor located in the exhaust stream of the engine to determine the amount of residual oxygen remaining in the engine exhaust.
Rich Mixture - An air/fuel mixture that has too much fuel compared to the amount of air in the mixture, a lambda measurement less than 1.0, an air fuel ratio less than 14.7/1 for gasoline engines.
RPM - Revolutions per Minute. A measure of rotational speed.
Stoichiometric - An ideal air/fuel mixture that contains exactly enough oxygen to completely burn all the fuel in the mixture. A stoichiometric mixture theoretically leaves no residual fuel or oxygen in the exhaust after combustion. An air fuel ratio of 14.7/1 for gasoline engines.
Throttle Position - The amount of rotation of the throttle grip expressed in percentage.
Torque - A measure of rotational force expressed as force times distance. Example - imagine a 1 foot long lever, welded to and perpendicular to a drive shaft. 1 pound of force applied to end of the 1 foot lever would result in 1 ft-lb of rotational force at the end of the drive shaft. 2 lbs applied to a 1 foot lever, or 1 lb applied to a 2 foot lever would both yield 2 ft-lbs of force. Torque combined with speed (rpm) is used to calculate horsepower (hp).
CO - Carbon Monoxide, an exhaust gas useful in dyno tuning for determining Air/Fuel Ratio.
CO2 -Carbon Dioxide, an exhaust gas useful in dyno tuning for determining combustion efficiency and optimum ignition timing.
HC - Hydrocarbons, exhaust gases useful in dyno tuning for determining combustion efficiency and detecting misfires.
O2 - The natural state of oxygen in the atmosphere, two oxygen atoms bonded as an O2 molecule, useful in dyno tuning for determining air/fuel ratio.
