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Engineering the new engine

The new engine would be called 1FZ-FE and it would a 4.5 liter inline 6 cylinder. The engine designation read as follows. (1) stood for the first
generation of this engine. As it would turn out, there never would be 2nd generation of this engine family as Toyota got it right the first time.
(FZ) stood for engine family. Although designated an "F" engine, it shared no parts or design with the original F series engines. The next (F) stood
for it being a narrow angle, dual overhead cam design, and (E) stood for electronic fuel injection. It should be noted here that not all 1FZ motors
were fuel injected. Some overseas models were carburated and thus the (E) was dropped and they were called 1FZ-F motors.

4.5 liters is huge for a 6 cylinder engine and the bore x stroke of the engine would actually be the similiar in size to a typical 400 cubic inch V-8. What
is amazing about the 1FZ is that Toyota was able to significantly increase the displacement of the 1FZ within roughly the same block dimensions of
the 3FE. However, make no mistake, the 1FZ shares no design features of the 3FE as they are completely two different motors.

Head and Intake system

For the new motor, Toyota would go with a long proven and fairly conventional design, by then. A cross flow intake system, where exhaust was on
one side and the intake was on the other would be combined with a 4 valve per cylinder and double over head cam valve train design. Instead of
using a timing belt as on it’s earlier 6 cylinder designs, it went with a single heavy duty timing chain, to rotate the intake cam, which then rotates the
exhaust cam with scissor style gears and the two camshafts. The chain would ride on metal guilds with plastic lining. This design was fairly
efficient and helped makes lots of power, but more importantly, it was extremely reliable. No timing belts needed to be replaced and although only a
single timing chain, the chain rarely wore out. The valve train was a narrow design for compactness to keep the dimensions of the head as close
to the 3FE as possible, allowing it to fit in the same vehicles as the 3FE did. One major distinquishment between the 3FE and the 1FZ is the use of
aluminum instead of cast iron in the head design.

The intake manifold was designed to use long 400mm runners and shaped so that each cylinder had an equal length runner. This significantly
improved the flat torque curve. The intake manifold is a two piece unit made of aluminum. The fuel injected version of this motor is by far the most
common and it uses a multi-port fuel sequential injection system. Fuel injection is controlled by a digital ECU unit that is located inside the vehicle.
Early models 1993-1994 were OBD-I compliant, which meant they used a less advanced, but somewhat simplier standard for the ECU. 1996 and
1997 models used the newer OBD-II standard, which basically includes more sensors, and on board diagnostics, making it easier for smog
stations to test the engine. 1995 models were a transition year and sort of combined OBD-1 with partial OBD-II compliance. It’s not clear how 1998
and later models were designed as OBD was a North American standard and the 1FZ ceased being imported in the U.S. in 1997.

Ignition System

The ignition system of the 1FZ is fairly conventional. A gear driven distributor is located near the front of the head is run off of the timing gear. The
distributor is an electronic type with an external coil/igniter. On some later non U.S. spec models made sometime after 1998, Toyota introduced a
direct ignition type system, where each cylinder has it’s only coil pack and the distributor was eliminated from the system.

The Block and Internals

The 1FZ would be equipped with two knock sensors in a system known as KCS (knock control system). They would be installed in the block side
wall above No. 2 and No. 5 cylinders. The KCS can accurately and quickly detect knocking and control the ignition timing to compensate as needed.

The block of the 1FZ is conventionally made of iron and makes up a significant portion of the almost 600lb weight of the engine. However, it’s
unique in that it’s a short skirt block design to reduce weight and has a cast in rear transmission bell. The outer wall curves outward towards the
bottom to increase rigidity. As part of the short skirt design a two piece oil pan is used. The upper piece is made of thick die cast aluminum and
makes up for the short skirt block design while reducing weight. The lower sump half of the oil pan is made of rust resistant sheet steel. A sensor
is located in the oil sump that indicates oil level and once the level reaches a certain level a light turns on, on the instrument panel. Also cast into
the block is a built in oil cooler and a mount for the power steering pump, which is gear driven (not belt) off of the valve train system.

The 1FZ uses a conventional lubrication system including an engine mounted sump, which holds a whopping 8 quarts of oil, and a gear driven oil
pump. A special oil jet system is used to keep the pistons cool. A feature usually reserved for turbo charged type engines. The oil filter is located
high on the block on the intake side and depending on vehicle model and engine accessories can be easy or difficult to reach.

The pistons are Strutless type made of aluminum alloy and are connected to forged connecting rods, that have been double shot peened and then
connected to the crankshaft. The crankshaft uses 7 journal and 12 balance weights. Bore and stroke is 100 x 95mm. The stroke is equivalent to
the 3FE, but the bore is about 6% wider. The compression ratio of 9 to 1 is significantly higher than the 3FE’s 8 to 1, but still fairly low by modern
standards. This allows the 1FZ to easily run on low grade pump gas often found in 3rd world countries. It also helps to improve longevity of the
engine.

Cooling System

The cooling system is fairly conventional. A radiator holds water/coolent, which is fed to the engine via bottom bypass thermostat. The water pump
and fan are run off of the same pully which is connected to the crankshaft pully via a double belt fail safe system. The fan is an 8 470mm blades
and uses a three stage temperature controlled fan clutch. Early models, 1993-1994 used a larger copper 3 core radiator. Later models,
1995-1997 and possibly later used a 2 core aluminum type radiator. The reason for the change is not clear, but the later design is often criticized as
been not as good as the earlier copper models, although both cooling systems work quite well.

Final Notes

Instead of reinventing the wheel, Toyota engineers took the best of it’s past motors and incorporated them into the 1FZ to make it one of the most
reliable engines ever built. The 1FZ is often criticized as being a fuel guzzler. To some degree that’s true, but one must remember that the 1FZ is
the powerplant to vehicles that weight in excess of 3 tons. Also, the motor was designed to be reliable and have tremendous low end torque first
and foremost. Economy was on the list, but further down in day and age before fuel efficient was a major concern. What was a concern to Toyota
engineers was that this motor would see duty in countries where repair and service would be rare if ever and the vehicles they were power would be
required to carry and/or tow tremendous amounts of weight. So consideration was given to making the motor as durable as possible, while
dramatically improving extreme low and mid range torque.

The 1FZ has few inherent mechanical issues, but there are some things to consider. Toyota and other manufactures had issues with headgasket
material in the 1980s to mid 1990s as asbestos was outlawed and could no longer be used in headgasket material. During this interim period,
manufactures had a difficult time finding a suitable replacement material and as a result, many Toyota engines, including the 1FZ can blow
headgaskets at higher mileage. Usually around 150,000 miles. The new headgasket designs are superior and should last the remaining life of
the engine.

The 1FZ has a unique cooling hose issue, in which several small external cooling hoses can wear out after 100,000 miles and leak. This would not
normally be a big deal, except some of these hoses are hard to reach and time consuming to repair. It’s often recommended to replace these
hoses before they start to leak.

As for longevity, the 1FZ typically lasts well over 300,000 miles when basic care is given to the motor. I’ve often read reports of engines being tore
down with 300,000 miles and no major wear to the bottom end. 200,000 and higher mileage vehicles are extremely common and most of these
have had no major repairs.

Oil recommendations:

This has been a major source of controversy. For U.S. spec vehicles, Toyota recommend 5w-30 for most conditions and 10w-30 for extreme hot
conditions. However, this likely has less to do with what is best for engine longevity and more to do with fuel economy. The lighter oil just barely
improves fuel economy and the government mandates that manufactures recommend an oil that is fuel saving.

However, in Australia where the weather is mild to hot and there is no such fuel economy requirement, Toyota recommends a 20w-50 type oil.
One has to assume the heavier weight oil is better for the engine, but more research and debate is needed.