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 that the 3.0L is offered in.
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 pretty dull. We also found ourselves wishing it had a bit more power in the lower end to help make the vehicle feel 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 LM2 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 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 towing tests 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 the drivability of the 10-speed certainly doesn't add to the thrill. In our experience, we found the 10-speed transmission constantly shifting when accelerating. This really causes drivability and the feeling of power to suffer. When the transmission is constantly shifting it also feels like the turbo never really has the 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.
We knew the 3.0L could handle some added power and that custom tuning was the best place to get started. With this in mind we wanted to develop 2 custom tunes designed to bring out the best in both top-end power and towing performance for the 3.0L Duramax. We also wanted to offer LM2 owners the best experience they could get out of their trucks. With all of that in mind, we knew that we also had to be able to provide our customers with a TCM tune to clear up the undesirable tendencies of the 10-speed transmission .
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 holding up 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 40hp proved to be enough to make a noticeable improvement in drivability and performance.
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. It was hard to get that extra power to make it to the wheels. This is why TCM tuning should be considered a necessity for this 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.
We started by adjusting the shift points so that the truck would reach a higher RPM before shifting. This improved the amount of power making it to the wheels and made each gear last slightly longer before the next shift was made. This reduced the feeling of the transmission constantly shifting and finally allowed the truck to reach closer to its peak power before it made a 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 the average horsepower making it to the wheels when going through gears increased after TCM tuning. The graph above shows our TCM tuning on a 10-speed L5P and how the decrease in de-fuel time can increase the average HP. Before tuning is represented by the green line and after tuning is represented by the red line.
With an added 40hp and 100ft-lbs of torque from custom tuning, we finally felt like the truck had some substantial power behind it. The added power made the truck feel lighter when accelerating and gave us more confidence while passing on the highway especially when in the tow tune with a load behind the truck. The truck also felt more responsive as well as more fun to drive. We also saw an improvement in MPGs. Netting us an additional two miles per gallon on the highway with cruise control on. Overall we thought the truck felt a lot more like its big brother the L5P in terms of power and acceleration. Plus this is one of the quickest and easiest ways that we have found to add substantial power to the 3.0L Duramax. If you would like to learn more about custom tuning for the 3.0L Duramax please click the link below.
