Home > 2017 snowmobiles > Q&A: Yamaha Engineer Explains Technology Of New 998 Turbo

Q&A: Yamaha Engineer Explains Technology Of New 998 Turbo

By Andy Swanson

To learn more about how the new, turbo-boosted Yamaha engine was developed for the company’s 2017 Sidewinder models (and Arctic Cat 9000 Series machines, such as the Thundercat), Snow Goer talked with Yamaha Snowmobile Product Development Division Manager Jim Vizanko. He shared information about why the mega-powered engine was created, how it was developed and what unique technologies it brings to the snowmobile industry. The complete interview is below, and the full story about the engine is in the October 2016 issue of Snow Goer magazine that’s on newsstands now.

Yamaha Genesis 998 Turbo engine

Yamaha Genesis 998 Turbo engine

Not long ago, Yamaha’s stance was that if it wanted a 200 hp snowmobile engine, it would build one without needing to rely on turbo. Why the change of heart?

We can build a naturally aspirated engine to be 200 hp at sea level. We can do that under a thousand cc – that’s not a problem. The problem becomes when we get up at higher elevation and if we wanted to guarantee 200 hp at 10,000 feet we couldn’t do that naturally aspirated due to the dynamics of how air density works as you go up in elevation. We wanted to design an engine that worked at sea level and at high elevation and so with that in mind, basically we turned to the turbo and said this is what we’re going to need to do to meet that target at elevation. We looked at the technologies of both superchargers and turbochargers – [and concluded] super has an advantage in this area and turbo has an advantage in this area – [but] if we can make the turbo to act like a supercharger or somewhere between a naturally aspirated, we’d be happy with that type of arrangement. That’s what we did, we set our goal, ‘Alright, we’re going to make a turbo feel as naturally aspirated as possible.’ And that’s where we ended up. There was a lot of playing around with different things on the naturally aspirated side to get, quite honestly, more response out of the engine so that it didn’t feel lazy. I think that’s probably the biggest downfall of a turbocharged system is, typically, you go from naturally aspirated to boost and you get this rush or wave of energy come through. What we wanted to do with this engine is have that transition real seamless and we didn’t want to have the turbo side feel soft so we worked real hard on the turbo side to get that very responsive so that when it did go from N-A to boost you’d already be up in the range that you wanted to be.

When did this engine project begin and when did those of you in North America first become aware of its development?

We’ve been working on turbo systems since about 2005. We tried some things on other engine packages and learned that they may work good at sea level but once you bring them up to [elevation] they may start to struggle, and we didn’t see a huge demand at the time where we needed to invest in this type of an engine. We were bringing out two-cylinders, three-cylinders, four-cylinders and the market seemed pretty happy with what we had to offer at that time. But as that 150 hp class expanded there was the opportunity there to maybe come out with an engine like this and satisfy those customers looking for that high-end side of things. So, we’ve been playing with these things for quite a long time and we looked at the [aftermarket] MPI system and we played around with the Push system, just to kind of dabble in it there – we looked at it from an arm’s length. But it was a supplier-sourced product so we couldn’t do too much with it. As the momentum continued to grow and customers were more vocal about [wanting] more power, [that] is when we really went on our own. Three, four years ago we went and built some engines with turbochargers and superchargers on them and rode them in various environments and we did that with [Arctic Cat] and exposed them to the opportunity as well. They gave their opinions of where they thought the market was going and we gave our opinions and settled on a plan and said this is what we’re going to do and this is how we’re going to do it and put it on the product plan – started chugging down that road to bring it to market. We’ve been at this for quite a while I guess.

Did the Arctic Cat partnership and the fact that the Cat/Suzuki partnership will be ending soon affect timing of this project?

If we were going to do this by ourselves, purely Yamaha, then it’s very difficult to design and tool up an engine just due to the costs associated with these, both from a tooling standpoint and a manpower standpoint. But if you can sprinkle the tooling across two different brands it makes it a lot more attractive from that standpoint. They knew that their negotiations for Suzuki engines at some point were going to end and so that gave us also an opportunity to step in and offer this engine as well. We are two separate companies, but we are working together on a common product. There is some of that back-and-forth with the planning side of things.

What role did Arctic Cat play in developing this power package?

They had quite a bit of knowledge on some strategy as far as turbo sizing, intercooler sizing, intake air management, cooling. They’ve had their Suzuki turbo in the market [for quite some time]. They updated their chassis in 2012 and that sold over really well but there were some limitations of that Suzuki engine so there were discussions as far as, initially, some of the roadblocks they ran into and how do we get around them with this next design. Absolutely, Arctic Cat was very involved in the design and development of the engine. The design basically came from Y-M-C in Japan. The discussion would come back and forth between Arctic Cat and our group here in Minocqua [Wisconsin] and as we continued to evolve and we continued to test the engine [we’d ask], ‘Where does this engine need to go?’ and ‘Where is it lacking?’ There’s quite a bit of testing that goes back into it. Getting agreement with Arctic Cat saying, ‘Yeah, we think the same thing’ was important to draw a conclusion as far as where to go because all of this costs money, right? So we wanted to [provide] as direct information as we can to the development folks in Japan in what we needed to do. Arctic Cat was very, very happy with the performance and we were as well. I believe that they’re just as happy as we are as far as how this project ended.

Some powertrains have built-in controls to limit low-end power and response to, presumably, limit stress and wear on components. Is there any concern about this powerplant putting undue stress on the drivetrain or chassis?

We look at what our design loads are in the beginning. We redesigned quite a few components to handle the power of this engine. We came out with our new CVT system on our side, specifically. Our original CVT system was designed for that 150 hp area because that’s what our [Apex] four-cylinder made, so if we are going to guarantee in this 180 hp range we want to make sure the CVT system can handle it. The gearbox has been redesigned as well – we’re using a wider chain and using wider gears to handle the loading there. We’ve gone from a 13-wide chain to a 15-wide chain so that’s something that we needed to do to make sure we didn’t have problems in the gearbox

Reading the Powerpoint about the engine and hearing details about its design shows that the engine was built to be durable and long-lasting. How do its service and maintenance intervals compare with other Yamaha powerplants?

That’s kind of our bread and butter. We build products that last [and] that customers can depend on. Our design and our testing process, we do the testing and development before it gets in the customer’s hands – that’s just something we’ve always done here at Yamaha. We have a pretty good understanding of what we’re looking at for wear items. Our prior CVT system was bulletproof. [From] primary to secondary to belt, you just don’t wear these things out. That’s a pretty lofty target to meet that same requirement with a bunch more power, but that’s what we do. Product reliability, that’s our reputation. Going out and testing this thing, I think we had probably four or five dedicated durability tests this winter to look at and make sure that we had things where they needed to be. With each durability [test], you learn more. By the end of these durability tests, a CVT system will be tested maybe 10 different times in a controlled environment. We also do stuff in the lab as well [and] that’s something we do before we get to the field.

Yamaha Genesis 998 Turbo engine

This photo shows one of the oil squirters that helps keep Yamaha Genesis 998 Turbo piston domes cool.

What is the horsepower number readers should expect and why are the “published” results we’re seeing so variable so far (180, 204, 211 hp)?

We’re guaranteeing 180 hp. If it makes more than 180, we’re still guaranteeing 180, right? So that’s the number that we’re going with at this stage. As you go up in elevation, as the day changes, as the conditions change you may not make as much horsepower. So what we’re guaranteeing is 180 hp up to 10,000 feet.

When talking about the crankshaft, what does “press-forged” mean? Is this a unique manufacturing method?

Any time you machine something you’re changing the material properties. In some cases you’re hardening it, in some cases you’re moving it around. So when you’re dealing with harder materials like you have with a crankshaft, the less machining you can do, the better, typically.

Regarding the defriction coating on the connecting rods, where on the rod is that applied and what is the coating?

Any time you machine something you have voids, cavities, that sort of thing. It’s just part of the machining process. You’re not completely, 100 percent smooth so you have surface roughness that’s associated with it. In areas where you have high stress, these friction coatings are something that have been more and more common on higher-end engines just to make things last longer. This is a Yamaha engine so we go the extra level to make sure that these things don’t wear out or break. There are many different suppliers out there that offer this type of technology.

What is different about the water and oil pump so that it’s more capable to handle the demands of the engine?

[The Sidewinder’s] water pump is the same as the Viper. The oil pump has the ability to deliver more oil to more areas. You’re not only lubricating the crankshaft here, like in other applications, [but] you’re also putting oil into the base of the piston. You’re also supplying oil to the turbo system. Sizing that oil system up for that type of application is important. Oiling a four-stroke is an art in itself, especially on the snowmobile side of things with the dry sump.

The 998cc base engine has its roots in the Yamaha YXZ off-road vehicle, right? Does the engine bolted in YXZs have the same connecting rods and other measures to improve durability?

The 998 was designed to fit a couple different applications. If we can amortize the tooling across the product lines we have a whole lot better success of developing engines. In this case, we worked with our friends on the side-by-side side. It’s not the same engine but [there are] a lot of the same components. You’re going to do different things on those engines in order to meet the market requirement. The cases are very similar I’m sure, but your intake and your exhaust system, those obviously are going to be different. And then your internals are going to be different as well. There is some commonality to them. There are common layouts to them, there’s common parts to them but how far that common-ization goes is dependent to what the market requirement is.

The pistons are forged aluminum. What is different about the crown design for turbo use?

Typically the dome of the piston determines what your compression ratio is. And so, we’re down on compression on this engine compared to a naturally aspirated engine. It’s dished for both the intake and the exhaust valve and then it’s pretty smooth in the middle and that is to handle the increased, pressurized air to basically make as much power as you can and be clean power.

Is it especially challenging to develop a turbo engine with multiple throttle bodies? The reason we ask is because the presentation that was shown at the media sneak peek in January specifically pointed out this fact.

No other manufacturer is using multiple throttle bodies with a boosted engine for a D-type fuel-injection system. Mainly automotive they use L-type fuel-injection systems and our competitors use a single throttle body. So, creating that logic with the D-type fuel-injection system was unique.

What is the difference between the D and L fuel injection systems?

A D-type fuel injection system is based off of pressure where L is based off of volumetric airflow. With this type of engine you are pressurizing the intake system and that’s where these sensors are located in the intake manifold, so you can get a more accurate on/off situation with the sensor. D was kind of the original type of system. L is probably more common today and it’s based off the volume of air flow where the D is based off of pressure so that’s more in line with this type of application. We can sense a little more quickly with the D-type of system, but the L system is probably a little bit more widestream right now. So going back to a D system is something that is unique here.

The Genesis 998 Turbo engine has an IHI turbo with ceramic bearing. Why was IHI chosen and what advantage does a ceramic bearing provide? Are there any concerns about longevity of the ceramic bearing?

[IHI] is a common vendor to us and we felt that they had the best opportunity to meet the criteria that we were looking for here. Ceramic bearings are something that’s pretty common in a turbo system. We’re way past the age of aluminum and steel and pretty much any time you get into a higher loading application you’re looking at metal matrix. The ceramic is going to be more on the hard side of things. That is what they needed for this application based on speeds [and] loads. That’s the design criteria and lubrication life, that sort of thing. They’ll fit the material for the actual application. Just like the defriction coating: You’re fitting the application to meet the demands.

Is this an off-the-shelf turbo unit or was it built specifically for Yamaha?

These guys have probably 150 different variations of the same turbo. It’s specific for each application. Whether we could’ve used something that they use in a Mazda, for instance, [it] might be the same turbo there, but we don’t know.

The turbine blade is made from Inconel because it’s not subject to creep like steel or metal. What does “creep” mean and why does that matter?

Creep is cold flow of a material. With a solid material, when you have creep, it’s basically deforming or moving the material slowly. In materials, you have plastic deformation and you have permanent deformation. Creep is a form of permanent deformation. You don’t want a turbine blade reshaping itself in there, and that can happen. If you think about materials that first are either forged or rolled, and then a lot of times they’re heat-treated [so] they’re moved again. Making a plastic ski or something like that, it has shrinkage [or] after it cools it kind of takes a different shape. But if you’re continuously heating this material and cooling this material, so it’s got to live from minus 50 degrees F to some insanely high temperature [probably] above 1,000 degrees F. That’s a huge variation for a material to not break down and either reform itself or become very brittle. Inconel is a material that has been developed to live in this type of environment. It doesn’t stress out in high pressures of this type of heat. It’s very stable across a wide range of temperatures.

Yamaha Genesis 998 Turbo engine

A nickel alloy material for the turbine’s body is tremendously strong and can handle extreme heat.

The video on YouTube that shows how this new engine works says the turbo is fed fresh air. Is that correct? Don’t turbos normally receive air from the exhaust?

You have a hot and a cold side of a turbo. The hot side deals with the exhaust, that’s where the power comes from and the pressure comes from. That power gets delivered to the cold side and is basically under vacuum on that side. You have pressure on the hot side and vacuum on the cold side. You have positive pressure on the hot side [and] negative pressure on the cold side, so that’s where you’re drawing the air into the system and re-pressurizing. There’s pressure on both sides of the equation.

Automatic boost pressure adjustment: Is that unique to this system or are there other systems that also do it? What happens when the engine is run above 10,000 feet?

The system itself is the same as automobile, but it’s been modified to work in this application.

The Idle Speed Control (ISC) valve lets “precise amounts of air in” to reduce engine braking. Where is the air let into?

It goes around the throttle. There’s the butterfly valve there that controls the airflow in, and it’s basically a leak around the dam. It lets the air in past that throttle body [into the engine].

How does the engine braking control on this 998cc turbo engine differ from the system used on other Genesis-powered Yamaha snowmobiles?

It’s just the calibration that would be different, meaning: how much to add, how little to add. Generally we’ve been going in the direction of less engine braking is better, we’re going for more of a coast feeling. You have less disruption in the handlebar if your body isn’t moving around on the snowmobile all the time.

Why doesn’t it make a wastegate sound?

We continually circulate the air so we’re not dumping the air off into never-never land. We’re recycling it. You’re not getting that huge pressure change.

Why were new clutches developed for the Sidewinder models?

With this much power, we needed more weight for the primary to use this type of power. We’re up in the land of forces we’ve not had before so designing the actual weight profile and the characteristic of the weight we wanted a little bit more freedom there so there’s the ability to put more mass in the primary clutch. And then also we’re using a roller system on the secondary now. In certain areas you can feel an improvement with how it shifts. So we said ‘We need more ratio for this system, we need more durability for this system and maybe we can offer a little bit more feature for this system.’

The secondary sheave’s angle changed, slightly. Why was there such a minor change and why was only the secondary’s angle changed?

The angle was changed to get more gear ratio out of them. For a given gear in the [chaincase], you will make more top speed with the new clutches because of that angle. That angle gives it the ability to shift out further so you get more ratio with it.

 

2 comments

  1. Actual dyno test results of the new Yamaha 993 turbo (and compared to the Arctic Cat 993 turbo) on the SuperFlow engine dyno are posted on DynoTechResearch.com. 180++++

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