Could the upcoming 2028 Chevy Silverado HD and 2028 GMC Sierra HD have an updated turbo-diesel engine that produces over 600 horsepower? We have talked about the rumored 8.3L MegaMax turbo-diesel engine before. Now, we have a new report that GM is testing a turbocharger that is about 30% larger than the previous one. Here is everything we know. Let’s dig in!
If the next Duramax engine will use a larger turbocharger, then the truck will make more horsepower and torque. If the turbocharger is 30% larger, then it could make at least 30% more horsepower. The current L5P-v2 6.6L Duramax V8 engine is rated at 470 hp and 975 lb-ft of torque. If you add 30% to it, then the engine would be rated at around 611 horsepower.
There is a side effect of using a larger single turbocharger. It will spool up slower, hence an increased turbo lag. There are ways to solve this. You can create a sequential turbocharger system with a small turbo that feed a larger turbo. You can also add a 48-volt electric system and use an electrically assisted turbocharger.
Let’s say you solve the turbo lag problem, but there are many other problems. Will this engine be rated to tow much more than the current 36,000 lbs trailer rating? This will be very difficult to accomplish because the engine must be rated to J2807 SAE standards. It means it must not overheat while pulling a maximum trailer weight up the Davis Dam incline with an ambient temperature of at least 100F. The maximum cabin cooling must also be enabled.
If the cooling system is upgraded, then what about the other powertrain and drivetrain components? We are talking about the transmission, 4×4 transfer case, differentials, axles, frame, and the rest?
While we are contemplating these possibilities, here is a look at the timeline of the recent General Motors pickup truck generations. You can see how the HD pickup trucks follow the light-duty 1500 series trucks by about a year. GM already stated that we will see the official debut of the Silverado 1500 and Sierra 1500 trucks some time this year. If these trucks will be 2027 models, then the updated GM HD trucks should be 2028 models.
It shows the L5P turbo-diesel generation spanning from 2017 to 2026. However this generation of the engine was updated twice within this time. The 2017-2019 L5P engine was mated to a 6-speed automatic transmission. The engine output remained the same for the 2020-2023 period, but the transmission was changed to a 10-speed unit. In 2024, the L5P-v2 came out with a significant power increase and other changes.
Here is a video that shows Roman catching several Chevy and GMC heavy-duty test trucks in the Rocky Mountains of Colorado. This was about seven months ago.
