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Next-gen 2022 Toyota Tundra could get new diesel engine: No def? Better MPGs?


The rumors are circulating about the next-gen 2022 Toyota Tundra with a lot of speculation about the engine. New patent filings suggest Toyota engineers are working on something and that something could be pretty special — a Toyota Tundra diesel.

Filled on July 2, 2020 the patent, posted to a Rivian forum,  seems to follow up on the trademark news Toyota made recently on a new iForce Max engine. This fueled speculation about Toyota taking the current 5.7L V-8 iForce engine to a whole new level.

Taking into consideration a new Toyota Tundra should hit dealer lots in the Fall of 2021, the trademark filing and now this patent filing, there is a lot of speculation that 1+1+1=3.

We spoke with several sources off the record to get their thoughts as well as asked our own G.R. Whale for this thoughts on a Toyota Tundra diesel.


2007 Toyota Tundra Diesel Dually

We aren’t saying a HD diesel is coming, but it is fun to think about.


Here is what Whale had to say:

Earlier this year a Toyota trademark application for the name iForce Max fueled speculation of a twin-turbo gasoline V-6 for the next Tundra, with output of 450 horsepower and 500 pound-feet or better. Given that Lexus already has a twin-turbo gasoline V-6 and iForce is a known Toyota truck engine moniker it seemed reasonable, and given Toyota’s hybrid experience, ekeing out a few extra pound-feet would be easy.

However, a patent application filed in December last year leads me in a different direction: a ducted fuel-injection diesel.

I’ll say right now it does not mention the words “diesel” or “Tundra,” and “gas” appears used only as the state and not short for gasoline. I’m also not an engineer and only make a habit of tearing down engines after I or friends wear them out or blow them up.

So, what do we really know?

The documents reference a “compressed self-ignition type internal combustion engine” but this could apply to a diesel-cycle engine or an HCCI (homogenous charge compression ignition) engine that runs on gasoline or diesel. The documents frequently mention a “glow plug” but these appear to be pieces used to heat fuel rather than air as they do in a conventional diesel. I can find no indication there is or is not a spark plug or a conventional glow plug in the accompanying line drawings, and the only materials named are an aluminum head with some chromium steel hardening points. The drawings show a couple of arrangements, one with ducts fitted to the chamber side of the cylinder head (and depending on assembly this could be part of the injector inserted from the chamber side) and one that depicts ducts inside the head in the roof of the chamber.

In one section the fuel is injected at a compressed charge, more indicative of a diesel wherein combustion begins when fuel is added, rather than an HCCI gasoline engine where fuel is injected during the intake stroke and combusts spontaneously when compression drives temperature and density high enough. However, HCCI has been tested on diesels in the past so it’s possible Toyota has figured out a way to make that feasible over a broader speed and load range.

The text frequently mentions “suppression of smoke.” Smoke most frequently applies to diesel engines — and really rich-tune hot rods, but that doesn’t guarantee a diesel and particulate matter doesn’t either: Some gasoline-powered cars in Europe have particulate traps, the majority of them direct injection.

What really makes me think this is a diesel is work done at the Sandia National Laboratories by Charles Mueller and associates, who found that better mixing the fuel and air before the point of ignition would make a cleaner, more complete, leaner and cooler burn, lowering NOx and soot. For one analogy consider your propane torch, which has a fitting on the end of the pipe (ironically mimicking a modern diesel exhaust tip) to better mix the air and fuel and make that nice, clean blue flame, against the smoky orange flame when you first light an oxy-acetylene torch.

My reading of the patent document makes me think it’s for diesel engines, but I’ve been wrong before. And there is no guarantee ducted fuel injection will arrive on any Toyota engine in the next couple of years, nor that it would show up in a Tundra. But think how many diesel engines Toyota sells around the world and that ducted fuel injection could likely be implemented at the same or lower cost than typical diesel after-treatment systems, and amortization comes quickly.



We also reached out to several off-the-record engineers who said a variety of things about a Toyota Tundra diesel.

One of them mentioned it might be a Homogeneous charge compression ignition aka the Mazda SkyActiv X engine — which achieved a 15% improvement over their other gasoline engines. HCCI engines work by using compression to ignite the air and fuel mixture, just like in a diesel. Normally in a gas engine, you use a spark plug for the ignition.

This has long been considered the “unicorn” of engine design and many manufacturers have spent decades trying to perfect it.

Why would Toyota copy Mazda? Toyota and Mazda have some history of working together. Currently, they are working on jointly building vehicles in a plant in Alabama and Toyota owns a small stake in Mazda (very typical for Toyota to take an ownership stake with companies it is working with). This leads one to think if Toyota owns part of Mazda, is working to build vehicles with Mazda, then why not also take a look at their engines. The patent could then be utilizing some of Mazda’s breakthrough while making small tweaks to allow Toyota to have a patent on their own design.

This, then, would mean the engine would be utilizing gasoline since Mazda’s current SkyActiv is a gas motor. However, the way the patent is written and the way diesel engines work it could be just that this patent shows how a gasoline engine could use the combustion principles of a diesel engine.

Another source we spoke to, who has years of diesel engine development for a major automaker, said it looks a lot like how Whale described it — pre-heated fuel mixed with air causing an automatic ignition within the combustion chamber. Basically, eliminating the need for spark plugs, reducing emissions and improving fuel economy. While this would mean Toyota would need tight controls on the block temperature and other factors, it is possible to make such an engine work.

The really interesting application of this is in a diesel engine and in vehicles used overseas like monthly car rental Dubai. It is possible this engine would eliminate one of the after treatment systems currently on a diesel engine. Right now, you have to add diesel exhaust fluid, go through a regen process and replace your diesel particulate filters as well as keep an eye on your injectors. Basically, as many see it, the diesel engine has been gutted by emissions equipment and is now a very costly engine to maintain. Eliminating just one of those after treatment systems would allow for reduced costs to purchase, reduced maintenance, better fuel economy through reducing unspent fuel as well as possibly improving performance by eliminating one of the airflow restrictions off the engine. In other words, we could see a Toyota Tundra diesel engine that is more superior to gas, more efficient to operate and less costly to buy.

We reached out to Toyota and they had this to say:

“As a result of our commitment to innovation and continuous improvement, Toyota has been awarded 23,611 patents over the past thirty-five years; the most patents of any automaker. These patents represent the brainpower, innovative spirit, diligence, and passion of Toyota’s Engineers and Researchers but may not always find their way into production.”

What do you think? Is a Toyota Tundra diesel just big dreams or does this get you very interested in hearing more?

Here is the full PDF document of the patent.

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Tim Esterdahl

Automotive Journalist Tim Esterdahl has been a lover of trucks and SUVs for years. He has covered the industry since 2011 and has pieces in many national magazines and newspapers. In his spare time, he is often found tinkering on his '62 C10 pickup, playing golf, going hunting and hanging out with his wife and kids in Nebraska.

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  1. breathing borla July 9, 2020

    I don’t know Tim, listening to sweers for years, I think a diesel is out of the question. I also think the V8 maybe on the chopping block, but I sure hope not.

    My guess is we get a turbo 6, which Im not sure Im even interested in.

    if they go the hybrid route or that, Im likely heading for a GM AT4 6.2

    it’s been so long since they made any improvements, Im losing interest a bit, fo row my current tundra is fine.

    1. Tim Esterdahl July 16, 2020

      Agreed diesel is a tough sell for me with the way he has talked about it in the past. I also have a tough time seeing the 5.7L V8 going away as well. Hopefully, I’m wrong on both accounts.

    2. Dave December 16, 2020

      A new ducted fuel injection diesel could have the diesel particulate filter removed as well as DEF fluid injector, and still burn way cleaner than current diesels, and removing 11,000.00 dollars in emission controls will make a new diesel truck way more affordable. Its a no brainer. Its coming soon.

  2. CMK1 July 16, 2020

    No, Twin Turbo Hybrid V6. iForce Max is not diesel.

    1. Tim Esterdahl July 16, 2020

      I see that as a tough sell to the truck crowd.

      1. Boco LWN July 17, 2020

        Agreed. Here’s why: the Toyota of today is not the Toyota of 2006/07 when they had some of the best truck marketing ever with Killer Heat, Pendulum, etc.. That marketing and their aggressive push in to the light truck market with class leading improvements, back then, is what propelled them to hit 196,000 units, their best sales year ever for the Tundra. Since then, their average units sold is about 120K.
        For Toyota to reclaim that glory will take the same aggressive effort of yesteryear. There’s no way they can do it as it will take an all new truck and with that, it will have problems that will further tarnish their claimed QDR. The early 2nd gen Tundra had problems, and so did the recent mild refresh of the Tacoma. They need guts and glory, something they don’t have.

        As for diesel, nothing says truck more, period. If the did find a way to simplify emissions and more forward with it, it could be a game changer.

        1. Joseph Veress August 25, 2020

          When they come out with the diesel engine…all the others will have to close the doors. The diesel what they make will be last maintenance, (last money)
          more efficient than any type of diesel including the German. Big-time game changer. They work on this so call new diesel engine for 7 years now with the Japanese engineers.

  3. Brian Finn September 11, 2020

    It’ll be some uber clean gas. Toyota and diesel in Merica is a tough sell. Mexico one problem. Saw diesel Tacos everywhere. They were quite too.

  4. Andre October 29, 2020

    Well I hope they go with a iforce v6 or the same in V8 twin turbos. My 2000 4 runner is the best truck I’ve ever owned 418,000 miles on it and I will drive it anywhere anytime. Why can’t they spray something like redguard underneath all their cars and trucks to deal with corrosion issues. Man if the put that iforce engine from the Lexus in the tundra I am buying it because their stuff works less the corrosion issues, he’ll the starter lasted 17 yrs I am still rolling on the same engine I just rebuilt the tranny that was 20 fucking yrs old I still have never had to service the ac unit even when I did the timing belt change at 300k miles without disconnecting the compressor.

  5. Fred Rose December 29, 2020

    My only concern with any turbo gas engine is that the average life expectancy of a turbo is about 100,000 miles which will cost around $3,500 to replace including labor, now you want to put 2 on? I won’t buy a turbo-powered car due to the expense of the turbo repair, not alone twin turbos.

    What I can’t figure out though is why do turbos in diesel engines last over 250,000 miles but gasoline engine turbos do not?

    While I own a 2010 Toyota Tundra 5.7 IMax I won’t be buying a newer Toyota truck with the twin-turbo setup, I’ll just keep mine running which it should run for a very long time.

    1. Tim Esterdahl December 31, 2020

      Your comment nails the confusion many people think they have about gasoline engine turbo engines. The assumption is that turbos don’t last in gas engines, however, in all of our research into Ford’s EcoBoost engine with its twin turbos, we haven’t found that to be the case. Just old wisdoms about turbos that are turning out to be not true.


  6. Marq January 15, 2021

    Sign me up to test the prototype. My business would give it a lot of exposure. I own a 2010 Tundra that lives up to its reputation, but would like something more fuel efficient along with reliability. I went from a Tacoma to a Tundra and would not want to change from what I consider the most reliable trucks on the road

  7. fernando mejia February 11, 2021

    omg diesel trucks are hot on other countries especially in south and central america and most of there car come directly from japan lets just hope that they give as the opportunity to drive one of there best trucks on the USA i’m ready for it ,,, diesel baby ////


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