Now that General Motors has announced its all-new 6.6L V8 L8T gasoline engine for the 2020 Chevrolet Silverado HD and 2020 GMC Sierra HD, we can start wondering what other GM vehicles will get it next. And immediately, a perfect candidate come to mind: the Chevy Silverado Medium Duty.
The 2019 Silverado Medium Duty lineup, comprised of the Class 4 Silverado 4500HD, Class 5 Silverado 5500HD, and Class 6 Silverado 6500HD, launched with a Duramax 6.6L V8 turbo-diesel engine mated to a wide variety of Allison transmissions – a legendary combination that has been the powerhouse behind nearly two million trucks.
Specifically, the Duramax motor in the Silverado Medium Duty – the 6.6L Duramax Diesel V8 L5D – is rated at 350 horses and 700 pound-feet of torque. The L5D is a derivative of the 6.6L Duramax V8 L5P offered in the Silverado HD and Sierra HD. GM claims that only “minor differences” separate these two diesel engines, but it’s worth noting that the L5D makes 95 horsepower and 210 pound-feet of torque less than the L5P. The L5D Duramax is currently the only engine offered in the Silverado Medium Duty. And all that brings us to the L8T.
Not everyone wants or needs a turbo-diesel V8 in their Class 4, 5 or 6 commercial truck. Many would be just fine having a modern gasoline engine, and some would probably prefer a gasoline powerplant over the turbo-diesel heart.
Then there is the fact that a gasoline engine is less expensive than the Duramax turbo-diesel to produce (for GM) and potentially to operate (for owners), enabling Chevrolet to offer the Silverado Medium Duty at a lower base price than the current $46,970 starting MSRP.
In all, the Silverado Medium Duty already has the diesel engine from the Silverado HD, albeit in detuned form. Bringing over the new gasoline engine from the new HDs to the MDs seems like a no-brainer to us.
About GM’s 6.6L V8 L8T Engine
Based on GM’s fifth-generation Small Block engine architecture, GM’s new 6.6L V-8 L8T gasoline engine is SAE-rated at 401 horsepower and 464 pound-feet of torque in the 2020 Silverado and Sierra HD. It runs an iron block with aluminum heads while featuring direct injection and variable valve timing at a 10.8:1 compression ratio. All that enables it to make robust power low on the power band, which is particularly helpful when it comes to towing.
Notably, the new L8T foregoes Active Fuel Management, Dynamic Fuel Management, and Auto Stop-Start technologies.
Stay tuned to GM Authority for more Chevrolet news and Silverado news.
Comments
This is a no brainer for many companies who don’t want the extra complexity of modern Diesel engines.
I would say yes it will. I also wouldn’t be surprised to see the L8T in the 6500XD LCF and Isuzu FTR.
There are thousands of companies, towns, states and the federal government agencies that want to run a green fuel such as LPG propane or CNG natural gas in the 4500HD, 5500HD and 6500HD Medium Duty Sliverados. The very high compression ratio ( CR ) of 10.8 to one on the new 2020 gasoline 6.6 liter engine, will take maximum advantage of the very high octane levels of both propane ( 105 octane ) and natural gas ( 120 octane ). Compared to the much lower CR of the existing 6.0 liter GM truck engine of 9.5 to 9.9 to one, the engine computer will advance the engine timing to suit the higher octane. This will give better MPG and more power when the engine computer advances the timing. The GM engineer at the truck show a few weeks ago, said that there are mini water jackets between each cylinder, even though the cylinders are a siamese configuration. The existing 6.0 liter does not have those mini water jackets between each cylinder, so they run too hot when using propane. Propane contains about 37 percent hydrogen by weight, which means the fuel burns very hot and very clean. This means the 2020 new 6.6 liter engine will run much cooler on propane than a 6 liter engine, all engine demands under load being equal.
The L96 6.0L is not a siamesed bore block, it has cooling passengers between the cylinders. I run a lot of them on CNG, never had an overheating issue. Propane is a little different, but generally speaking if it’s overheating is probably too rich (not lean like a gasoline engine).
I think the 6.6L will eventually be a good gaseous fuel engine. The high compression ratio is definitely a plus, but the direct injection presents an issue. DI gaseous injection is new technology, recently introduced in Europe but I don’t know of any DI CNG/LNG engines in the U.S. yet.
I thought it was already confirmed that this and the LCF medium duty trucks are getting this engine.
I’m pretty sure that it was and rennet reading that Navistar was also testing/validating it for use in their version.
No, not confirmed. Rumored, but not confirmed.
Navistar testing GM gas V8 in their trucks sounds like more than just a rumor.
Navistar is in a joint venture with GM to design and along with providing the chassis for this truck. They will also use the same Duramax Allison combination for their trucks, not a rumor.
DON, You have come to the party very late. These trucks are already being delivered to dealers in both Canada and the U.S. The Chevy medium duty versions are not sold in Canada, only the Navistar version.
Mark, not late to the party, I’ve been following these trucks since the first announcement of the GM Navistar joint venture. My comment was in reference to the comment above about Navistar testing GM engines rumor.
I know how far along these trucks are and actually had the opportunity to see one at the Philly car show. GM did a great job with these trucks, the one thing I didn’t care for is where they placed the DEF fill pipe. It is right behind the right front wheel, opposite side of fuel fills.
Another person there also commented that the old medium duty cab which were based on the cut away van cabs had much more headroom, though still a job well done!
I would think they would offer it here and the International (Navistar) truck as well.
Yes… Uhaul is a large customer for gm.. They don’t use diesels…
I get it, this is intended to be a low stress detuned motor for very long term use but, for crying out loud, couldn’t they at least muster the courage to tune another 30 hp into it so we dont have to look longingly at the 6.2 in the 1/2T trucks?
As a regular driver of an HD with L5P, I would never advise going with less output in a bigger chassis. L5p is adequate but no hot rod in actual street driving. If I were shopping the MD market I would not be impressed with trucks that tow worse than the 2500/3500.
Ford is going to have a field day advertising their new 7.3 with superior output and likely no penalty in fuel consumption….I think gm just got tired of winning a couple of years ago and decided to quit trying.
I think focusing on fuel economy and engine durability is more important than flashy numbers. I think GM figured a torque curve similar to the 8.1 is enough to get any job done. I would love to have 600 ft/lb torque but at some point you gotta figure out whats good enough and focus on mpg and reliability.
Matt, the words out of the Ford engineer’s mouth was mid power between the gas 6.2 and the 6.7 diesel. , meaning HP, not torque. This means HP of about 400 to 425 HP. The max performance is when the torque reaches max RPM as low as possible. Ford has some previous V8 engines ( bothe the 5.4 and the 6.8 ) with max torque of 2500 and another at 2800 RPM. If Ford puts a variable valve timing on the new 7.3 gas truck engine, they should target for 2500 RPM or lower for max torque. Why? Because Ford is putting a 10 speed automatic behind it and with a 2 1/2 to one torque multiplication of a truck type torque converter, it will be just about perfect. Car auto trans only have a 2 to one ratio torque converter.
No penalty in fuel consumption? Huh?
The 7.3 is going to burn more fuel than this 6.6 will. The 7.3 will almost certainly run a lower compression ratio, it will likely use port fuel injection only, and probably won’t have a high efficiency 2-stage oil pump. Tack on the extra displacement and it’s pretty easy to assume that the L8T will be more efficient than the 7.3. The 7.3 will be helped slightly by the 10-speed but it probably won’t be enough to close the gap. The L8T will get better fuel economy than the Ford 6.2+6speed combo, but probably won’t beat the 6.2 when it gets the 10-speed. The fuel economy gap will be very small though.
A Ford engineer at the truck trade show a couple of weeks ago said this “IT WILL HAVE A TWO STAGE OIL PUMP”.
The info posted today February 18th, about an even bigger than the 6.6 liter gasoline engine makes sense. The 400 cubic inches of the 6.6 is not really suitable for the 6500 and the future 7500 GM trucks hinted at today. The LPG 8.0 liter LFI engine ( 488 cubes ) that GM sells to Freightliner and others for school buses, only has a 4.25 inch stroke. It’s designed as a high block, so it can be stroked to a max of 4.75 inch, according to Brain Thomson of Thomson Automotive. ( Brian sold it a few years ago) Since the original testing with a 4.27 inch bore, with the same bore and a 4.5 inch stroke crank it will be 515.73 cubic inches or 8.45 liters. For more torque, with the same bore, a 4.6 inch stroke will give 527.19 cubes or 8.64 liters. If i was GM, i would use the much smaller pistons ( 3.935 inch bore ) from the 366 big block and go with the longer 4.5 or 4.6 inch stroke. With a new design small piston ( the old tech 366 cube 6.5 L piston had 4 rings, not 3 ) of 3.935 inch with a 4.5 inch stroke, brings the engine size down to just 438 cubes or 7.17 liters. This way, the higher torque level is retained but reduces the amount of fuel burned by a huge amount ( 7.17 L versus 8.45 L ) GM should use an 8 or 10 speed automatic to reduce engine noise, fuel use and allow for 2 or 3 overdrive gears. OK, guys, for offshore ( street ) racing with a 4.75 inch crank and the original 4.27 inch bore you get 544.38 cubes or 8.92 liters. Cummins offers a 9 liter CNG engine option. GM wants some of that business.
Will GM’s new 6.6L V-8 L8T gasoline engine be available in the Denali’s Light Duty 1500?
I don’t think so. The L8T does not have AFM or start-stop, so it would likely not have good enough fuel economy or GHG emissions for a light duty truck. That’s not to say GM couldn’t do an aluminum block 6.6L with those features for the 1500’s.