How does a Dyno work?

[BDII]

I've noticed lately that there has been quite a bit of discussion about Dyno's and their use, accuracy and function.

 

I'm going to do my best to make this as detailed as possible

 

 

Originally Posted by Wikipedia

Dyno = Dynamometer is a device for measuring force, moment of force (torque), or power. For example, the power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed (RPM).

 

There are hundreds of types of dynamometers but for this discussion we will concentrate on the various types of Vehicle Dynamometer.

 

 

Engine Dynamometer

An Engine dynamometer is used to mesaure HP/TRQ directly from the Engine.

 

This is what most Car Manufacturers use to establish HP/TRQ numbers for their vehicles. It also used by some shops to baseline tune a motor before it is placed in the car.

 

http://www.huff-tech.com/images/small_engine_dyno.jpg

 

 

 

 

These types of dynos do not calculate for drivetrain loss. This is why the Legacy GT is listed as 250bhp, but makes 190-210 on most Chassis Dynamometers.

 

 

Chassis Dynomometer

This is the most commonly used dyno for performance shops. It is used to measure the twisting movement (torque) and the power or the energy emitted by the power train of an automobile directly from the wheels or the drive wheels.

 

http://i.ytimg.com/vi/A35na01T4lw/0.jpg

 

 

 

Types:

 

Quote:

Eddy Current dynamometer is the most commonly used dynamometer in modern Chassis dynos in the present days. They are capable of changing the load most efficiently at a rapid speed. Most of them require an external cooling system where as some, although very few, have an automatic cooling system. In a good model 5 amps at 220 vac can give more or less 150 HP load. Eddy current Dynamometer has a core made of iron, which rotates in the magnetic area to produce the twisting movement known as Torque. Due to this technique present in the Eddy Motor current stopping a motor is not feasible.

Quote:

Power dynamometer is another kind, which is very similar to eddy current. The only difference between the former and the latter is that a magnetic powder is present in the space between the coil and the rotor. The fluctuation lines generate metal chains, which are continuously built up and are broken due to the twisting movement (torque). The speed of the power dynamometer is restricted due to the indulgence of heat.

Quote:

Hysteresis dynamometer. It uses the rotor made of steel, which moves in between the fluctuation lines, which are further in between magnetic poles. It enables the torque to be produced at the speed of zero and also in full speed. The air that is forced in produces heat. Electric motor or the Generator motor is also another type. It adjusts the speed of the drive. It can have both alternating and direct current motor. This motor when prepared properly with proper mechanism can be used as universal motor. It can also transfer the power to electric current if the situation demands.

Quote:

Hydraulic Brake

The hydraulic brake system consists of a hydraulic pump (usually a gear type pump), a fluid reservoir and piping between the two parts. Inserted in the piping is an adjustable valve and between the pump and the valve is a gauge or other means of measuring hydraulic pressure. Usually, the fluid used was hydraulic oil, but recent synthetic multi-grade oils may be a better choice. In simplest terms, the engine is brought up to the desired RPM and the valve is incrementally closed and as the pumps outlet is restricted, the load increases and the throttle is simply opened until at the desired throttle opening. Unlike most other systems, power is calculated by factoring flow volume (calculated from pump design specs), hydraulic pressure and RPM. Brake HP, whether figured with pressure, volume and RPM or with a different load cell type brake dyno, should produce essentially identical power figures. Hydraulic dynos are renowned for having the absolute quickest load change ability, just slightly surpassing the eddy current absorbers. The downside is that they require large quantities of hot oil under high pressure and the requirement for an oil reservoir.(source)

Quote:

A brake dynamometer applies variable load on the Prime Mover (PM) and measures the PM's ability to move or hold the RPM as related to the "braking force" applied. It is usually connected to a computer that records applied braking torque and calculates engine power output based on information from a "load cell" or "strain gauge" and RPM (speed sensor).

Quote:

An inertia dynamometer provides a fixed inertial mass load and calculates the power required to accelerate that fixed, known mass and uses a computer to record RPM and acc. rate to calculate torque. The engine is generally tested from somewhat above idle to its maximum RPM and the output is measured and plotted on a graph.

 

 

Quote:

A motoring dynamometer provides the features of a brake dyne system, but in addition, can "power" (usually with an AC or DC motor) the Prime Mover (PM) and allow testing of very small power small outputs. Example, duplicating speeds and loads that are experienced when operating a vehicle traveling downhill or on/off throttle operations.

 

 

Common Brands of Dynamometers

 

Mustang MD-500

Typically shops will purchase the Air Cooled Eddy Current Version for use with Subaru/AWD Vehicle applications.

Max Horsepower:1,500 hpMax Absorption:900 hp/1,800 hp (DE Model)Inertia:1,190 lbs baseType:Air-Cooled Eddy CurrentMax Speed:190 mph Roll Diameter:12.625"Air Requirements:80-100 PSI, Dry, Reg. oil freePower Requirements:230 VAC Single Phase, 50-60 Hz, 40 Amps

(SOURCE)

 

Dyno Dynamics

Typically shops will purchase the Magnetic Eddy Current Version for use with Subaru/AWD Vehicle applications.

Specs: http://www.dyno.com.au/dyno/controll...owAWD450DSPage

 

 

Dynapack Dyno

The wheels are removed from your car and the "dyna packs" are attached to the hubs. Dynapaks are hydraulic brake Dynos.

http://www.dynapackusa.com/index.htm

http://us1.webpublications.com.au/static/images/articles/featurepics/111343.jpg

 

AirBoy Virtual Dyno

This is generally used by tuners who do not have access to a dyno or have customers that do not wish to utilize a dyno. It uses a series of recorded information to calculate WHP/TRQ based off:

Atmospheric Pressure

Engine Load

Engine Speed

Intake Air Temp

Manifold Relative Pressure (direct)

Throttle Opening Angle (%)

Vehicle Speed

 

 

Why do I get different readings on different dynos?

 

Here are some basic reasons:

 

1. A decrease in Atmospheric/Barometric Pressure will cause a decrease in Air Density.

 

2. A decrease in Temperature will cause an increase in Air Density.

 

3. An increase in Temperature will cause a decrease in Air Density.

 

4. An increase in Humidity will cause a decrease in Air Density.

 

5. A decrease in Humidity will cause an increase in Air Density.

 

6. Different dynos read differently. Some high, some low. Who really cares? BMX45, that's who.

 

So.... what you made last spring will different from what you will make this Summer/Fall/Winter on the same dyno.

 

Additionally, If you read what I have written above you will see that each dyno is different. Comparing a Mustang to Dynapak is like comparing apples to oranges. YES they have the same purpose (measuring WHP/TRQ--Food) but they are totally different in concept and will read differently.

[TRSCobra]

Different dynos read differently. Some high, some low. Who really cares? BMX45, that's who.

 

[HipsterDoofus]

All this time i thought it was prehistoric magic.

[bmx045]

I CARE

 

 

http://i.imgur.com/Nh0pL.png

[BDII]

this should be stickied, added to my new member thread and force fed to anyone who claims all dynos read the same or similar.