B-Max launches downsized EcoBoost engines

  • 08-Mar-2011 11:39 EST

The small B-Max MAV uses familiar Ford "kinetic" design cues.

Drawing heavily on Ford’s Iosis-Max concept from the 2009 Geneva Motor Show, the Ford B-Max unveiled at the 2011 Geneva Motor Show is a near production-ready model, which features the sliding rear doors and lack of B-pillar from the Iosis-Max. Ford says the door arrangement has already been engineered for production.

B-Max will extend the Ford MAV (Multi Activity Vehicle) range downward from the C-Max and will effectively serve as a replacement for the European-market Fusion based on an earlier Fiesta B-segment platform. The new MAV is based on Ford’s global B-car platform first used with the latest generation Fiesta three years ago. The new car measures 4060 mm (159.8 in) long, 110 mm (4.3 in) longer than a Fiesta five-door and 320 mm (12.6 in) shorter than the latest C-Max. It stands 110 mm taller than a Fiesta. With the front and rear passenger seats folded, it can accommodate items up to 2350 mm (92.5 in) long.

The body features conventional front-hinged front doors with sliding rear doors. To compensate for the lack of B-pillars, the doors are fitted with safety interlocks and reinforced latch mechanisms. For the rear doors, these latch into the cant rails. The car on display featured a single glass panel roof, although this is unlikely to transfer to production models. Ford has used ultrahigh-strength Boron steel in important load-bearing areas.

In design terms, Ford draws on the kinetic design language used in all recent Ford models. This includes the trapezoidal grille, the headlamp graphics, and a “muscular" shoulder line.

The door arrangement gives an access aperture to the interior over 1500 mm (59.1 in) wide, which, according to Ford, is around twice the width provided by competitor vehicles. The dashboard uses Ford’s HMI (human/machine interface) system with a 6-in color display mounted centrally above the mobile-phone-style control panel first seen on the Iosis concept.

B-Max is powered by what will be the latest addition to the Ford EcoBoost engine range. The 1.0-L three-cylinder gasoline engine features direct injection, turbocharging, and variable cam timing for each camshaft. Expect to see the 1.0-L engine in larger Ford models, too.

AEI asked Andrew Fraser, Manager Gasoline Powertrain Development and Integration, Powertrain Engineering, based at Ford’s Dunton Technical Center in the U.K., what issues the engine designers had faced in downsizing from the current 1.6-L EcoBoost four-cylinder engine: “Going from 400 cm³ per cylinder to 330 cm³ per cylinder, we’ve tried to keep the combustion system the same because we have some quite good experience with that now, and that has helped to get off to an initial strong start. We knew that certain valve/piston/injector configurations would work quite well.

“The main challenge is really the degree of downsizing—getting enough torque at low engine speeds off-boost, so that’s the area we focused on most to get the degree of responsiveness. It’s easy when you get to 2000 rpm and you’re on full boost, so that’s really been the main area of focus, the turbocharger matching and development.”

This has involved a lot of attention to detail on the turbocharger design. “It’s a very small turbocharger, very low inertia, so we get excellent transient response,” said Fraser. “The three-cylinder layout inherently works well with the turbocharger. The pulse separation of the exhaust is wider than it is in a four-cylinder, so you get more pulse tuning in the exhaust. Both the turbocharger and the scavenging effect that you get at low rpm when you open up the cams is better on a three-cylinder than it is on a four-cylinder because you don’t get the pulse interference across the cylinders as much as you do on a four. All those things have helped push the bottom end torque up at the lowest possible rpm. That’s been a key area of focus for us, while maintaining decent power and torque output at the top end.

"Turbochargers are a classic trade-off. You put a really, really small one on and get great bottom end, and it runs out of puff at the top end or vice versa. So there’s been a lot of computer aided analysis work, simulation of both the engine and the turbocharger. The Ricardo Wave software has been used quite a lot to model the gas dynamics of the engine.” The cost of a heat-resistant variable geometry charger for a gasoline engine would have been too great for a mass-market engine. “We found out that by using the camshafts in clever ways; it’s not variable geometry, but you can vary the way the air flows through the engine in quite different ways and make it behave quite differently at different operating points on the map, so that certainly helps," Fraser continued. “We’re gradually exploring more and more the use of split injection, again to vary the operating characteristics of the engine.

The 2.0-L EcoBoost is predominantly a single-injection system, but it uses split injection at low rpm and at very high power, and likewise with the 1.6. A diesel can have up to about five injections per cycle now, he said. "We haven’t quite got there with the gasoline engine, but we’re looking at different parts of the map. There are about eight degrees of freedom there. We’ve got two camshafts, injection timing, injection pressure, and ignition timing. Playing with all those variables and finding the optimum operating point in the map is quite complex.

"Some of the guys in my team are very good mathematical modelers. They can design an experiment that will test the key points in a matrix and then fit the maps between those points and show where the minimum or maximum point will be, depending on what you’re looking for—maximum torque or minimum fuel economy. Then you can run the engine at both points and literally join the dots across the operating map.”

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