B3.9-125 Cummins B3.9-125 Specifications & Technical Data (2017—2021)

Meeting Every Standard

Cummins B Series engines meet all current Tier 2 standards and will achieve Tier 3 compliance with in-cylinder technology that maintains a compact, simple and cost-effective design solution. Plus, Cummins B Series engines are designed for minimum noise output, so you can operate in high-density areas such as business or residential districts. For even quieter operation, Cummins offers optional noise reduction packages that eliminate up to 4.5 dBA of acoustic output.

Torque Rise

While peak torque is important, torque rise is equally critical to the operating capabilities of your equipment – and Cummins B Series engines deliver. The B3.9 gives you up to 45% torque rise while the B4.5 has a torque rise of up to 47%, and the B5.9 hits a torque rise of 48%.

Cummins Advisor

Getting every installation right – the first time – is what Cummins Advisor is all about. Advisor software builds a virtual model to make sure every system (air, intake, exhaust, cooling, etc.) is integrated for optimum performance. It takes into account everything from load factors to operating climates to duty cycles – then identifies systems or components that could negatively impact reliability – listing alternatives that deliver the performance you expect the first time – every time.

B Series

In every time zone and every work site, every farm and every forest, chances are good that you’ll find Cummins B Series engines hard at work. Millions of B Series engines are currently in use, from paving compactors to telescoping material handlers, tractors to mobile generators. Our mechanical B Series engines are small enough to fit the equipment but big enough to handle the job. Highly reliable, durable rotary fuel pumps deliver a steady stream of pressurized fuel for strong performance across a wide range of environmental conditions. Whether you need a low-horsepower engine with a flat torque curve or a little more horsepower with a sharp torque rise, you’ll find it in a Cummins B Series. Three different models are available: the four-cylinder B3.9 and B4.5, plus the 6-cylinder B5.9.

Features And Benefits

Cummins B Series engines have been proven by millions of customers over the past 20-plus years. Design features include:Common Power Cylinder Technology – For reliability and reduced parts inventory.Plateau-Honed Cylinders – To virtually eliminate oil consumption.Parent Bore Cylinder Block – Structurally designed for reduced noise, increased durability.Forged-Steel Crankshaft – Built stronger to last longer.Holset Turbocharger – Wastegated design optimizes operation across the torque curve with improved response.Integrated Design – Eliminates potential leak points. Has 40% fewer parts than traditional diesels for superior reliability.Rotary Fuel Pump – Highly dependable and durable, it delivers a steady stream of pressurized fuel for strong performance in every environmental condition.Edge-Molded Gaskets – Help reduce oil use.

Maintenance Intervals

The combination of plateau-honed cylinders, an innovative ring pack design and edge-molded gaskets significantly reduces oil consumption while the integrated design of B Series engines eliminates leak points. So little or no top-off oil should be needed between oil changes that can be extended to 500-hour intervals.