Holset Turbochargers, now also known as Cummins Turbo Technologies (CTT), has been in business since 1952. Holset Engineering Co. Ltd. was incorporated in 1952 as a subsidiary of BHD Engineering. Holset has been a part of the Cummins Engine Company for over 30 years, since the time it recognized Holset as a market leader in turbocharging, purchasing Holset in 1973.

Holset is a world leader in turbocharger technology and it represents the boost sophistication that sets the Cummins brand apart in Oregon. Holset brand turbochargers are installed as OEM on many applications beyond Cummins, including Volvo, Detroit Diesel and more.

Cummins Automotive & Diesel Service focuses on medium and heavy duty diesel engine turbo technologies. Commercial diesel engines require advanced technologies that deliver efficiency while meeting strict emissions requirements. Holset’s fixed geometry, wastegate technology, variable geometry, two-stage turbo performance, turbo compounding and waste heat expander technologies were specifically developed to deliver higher efficiency and lower cost.

Image presents the Holset Turbochargers logo, Cummins Turbo Technologies, for diesel engine applications and repair at Cummins Automotive & Diesel Services in Oregon.

The Emissions Regulation Challenge

Diesel engines produce exhaust. This exhaust contains particulate matter (PM). PM is a pollutant, a combination of sulphates, carcinogenic compounds, elemental carbon and heavy metals. Beginning in 1991, more stringent federal emission standards were introduced by the EPA to get engine manufacturers to cut down on particulate matter. From that time to the present, emissions standards continue to tighten, driving diesel engine and diesel engine component manufacturers to innovate to get their product to meet these standards. Holset Turbochargers has been at the forefront of this innovation.

A wide range of pollution reducing technologies have been developed over the years since the early 1990s. Changing piston design, altering injector spray angle and switching to electronically controlled injection systems helped curb a lot of emissions, but there was still work to do. As a result, higher injection pressures and high pressure common rail systems were developed to meet PM requirements. Eventually, exhaust gas recirculation (EGR) systems helped drop Nitrogen Oxides (NOx) levels.

Particulate matter and NOx reducing technologies have flourished beyond the EGR, inspiring the development of the diesel oxidation catalyst (DOC), diesel particulate filters (DPF), active and passive regeneration, selective catalytic reduction (SCR) and diesel exhaust fluid (DEF) along with the turbocharger innovations of fixed geometry, wastegates and the variable geometry turbocharger (VGT). This is where Holset Turbochargers really shined.

Image presents a semi-truck driving up a steep grade hill with a diesel engine intake exhaust measurement diagnostic from CummIns Automotive & Diesel Service in Sherwood, Oregon.

Fixed Geometry

Holset turbos are steeped in fixed geometry technology with turbocharger design that routes the the exhaust gas to the turbine to boost engine power. This technology is tried and tested and has not changed in decades. With this enduring design, Holset produces optimized, efficient and reliable turbochargers; all of which translates directly into engine fuel economy. Fuel economy represents to fleet managers and independent operators a hedge against ever increasing emissions regulations and bottom line profits.


Holset turbos optimize the use of wastegates. Wastgates are devices that control the amount and the timing of excess exhaust gas release. Wastegates are available in pneumatic and electronically controlled configurations. Holset Wastegate turbochargers are reliable and durable. In the low to mid power ranges, the Holset Wastegate technology diverts waste exhaust for a better match in most conditions.

A key benefit of the Wastegate technology is the fact that it helps to prevent turbocharger surging, known as turbo overspeeding. Overspeeding occurs when the turbo rotates at a greater speed than its operational limits, pushing the turbo beyond its safe operating parameters and causing it to fail by damaging the turbine or the compressor wheels and bearings.

Another benefit of the Wastegate technology is that it helps to prevent engine overboost. Overboost is a turbocharger output pressure that is higher than the rated pressure of the turbo engine; it can lead to the exposure of an engine to the subsequent, continual high heat that can lead to overheating. Thus, overboost protection protects engines from high pressure which leads to high heat, potential overheating and the possible resultant failure of components that are vulnerable to heat.

A third benefit of the Wastegate technology is the efficiency derived from the engineering of the Holset Wastegate turbochargers. This engineering improves upon the already efficient fixed geometry design, adding an overall 3% increase in efficiency. Furthermore, they can be optimized for aftertreatment systems of varying capacities.

Variable Geometry Technology – VGT

The Holset VGT provides variable geometry (VG) for commercial vehicle fleets and operators. With a sliding nozzle ring, the Holset VGT provides a wide flow range that allows for higher boost pressures at low engine speeds. VG technology provides the best fuel economy potential of driving short-route Exhaust Gas Recirculation (EGR) in the emission challenge of reducing NOx levels.

The Holset VGT is unique in its durability and reliablity because the vanes slide axially so it has fewer moving parts and less wear sites, making it one of the reasons today’s commercial diesel operators rely on the Cummins Turbo Technologies for improved total operating costs and fuel efficiency.

Holset Turbocharger Repair, Replacement & Install

Cummins Automotive & Diesel Service provides professional, ASE mechanic expertise to repair or replace and install the applicable Holset turbo on your medium or heavy duty diesel engine.

Cummins Automotive & Diesel Service can check for impact damage to the impeller and turbine wheel, looking for foreign object damage to either one. Impact damage can be caused by foreign material entering the turbine housing or the compressor housing.

Cummins Automotive & Diesel Service can check for possible signs or causes of an Insufficient supply of lubrication oil to the turbocharger. If a repair shop had previously refitted your turbocharger without adequate priming, it could experience premature wear due to insufficient lubrication. Long periods of non-use can contribute to insufficient turbo lubrication as well. If a replacement oil filter has been installed without priming the oil filter with new oil, the turbo can suffer from insufficient oil lubrication.

Cummins Automotive & Diesel Service can check for other causes of low oil supply to the turbo, such as a broken or restricted oil feed pipe, low engine oil pressure due to a malfunctioning lubrication system, low oil or no oil in the sump and the improper use of sealants in previous repairs which can restrict the oil flow.

Cummins Automotive & Diesel Service can check your turbo for signs of excessive dirt in your oil, such as a dirt scored shaft or dirt scored bearings.

Dirty oil damages the turbocharger by causing heavy scoring of the bearing surfaces. Cummins Automotive & Diesel Service can check to determine if your oil and filters are of a quality recommended by the engine manufacturer. These should be changed when a new turbocharger is fitted and at regular intervals according to the vehicle or engine manufacturer’s specification.

Cummins Automotive & Diesel Service can check for additional signs of dirty oil damage that may have resulted from a blocked, damaged or poor quality oil filter, from dirt introduced during prior servicing, from engine wear or manufacturing debris, from a malfunctioning oil filter by-pass valve or from degraded lubrication oil which occurs when oil remains in the system past its recommended period of service life hours or miles.

Carbon build-up can be a sign of excessive exhaust temperatures or the hot shutdown of the engine when the engine is shut down without following the protocol of the manufacturer recommended period of idle before shutdown for the purpose of cooling of the bearings.

Turbine end heat extending into the bearing housing can result in oil carbon and corrosion of the bearing system. Damage to the shaft seal ring and grooves as well as damage to the turbine end bearing can occur as a result, along with the possibility of the bearing housing oil drain cavity becoming blocked.

Cummins Automotive & Diesel Service can check your turbocharger for carbon build-up by checking for degraded oil quality that has carbonized in service, by checking your oil change log or records to determine if any oil change intervals were of a period of time longer than recommended and thereby potentially causing oil breakdown in service, by checking for air and fuel leaks and by checking for a faulty fuel injector pump or faulty injectors.

Cummins Automotive & Diesel Service can also check for these causes of excessive smoke that can be related to your turbo, such as the contributing factors of a dirty air cleaner, an air intake system restriction, a cracked mounting flange or a missing gasket, fuel pump, injectors or valve timing that is incorrectly set, a Wastegate mechanism that is set incorrectly or a turbocharger that is damaged.

Cummins Automotive & Diesel Service can check for these causes of an engine lacking power which can be related to your turbocharger, such as a dirty air cleaner, an air intake system restriction, a cracked mounting flange or a missing gasket, an exhaust restriction due to a foreign object, the fuel pump, injectors or valve timing being incorrectly set, burnt valves, burnt pistons or a turbocharger that is damaged.

Cummins Automotive & Diesel Service can check for these symptoms of noise and whistling which can be related to your turbocharger, such as noises coming from air or fuel leakage that could be due to pre-turbine exhaust gas or due to air or boost leaks. Cummins Automotive can check all joints for leaks and if the noise continues they can check your turbocharger clearances and your compressor and turbine wheels for housing contact.

Cummins Automotive & Diesel Service can check for a seized or sluggish turbocharger. Problems they can check for in relation to a seized or slow, encumbered rotating turbocharger rotor assembly are the degradation of the lubricating oil, which can cause the high build up of carbon in the bearing housing interior, restricting rotation. Cummins Automotive can also check for dirty lubrication oil while checking for an insufficient oil pressure or an intermittent drop in oil pressure, all of which can cause the rotor to seize.

Cummins Automotive & Diesel Service can also check for a worn turbo with excessive axial and radial rotor clearances. If the clearances are out of specification, Cummins Automotive can check for the cause, looking to determine if it has a lubricating oil problem such as insufficient oil, dirt introduced into the system or oil that is contaminated with coolant.

Holset Turbocharger Models

Holset HT60 Turbocharger
Holset HX20 Turbocharger
Holset HX25 Turbocharger
Holset HX27 Turbocharger
Holset HE200 Turbocharger
Holset HX30 Turbocharger
Holset HE300 Turbocharger
Holset HX35 Turbocharger
Holset HX40 Turbocharger
Holset HE400 Turbocharger
Holset HX50 Turbocharger
Holset HX52 Turbocharger
Holset HX55 Turbocharger
Holset HE500 Turbocharger
Holset HX60 Turbocharger
Holset HX82 Turbocharger
Holset HX83 Turbocharger

Trust your Holset, Cummins Turbo Technologies turbocharger repair, replacement or installation to the experts at Cummins Automotive & Diesel Service.