Heavy Duty Alternator

Delco Remy 40SI™ High Output Brushless Alternator

The 40SI™ is a durable brushless model available in output ranging from 240 to 320 Amps. Its efficiency rating is best-in-class.  High efficiency translates to less engine horsepower requirements, resulting in substantial fuel savings. The 40SI is available with three mounting styles allowing flexibility when switching form a competitive model.  The premium brushless design of the Delco Remy 40SI provides added durability and life of the alternator.  Remote sense is standard on all 40SI models.

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Performance Output 12 Volts 240 Amps (160 Amps at idle)
12 Volts 275 Amps (180 Amps at idle)
12 Volts 300 Amps (190 Amps at idle)
12 Volts 320 Amps (190 Amps at idle)
Maximum Speed 8,000 RPM Continuous
10,000 RPM Intermittent
Rotation Clockwise
Temperature Rating 240 & 275 Amp: 125°C / 257°F
300 & 320 Amp: 115°C / 239°F
Mounting J180 Short Hinge
J180 Long Hinge
Polarity Negative Ground
Efficiency 72%
Weight 31.0 lbs / 14.1 kg
Stator Diameter 5.98 in / 152 mm
Length 9.92 in / 252 mm
Remote Sense Standard
*(US /Canada Only)
3 year / unlimited miles



Brushless Durability

The Delco Remy 40SI brushless alternator design dramatically increases both the durability and the life of the alternator.

Here’s why: Brushless alternators have fewer moving parts, which means less wear on the alternator. The end result is longer life. Alternators pull air from the back to the front in order to cool the internal electronics. This process introduces contaminants to the alternator. With a brushless alternator, there are no issues of contaminants hanging up brushes and causing failures. Without brushes, there are 13 fewer moving parts, eliminating components that wear out.

Bottom line: Delco Remy’s 40SI brushless alternator design leads to reduced downtime and longer life.

Remote Sense

Remote Sense can reduce battery charge time by 50%.
The 40SI is equipped with Remote Sense which utilizes a second wire that reads the actual to boost its output to compensate for the voltage drop, ensuring 14 Volts at the battery.  The proper voltage forces more current into the battery bringing it to a full state of charge between vehicle stops.

Improved Bearing Design

The Delco Remy 40SI high output alternator features bearings with enhanced steel and seals. This design improves the durability and life cycle of the alternator.

High Temperature Rating

With higher temperature ratings than the competition, the Delco Remy 40SI high output alternator is able to handle high loads on the charging system.

Instead of conducting heat from the diodes into a smaller heat sink surface, the entire housing is used as a heat sink.

This allows for a greater amount of heat dissipation, allowing the fan to cool the diodes more quickly and efficiently.

Improved Digital Regulator

The Delco Remy 40SI high output alternator is equipped with a digital regulator that features advanced detection of faults, including fail-safe, overvoltage, undervoltage, fail-soft and open field.

This technology allows the engine control module (ECM), to provide technicians with testing criteria to help troubleshoot and find the root cause of the problem. This reduces downtime and gets the vehicle back on the road faster.

Unique Stator Design

The patented design of Remy’s hairpin stator technology provides high power output and delivers maximum torque. The unique design of the 40SI stator reduces energy loss, providing best-in-class efficiency.


As one of the leading brushless alternators in the industry, the 40SI is at the top of the class in output performance and efficiency. The 40SI provides superior output performance at low RPM and at road speed.