Making Sense Of Loader Engine Power Output

The power output of mini loader, mini digger, skid steer, wheel loader and front end loader engines can be measured in Kilowatts (kW), metric horsepower (PS) or imperial horsepower (hp). It is important to note when comparing different makes of industrial loaders what engine output is being stated, for example is it the gross output, net output or net continuous output that is stated in the specification sheet. Each measurement is significantly different so they cannot be compared. Most mini loader manufactures' brochures use gross output as this is the highest rating of the engine, however it is important to know what output is being referred to.

For example the Kubota engine V2203, which is used in many different brands of earthmoving machinery, including the Schaffer Loader 3150, has a Gross Intermittent output (SAE J 1995) at 2800RPM of 36.4kW or 49.5PS. The Net Intermittent output (ISO 3046 IFN) at 2800 RPM is 34.3kW or 46.7PS. However Net Continuous output at 2800RPM is 29.8kW or 40.5PS.

You can see from the Kubota engine used in the above example how the output rating changes by up to 20% depending on what output rating method is used. This shows how important it is to compare the right output readings with loader engines.

To calculate between kW and PS (metric horsepower), you simply multiply the kW value by 1.36 or if you only know the PS reading simply divide that figure by 0.735. Just a side note, there are two forms of horsepower - metric (PS) and imperial (hp or HP). The imperial horsepower has a slightly lower value than the metric horsepower.

The acronym SAE above refers to the standards produced by the Society of Automotive Engineers. ISO refers to the International Organization for Standardization standards. Both these groups publish standards so manufacturers in this case can all rate their engines with the same method to enable direct comparisons to be made.

Another big talking point between operators is whether or not to use a turbo engine.

Turbo engines have advantages and disadvantages. Some advantages of turbo engines include - low emissions as the turbo runs very hot burning particulates, this is the big reason many manufacturers are starting to add turbo's to their small diesel engines - to gain compliance with Euro Level 3a and American Tier 4 compliance. Turbos also have good fuel economy; particularly at idle as a small capacity engine is running. Turbo engines are also of a lower engine weight compared to equivalent PS engine, however weight of a loader effects how much it can pick up, so this may be a disadvantage.

The biggest issue with turbo engines often lies in the turbo lag - the turbo must kick in before power and usable torque is obtained. When using a front end loader or mini loader, the operator is often going at slow speeds digging into the material to be moved with their bucket. If the skid steer loader engine is operating at low RPM, then the turbo won't kick in and they don't have enough torque to load easily - the operator must always operate at higher engine speeds so the turbo is active and torque is available. A non turbo diesel engine however usually has a wider torque band so can be used at any RPM speed to load. The non turbo mini loader engine has a wider torque band simply because the bore capacity is bigger. Turbo's also add another layer of complexity to engines and most manufacturers say they are best idled down after use to protect bearings and stop-start operations such as front end loaders and skidsteers in soilyards generally try to avoid turbos, mainly if no turbo timer has been incorporated on the engine.

So when comparing engine output to determine the best front end loader, wheel loader, mini loader, skidsteer or fork-lift for your application it is important to check how the output has been measured ie. according to which standard and also, the type of output readings, so you are really comparing the same measurements.