gritt
08-31-2006, 05:11 PM
Why is a loading dyno (Dyno Dynamics) better than an inertia dyno (dynojet)? - Loading dynos are better than inertia dynos for a number of reasons.
A) Steady State Tuning - Steady state tuning is the highlight of the loading dyno. Because the loading dyno uses an electric brake to keep the rollers from accelerating it is able to precisely vary how much load is placed on the cars engine. When the dyno exerts as much load on the engine as the engine is putting out, the rollers will stop accelerating and hold a constant speed. Because the engine is not accelerating we call this a steady state. During this time the dyno is measuring the load between the brake and the car and outputs a live power number. This is very useful for tuners because it allows them to make changes to each part of the ignition/fuel map and monitor the power gains or losses in real time. With an inertia dyno there is no way to keep the rollers from accelerating and therefore no way to hold a steady state. The engine simply accelerates through the ignition/fuel maps too quickly.
B) More precise measurement - Because inertia dynos use a heavy mass to simulate the inertia of the car being tested it is hard to monitor minor changes in power. The large mass of the rollers results in very minor changes in roller speed that inertia dyno sensors have a hard time picking up. If the sensor and computer don't see the change in roller speed the the dyno graph will not show a dip in power. However, a loading dyno uses rollers with very little mass and directly measures power rather than calculating it. Quick drops in power will be picked up by the load sensor and will show on the dyno graph. This is very useful for finding problems and ensuring that your engine is running correctly.
C) Load can be controlled - With an inertia dyno the load exerted on the engine as it accelerates is based on the inertia of the dyno rollers. This inertia is set by the mass of the rollers and is not able to be changed. The inertia of the dyno rollers directly determines how fast the cars engine will accelerate through each gear. Ideally this inertia would be equal to the inertia of the car being tested but this is rarely the case. The inertia is almost always going to be higher or lower than the inertia of the car and as a result the engine accelerates faster or slower than it would on the street. This can have a bearing on how the engine is tuned and how accurate the dyno replicates real life conditions. Because a loading dyno is able to actively alter the load on the rollers it is able to change the rate of acceleration as the operator pleases. Realistic loads for the particular vehicle can be used or loads simulating driving up a hill can be used. This is easily controlled by the dyno operator.
D) Problem Diagnosis - This feature goes back to the ability to control load and do steady state tuning. A loading dyno is able to simulate road conditions in a safe environment while allowing the technician to monitor the car and it's engine. An inertia dyno is unable to accurately simulate all but a few road conditions making it much more difficult to diagnose problems.
A) Steady State Tuning - Steady state tuning is the highlight of the loading dyno. Because the loading dyno uses an electric brake to keep the rollers from accelerating it is able to precisely vary how much load is placed on the cars engine. When the dyno exerts as much load on the engine as the engine is putting out, the rollers will stop accelerating and hold a constant speed. Because the engine is not accelerating we call this a steady state. During this time the dyno is measuring the load between the brake and the car and outputs a live power number. This is very useful for tuners because it allows them to make changes to each part of the ignition/fuel map and monitor the power gains or losses in real time. With an inertia dyno there is no way to keep the rollers from accelerating and therefore no way to hold a steady state. The engine simply accelerates through the ignition/fuel maps too quickly.
B) More precise measurement - Because inertia dynos use a heavy mass to simulate the inertia of the car being tested it is hard to monitor minor changes in power. The large mass of the rollers results in very minor changes in roller speed that inertia dyno sensors have a hard time picking up. If the sensor and computer don't see the change in roller speed the the dyno graph will not show a dip in power. However, a loading dyno uses rollers with very little mass and directly measures power rather than calculating it. Quick drops in power will be picked up by the load sensor and will show on the dyno graph. This is very useful for finding problems and ensuring that your engine is running correctly.
C) Load can be controlled - With an inertia dyno the load exerted on the engine as it accelerates is based on the inertia of the dyno rollers. This inertia is set by the mass of the rollers and is not able to be changed. The inertia of the dyno rollers directly determines how fast the cars engine will accelerate through each gear. Ideally this inertia would be equal to the inertia of the car being tested but this is rarely the case. The inertia is almost always going to be higher or lower than the inertia of the car and as a result the engine accelerates faster or slower than it would on the street. This can have a bearing on how the engine is tuned and how accurate the dyno replicates real life conditions. Because a loading dyno is able to actively alter the load on the rollers it is able to change the rate of acceleration as the operator pleases. Realistic loads for the particular vehicle can be used or loads simulating driving up a hill can be used. This is easily controlled by the dyno operator.
D) Problem Diagnosis - This feature goes back to the ability to control load and do steady state tuning. A loading dyno is able to simulate road conditions in a safe environment while allowing the technician to monitor the car and it's engine. An inertia dyno is unable to accurately simulate all but a few road conditions making it much more difficult to diagnose problems.