13B-REW in a FC3S

The idea of swapping to a newer, more powerful engine is always tempting, especially with the mechanics of the 13B-REW of a FD3S, which uses sequential twin-turbos, producing a stock horsepower of 255hp (nearly 55hp more than the FC3S Kouki). In reality, swapping a 13B-REW of the FD3S into an FC3S is NO easy task.

There are two methods to solve the engine support issue, which we’ll cover in this article.

The most popular methods is to adapt the 13B-REW engine mounts to the chassis of the FC3S, which is not a simple job, and is not recommended. The 2 factory mounts found on the 13B-REW are located on the rear side housing, while on the 13BT of the FC3S they are on the center side housing. This gives a sharp angle to connect the two points. When considering engine mounts in general. Weight distribution on the vertical plane is universal, the weight of the motor (top) puts downward pressure on the supports to stay straight and low. We need to keep this concept in mind. The easiest way to acheive this is by keeping the stock 13B-REW mounts and weld a new crossmember to the cradle, which is situated behind the motor of the FC3S. There is just enough space to weld a 3” crossmember, then the 13B-REW supports will be set in place easily, which allows you to keep nearly all of the 13B-REW components.

The method of welding a crossmember is by way of drilling and tapping the center housing of the 13B-REW to accept the original passenger-side support of the 13BT, 3 holes, M14 x 1.50 need to be drilled and tapped on the side under the intermediate side housing (middle) of the 13B-REW so it can accept three (3) 17mm bolts the bottom of the motor to the passenger side. This requires a custom oil pan, or the 13BT oil pan. The driver side support on the 13BT is secured by two (2) nuts on studs that are already present on the 13B-REW. The passenger side support is in the middle of the motor, which is why the oil pan change is required. If you decide to use the 13BT pan, you’ll need to seal the front of the 13BT pan, as it is longer than the 13B-REW by +/- 1/4”. Once you have solved the support problem, the rest gets easier. The FC3S clutch can be bolted to the factory 13B-REW flywheel if you’re on a tight budget. The 13BT transmission should on the 13B-REW without too many issues. If the 13B-REW was equipped with an automatic transmission, there will be a hole for an extra bolt on the bell-housing, and the 5-speed of the FC3S will not fit at all on the 13B-REW. The starter of the FC3S should fit with very little adjustment.

If you’re running the stock ECU of the 13B-REW, you’ll need the engine harness, ignition system harness, ignitor and coils from the FD3S 13B-REW. Going the aftermarket route, EMS fuel and ignition control will give you more flexibility but will require additional parts for the ignition system. Chosing an afermarket EMS as your controller will allow you to use the factory ignition input system (trigger wheel and magnetic pickups) of the 13B-REW or any ither pattern with the coil/igniters of the 13BT.

Since the 13B-REW already uses a front mount intercooler, you’ll need to do the same with this setup. This will likely be the most expensive part to complete the conversion. A popular option is to install a Greddy elbow at the throttlebody, since it is aluminum and not plastic like the original part.

A higher flowing fuel pump is a necessity, since the 13B-REW uses 2x550cc + 2x850cc injectors while the 13BT uses 4x550cc. Denso supra or Aeromotive/AEM 340LPH  are all perfect for the job

The radiator hoses for the 13B-REW are also different, so to connect it all up with the factory 13BT radiator will require some custom work. It is highly recommended to upgrade the radiator if you are still using the original one. An idler pulley is required to have a good contact surface on the water pump’s pulley, Greddy pulleys are a suitable option to slow down the water pump and alternator rotating speeds. Both options comes with its own custom belt to fit.

The stock twin turbos will fit easily into the FC3S engine compartment, but you’ll need a custom downpipe in order for it to fit with the chassis exhaust of the FC3S. You can keep the air intakes for the twin turbos, but consider upgrading to new aftermarket filters.

You will need custom oil lines so the 13B-REW fittings can connect to the stock FC3S oil cooler. The front oil lines on the 13B-REW are similar to the setup in the 13BT, but the rear oil lines are fixed a little higher than those on the 13BT. They are on the motor, close to the oil filter.

Parts and comments:

-13B-REW

-Clutch kit

-Downpipe (Wether you are twin or single turbo, this has to be changed, like the rest of the exhaust system.)

-Front-mount intercooler (The GReddy V-spec front-mount intercooler kit is the standard for nearly all front mounts for the FC3S)

-Oil cooler lines

-Denso supra or 340 LPH upgrade fuel pump

-Aftermarket EMS(Optional – can replace the ECU, engine harness,  stock ignition system of the 13B-REW)

-Upgraded radiator

-GReddy elbow (Optional)

-Idler pulley kit or GReddy pulley kit 13B-REW (Optional)