Back in February, GM Authority was the first to report that the 6.6L V8 L8T engine was imminent for the Chevrolet Low Cab Forward truck. First introduced in the all-new 2020 Chevrolet Silverado 2500 HD and 3500 HD pickups trucks, the new L8T engine was later announced for the 2021 Chevrolet Low Cab Forward truck in March, offering up more power and torque than the 6.0L V8 L96 engine which it replaces. Now, we’re taking a closer look at how these two engines compare.
When equipped in the Chevrolet Low Cab Forward truck, the 6.6L V8 L8T produces 350 horsepower at 4,500 rpm and 425 pound-feet of torque at 3,800 rpm. That’s a boost of nearly 18 percent horsepower and 14 percent peak torque compared to the outgoing 6.0L L96 V8. The transmission used is the six-speed 6L90-E Hydra-Matic (RPO code MYD) with lock-up converter and overdrive.
Meanwhile, under the hood of the Chevrolet Express cargo van, the 6.6L V8 L8T engine produces 401 horsepower and 464 pound-feet of torque, bringing gains of 17 percent more horsepower and 24 percent more peak torque compared to the outgoing 6.0L L96 V8 in that particular application.
Check out the specs in the detailed table below:
| Vehicle | Chevrolet LCF | Chevrolet LCF | Chevrolet LCF | Chevrolet Silverado HD | Chevrolet Express |
|---|---|---|---|---|---|
| Model Year | 2017-2020 | 2021+ | + / – 2021 | 2020+ | 2021+ |
| Engine | 6.0L V8 L96 | 6.6L V8 L8T | +0.6L | 6.6L V8 L8T | 6.6L V8 L8T |
| Aspiration | Atmospheric | Atmospheric | - | Atmospheric | Atmospheric |
| Horsepower @ RPM | 297 @ 4300 | 350 @ 4500 | +53 | 401 @ 5200 | 401 @ 5200 |
| Torque @ RPM | 372 @ 4000 | 425 @ 3800 | +53 | 464 @ 4000 | 464 @ 4000 |
- LCF = Low Cab Forward
The 6.0L V8 L96 is an old workhorse of an engine, producing 297 horsepower and 372 pound-feet of torque. However, it’s not the most power-dense, nor is it the most efficient. By comparison, the 6.6L V8 L8T is an all-new, modern truck engine.
That said, there is one drawback for the new L8T, namely the lack of a gaseous variant (CNG / LPG), which the L96 did originally offer. That said, the L8T should be able to run gaseous fuel quite well when such a configuration is offered, given its higher compression ratio.
The GM 6.6L V8 L8T engine
As a reminder, the Chevrolet Low Cab Forward line of vehicles is a series of medium duty trucks offered as a result of a partnership between General Motors and Isuzu Motors, currently spanning two generations. The new L8T engine is destined for 3500 and 4500 models, while the other models in the LCF line include the 4500HD/XH and 5500 HD/XD diesels. The 3500 and 4500 models are also available with diesel engines, as supplied by Isuzu. The flagship of the Chevy LCF family is the 6500XD LCF Diesel, which is technically a totally different, much larger truck.
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Comments
Ninety-five percent of the people reading this web site just want to know if the ECU on L8T will work on older GM cars in-line with the L96.
Because if so, then we have a CARB-approved direct swap modern engine for a whole host of older GM cars.
Controllers for L8T vs. L96 and previous 6.0 are incompatible hardware and software. Direct injection L8T communicate via Global B Lan Architecture and security protocols. Previous 6.0 LS based port fuel injected engines are on Global A, GMLAN, or even Class II depending on MY. Different engine wiring harnesses and controller pinouts. Many previous gen 6.0 l setups do not have a TOS line to EBCM to get specific Input signals. If it were to be done, a dedicated Lan translator would be required, as well as new engine/chassis harness and new calibrations, possibly software too, for other modules such as EBCM and TCase.
Good luck converting a DI gasoline engine to bifuel with LPG/CNG.
Different fuel systems, FSCM, and eval controls as well.
Fuel system can go DI by sourcing injectors from the Camaro, that was a known problem but solvable.
Unfortunately the ECU is a much greater problem and will probably leave older cars with LS motors until someone makes a signal adapter.
For the first time, because of the much higher compression ratio of the 6.6 liter, it will produce more torque on propane than on gasoline. The jump up in the CR from 9.7 to one ratio in the old 6.0 liter to 10.8 to one in the 2021 6.6 engine is a world of difference. Remember that LPG propane is extremely high octane at 104. Propane contains about 37 percent hydrogen by weight, so it burns very hot and clean. Low RPM engine torque will be the biggest difference between the two sizes of engines, which for a truck, is everything. Expect about the same MPG because less gas pedal is required to get up to speed. The higher CR will allow much faster acceleration from a stop to the mid 2,000 RPM range. Mitsubishi Fuso is also using the same larger 6.6 engine in it’s 2021 models as well. The Fuso uses the Allison auto trans instead of the GM trans. The Fuso is available with a 4 wheel drive option.
The L8T 6.6L is only offered with the 6L90 at this point Powertrain Solutions has taken over the L96 6.0L program and several years ago teamed it with the Allison 2000 series automatic transmission for Freightliner. This powertrain is currently used in many Freightliner stripped chassis, as used by U.P.S. and FedEx. Last year, Fuso offered the L96 6.0L/Allison 2000 in their LCF. They never offered the L8T 6.6L, and they have discontinued all new truck sales in North America for 2021. What is interesting is that along with Chevy, Isuzu will offer the L8T 6.6L/6L90 in their NPR (LCF 3500/4500 equivalent), but Isuzu has plans to use the PSI sourced L96 6.0L/Allison 2000 in some of their larger NRR series trucks (this was reported by GM Authority on March 6). No word if Chevy will follow suit on their LCF’s.
It’s a very good engine. General Motors needs to make it an option in the medium duty conventional cab Silverados. Seeing a lot of those in the wild lately…we’d see even more if a gas motor was offered.
I hope that the L8T supports aftermarket tuning. That sure woke up my L92 and L96 engines.
Is there a full Electric model.