Fiat has seized the presentation of the 2017 model of the Uno to introduced a much more important element: the new Firefly engine family. This is the name Fiat chose for them, even though it still calls them GSE (Global Small Engine), as we have announced previously that they would be named. And we will probably stick with calling them that, since GSE makes much more sense than Firefly. These engines will power small cars not only in Brazil, but also in other markets, such as Europe, Africa and Asia. And here they are.
This is the most important one for the Brazilian market, the 1.0 3-cylinder flex engine. Each cylinder has a capacity of 333 cm³. What would imply that a 4-cylinder powerplant would have a total capacity of 1,332 cm³. Precisely the size of the 1.3 4-cylinder unit that is the other GSE model so far.
I have asked Aldo Marangoni, Powertrain Engineering Director for FCA Latin America, why haven’t Fiat chosen to create a 1.0 2-cylinder engine, what would allow it to have a larger modular 3-cylinder, a 1.5 liter unit. And to eventually replace the 1.4 MultiAir engine with something more torquey, especially in low revolutions.
“A 333 cm³ chamber allows for a perfect combustion, while a 500 cm³ would not be the ideal”, the engineer told us. Curiously, Marangoni has been elected by Automotive News Europe as a Rising Star in the automotive industry in 2011 due to his work on the TwinAir engine, also known as SGE (Small Gasoline Engine). This engine is a 1.0-liter 2-cylinder unit in its naturally aspirated version. More precisely 964 cm³. And a 0.9-liter in the TwinAir version, which you can see above. It is a 875 cm³ engine, with 437.5 cm³ for each cylinder. Go figure…
Our explanation for this situation is that FCA has apparently preferred to follow the industry standard, even if Marangoni claims that this standard has been established exactly due to a more efficient combustion chamber. Besides, Fiat already has a 2-cylinder and it is still produced. What we do not get is that it had the chance to make all of its small engines modular with such a move: a 1-liter 2-cylinder, a 1.5-liter 3-cylinder and a 2.0 4-cylinder engine. All built with the same pieces, able to replace all small engines of the company, with huge scale gains. And with amazing features in all of them, if we are to consider what Fiat has done with the current GSE units.
Unlike most other 1.0 3-cylinder engines, GSE uses only 2 valves per cylinder. “It was not a cost requirement, but rather a technical solution. The GSE engines have been conceived to be naturally aspirated ones”, said Erlon Rodrigues, product analyst at FCA and directly involved in the development of the new family engine, at the presentation. And the solutions they have achieved could support that claim, even if not entirely. It is clear that the GSE family has been designed to be cheap to build and the least complex possible, but with a lot of care to details.
There is no question 2 valve per cylinder engines are simpler and cost less to build, but both block and cylinder head are made of aluminum, a solution that has both made the GSE units lighter (7 kg less than an equivalent engine) and faster to heat up until its optimal working temperature. If cost was the only concern, it would have been made of iron. There is no balance shaft axle on the 3-cylinder. It relies on an unbalanced flywheel to minimize vibration. As you can see above, the exhaust manifold is sculpted on the cylinder head, a solution that surely lowers cost, but also makes the catalyst heat faster, according to FCA engineers. The crankcase and the oil strainer are made of steel so that they do not crack in case they are hit by stones or other obstacles in the awful Brazilian roads.
Improving thermal efficiency
All GSE engines count on a system called CVCP (Continuous Variable Cam Phaser). It is a similar system to Toyota’s VVT-i, but applied to only one camshaft. That allowed FCA to adopt a daring strategy in order to achieve lower fuel consumption.
When the engine is in partial loads, such as on the road at a constant speed, the CVCP can retard the camshaft in up to 60º. “When that happens, we manage to increase the expansion ratio by leaving the intake valve open more time after bottom dead center. We also lower pumping losses. Some people prefer to call that Atkinson cycle, but the true Atkinson cycle had a physically different expansion ratio. This is why we preferred to name it Miller, even if it is typically associated with a turbocharger or a supercharger to compensate the power loss. We could have named it something completely different”, said Rodrigues.
Audi has done so, calling their Miller cycle as B cycle. “When we thought about the communication strategy, we did not want to use something new in order for people to have a better reference of it. The important part is that we have increased the expansion ratio and that helps us improve thermal efficiency”, the analyst added. With the camshaft retard, isn’t there a risk that high temperature gases could cause detonation? “Good question, but remember we only retard the camshaft in partial loads, so no one has to worry about engine knock in this case”, said Rodrigues.
Designed to breathe
If the engine was a DOHC, it would demand two CVCP, what would make it more expensive and more complex. According to Marangoni, the 2 valves per cylinder also help to optimize combustion speed and stability. Have a look at the green image above. It is apparently a representation of the recess that GSE piston heads have just under the spark plugs. They have been calculated to provide a better combustion flux. “Our engines have a better air flux than half of all 4-valve per cylinder engines. It is much superior in this matter than all similar competitors and than half of the engines with double the valves”, said Rodrigues.
Engines that breathe better produce more power. And this is pretty much the case for both GSE mills. The 1.0 3-cylinder produces 57 kW at 6,250 rpm and 107 Nm at 3,250 rpm on ethanol (it is a fuel flexible engine) and 53 kW at 6,000 rpm and 102 Nm at 3,250 rpm on gasoline.
The 1.3 4-cylinder generates 80 kW at 6,250 rpm and 139 Nm at 3,500 rpm on the renewable fuel, while petrol makes it deliver 74 kW at 6,000 rpm and 134 Nm at 3,500 rpm. You can check their torque curves above and be as impressed as we were. Especially because they are not turbocharged to present such even curves. Check them below when compared to the competition.
Higher torque appears earlier and take a long time to go down. In a rotation range that is much more comfortable to the regular driver, below 4,000 rpm. In both engines. The 1.3 has a bigger torque than 1.4-liter opponents.
Focus on reliability
Achieving these numbers is only part of the GSE units’ mission. FCA also claims that they must be extremely reliable. And one action towards this goal is the use of a chain instead of a belt to run the camshaft. The chain is of the silent kind, and there is really very little noise coming from these engines. We cannot credit that just to a better sound insulation for the Uno.
Being a fuel flexible engine poses some questions, such as cold start with ethanol. FCA has solved the problem by using a resistance inside the fuel rail that heats ethanol and allows the car to start even at -5ºC temperatures.
FCA has had a huge worry about construction. All GSE units are open deck, or else, there is a gap between the cylinders and the cylinder head’s bolt holes. This makes the cylinder suffer less from deformations when the block and the cylinder head are placed together. Any deformation could make the life of pistons more difficult and increase friction. Another way to reduce it was the offset crankshaft. In the compression stroke, when there is less force being applied to the piston head, there is a bigger angle between the center of the cylinder and the piston.
But when there is more force over the piston head, in the power stroke, the piston is almost perfectly aligned with the center of the cylinder. Much more aligned than it would be if the crankshaft was also on the center of the cylinder.
That allows it to suffer less structural stress and less deformation.
As a result, FCA has given the GSE family one of the highest compression ratios ever used in an Otto cycle engine: 13.2:1. With plenty of confidence that it will never knock.
FCA says these engines will only have 2 valves per cylinder, but the fact is that there is development going on for a 4 valves per cylinder variant. If the 2-valve GSE was created to be a naturally aspirated engine, the 4-valve GSE will be exclusively turbocharged. Douglas Mendonça, a very respected Brazilian journalist, has stated in his blog the turbocharged 1.0 GSE will deliver around 90 kW, while the 1.3 will get close to 120 kW. Way more than the current 1.4 MultiAir engine. And Mendonça has hit the nail in the head in everything he has anticipated about the new engines. Expect the new turbocharged GSE members of the family to also use the MultiAir technology, by the way.
We have driven the Uno with both these engines. And will tell you all about it in another article. The most important aspect of the car presentation was the GSE family, hence our priority on posting these information to you. Expect to see a GSE powerplant very soon under the hood of a car in your country, whatever it is.