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Tuesday, August 9, 2011

Inside the 2012 Fiat 500 Engine

The Fiat 500 has a jewel of an engine. It is based on a ground breaking design originating more than twenty-five years ago. Smooth, lively and full of character, it delivers as many smiles per mile as miles per gallon. In this post, we will look at the construction of the Fiat 500's engine with the help of some never before published images and specifications for the North American 1.4L MultiAir engine.

Let's take a look inside this special engine:

Fiat 500 Cylinder Block

Description Specification
The engine block (1) is made from cast iron. The crankshaft is supported by five main bearings. The thrust bearings are attached to the center upper main bearing. To keep the pistons cool, the cylinder block has four piston cooling jets located under the main bearing shells. The cylinders are formed directly into the engine block. A knock sensor is located on the left side of the block.

The bedplate (2) is made from die-cast Aluminum alloy and has cast iron cast-in bearing caps. For accuracy, the supports and main bearing caps are machined while assembled together with the engine block. Bolts and locating dowels are used to assure precision assembly of the bedplate and engine block. There is a bead of sealant between the bedplate and engine block to prevent oil leaks.

The function of the bedplate is to:
  • form the load carrying structure with the engine block support the crankshaft
  • allow return of the engine lubrication oil to the pan support the engine oil pan

Fiat 500 Crankshaft

The crankshaft is made from induction hardened forged steel. Eight counterweights at 180° balance the crankshaft rotary mass. The main journals are crossed drilled for rod bearing lubrication. The crankshaft is supported by five select fit main bearings with the center bearing serving as the thrust washer location. Both the front and rear seals are a single piece design and are mounted to the oil pump and cylinder block.

Fiat 500 USA Piston and and Connecting Rod

The pistons are a lightweight design with low tension piston rings that improve fuel economy. The pistons are made of a high strength silicon aluminum alloy and the piston skirt has a Moly® coating. The piston pin is a press fit into the rod. The connecting rod is forged steel with a bolted cracked cap design that provides more precise crankshaft bearing geometry than the traditional  procedure in which rods are sawed in two.

Fiat 500 Vacuum Pump

The vacuum pump supplies vacuum to the brake booster and is mounted to the rear of the cylinder head, driven by the camshaft.

Fiat 500 Oil Pan

The lubrication system consists of the following components:

  • Oil pump pick-up tube attached to the oil pump
  • Oil pump that is directly coupled to the crankshaft and is mounted to the front of the engine as part of the oil pump housing
  • Pressure relief valve in the oil pump that controls system pressure
  • Oil filter housing that supports the oil filter and oil cooler
  • Oil cooler mounted to the oil filter housing
  • Oil filter located in the oil filter housing
  • Four piston oil cooler jets mounted to the engine block
  • Filter screen mounted in the variable valve actuation assembly
  • Variable valve actuation assembly that uses pressurized engine oil to open the intake valves
  • Oil pressure switch located on the oil pump housing
  • Oil temperature sensor located on the variable valve actuation assembly

Fiat 500 Oil Filter and Oil Cooler

The oil filter housing is located on the left side of the cylinder block and is connected to the oil pump. The oil filter element is located within the housing and the engine oil cooler is attached to the side of the housing.

The oil pan in the Fiat 500 is made from aluminum with a threaded oil drainage opening and a threaded port for an oil viscosity sensor.

Fiat 500 Oil Spray Piston Coolers

The 1.4L engine has four engine blocked-mounted oil jets (1) installed to cool the underside of each piston. The oil jets are fed by the main oil gallery, and spray upward on the bottom of the pistons and cylinder walls. Each jet has a check valve which closes to maintain ample oil pressure at idle. All four oil jets are identical and are a press fit to the engine block.

OIL PUMP Specification:
Pressure @ Curb Idle Speed* > 0.7 bar > 10 psi
Pressure @ 4000 RPM* > 4.0 bar > 58 psi
*At Normal Operating Temperatures

The exhaust port of the Fiat 500 1.4L MultiAir engine

Intake port of the Fiat 500 1.4L Multiar engine. Notice the smooth, sharp port divider.

Fiat 500 Cylinder Head

The 1.4L aluminum cylinder head features four valves per cylinder with pressed in metal valve guides.

Cylinder head specifications:
Combustion Chamber Volume: 14.30 ml 0.484 oz

Valve sizes: Intake 26.75 - 27.05 mm, Exhaust 22.25 - 22.55 mm

Fiat 500 MultiAir Camshaft

The 1.4L engine uses a Single Over Head Camshaft (SOHC) to provide valve actuation but the camshaft is in the standard position of an exhaust camshaft in a Double Over Head Camshaft (DOHC) engine. The camshaft has five bearing journal surfaces and three cam lobes per cylinder. The camshaft is built up on a hollow tube with cam lobes, bearing journals and end caps pressed into position. The front end cap includes the camshaft sprocket mounting and front bearing journal with end play thrust walls. The rear end cap is the camshaft position sensor pick-up wheel and also drives the vacuum pump.

Camshaft specifications:
LOBE LIFT - Intake 3.81 mm 0.145 in. LOBE LIFT - Exhaust 7.5 mm 0.295 in.

VALVE TIMING - MULTIAIR PUMPING ELEMENTS Specification Opens 11° (BTDC) Closes 58° (ABDC) Duration 249° Centerline 125° Note: Units are in crank degrees.   

VALVE TIMING - EXHAUST VALVES Specification Opens 34° (BBDC) Closes 2° (ATDC) Duration 216° Note: Units are in crank degrees.

North American Fiat 500 Dyno Sheet
The North American Fiat 500 engine produces 101 hp and 98 lbs.ft of torque, however, that is just part of the story. MultiAir enables the 500's engine to have increased throttle response and optimizes torque at part throttle openings, allowing the 1.4 liter engine to have the flexibility of a larger engine.

How MultiAir Works and the Advantages

MultiAir technology manages the torque and power delivered by the engine by varying the lift profile of the intake valves without direct use of the throttle body. The main features of the MultiAir engine are:

  • Single camshaft
  • Standard and hydraulic exhaust tappets
  • Intake tappets integrated in the MultiAir actuator
  • Brake servo vacuum pump  
Compared to a traditional engine, the special characteristics of the MultiAir system offer better combustion control and a faster response to torque requests, both of which are available and exploitable at each top dead center (TDC). This means:
  • Reduced fuel consumption
  • Reduced CO2 emissions
  • Increased power and torque
  • Increased driver responsiveness
  • Less pollution
  • Easier start-up

The MultiAir system consists of a hydraulic-mechanical actuator fitted inside the MultiAir engine. MultiAir also includes hardware and software electronic components, built into the powertrain control module (PCM) to manage the engine intake valve motion. At each engine cycle, the MultiAir system controls the quantity of fresh air entering each cylinder by managing intake valve motion.

The primary component of variable valve actuation is the variable valve actuation module. The variable valve actuation module is bolted to the top of the camshaft bearing housing above the intake valves, next to the camshaft. The intake lobes on the camshaft operate hydraulic pumping elements instead of directly acting on the valves. The pumping elements provide high-pressure oil to open the intake valves. The relationship between the camshaft lobe and the intake valves is controlled by a solenoid operated hydraulic port. By varying the solenoid operation, the Powertrain Control Module (PCM) is able to control intake valve lift and duration.

Variable valve actuation provides five possible phases of operation. Each phase offers unique advantages compared to normal camshaft operation. The five phases are:

Fiat MultiAir Cam Profile - Full Lift

Full Lift. When variable valve actuation functions in the full lift phase, all of the camshaft lobe lift is transferred to the intake valves. The intake camshaft lobe is designed with a very aggressive lift and duration profile. This results in good power in the upper RPM ranges with high loads. This profile would rarely be used in everyday driving.

Fiat MultiAir Cam Profile - Early Closing

Early intake valve closing (EIVC). When variable valve actuation functions in the EIVC phase, the camshaft lobe lift is transferred to the intake valves at the beginning of the lift duration cycle. However, the hydraulic connection between the camshaft lobe and the valves is taken away before the lobe reaches full lift. The exact timing and lift can be infinitely varied to meet driver requirements. EIVC provides smooth engine performance and more torque at lower engine speeds.

Fiat MultiAir Cam Profile - Late Opening

Late intake valve opening (LIVO). When variable valve actuation functions in the LIVO phase, the camshaft lobe lift is NOT transferred to the intake valves at the beginning of the lift duration cycle. The hydraulic connection between the camshaft lobe and the valves is completed after the rocker arm has already begun riding the ramp of the camshaft lobe. When the hydraulic connection is completed, the intake valves will begin to open. The valve lift timing can be varied infinitely within the full profile of the camshaft lobe.

Therefore, as long as the hydraulic connection is completed before the camshaft lobe reaches its maximum lift, some valve lift will result. The lift profile will follow the camshaft lobe profile for the time that the hydraulic link is complete. Like EIVC, the exact timing and lift can be infinitely varied to meet driver requirements. LIVO provides lower emissions and a higher efficiency at lower loads or idle conditions.

Fiat MultiAir Cam Profile - MultiLift

Multi-Lift. Multi-Lift is a combination of EIVC and LIVO because the hydraulic connection between the camshaft lobe and the intake valves is closed early and then re-opened later in the cycle. This creates a longer duration valve lift with a smaller amount of lift. The result is a higher velocity of air flow into the cylinder over a longer period of time. Multi-Lift may be used in mixed driving of acceleration and deceleration with moderate engine speeds.

Fiat MultiAir Cam Profile - Closed

Closed. The closed phase simply leaves the intake valves closed by not utilizing the camshaft lobe to lift the intake valves.

Fiat 500 Firing Order


Type SOHC I-4 16-Valve MultiAir
Compression Ratio 10.8:1
Lead Cylinder #1 Timing Drive End
Firing Order 1 - 3 - 4 - 2
Metric Standard
Displacement 1.368 Liters 83.5 Cubic Inches
Bore and Stroke 72 mm x 84 mm 2.83 in. x 3.31 in.
Maximum Power (EEC) 75 kW @ 6500 rpm 101 HP @ 6500 rpm
Maximum Torque (EEC) 133 N·m @ 4000 rpm 98 ft. lbs. @ 4000 rpm

With thanks to Chrysler LLC and Fiat SpA

Sources: Fiat USA, Chrysler LLC, Fiat 500 Abarth repair manual


TK said...

After seeing this, now I understand why I want to shift at 4000 rpms!

Anonymous said...

The Multiair system, while "clever", does not seem to yield any appreciable differences in either the power or torque curves from more standard valve actuation methods. What am I missing here ... ??? said...

Hi Anonymous,

What is missing is driving the car. The biggest difference isn't on these dyno sheets, it is part throttle response and drivability. For example, MultiAir allows you to drive at lower rpms and have the small engine still accelerate without lugging. You have to drive the car and compare it to the car without MultiAir to see and feel the difference.

Spydr124 said...

Love the site, love the cars. My first Fiat was a 68 850 Spider in 1970. Tons of Fiats later, I now own a 500 and am proud as new father is of his son. I also own a 72 124 Spider I purchased new in the fall of 1972. The MultiAir is at 4500 miles now and just keeps getting stronger. It's a 5 speed and that tranny really shows off what you mention. The lack of "lug" gives the stick a very managable feel in city driving; not having to down shift constantly. I do have oil questions however; access to the oil filter, drain plug and how much does it hold?
Loving this car and heading for another one as soon as the $$$ show up. said...

Hi Spydr124,

Thanks fot the kind words. Sorry for the delay getting back to you, the storm in the northeast knocked me offline for several days!

The car hold 4 qts. Here is a link to the Fiat 500 USA Forum that shows how to change the oil:
Fiat 500 USA Forum Oil Change Post

Best regards,

Anonymous said...

Does anyone know what the valve lift is on the multiair engine? The article mentions cam lob lift but this will be mechanically/hydraulically multiplied to give the valve lift. Thanks