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AJAX integral engines
& compressors

Since 1877, Cooper has provided O.E.M. services for AJAX engines, compressors,
and integral engine-compressors.
Cooper Machinery Services is the O.E.M of AJAX Engine-Compressors


Cooper has successfully tested a slow-speed integral engine running on a hydrogen (H2)-natural gas fuel blend. The groundbreaking test comes 5 months after the announcement of Cooper’s joint hydrogen research project with a major U.S. gas pipeline company to demonstrate the safe operating range of H2 blends in large-bore internal combustion engines.

“Cooper’s hydrogen development initiative took another large step forward today. We ran an unmodified large-bore, slow-speed integral engines-compressors with an H2 blend of 5% by volume, and we achieved significant reductions of methane in the exhaust. This is the first such run using significant amounts of hydrogen in an engine of this design.” said Cooper COO, Malcolm Holmes. “In May, we will be running up to 33% by volume in the same stock engine. Our customers have thousands of similar units running globally, so the potential reduction of methane is substantial.”

The Cooper test was conducted at their slow-speed integral engine test cell at corporate headquarters located in Houston, Texas. The test engine is the current production, NSPS compliant CleanBurn PlusTM AJAX® 2802 with 15″ piston bore, 16″ power stroke, and a speed range of 360-440 RPM. Cooper selected the AJAX engine due to the similarities of its combustion system to that of the large fleet of the other engine brands the company services (Clark, Cooper-Bessemer®, Ingersoll Rand, and Worthington).

Cooper's engineering team, CMO, Matt Forcey, and COO, Malcolm Holmes
in the control room during the hydrogen test.

AJAX Overview

Since 1959, Cooper has been the O.E.M. of AJAX integral engines-compressors and after-sale support. During our ownership, the AJAX product line has earned a reputation for reliability, efficiency, and durability of service. Our AJAX product line, ranging from 147 to 845 hp (110 to 630 kW), reduces overall operating costs and maintenance expenses and delivers worry-free service.

Cooper’s after-sale support structure delivers full service for AJAX integral engines-compressors from parts, to repairs, to engineering, to field support for any make or model, all from one source.

ajax Engine-Compressor parts

Genuine O.E.M. Cooper parts for AJAX integral engines and compressors are backed with decades of engineering, manufacturing, and in-field experience in material wear. We provide spare AJAX engine parts that are manufactured to the latest standards and technical advancements. From our AJAX parts manufacturing center in Houston, Texas, we are committed to making every AJAX part with our own brand of O.E.M. quality and to O.E.M. standards. We are committed to stocking and delivering AJAX engine parts to our customers quickly and efficiently, and that’s why we house thousands of AJAX part numbers at our dedicated central distribution center in Houston, and in field locations around the world.


For decades, Cooper has provided a complete line of field and shop services for AJAX integral engines and compressors. From preventative maintenance, to shop and field overhauls, to field machining, to repairs throughout our global shops, our Cooper service teams are fully trained on AJAX engines and compressors, and stand ready to assist our customers with all their service needs.

AJAX Engine-Compressor UPGRADES

Cooper has spent decades providing technology and engineering services for AJAX engine and compressor upgrades. With our advanced technologies, expertise, and project management experience, we offer AJAX upgrades to reduce engine emissions, increase horsepower, improve efficiencies and reliability of your equipment, and reduce maintenance costs.

To further strengthen our upgrade portfolio for AJAX engines, Cooper acquired HOERBIGER’s Engines Services (HES) division in 2019. Cooper now offers even more upgrade technologies including the HyperLogic™ and ePCC™. The Engine Services team has been offering engine emissions reduction and efficiency improvement upgrades, applicable to all types of AJAX integral engines.  


Legendary AJAX integral engines and compressors have been serving the industry’s compression needs for decades. Ranging from 148 to 845 hp (110 to 640 kW), the reliable two-stroke design of AJAX equipment results in one of the most maintenance-free engines-compressors on the market. Today, AJAX integral engines-compressors continue to earn their distinguished reputation for being as close to worry-free as any compressor product in the world. The AJAX product line maintains a compressor cylinder offering capable of handling a wide range of pressures, from vacuum to 5,500 psi (379 bar). AJAX compression cylinders offer up to six ratios of capability and the lowest brake hp per million flows for a wider range of applications, including sour gas.   


Since 1877, the AJAX brand has been synonymous with exceptional quality, absolute dependability, and unbeatable performance. To this day, AJAX offers the highest compression per brake horsepower in the industry.

AJAX balances performance and product design while meeting the industry’s stringent compliance requirements. AJAX customers can be confident knowing they have Cooper’s support from initial planning and purchase to installation and field service for legacy and new equipment.

Cooper is proud to service AJAX legacy engines, integrals, and compressors, as well as provide standard replacement and overhaul parts. A vast inventory stands ready to ship new and reconditioned parts, exchanged parts, and conversion kits where you need them most.


AJAX Engine & Compressor Upgrades

AJI20001440 RPM UpgradeThis upgrade increases the speed of large-bore AJAX units from 360 and 400 rpm to 440 rpm, increasing horsepower ratings while maintaining emissions ratings. Power Increase
AJI20002Auto Pre-Lube SystemsPre-Lube systems are standard equipment on current production AJAX units, offered with manual, electric or pneumatic configurations. Now retrofit kits are available for all AJAX units.Safety, Reliability, Maintenance
AJI20003Compressor Poppet ValvesPoppet valves deliver the highest efficiency of any valve design. Compared to conventional plate, channel or strip valves, poppet valves offer significant fuel or horsepower savings through more efficient and reliable operation.Efficiency, Reliability, Maintenance
AJI20004Dry Type Air Filter ConversionNew AJAX integral engine-compressors are packaged with “Dry Type” engine air filters. Now AJAX owners with the older oil bath type air cleaner can benefit from this product improvement.Efficiency, Power Increase, Reliability, Maintenance
AJI20005Exhaust Expansion ChambersThe AJAX exhaust expansion chamber uses exhaust pulsations to optimize the scavenging of the power cylinders while providing substantial increases in the mass of fresh air that is trapped inside the cylinders, recovering horse power losses often associated with high elevation and/or emission compliance. Efficiency, Emissions, Power Increase, Maintenance
AJI20006Flexible Fuel Header SystemThe flexible fuel header system eliminates header misalignment by utilizing single piece fuel header system and eliminates stress and distortion on gas valve body.Maintenance
AJI20007"Economizer" Gas Injection SystemThe advantage of an AJAX engine equipped with the available “Economizer” gas injection system versus the standard low pressure fuel system is to reduce fuel consumption by up to 33%.Efficiency, Reliability
AJI20008HCR (High Compression Ratio) Power PistonsThe HCR pistons provide enhanced air flow at higher elevations where air density is lower. More air flow equates to better engine performance, lower emissions and improved fuel consumption at higher elevation applications.Efficiency, Emissions, Power Increase
AJI20009Integrated Governor Throttle Body (IGTB)This product can be used for units that use automatic variable speed operation for load control and is now standard equipment on all new 2801, 2802, 2803 and 2804 units.Efficiency, Reliability, Maintenance, Safety
AJI20010Integral Concrete SkidAJAX engine-compressors can be purchased with a skid design that allows for the unit to be portable.Installation Costs, Portability
AJI20011Low Emissions "LE" Conversion KitThe main component of the system is the ignitor assembly that creates a high energy ignition source, igniting a leaner mixture of fuel, resulting in lower NOx formation and cleaner exhaust.Emissions, Reliability
AJI20012Noise ControlCooper offers a variety of methods for meeting your sound level requirements.Noise Control
AJI20013Oxidizing Catalytic ConverterThe AJAX oxidizing catalytic converter is designed to meet the new environmental guidelines for 2-stroke, lean-burn (2SLB) gas engines, with impressive removal efficiencies of CO, VOC, and H2CO.Efficiency, Emissions
AJI20014Integral Engine-Compressor ReconfigurationCooper offers complete reconfigured compressor package solutions for your legacy equipment.Repurposing
AJI20015Rebecca Fuel CartridgeWith Rebecca system, fuel gas injector valve removal, inspection and replacement are fast and easy. The two-part system consists of a permanent valve body and replaceable cartridge assembly. Efficiency, Maintenance
AJI20016Ring Gear StartingMany end-users are faced with declining site gas pressures. Air-in-head start systems require 200-250 psig pressure. Ring gear start systems only require pressures as low as 30 psig.Maintenance, Safety
AJI20017Scavenging Intake Poppet ValveThe Scavenging Intake Poppet Valve is the latest step in airflow improvement. The poppet valve design increases the flow area over the reed strip design, allowing more scavenging air to the combustion chamber that subsequently increases combustion efficiency.Efficiency, Emissions, Power Increase, Maintenance
AJI20018Screw In Pre-chamberThe AJAX screw-in pre-chamber (SIP) can be the first step in your emissions-reduction program by reducing NOx emissions. Adaptable to other emissions-reduction technologies, the SIP provides proven reliability, reducing NOx emissions and fuel consumption.Efficiency, Maintenance, Safety
CPE20001Electronic Pre-Combustion Chamber (ePCC)Electronically controlled pre-combustion chamber check valve (ePCC™) precisely controls fuel injection and allows the engine to run consistently smoother and cleanerCombustion stability, Reliability, Maintenance
CPE20002HyperLogicTMAdvanced air/fuel ratio control system for two- and four-stroke, turbocharged, spark-ignited enginesEfficiency, Emission, Reliability, Maintenance
Engine ControlsControl Panel UpgradesControl panel upgrades tailored to customer’s specific needs and requirements for most makes and model of gas compression and power generation engines.Combustion stability, Efficiency, Emission, Reliability, Maintenance
Lubrication SystemSloan Lubrication SystemProtect your investment with a leading lubrication system. Optimized design, maximized compressor valve life, reduced lube oil carryover, preventative equipment damage and downtime, and fail-safe protection for your critical machinery.Efficiency, Emission, Reliability, Maintenance

AJAX Integral Engine-Compressor Legacy and Current Product Models

Designed for simplicity and durability since the 1950s, many AJAX integral engine-compressor units are still in service today. A low-maintenance, reliable piece of equipment is comprised only of components that are strictly necessary. Fewer parts means a smaller margin for error.

ModelBore × Stroke (in)Rated Speed (rpm)Rated HP (bhp)BMEP (psi)Number of Power Cylinders
DPC-609½ × 124755856.51
DPC-1209½ × 1247511556.52
DPC-8011 × 144007757.11
DPC-16011 × 1440015457.12
DPC-8110½ × 124757862.41
DPC-16210½ × 1247515662.42
DPC-10512 × 1442510159.31
DPC-11513¼ × 16360110551
DPC-115LE13¼ × 16360110551
DPC-23013¼ × 16360221552
DPC-230LE13¼ × 16360221552
DPC-14013¼ × 1640013460.31
DPC-140LE13¼ × 1640013460.31
DPC-28013¼ × 1640026960.32
DPC-280LE13¼ × 1640026960.32
DPC-450LE13¼ × 1640043264.63
DPC-30015 × 16360288562
DPC-300LE15 × 16360288562
DPC-18015 × 1640017360.51
DPC-180LE15 × 1640017360.51
DPC-36015 × 1640035660.52
DPC-360LE15 × 1640035660.52
DPC-54015 × 16400540633
DPC-540LE15 × 16400540633
DPC-72015 × 16400720634
DPC-720LE15 × 16400720634
DPC-60015 × 1640057667.23
DPC-600LE15 × 1640057667.23
DPC-80015 × 1640076867.24
DPC-800LE15 × 1640076867.24
DPC-220113¼ × 1644014860.41
DPC-2201LE13¼ × 1644014860.41
DPC-220213¼ × 1644029660.42
DPC-2202LE13¼ × 1644029660.42
DPC-280115 × 1644019261.11
DPC-2801LE15 × 1644019261.11
DPC-280215 × 1644042267.22
DPC-2802LE15 × 1644038461.12
DPC-280315 × 1644063467.33
DPC-2803LE15 × 1644060063.73
DPC-280415 × 1644084567.24
DPC-2804LE15 × 1644080063.74

AJAX Gas Engine Product Models

The AJAX gas engine offers less maintenance, lower field costs, and a proven, rugged design. The standard single-cylinder, two-stroke, clean-burning engine meets current federal emission regulations without additional control systems.

ModelBore × Stroke (in)Rated Speed (rpm)Rated HP (bhp)BMEP (psi)Number of Power Cylinders
EA-155 × 6½9001449.61
EA-226½ × 86502148.51
EA-307¼ × 86502953.11
C-307½ × 105252949.21
C-428½ × 105254053.61
E-428½ × 105254053.61
E-5658½ × 105254053.21
DP-609½ × 124755856.51
DP-8011 × 144007757.11
DP-16011 × 1440015457.12
DP-8110½ × 124757862.41
DP-11513¼ × 16360110551
DP-23013¼ × 16360221552
DP-12513¼ × 1638012056.71
DP-25013¼ × 1638024056.72
DP-16515 × 1638015858.41
DP-32515 × 1638031257.52

AJAX Separable Compressor

The environmentally friendly AJAX separable compressor has the economic advantages of an AJAX slow-speed compressor without the air quality permit issues related to an internal combustion engine.

ModelStroke (in)Rod Diam (in)Rated Pwr (bhp)Rated Speed (rpm)Number of ThrowsCon Rod Length (in)GAS Rod Load (lbf)
C-202   11.000    2.500    200.0      455        2   23.750  33000.0
C-302   11.000    2.500    300.0      455        2   23.750  33000.0