Series Overview#
The Airman SDG Series is Airman's primary portable diesel generator lineup, spanning 9 models from 11 to 336 kilowatts of standby power. Built by Hokuetsu Industries in Japan and distributed through Airman USA, the SDG Series covers the full range of construction, rental fleet, temporary power, and event applications with Tier 4 Final certified engines from Kubota, Isuzu, and John Deere. The defining characteristic across all SDG models is 110% fluid containment as standard equipment — a baseline that most competitors offer only as an option.
The engine progression follows the power tiers: Kubota small-displacement engines at 11–30 kW (SDG13, SDG40), Isuzu engines across the 22–320 kW range (SDG25, SDG45, SDG65, SDG125, SDG400), and John Deere 6068 six-cylinder engines at 120–176 kW prime (SDG150, SDG220S). All models are Tier 4 Final certified and CARB compliant, making the SDG Series specification-ready for California construction projects and other air-quality-sensitive environments without modification.
Airman SDG generators are consistently specified on California job sites where two requirements are non-negotiable: Tier 4 Final emissions compliance and fluid containment. Meeting both as standard — not as options — simplifies procurement and reduces the risk of a specification mismatch during equipment substitution. Rental fleet operators who serve the California market standardize on SDG units for precisely this reason.
How to Choose#
The nine SDG Series models are organized by engine platform, with selection driven primarily by kW requirement and phase/voltage needs:
SDG13 (11 kW prime, Kubota D1503): The most compact Airman generator, at 1,290 lbs dry. Fits into spaces where larger units cannot. Single and three-phase output at 120V–480V. For small construction sites, single-tool setups, or light temporary power. Runtime is approximately 27.7 hours at full load.
SDG25 (20 kW prime, Isuzu 4LE2T): Entry-level Isuzu model. 32-hour runtime at full load on 51.5 gallons — the longest runtime in its class. Switchable voltage from single-phase 120V through three-phase 480V. Appropriate for small-to-mid construction crews and events.
SDG40 (29 kW prime, Kubota V2403-CR-T): Common-rail Kubota diesel at 29 kW prime. Despite sharing the same compact footprint as the SDG25, the SDG40 carries an 84.5-gallon tank providing approximately 37 hours at full load. Good choice when runtime between refueling is the priority at 30 kW class.
SDG45 (36 kW prime, Isuzu 4LE2X): Steps up from the SDG40 with a larger enclosure and 80.5-gallon tank. At 3,337 lbs operating, towable and compact for urban sites.
SDG65 (51 kW prime, Isuzu 4JJ1X): Mid-range bridge between the 36 kW SDG45 and 100 kW SDG125. 111-gallon tank, 28.5 hours at full load. Mid-size portable footprint at 4,189 lbs.
SDG125 (100 kW prime, Isuzu BR-4HK1X): First model in the 100+ kW class. 168-gallon tank, 23.3 hours at full load. 6,702 lbs operating — requires a trailer. Single-phase 120/240V through three-phase 480V.
SDG150 (120 kW prime, John Deere 6068 HFG 05): First John Deere-powered model in the SDG lineup. 204-gallon tank, 24 hours at full load. Operates at 66 dBA — quiet for this power class.
SDG220S (176 kW prime, John Deere 6068): Second-largest SDG. Three-phase 277/480V only. At 176 kW prime, this is the workhorse for large commercial construction and temporary facility power.
SDG400 (320 kW prime, Isuzu 6WG1X): Flagship of the SDG Series. 491-gallon tank, 21.3 hours at full load. 17,042 lbs — requires heavy-duty trailer. Single and three-phase output. The Isuzu 6WG1X returns to the Isuzu family for the largest model in the range.
Common Applications#
- Construction (all scales): Every SDG model is rated for construction applications. The SDG Series' Tier 4 Final compliance and 110% fluid containment make it the default specification for California construction and a competitive choice on any project with environmental requirements.
- Rental fleet: All 9 models are in rental fleet service. The SDG Series' combination of reliable Tier 4 Final engines, straightforward service intervals, and fluid containment reduces fleet operators' compliance risk and environmental liability exposure.
- Temporary power and events: The SDG Series' long-runtime integral tanks minimize refueling logistics for multi-day events and temporary installations. The SDG150's 66 dBA sound level makes it suitable for events where noise is a concern.
- Emergency standby: Three SDG models are specified for emergency standby applications where a portable generator provides backup power to a facility temporarily without permanent installation. The Tier 4 certification and switchable voltage configurations simplify emergency deployment.
- Film production: The SDG13 through SDG150 are used on film sets where clean, quiet power is required at varied locations. The SDG150's 66 dBA level and switchable voltage configurations meet typical film production power requirements.
Service & Maintenance#
SDG Series generators share a consistent service schedule: oil and fuel filter changes every 500 hours or 12 months, air filter service every 500 hours. The calendar interval typically governs for rental fleet units that operate intermittently.
The three universal failure modes across all 9 SDG models are fuel filter clogging from contaminated diesel, starting battery degradation during storage, and coolant hose weeping at clamp points from thermal cycling. For rental equipment that may sit between jobs, these are the three items most likely to cause a no-start or coolant leak at the beginning of a new deployment.
Fuel quality management is especially important for diesel stored in integral tanks between long jobs. Test fuel at each service interval and consider polishing or tank replacement if contamination is present. Battery maintainer connections are recommended for any unit stored more than 30 days between uses. Coolant hose clamps should be re-torqued and hoses inspected at each oil change — thermal cycling loosens clamps over time.