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.
Here is what Mr. 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.
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 though. 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.