Atkinson Variable Displacement V8 Coming To The Tundra

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A note from the Editor: with the new Tacoma coming to market with an Atkinson cycle engine, we thought it made sense to republish this older post that explains how it works.

When rumors of a V8 Lexus coupe with “variable displacement” hit the automotive press a few months ago, I was more than a little skeptical. Quite a few Toyota employees have said that the typical variable displacement technologies employed by GM and Chrysler-Fiat are “not in the best interests of the consumer,” which is Toyota-speak for “variable displacement is a stupid gimmick,” at least when GM and Chrysler-Fiat do it.

Considering all the problems GM trucks have had with their active fuel management systems (which can consume 1-2 quarts of oil between changes), Toyota’s stance makes sense. Yet a number of sources claimed Toyota’s new V8 Lexus coupe would have variable displacement technology, and I found myself a bit dismayed. Would Toyota succumb to the allure of variable displacement systems that raises a vehicle’s EPA rating without any real-world benefits?

The Lexus RC F 5.0L with variable displacement.

Today’s announcement from Toyota about a new family of “thermally efficient” engines all but guarantees that the Tundra will be getting a variable displacement V8, similar to the system found on the new Lexus RC F 5.0L V8 (shown).

Fortunately, the answer is no. The new Lexus RC F comes with a 5.0L V8 that can operate both as a traditional Otto cycle engine and as an efficient Atkinson cycle engine, which – in a manner of speaking – means the engine is variable displacement. When you combine this news with today’s announcement from Toyota about a “new series of gas engines,” it’s safe to say that the Tundra will be getting a variable displacement V8. Probably in the next 2 years.

The 5.7L and 4.6L Are Reaching End of Life

Toyota’s typical pattern is to produce an engine for about 10 years. The Tundra’s 5.7L came out in 2007, and since the 4.6L is basically a down-sized variant, it’s probable both of these engines will be replaced or substantially upgraded in the next couple of years.

Tundra 5.7L engine

Toyota’s 5.7L V8 is 7 years old now, and Toyota engines don’t tend to live longer than 10 years without major improvements. The odds that we’ll see a new engine family – or a major improvement to the existing engines – by 2016 or 2017 are very high.

But the question is, replaced with what? Diesel rumors aside, designing a new V8 just for the Tundra doesn’t seem probable. New engines cost money, and the existing 5.7L and 4.6L V8s are adequate as-is. With some “tweaking,” they could both be considerably more efficient…which brings us to the Atkinson cycle.

Atkinson vs Otto – What’s The Big Deal?

There are a lot of explanations about the function of the Atkinson cycle as compared to the standard 4-stroke “Otto” cycle we’re all familiar with (if you’re not familiar with the standard Otto cycle, read this –, but my favorite explanation of the Atkinson cycle goes like this:

  1. When the power stroke is completed on an Otto cycle engine, the cylinder has some ambient pressure. While this pressure helps to “push” the spent exhaust gases out of the cylinder, it’s also wasted energy. After all, this is “left-over” pressure that could have been used to drive the piston a little further.
  2. When the power stroke is complete on an Atkinson cycle engine, there is no (or almost no) remaining pressure in the cylinder. Every bit of pressure from the combustion process is used to drive the piston, and that is very efficient.
  3. You can convert an Otto cycle engine into an Atkinson cycle engine by leaving the intake valve open for a portion of the compression stroke. This “shortens” the length of the compression stroke, which means the power stroke is essentially longer.
  4. To make an Atkinson engine work, you have to figure out how to get the exhaust gases to leave the cylinder without the benefit of ambient pressure. In the old days, all Atkinson cycle engines had superchargers to combat this problem. Toyota, however, invented a “tumble flow” intake system on the Prius that uses atmospheric pressure to “push” the exhaust gases out. This system is also used on the RC F’s 5.0L V8.

The “variable displacement” system in the new Lexus RC F (which, for the record, is a beautiful car) works as described above.

Lexus RC F Coupe

The new Lexus RC F comes with a 450hp 5.0L V8 featuring “variable displacement.” Basically, the engine will switch between Atkinson and Otto cycles, balancing the power capabilities of the Otto cycle against the efficiency of the Atkinson.

NOTE: Holding intake valves open during the compression stroke sacrifices total power output about 30% (give or take). A 30% power sacrifice is not something truck or sports car owners want during acceleration, towing, etc…which is why switching between the Otto and Atkinson cycles is so valuable. The engine’s maximum efficiency improves without sacrificing peak output.

What Engine(s) Will We See in the 2016/7 Tundra?

If the Atkinson technology used in the Lexus RC F were brought over to the Tundra’s 5.7L and nothing else was changed, we’d see no loss of peak torque or horsepower, yet about a 10% improvement in fuel economy. If the transmission was updated to 7 or 8 speeds, we’d see another 5-10% increase in gas mileage.  Add these two improvements up and the next-generation Tundra 5.7L might be able to hit 22mpg on the highway, while the 4.6L might hit 23 or 24mpg.

Throw in some other fuel economy enhancements (electric power steering, variable valve lift, an ‘eco’ driving mode that reduces power to save gas), and it’s conceivable that the next Tundra powertrain could hit 25mpg+ highway, and 17-18mpg in the city.

If these numbers don’t impress you, consider:

  • The engines won’t have to sacrifice any power or displacement to achieve these improvements
  • The fuel economy gains won’t rely upon any complicated or expensive “tricks” like turbocharging, replacing steel with aluminum, or direct injection

Going this route, Toyota would be able to keep the costs of the Tundra’s new powertrain low and improve fuel economy without sacrificing any power.

To be clear: The fuel economy ratings offered above are just informed speculation. I also have no confirmation on the notion that Toyota will keep the 5.7 and 4.6L V8s. However, it says here that Toyota will be bringing a variable displacement V8 to the Tundra at some point in the next 2 years, using the same system found on the RC F.


Filed Under: Tundra News


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  1. Randy says:

    Toyota has been doing the Atkinson on the Prius since 1999. That’s about 14-15 years now so they know what they are doing. Making it variable and I hope size it up to the 5.7L to give use truck buyers the tow power and load power we want is a win win. This type of design should not have all the problems GM has had using other methods.

  2. DJ says:

    Very interesting stuff, the kind of stuff that I held off buying a 2014 for. I knew Toyota had to do something with the 5.7 to get some more fuel economy. This appears to be it. I thought it would be something along the lines of direct injection or something, but the scenario laid out here sounds very promising.

    This is why I’ll be holding out until 2016-2017 to get my next Tundra. Hope it mirror’s what they did when the 5.7 came out and blew away the competition.

    • T-towing says:

      I agree!

      I guess I should of refreshed before posting my previous comment. You said it better than I did.

  3. T-towing says:

    Good article. I’ve been waiting for any indicators of what Toyota may have planned for the Tundra. I was considering a 2014, the interior and exterior changes are nice but the minor power train tweaks were disappointing and did not warrant the purchase. If the ideas mentioned in this article come to fruition I would definitely upgrade from my 08 as I’m sure would many others.

  4. mk says:

    yota has to do something in either 2015 or 2016 for the competition is now beyond what toyota is now offering. I say 8 speed tranny and direct injection are worth noting hoping for 2 more mpg gain and same or slightly better power. I just don’t see a small diesel in the works for the tundra and other large SUV’s that have the 5.7 V8. diesels are usually a lot more money for not much gain in power if it is truly a small displacement diesel. Plus, diesel gas right now is crazy high vs. unleaded gas.

    • Anonymous says:

      Do some research…
      Its already stated a 5.0L Cummings for the tundra.

      I have a 07 tundra… how does one get poor fuel mileage?
      First off its a pickup…not a truck.
      If you want mileage… buy a tree hugger ride.
      I get 22 on the highway. 18 in town.

      I’m happy with what my tundra gets.
      I’m afraid if they keep messing around with the new engines it will be the same result as what the new diesels are compared to the late 90’s-2000 diesels.

      • Anonymous – Sorry, but that 5.0L engine is still just a rumor. I’ve been told the prototypes exist, I’ve seen the original story from Ward’s (which is reputable to be sure), but I have my doubts. We’ll see if the diesel is really going in a Tundra or not.

    • Larry says:

      Diesel is a problem for sure at a 25 percent fuel premium. Add UREA injection and exhaust filters and it just isn’t practical for anything but heavy freight. As for power the gas motors are not the same. HP yes but not raw pulling power at 2000-2500 RPM. The up front cost of a Cummins 5.7 Tundra will never have a pay back. I know several people who buy for fleets, construction, municipal etc. Most are moving away from diesel due to cost, up front and down the road. They all run Bosch fuel pumps and injectors which go over 5000 dollars when they need to be replaced and with fuel pressures of up to 25000 PSI it’s not uncommon for them to go out. Add that to the FEDs requirement for a diesel exhaust and it just doesn’t work for anything but very heavy towing. 3 gallons of oil, 7 gallons of coolant, on and on, heavy diesel isn’t cheap any more. The new gas motors are the way to go. The manufacturer which gets it right and builds a 200,000 mile motor will be in good shape.

      I have a friend with a luxury F150 4 door, V8 4 speed auto. It might be 3 or 4 years old, just before the 6 speed trans came out. On a trip last year towing a boat at 70 and into high wind in Wyoming, it only got 8 MPG. In those conditions I don’t see how 12 would be possible from any gas motor.

      It looks to me like Toyota has played this very smart. Let the other come to market before it’s all worked out while they do R&D. Release it when it’s right not just to get a review in a magazine.

      I question how all of them are going to meet the 25 MPG requirement which is only a few years away and still have a truck which can do any real work. There is going to be a point were trucks will separate into people transport and work units and I guess they already have. When that is finally complete, people may need to accept less power and slower speeds wheel towing the fifth wheel up hill. IF CAFE were to move into the commercial 3/4 and 1 ton truck market, I have no idea how could build such a truck.

      Those buying into the leading edge may pay a price.

      • Larry – Absolutely agree on diesel. As much as I like the technology in a newer small diesel engine, the ROI sucks. The higher up-front, the mounting maintenance costs, the ham-fisted emissions systems…it’s all too complicated and too costly. I’d much rather have a gas engine.

        As for 25MPG, I’ve been reminded that it’s a fleet goal. Toyota – unlike Fiat-Chrysler, GM, or even Ford – sells an awful lot of highly efficient cars. They’ve also got zero-emissions fuel cell vehicles (FCVs) coming, and they plan to sell the hell out of those, as they’re supposedly going to be very cost competitive.

        Each Prius, FCV, and uber-efficient Yaris Toyota sells can be used to offset the penalty of selling a Tundra that doesn’t quite hit the standard.

        I see a day where Toyota will offer a Tundra that doesn’t compete with Ford or GM on fuel economy. Consumers won’t care because this Tundra will cost substantially less and be far less complex (and therefore cheaper to own). Toyota won’t be able to sell a whole lot of these trucks without incurring a CAFE penalty, but that won’t matter much because Toyota’s truck capacity is constrained anyways.

        Finally, while I’m prognosticating about 2025, I’ll go ahead and suggest than an fuel cell powered Tundra makes a hell of a lot of sense. Even if Toyota just sold fuel cell powered Tundras in California to fleets and local govt., they’d have enough credits to offset all kinds of gas-slurping V8s. Not to mention, fuel cell technology work fit into a truck platform very, very easily.

        • Larry says:

          For some reason I thought the FEDs were demanding trucks move up to around 25 MPG by 2025. I need go back and check again.

          Fuel Cells, it’s worth doing but that one would be way out there. I have invested in a natural gas engine company, Westport Inovations. Nat gas is much farther along then fuel cell development and I can tell you I have gotten killed on that one. Nat Gas is really struggling to reach the build out to make it happen. It could still be at least 5 years more. No doubt that Fuel cells work but there is even less hydrogen infrastructure then there is nat gas but, it is worth the R&D or it will can’t happen at all.

  5. hemi lol says:

    I have wondered for years why Toyota didnt start using Atkinson cycle tech on the reg. engines it just makes sense….Heres to hoping for that with addition of 8-10 speed trans and Variable lift (already in use on the 14 Corolla ECO model).

    • hemi lol – Thanks for commenting – I see you on all the time.

      • hemi lol says:

        thanks Jason. Just branching out now because of how biased and ridiculous that site has become! its just terrible, but its one of the only sites to see all truck news going on.

  6. Mike P says:

    Where exactly did it say that the Tundra would be getting this? It said fourteen new engine variations, does that include the Tundra because it wasn’t too specific.

  7. Larry says:

    I am not surprised by this. With FED CAFE demands down the road what choice do any of the manufactures really have.

    Having worked on piston engines of all kinds for about 50 years, I know how they work. Will this prove to be the last development in the advance of the piston engine. What else it left to be done.

    Things have come a long way from the iron 350 V8s with 3 speed automatic transmissions which would drink fuel. We must be near the end of the line. Next will be to find a way to get 1500 pounds off the truck. Carbon fiber everywhere?

    • Randy says:

      Cars and trucks have come an even longer way from my 68 LeMans with the 350 (Chevy or Olds V8) with the Chevy 2 speed “Power Glide” tranny. That was so Kewl at 60mph you could floor it, the revs would go all the way to the top and the car would then “slow down”.

      This was a fully adjustable automatic tranny; you just move the wire gizmo above the gas pedal to adjust your Kick Down switch. LOL

      • Larry says:

        I though I was the only one old enough to remember,,,,,,,,, “slip and slide with power glide”. I had a 350 Impala with one of those thing. 2 speeds yikes.

  8. Larry – Have you seen the pnuematic valves that Koenigsigg (sp?) is working on? That’s probably the “next big thing” in ICEs – valves without cams. From what I’ve read, costs and noise are the biggest problems. If someone devises a way to make them cheaper and quieter, the fuel economy improvement could be dramatic (perfect timing, as they say).

    Randy – LOL. I like your adjustable transmission trick.

    • Larry says:

      No, I have not, thanks for the information and I will check it out for sure.

    • Larry says:

      I checked it out and it makes a lot sense when it’s perfected. Under computer control it will make variable displacement and variable timing much easier then with a rotating cam and and phasors. Valve lift can happen any time needed and duration time can also be tuned for RPM.

      Looks like good stuff. Which brings me to my previous comment, other then newer lighter alloys, how much efficiency is left to be extracted from piston engines. They are already very efficient for their motion and the next level of improvement is under development. Then what?

      Thanks for pointing this out, strange that I had not run across it before. Because it makes perfect sense.

      On some high RPM motorcycles like Ducati the mechanics lift and close the valve, they don’t just press it down and have the spring close it. NASCAR has also done a lot over the years to develop valve springs strong enough to close the valves after lift in high RPM push rod motors.

  9. It just leaves us wondering what would’ve happened if Atkinson technology was indeed used for the Tundra. Fuel economy advancement maybe but well, there might be other sacrifices. Toyota seems to know what they’re doing and we’ll just have to wait on what next they can offer.

  10. Rick says:

    This is an informative article.

    I remember the Atkinson on an older Mazda 626. It did get a slight improvement in MPG but that was in front of a 4 spd trans. I agree that pairing this to a modern 8spd would further improve MPG and maintain reliability.

    GM’s newly employed direct injection, drinks oil and the public now knows about that. Running to some unproven technology or worse applying something that is documented to cause major engine issues is cause for disaster. Toyota seems to be taking a measured approach to the Tacoma’s new 3.5L V6.

    “The new powering option for the 2016 Toyota Tacoma is a 3.5L Atkinson-cycle D-4S
    V6 with Direct/Port injection…”

    Direct injection has long been linked to carbon fouling on the neck of the intake valve and subsequent, premature engine break down. See article reference DI:

    A careful combination of some innovative technologies such as a defeatable start-stop, VVTI, high strength steel for weight loss and Atkinson combined with a modern 8spd transmission would perhaps be a better alternative for the consumer who wouldn’t be burdened with engine failure in 6 or more years of ownership.

    This is an informative article. I trust Toyota’s ultimate decision will will be a cautious culmination of research and trial that will result in providing the consumer with a safe and reliable product.

    • Tim Esterdahl says:


      Consider this, the Prius first went on sale in 1997. That means Toyota has been working with the Atkinson cycle for more than 20 years (if you count Prius development time). I think it is safe to say this system has been tested quite a bit by now!


      • Rick says:


        I forgot about the Prius. Love that car!

        It’s interesting that other manufacturers haven’t employed this technology. I bet Mazda didn’t see a return on investment in a time of falling oil prices – though we thought they were going to remain low at that time.

        I hear more negative feedback on GM’s new 6.2L and how owners are both being ignored by GM and not getting any headway through the legal process.

    • Rick – Thanks for commenting.

      The key to making sure direct injection doesn’t foul valves is to use both port AND direct injection. At lower speeds, port injection sprays fuel onto the valves, “washing” away the carbon that may build up. At higher speeds, direct injection provides more precise fuel mix to maximize power.

      Toyota has mostly solved the carbon build-up issue by mixing port and direct injection, as has Audi/VW. Ford is choosing to try and solve this issue with software…the results remain to be seen.

  11. Marko says:

    What Rick said +1
    DI removes fuel cleaning of intake valves needed because of the PCV system. Beware of DI. Been there, not doing that.

    • Goldie says:

      That’s why Toyota’s D4-S system uses both port and direct injection. This greatly reduces the carbon buildup problem.

      The D4-S system has been in production since 2005 if I recall correctly. And Toyota has been producing engines with direct injection, called D4, since 1998. The belief that Toyota is behind the competition when it comes to engine technology (e.g. direction injection, turbocharging, variable displacement, etc.) is just plain false. Toyota have been producing engines with these technology for a long time now. They just don’t like releasing them to the masses until it has been proven to be reliable and durable.

  12. BrianJ says:

    Wow! Some enlightening news, for sure. If Toyota can get 24mpg hwy/18 city with a 5.7 just might be enough to get me back in the showroom. Still waiting to see what the Nissan Titan does with the Cummins. In the meantime, the Detroit 3 have most of my attention. Interesting to see if this truly plays out.

  13. breathing borla says:

    I’ll believe it when I see it for the tundra. Let’s hope if they do it, they don’t go down in displacement.

    need at least 400hp if it will come out in a few years.

    I still don’t think there will be a ISV5.0

  14. Larry says:

    If you need 400 HP how could we expect 20 MPG?

    The problem is we might want high power for that 5 percent of the time we need to transport loads. Then we are stuck with the loses in fuel the other 95 percent of the time because the engine is too big and too heavy.

    The only option is 2 engines. A 4.0L when we run empty and a 6.0 when we need it for work. Our only options are a small 4.0 engine that gets turbo boosted up to 6.0 or a 6.0 which moves down to 4.0 due to cylinder activation or Atkinson mechanics which can change cam profiles to reduce air intake by delaying the close of the intake valve.

    In any event, these are complex with many more parts. Any failure and we will have repair costs which will consume our fuel savings.

    For me it’s more cost effect to just live with less power for those few times I need to tow loads. For others they might want to carry the cost of a bigger motor which will last longer under heavier loads. The big 6.2L F250 gas motor is just too much for my needs. I want the frame and suspension of the 3/4 ton but I can’t get it with a 5.0L engine which is all I need.

    With a 33 percent price disadvantage to gas and 3000-5000 in up front costs for a diesel they just don’t work after we do the cost analysis. Nothing is free in all this.

    In my view the big three are going to pay a price for moving forward way to fast before they have the systems properly engineered. Toyota has no choice but to match these moves but it would be huge mistake to rush a half baked system to market. If Toyota puts out a Tundra with bad VVT or cylinder deactivation mechanics it will take them years to recover.

    I still won’t budge on the concept of the eco boost engine being a bad idea. It’s an Indy car motor in a truck and it won’t last. A rebuild will cost thousands and then we will be behind the cost of the old style 5.7 Tundra V8.

    It’s got to be right.

  15. […] had superchargers to combat this problem. However, Toyota devised a “tumble flow” intake system on the Prius to counteract the problem. This unique system uses atmospheric pressure to push the […]

  16. Ron Baran says:

    That’s some interesting and exciting news. I have a 2008 Dc and love my Tundra. I will keep it for a while longer, hoping Toyota brings it home with New engine options and more options for interior. Update sound system, maybe Klipsch or Bangs&Olufsen. Yeah that’s asking Alot, but would be sweet. Get it done Toyota!

  17. Don says:

    Is it possible to see a V6 variant of the Tacoma put in the Tundra. I am a loyal Toyota purchaser but the Tundra is too far behind to even consider a purchase. When 2016 model????

  18. miles says:

    you will see direct injection on a new tundra engine, toyotas new fuel injection uses both direct and port injections in one system.

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