FC3S Pro:  Kouki FC3S 13BT into a Zenki FC3S Turbo
Engine swap difficulty:  2 out of 5
The 1989 - 1991 Kouki FC3S 13BT engine can be easily swapped into a 1986 - 1988 Zenki FC3S
Turbo chassis. Both engines are of similar dimensions, and they both use the same
mount brackets. We need to address some of the differences in the two types of
motors.
Oil metering pump:
The 1986 - 1988 Zenki FC3S uses a mechanical oil metering pump that is actuated
by a mechanical linkage to the throttle body. The 1989 - 1991 Kouki FC3S
uses an electronic oil metering pump that is electrically controlled by the stock
ECU. The electronic oil metering pump cannot be controlled by the 1986 -
1988 Zenki FC3S Turbo stock ECU. To control the electronic oil metering
pump, you'd need a 1989 - 1991 Kouki FC3S Turbo stock ECU (and engine wiring harness,
etc.), which makes things complicated. You can convert over to the 1986
- 1988 Zenki FC3S Turbo mechanical oil metering pump by swapping over to the Zenki
throttle body, linkage, mechanical oil metering pump, and front cover. An
even easier option is to remove the electronic oil meter pump and cover the hole
with a block-off plate; go pre-mix to substituted for internal oil lubrication.
FC3S Pro: FAQ - Pre-Mixing
Turbo:
The 1989-1991 Kouki FC3S Turbo turbocharger is more desirable over the earlier
1986 - 1988 Zenki FC3S Turbo turbocharger. Since we are assuming we're using
a Zenki stock ECU, we need to modify the Kouki turbo control system. The
Kouki stock ECU uses a boost control solenoid to control boost; the Zenki stock
ECU cannot use this boost control solenoid. The "T" off the wastegate vacuum
pipe will need to be blocked or capped.
Fuel injectors:
The 1989 - 1991 Kouki FC3S Turbo 13BT uses high-impedence, top-feed Nippondenso
fuel injectors that utilize oval electrical plugs. The early Zenki FC3S
Turbo models uses low-impedence, top-feed Nippondenso fuel injectors that use
rectangular electrical plugs. The later Zenki FC3S Turbo models uses
high-impedence, top-feed Nippondenso fuel injectors that use rectanglar
electrical plugs. All Zenki FC3S Turbo's use fuel injectors with rectangular
plugs that are not compatible with the Kouki FC3S Turbo 13BT engines. It's
easiest to just swap over your old fuel injectors onto the Kouki 13BT engine.
Although the intake manifolds and fuel injector rails are slightly different,
the fuel injectors swap over no problem.
Water temp sensor:
The water temp sensor for the instrument cluster is located next to the oil pressure
sensor under the oil filter. The 1986 - 1988 Zenki engines use a bullet
connector for the water temp sensor. The 1989 - 1991 Kouki engine use a
spade connector for the water temp sensor. This plug needs to be modified
to get the water temp gauge to work correctly after the engine swap.
Throttle body / TPS:
Due to the slight differences in the throttle body, there are two different TPS
units available. The 1986 - 1988 Zenki FC3S uses a single, narrow-range TPS.
The 1989 - 1991 Kouki FC3S uses a double TPS with both narrow-range and full-range
TPS'. You can modify the Kouki double TPS to work with the Zenki stock ECU,
which only requires the narrow-range TPS. The throttle bodies are directly
swappable between Zenki and Kouki models.
Intercooler:
The Kouki intercooler has a 2.0" inlet, while the Zenki intercooler has a 1.75"
inlet. The outlets for both intercoolers are 2.0". Due to differences
in the intake manifolds (see below), the mounting tabs on the passenger side
of the intercoolers are different. The intercooler cores are identical, but
due to the larger inlet on the Kouki versions, the Kouki intercooler flows slightly
better.
Intake manifolds:
The Kouki FC3S Turbo upper intake manifold is slightly taller than the Zenki version,
which implies the Kouki intake manifold was designed for better low-end torque.
Due to the taller intake manifolds, the fuel injectors rails are slightly different
between the Zenki and Kouki models.
FC3S Pro: FAQ - Zenki Versus Kouki Upper Intake Manifolds
Questions?  Comments?  Send email to: 
reted@fc3spro.com
10/30/2004