Technically speaking

High levels of productivity

The KDI family of diesel engines has expanded with the new KDI 3404 model; this is now the new standard of reference for engines with an output of 56 kW to 100 kW.


The KDI 3404 is the effective, practical and innovative answer to the market’s increasing demands for compact engines that generate the highest levels of productivity. Thanks to the high power density, low fuel consumption and smooth yet uniform delivery of power throughout the entire RPM range, the engine offers an approach to limiting emissions that is effective, yet easy to manage from the technical standpoint and requires minimal maintenance. Produced in the KOHLER Engines diesel production facility at Reggio Emilia in Italy, the new KDI 3404 engine is available in two models and four power ratings. The new engine complies with Tier 4 Final – STAGE IV regulations within the 56 -100 kW power range and offers remarkable performance that translates into solid operational benefits for OEMs and end users alike.

The new KDI 3404 engine is the latest development of the KDI design into a product line with higher power through the use of advanced technologies such as a high-pressure (2000 bar) Common Rail injection system and an electronically controlled EGR valve for recirculating exhaust gasses, the four valves per cylinder allow for a more efficient combustion while reducing the fuel consumption and delivering levels of power equivalent to engines with larger displacements. With the new KDI 3404, KOHLER Engines is bringing these concepts to the next and higher level in terms of performance and operating efficiency. It should be noted this is achieved without the use of a diesel-particulate filter (DPF).

The new engine is available in two 4-cylinder models with a displacement of 3.4 litres:

– KDI 3404TCR (Turbo Common Rail) à rated at 56.4 kW, compliant to Tier 4 Final / Stage IIIB standards

– KDI 3404TCR-SCR (Turbo Common Rail with SCR) à rated at 100 kW, compliant to  Tier 4 Final / Stage IV standards and is also available in power ratings of 75 kW and 90 kW.

Consistent with the “Best Fit” philosophy for OEMs and end users, the new engine developed by KOHLER Engines is optimised for performance, load capacity, sturdiness and low levels of noise and vibration. Reduced fuel consumption translating to a minimum operating cost, long maintenance intervals coupled with a compact size and ease of adaptation for diverse applications makes for a truly unique and advanced engine.

Technical innovation

Performance that is equivalent to engines with larger displacements, thanks to excellent power density (30 kW/l); torque and power values that increase the productivity of machines by up to 15% and up to 10% lower fuel consumption than its closest competitors. As is true for the entire KDI family, the new KDI 3404 has no DPF, so customers enjoy 100% performance under the most severe operating conditions without being concerned about regenerating the filter. A sophisticated electronic control system that guarantees smooth, immediate response, and the lowest possible levels of noise and vibration: the new engine offers a host of operating benefits which demonstrate how unique it really is.

The new engine complies with Stage IV – Tier 4 Final standards for engines rated over 56 kW, thanks to the compact, high-efficiency SCR (Selective Catalyst Reduction) system, which is essential for reducing NOx in exhaust gases. The new engine is manufactured in the KOHLER Engines diesel factory in Reggio Emilia, Italy, which features the latest machining and assembly technologies. Technologically speaking, the remarkable characteristics of the KDI design derive from the use of a high-pressure (2000 bar) Common Rail injection system of the latest generation, combined with G3S solenoid-type injectors for precise metering of fuel during injection. An electronically controlled EGR valve is included for recirculating the right amount of exhaust gasses that are liquid-cooled by a water/air heat exchanger.

The EGR system consists of two cooling stages that optimise heat exchange without increasing external dimensions. Also, the system is installed on the hot side, thus preventing the EGR valve from seizing. The final result is unmatched reliability. The valve train incorporates architecture with 4 valves per cylinder that houses the injector in a perfectly vertical position and in the very centre of the combustion chamber. In this way, the cylinder is filled with the exact amount of fuel, which is atomised and mixed with air in the best way possible.

Operational benefits

The KDI family of engines was developed according to the “Best Fit” philosophy. In fact, the new KDI 3404 boasts a series of advanced technological and build solutions that are not found on other industrial engines in this category. These solutions translate into major operational and functional benefits for both end users and OEMs. With performance equivalent to engines with larger displacements (100 kW @ 2200 RPM and 500 Nm @ 1400 RPM), clean combustion made possible by the innovative high-pressure Common Rail injection system, and 4 valves per cylinder, an EGR valve and no DPF, the KDI 3404 consumes 10% less fuel than other engines in its category. With its high torque output at idle (412 Nm @ 1000 RPM), great specific performance and best-in-class torque and power in its category, the new engine maximises the productivity of the machines it powers and immediately responds to load even at low RPM.

With these superior characteristics and perfect integration of the turbocharger with the engine and its electronic control system, the new KDI 3404 offers smooth, pleasant driving that can only be called “excellent”. Driving smoothness is combined with exceptionally comfortable operation with minimum levels of noise and vibration, thanks to the use of “bedplate” architecture (crankcase + bedplate) for the engine block, and the (optional) counter-rotating shafts it contains. Also worth mentioning is a narrow profile that minimises steering radius for better handling – a feature that is particularly useful in agricultural applications. Versatility in application is also guaranteed by four power take-offs, which include two additional PTOs at the sides (SAE A and SAE B). These PTOs supplement the main and secondary take-offs designed and positioned to draw the greatest amount of power from the engine. With this practical design feature, the new KDI 3404 is the solution for OEMs and final users who demand the highest degree of flexibility in installation.

The KDI 3404 offers maximum efficiency from the operating standpoint as well. Its maintenance intervals of no less than 500 hours are due to clean combustion that requires no DPF.  Since the engine has no DPF, less space is required in any application. And, productivity is enhanced because operation needs never be interrupted to regenerate the filter. What’s more, no costly thermal protection is necessary for preventing excessive heat loss with resulting danger of fire. The final result is that the machines powered by the new engine are compact and easy to handle, and the operator enjoys better visibility, which enhances safety and improves productivity.

 by Federico Antonelli

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