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2.3L HSC / HSO History & Specifications

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When design of the Tempo and Topaz were initiated, development costs were kept down by using a modified Escort platform. The basic structure of both cars were identical from the firewall forward. This made the Escort's 1.6L OHC engine a natural fit in the new car. However, initial research for the Tempo and Topaz showed that a majority of Tempo and Topaz owners would forgo the manual transaxle and select the automatic transaxle. Due to the increased weight over that of the Escort, the 1.6L engine was deemed inappropriate for the Tempo and Topaz. As such, Ford powertrain engineers set about designing a brand new engine specifically for the new car.

Contrary to automotive design of the time, the new engine was designed for power output optimized for the 3-speed automatic transaxle. Whereas many motors were being designed to produce higher levels of peak power, the design engineers working on this project felt a motor that produced peak torque at lower rpm's would be more suitable for use in the Tempo / Topaz format. To achieve this, Ford powertrain engineers drew on past experience and selected an overhead valve configuration. They did this rather than go with a more modern overhead cam design, which tends to produce higher peak power at the expense of reduced low to mid-band torque.

Powertrain engineers started with the 200 cubic inch inline-six cylinder engine (which saw duty in a variety of small Fords including the Falcon, Mustang, Maverick, and Fairmont) and lopped off two cylinders. In doing so, they were left with a 144 cubic inch, 2.3L inline 4-cylinder engine. This new engine featured a cast iron block and head. This new head incorporated some of the results of Ford's Programmed Combustion (PROCO) research project. In fact, this new engine was the first production "fast-burn" engine from Ford to incorporate features from this project.

One of the most prominent design features of this motor occurs within the cylinder head. A shroud around the intake valve was used to purposely introduce turbulence, resulting in a swirling affect for the incoming air/fuel mixture. In conjunction with the modified wedge shape of the combustion chamber, the incoming air / fuel combo is then directed towards the centrally mounted spark plug. This gave the new engine it's High Swirl Combustion name, or HSC for short. The intake and the exhaust ports on this head were siamesed, meaning that they were located on the same side of the head. This allowed the spark plug to be located almost directly in the center of the combustion chamber, theoretically producing optimal combustion.

The valvetrain for both the HSC and HSO motors consists of hydraulic valve lifters, pushrods, and individual rocker arms for each. This is the type of system that was used on Ford's V8 engines of the time, and the basic specs of material strength and thickness were the same as those V8 engines. The valvetrain is driven by a rugged "old school" timing chain rather than a newer, albeit less reliable timing belt. The chain was designed to be simple and rugged, being very similar to the design of the chains used in Ford's heavy duty truck engines.

To help keep weight down, other major parts of the engine such as the water pump, oil pan, and intake manifold were made of aluminum. Also, by using aluminum for the intake manifold, engineers took into account the heat conducting qualities of this metal to transfer engine heat into the incoming air/fuel ratio, eliminating the need for a heat riser valve between the exhaust and intake manifolds. To help keep vibrations to a minimum, the accessory brackets were designed to keep the accessories closer to the engine. Sitting on top of the intake manifold was an electronically controlled one barrel Holley carburetor. The air/fuel ratio was controlled by Ford's new EEC-IV Engine Control Unit (ECU) that controlled over a million commands a second. Once the design specs were finalized, the engine went through thousands of hours of engine dyno testing and hundreds of thousands of miles of road testing. The new engine proved to be a very reliable engine, as well as providing ample power for "today's driving conditions" as well as the demands of stop and go traffic.

1984 - 1987 2.3L HSC : Carb
Horsepower 90 HP @ 4700 rpm
Torque 125lb-ft @ 2700 rpm
Compression ratio 9.0:1
1984 EPA rated Fuel Economy
4-speed "Fuel Saver" 29 city / 44 highway
5-speed MTX-III 26 city / 40 highway
3-speed FLC ATX 25 city / 35 highway

1985 brought along the first changes to the 2.3L HSC powerplant. The first change was the switch to Electronic Fuel Injection, controlled again by the EEC-IV computer. The 1 barrel carb was replaced with a single fuel injector mounted in the throttle body (often referred to as CFI for Central Fuel Injection). Any unused fuel is sent back to the fuel storage system through a return line. This new fuel system reduced evaporative fuel loss, made starting (especially in cold weather) much easier, and the engine ran smoother. Along with a drop in emissions and evaporative fuel loss, power did suffer slightly. Power output was down by 4 HP and 1 lb-ft of torque. All 2.3L HSC engines sold in the U.S. featured the new EFI system, while the 2.3L HSC in Canadian markets continued to offer the carbureted 2.3L until 1987.

The power problem was answered in the form of a revised engine, known as the 2.3L Higher Specific Output (HSO). The 2.3L HSO engine was the centerpiece of the new Tempo Sport GL and Topaz Sport GS Pacakges. This engine was based on the 2.3L engine and featured a 20 percent increase in horsepower (compared to the EFI 2.3L HSC) along with a slight bump in torque. This new power was largely the result of getting more air in and out of the engine quicker. A revised cylinder head featured larger, reshaped ports and a reshaped combustion chamber with less valve shrouding. A new higher lift, longer duration camshaft was used. The intake manifold featured larger runners, and the air cleaner and exhuast system had less restrictions. The new 2.3L HSO engine also featured the new EFI system, on both U.S. and Canadian market cars. This engine was available in the Sport models as well as in all models in select high-altitude areas. In 1987, the 2.3L HSO was also the standard engine on all All Wheel Drive models.

1985 - 1987 2.3L HSC : EFI
Horsepower 86 HP @ 4000 rpm
Torque 124lb-ft @ 2800 rpm
Compression ratio 9.0:1
1985 - 1987 2.3L HSO : EFI
Horsepower 100 HP @ 4600 rpm
Torque 125lb-ft @ 3200 rpm
Compression ratio 9.0:1

The basic structure and features on both 2.3L HSC and HSO engines did not change for the rest of the model run. In 1988, the EFI system was revised to a new Mutli Point fuel injection system. The new fuel injection system revamped the power output on both engines. The 2.3L HSC featured more horsepower higher in the rev range. Peak torque remained the same, but was reached lower in the rev range. THe 2.3L HSC featured the same HP rating as previous years, but it was reached lower in the rev range as was the increased peak torque. In 1992, the 2.3L HSO engine was dropped from the lineup. Also in 1992, the 2.3L HSC engine got a new revised Sequential Port Fuel Injection system. This revised power output on the 2.3L HSC ever so slightly.

1988 - 1991 2.3L HSC : MPFI
Horsepower 98 HP @ 4400 rpm
Torque 124lb-ft @ 2200 rpm
Compression ratio 9.0:1
1988 - 1991 2.3L HSO : MPFI
Horsepower 100 HP @ 4400 rpm
Torque 130lb-ft @ 2600 rpm
Compression ratio 9.0:1
1992 - 1994 2.3L HSO : SPFI
Horsepower 96 HP @ 4200 rpm
Torque 126lb-ft @ 2600 rpm
Compression ratio 9.0:1

Another variation of the HSC powerplant was offered in the Ford lineup, just not in the Tempo or Topaz. This was the 2.5L HSC, which was the base engine in the Ford Taurus (not available in the Sable) from 1986 until 1991. This HSC engine used a taller deck engine with longer rods to create an increased stroke. According to factory spec's, this supposedly dropped top end horsepower, but created more low end torque for the heavier Taurus.

The 2.5L motor utilized a slightly different head than the 2.3L HSC motors. From what we've been able to document, the ports are slightly larger and their is a lower amount of turbulence within the combustion chamber. The cam used in the 2.5L motor was also different than the HSC cam in the 2.3L motors, as the spec's are shown to be the same as the cam used in the HSO motors.

1986 - 1991 2.5L HSC : Taurus
Horsepower 90 HP @ 4100 rpm
Torque 135lb-ft @ 2100 rpm
Carbureted 2.3L HSC
Carbureted 2.3L HSC

HSC Combustion Chamber
HSC Combustion Chamber

EFI 2.3L HSC
EFI 2.3L HSC

MPFI 2.3L HSO Engine
MPFI 2.3L HSO Engine

SPFI 2.3L HSC Engine
SPFI 2.3L HSC Engine


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