The 2024 Duramax L5P Gen 2 does not get its power from a new short block. The crank, rods, and basic bottom-end architecture stay put because that foundation was already strong. The real changes are where combustion and airflow happen. The new piston bowl is the biggest clue. Its shape pushes air and fuel into a different mix pattern, which can improve combustion efficiency, cut soot, and help emissions by doing more of the cleanup in-cylinder. GM also raised injection pressure with a new high-pressure pump, then backed it up with thicker fuel rails built to handle the added load. Higher pressure means the fuel can be delivered through smaller passages with finer atomization, which helps the burn happen more completely. Up top, the heads get internal cooling revisions and a new head gasket design aimed at durability. Exhaust valve springs pick up seat pressure so the engine can use more exhaust backpressure for braking without losing valve control. The turbo system also changes in meaningful ways: revised turbine hardware, a different housing layout, and a faster, more powerful variable-geometry actuator. That gives the engine a better shot at quicker turbo response, stronger braking control, and the airflow needed to support the factory power increase. Put it together and the 2024 engine looks like a focused combustion-and-air-management update, not a cosmetic refresh.
Gale Banks begins by identifying the 2024 Duramax L5P as a significant update over the earlier version, with the most obvious change being a new turbocharger assembly. The turbo uses a completely different mounting arrangement, along with a new turbine housing, compressor housing, and a new high-speed variable-geometry controller. Banks also expects changes to the compressor and turbine wheels, so the plan is to tear the unit down and measure the critical dimensions, including compressor and turbine wheel sizes and the compressor-cover inducer diameter.
To support a direct comparison, Mike Keegan partially disassembled both a 2024 and a 2023 engine so the parts could be examined side by side. That setup allows Banks to separate what stayed the same from what GM changed for the 2024 model year.
At the bottom end, the 2024 engine is essentially unchanged from the 2023 and later L5P architecture. The crankshaft, connecting rods, and general lower-end structure remain the same, which Banks describes as a very durable foundation. He notes that Banks has pushed a stock-bottom-end Duramax past 1,000 horsepower in prior testing, including the "Killing a Duramax" series, and did not break the bottom end. A camshaft change was required after over-revving, but the core rotating assembly proved extremely robust.
The major change is at the piston. Banks sees the new piston crown as an effort to improve combustion efficiency while reducing emissions. In the L5P, the piston comes within roughly 0.030 to 0.040 inch of the cylinder head and actually protrudes slightly above the block deck. Injection begins before top dead center, and as the piston approaches the head, it pushes air back into the fuel plume. That motion works with the cylinder's clockwise swirl to improve mixture motion. Because diesel combustion does not occur with a uniform air-fuel ratio throughout the chamber, there are richer and leaner zones. Excessively rich zones can create soot, so reshaping the piston crown can reduce those localized rich areas.
Banks compares GM's new piston to ideas Banks previously used in racing pistons. Years earlier, Banks sharpened the center dome to occupy a lean region in the middle of the chamber and push air outward. GM appears to have taken that concept further by adding what Banks describes as a shelf around the perimeter of the combustion chamber and narrowing the squish area. He believes the revised bowl and crown geometry redirect the spray and air motion into a more favorable region of the chamber, potentially improving both power and emissions. If combustion efficiency rises at the same fuel rate, the engine can make more power; alternatively, it can make the same power with less fuel. Better combustion can also reduce soot and possibly lower peak combustion temperature, which would help reduce NOx.
Banks ties the piston redesign to injector targeting. The injector nozzle uses very small outlet holes, and peak injection pressure on the 2024 engine is 2,200 bar, compared with 2,000 bar previously. He describes that as roughly 32,000 PSI versus about 29,000 PSI. The spray does not exit straight down; it is aimed at an included angle of 155 degrees on the new engine versus 158 degrees on the older L5P. Banks estimates the plume included angle at roughly 16 degrees, though he notes that it likely varies with pressure and flow. With multiple holes around the injector tip, the revised targeting changes where the fuel plume enters the combustion chamber, and therefore changes the local air-fuel mixture where combustion begins.
The head gasket is also new for 2024. Both the earlier and later gaskets are multi-layer designs, but the stack-up differs. The earlier gasket uses four layers of uniform thickness, while the 2024 gasket uses three uniform layers plus one thicker layer. Banks interprets this as a revised approach to achieving higher unit loading around the cylinders for improved sealing and durability. Oil drainback and coolant passage locations remain identical, which they would need to be for backward compatibility, but the gasket itself is clearly an updated design intended to seal better and last longer.
The piston cooling nozzle has also changed. The 2023 and 2024 nozzles are similar in overall shape, but they appear to be made differently. Both spray upward into the piston cooling gallery, and both outlet diameters are a little over 2 mm. The retaining bolts differ as well, with the 2024 version appearing more fully machined. Despite the cosmetic and manufacturing differences, both systems serve the same function.
Banks explains that the retaining bolt contains a pressure-sensitive internal valve, essentially a spring-loaded ball check. At idle, when full piston cooling flow is not needed, the valve keeps oil directed to the crankshaft and the rest of the engine so idle oil pressure is maintained. Under higher demand, flow is allowed to the piston cooling nozzle.
From there, Banks reviews the evolution of Duramax oil coolers. He references the earlier lower-output designs, then the 2017-2019 L5P cooler, and then the larger 2020-up cooler. The 2020 trucks also received a much more powerful radiator fan, substantially more engine-coolant radiator capacity, and higher towing capability. Banks argues that the 2020-style oil cooler is valuable not just for newer trucks but for owners of 2001-2019 trucks who use their vehicles aggressively, including tuned applications. That observation led Banks to create a retrofit kit that allows heavy-duty oil cooling upgrades on earlier Duramax models.
Another major 2024 change is the high-pressure fuel pump. Banks describes the pump as somewhat analogous to a small V8 engine with one cylinder head removed. Inside, a flat cam ring rotates so that the cam surface rises and falls relative to the plungers. He points out that this arrangement gives a more uniform pressure profile across the plunger face than a conventional cam-and-lifter contact pattern, because the loading is distributed across the entire follower surface. There is still sliding friction, but it is more uniformly loaded, which should improve durability.
The new pump is rated for 2,200 bar, or about 32,000 PSI, while the 2023 version operates at 2,000 bar, roughly 29,000 PSI. Banks says the extra pressure allows the engine to deliver the required fuel quantity through smaller nozzle holes, improving atomization and refining the combustion process. He explains diesel combustion in terms of droplets burning from the surface inward, peeling away molecular layers as they move through hot compressed air in search of oxygen. If a droplet loses momentum, it can consume the oxygen immediately around it and stop burning efficiently. Higher injection pressure helps maintain droplet momentum so combustion can proceed more completely.
Because the rails must safely contain that additional pressure, the fuel rail itself changed. The earlier rail measures about 24.5 mm in diameter, while the 2024 rail is about 26.3 mm. Banks says that increase is effectively added wall thickness to preserve the necessary safety margin at the higher pressure. The rail is also shorter: about 359 mm on the earlier version versus about 343 mm on the 2024 engine. The fuel rail pressure sensor changed as well. Although the electrical connector appears identical, the sensor must now withstand and report an additional 3,000 PSI.
Externally, the 2023 and 2024 cylinder heads look nearly identical, but Banks says the 2024 head has revised internal structure in the water-jacket area for improved durability. The more obvious change is in the exhaust valve spring. The 2024 spring has a greater free length than the earlier spring, which Banks interprets as a deliberate move to support stronger exhaust braking.
On these engines, exhaust braking is created by the turbocharger's variable geometry, which raises exhaust backpressure. If backpressure becomes too high without sufficient valve seating force, the exhaust valves can be forced off their seats. In the worst case, that can lead to valve-to-piston contact. To prevent that, GM increased seat pressure on the 2024 spring.
Banks measured the earlier spring at roughly 80 pounds of seat pressure, while the 2024 spring comes in around 90.25 pounds, an increase of about 15 pounds. The installed height remains the same at 1.690 inches. Wire diameter is slightly smaller on the new spring, about 0.152 inch versus roughly 0.156 to 0.158 inch on the earlier spring, and the outer diameter is about 0.030 inch smaller. The new spring uses thinner wire but more turns. Open pressure measured over the nose at 1.330 inches, corresponding to 0.360 inch valve lift, is about the same between the two. Banks also notes that coil bind margin appears improved, suggesting the newer spring may tolerate slightly more lift. He connects all of this to stronger exhaust-brake performance, especially for trucks towing very heavy trailers.
Banks then returns to the turbocharger, since the variable geometry system is what creates the exhaust backpressure used for braking. The 2024 turbo uses a different turbine-mount casting and a revised bolt pattern. The earlier L5P arrangement used one conventional perpendicular bolt and one angled bolt on each side. The 2024 setup returns to a more conventional perpendicular-bolt arrangement, although the pattern is not perfectly symmetrical. Banks suspects the change may have been driven partly by assembly tooling clearance around the V-band clamp between the turbine housing and center bearing housing, while still maintaining sufficiently uniform clamping load through the casting.
At the turbine outlet, or exducer bore, the 2024 housing is about 0.040 inch, roughly 1 mm, larger than the earlier version. The turbine wheel blade count also drops from 11 blades to 10. Banks interprets both changes as an increase in exhaust mass-flow area. A larger outlet and fewer blades can reduce restriction, provided the turbine still produces enough power to overcome its own inefficiency, the bearing-system drag, and the compressor load. He ties this to GM's increase in rated output from 445 horsepower to 470 horsepower.
On the compressor side, the most visible change is the variable-geometry actuator. Both units are BorgWarner pieces, but the 2024 actuator is described as a quicker, more powerful mechanism. Faster actuator response allows the turbocharger to change speed more quickly, which helps reduce lag and improves control of air delivery. Banks notes that airflow itself cannot change instantaneously, but a faster actuator helps the system get closer to the desired mass flow and pressure ratio sooner. That benefits throttle response, fuel efficiency, and emissions control.
Some dimensions remain unchanged. The compressor inducer bores are the same, and the compressor blade counts are also the same. However, the center bearing housing and back-plate arrangement changed. Up through 2023, the water-cooled center housing used an integral cast-iron compressor back plate. For 2024, GM moved to a more conventional aluminum back plate bolted to the center bearing housing. The back plate now also mounts the actuator assembly, whereas on the earlier turbo the compressor cover carried the actuator mount. Banks sees the new arrangement as a more robust overall unit.
Taken together, the 2024 Duramax L5P updates point to a coordinated effort to improve combustion efficiency, emissions performance, durability, exhaust braking, and power output rather than a single isolated hardware change. The bottom end remains the proven L5P foundation, while the piston, injector targeting, fuel pressure, fuel rail, head gasket, valve springs, and turbocharger have all been revised in ways that support one another.
Banks repeatedly returns to the idea that better in-cylinder combustion reduces the burden on the emissions system. If the engine produces less soot and potentially lower NOx at the source, the aftertreatment system has less work to do and may last longer. At the same time, the turbo and fuel-system changes support the 2024 engine's higher output and stronger exhaust-brake capability.
His conclusion is that the Gen 2 L5P appears to be a meaningful engineering step forward, not just a calibration update. With Banks having already exceeded 1,000 horsepower on a Gen 1 L5P, he closes by wondering how far the Gen 2 platform can be pushed.