The 3.0L Duramax is a wildly capable inline 6-cylinder diesel engine designed for full-size half-ton pickup trucks and SUVs. Due to its amazing power-to-weight ratio and towing performance, GM has chosen to offer this engine in everything from Chevy Silverado 1500 to the Chevy Suburban and even the Cadillac Escalade. Clearly, GM is confident in its new design.
The new 3.0L Duramax shares very little in common with its predecessor the 4-cylinder 2.8L Duramax. It's been completely redesigned from the ground up and features many improvements such as a forged crankshaft, forged steel connecting rods, and a much stronger block design. The result is an engine that can produce 277 hp and 460 ft-lbs. of torque. Which is comparable torque to that of the more expensive 6.2L gas engine that is offered in most of the same vehicles.
In our testing, we noticed that the platform provided plenty of torque for pulling hefty loads along with a healthy amount of power for getting around town and passing on the highway. Although when it came to stepping on the pedal the desired response left quite a bit to be desired. The overwhelming amount of dead pedal made this trucks performance feel a bit lack luster. We also found ourselves wishing it had more low end power to help make the truck feel a bit lighter more nimble when taking off, especially when towing.
Where this engine really shines though is the amazing fuel economy it has to offer. With 22 mpg city and 26 mpg highway, this truck will get you far on a single tank. The unmatched fuel economy is in part made possible by the all-new 10-Speed transmission paired with the 3.0L Duramax. This transmission offers more gears and utilizes the same advanced controller as its big brother the 6.6L to keep the LM2/LZ0 in the optimal RMP range to provide the best possible fuel economy. Another place the 10-Speed shines is when it comes to towing. In our tow testing this truck outperformed a tuned 2.8L before any tuning was installed on the 3.0L. Considering the similarity in HP we attributed this mainly to the superior gearing of the new 10-Speed Allison.
However, when it comes to un-loaded daily drivability of the 10-speed can fall a bit short. In our experience, we found the transmission's constant and slightly drawn out shifting lead to an overall lack of power making it to the wheels. With the transmission is constantly shifting it also felt like the turbo never really had a chance to get into boost before the transmission shits, de-fuels, and puts the engine at an even lower RPM. In this aspect, the 10-speed is a major buzz kill when it comes to having fun behind the wheel of your 3.0L.
With features like a forged crankshaft and a robust block design, we knew the 3.0L platform could handle additional power—and that custom ECM and TCM tuning was the perfect place to start. Our goal was simple: unlock the best possible performance from the stock 3.0L while maintaining the safety, reliability, and drivability owners expect. Achieving that balance wasn’t easy. To deliver on our vision, we went beyond basic calibration by developing both ECM and TCM tuning to correct the undesirable characteristics of the 10-speed transmission, while also offering multiple power levels designed specifically for safe, confident towing.
For our first round of tuning, we wanted to add as much power as we could while still staying in a safe range for what the drivetrain can handle.
To find out what a safe level of power for the 3.0L Duramax is we ran the truck on our dyno and monitored things like drive pressure, EGTs, and transmission temp to see how the engine, turbo, and transmission were responding to the added power through the entire tuning process. After a few revisions, it looked like anything over 300hp was starting to negatively impact transmission temps and EGTs. However, the addition of around +40hp proved to be enough to make a noticeable improvement in power, performance, and daily drivability.
For our second round of tuning, we wanted to create a tune we knew would be safe for your truck even with a full load behind it. Considering our towing experience went very well with the stock tuning. We knew that improving the torque curve and adding just a bit more power could make a great experience even better. The second tune we developed provides 25 additional horsepower and 60ft/lbs of additional torque. This was enough to provide a noticeable difference when getting heavy loads moving from a stop and passing on the highway with weight behind the truck. It also made the weight of the load a bit less noticeable in general, all while keeping drive pressure, EGTs, and transmission temp in a safe range.
The factory torque curve of this engine is solid, extending all the way past 4000RPM. With ECM tuning we were able to bump the torque level up along that entire curve. However, the transmission still shifting before the turbo could really get into boost. Making It hard to get that additional power to the wheels. This is why TCM tuning was considered a must when approaching the 3.0L platform. The stock shift points simply don't allow the engine to rev out to its peak power even with ECM tuning. With our knowledge from tuning the 10-Speed Allison found in the 2020+ L5P we set out to create a better TCM tune for the LM2 as well.
By adjusting the shift points and timing so that the truck was able to reach higher RPMs before shifting we were not only able to massively improve the drivability and feeling of shits but we also saw an increase in the amount of power making it to the wheels from 0-60 accelerations. This also reduced the feeling of the transmission constantly shifting and finally allowed the truck to reach closer to its peak power output before making the next shift. Along with adjusting the shift points, adjustments were also made to the de-fuel time in between shifts. This not only helped mitigate the constant shifting problem. It also kept power going to the wheels for longer. This means higher average horsepower making it to the wheels when going through gears increased after TCM tuning. The graph above shows how our TCM tuning on a 10-speed L5P decreased de-fuel times can increase the average HP. Stock tuning is represented by the green line and "with TCM tuning installed" is represented by the red line.
With an added 40hp and 100ft-lbs of torque from custom tuning, plus our massive drivability and power output potential improvements from TCM tuning we finally felt like we had the drivability of the truck where we wanted it. The added power finally had the truck feeling lighter when accelerating and gave us more confidence while passing on the highway especially when in the tow tune with a load behind us. The truck also felt much more responsive with the additional power and improved throttle mapping. We were even able to observe a serious improvement to MPGs during the course of testing both sport and tow tunes. Netting us an additional two miles per gallon on the highway in the sport tune with cruise control on.
After all was said and done we were most exited that the truck now felt a lot more like its bigger brother the 6.6L L5P found in the 2500HD. Plus we now had a truck that was legitimately fun to drove both loaded and unloaded. If you would like to find out more on custom tuning for your 3.0L Duramax check out the product on Calibrated Power's website below.
