Fitting an A'PEXi AVC-R

S14 & S15 Tech Guides

The A'PEXi AVC-R (Actuator Valve Controller Type-R) is probably THE best electronic boost controller current available. It allows control over exactly how much boost to apply AND where to apply it throughout all gears and revs.

Fitting the AVC-R seems a pretty daunting task, especially when you first open the box! I had help from SXOC member, R.Sendout (actually, he did quite a bit! ). If you are fairly familiar with your engine layout, you should be fine fitting the unit yourself. If you are unsure, get help!

This guide applies to the S14, S14a and (on the whole) S15.

I would like to point-out at this stage that this guide is here to provide you with help to fit your AVC-R. The instructions are correct and my unit worked properly when complete. However, I accept no responsibility whatsoever for any damage that you do to your car and ECU. If you are not happy and confident fitting vacuum hoses and splicing ECU wires, pay to get it fitted professionally.

I would recommend buying a small bag of 6mm x 25mm bolts if you wish to mount the solenoid and sensor in the locations I have below. The bolts provided are too small for the existing holes and the Nissan bolts won't fit due to their washers. You will probably have to drill one hole. Ensure you have some waterproof sealant to cover the hole.


Familiarise yourself with the red circled areas in Figure 1, as these are the two where all the work is going to be done. The pipe on the left is where the pressure sensor is going to T in. The right circled pipework and boost solenoid is going to be completely replaced with new pipes and solenoid.

Boost hose arrangementFigure 1 - Boost hose arrangement


The first step is to remove the boost solenoid and all of the pipework attached to it. The small pipe on the air intake (Figure 2) needs blocking with a screw.

Block the air intake feedFigure 2 - Block the air intake feed


I bolted the boost solenoid onto the old solenoid mounting bracket. The rubber washer provides perfect cushioning and sound deadening. Note that one of the holes in the new solenoid's mount needs to be drilled slightly larger to allow one of the new 6mm bolts through (see note above). Place the wiring out of the way for now.

New boost solenoidFigure 3 - New boost solenoid


Carefully drill the two holes in the pressure sensor slightly larger to allow two new 8mm bolts to fit. The sensor will then bolt perfectly into the two holes on the suspension mount shown in Figure 4. The sensor MUST be fitted this way up.

Pressure sensorFigure 4 - Pressure sensor


Cut a piece of the 12mm hose provided to fit comfortably between the bottom solenoid connection and the actuator. Secure the hose using the metal grips provided (Figure 5).

Solenoid to actuator hoseFigure 5 - Solenoid to actuator hose


Cut a piece of the 12mm hose provided to fit comfortably between the side solenoid connection and the plenum-to-intercooler pipe (the one with the resonance box on S14s). Secure the hose using the metal grips provided (Figure 6). There are two plastic hose holders attached to the turbo hotpipe (the stainless one above). You can remove one and clip this hose into the other.

Solenoid to cold pipe hoseFigure 6 - Solenoid to cold pipe hose


OK. You now need to T in the smaller hose provided into the plenum-to-recirculation valve hose (check Figure 1). This should be a simple matter of cutting the existing hose and inserting the appropriately sized plastic T. It looks a bit complicated in Figure 7 due to my recirc valve having been removed and a boost gauge pipe already being inserted in the same hose. In my case, this hose had been blocked and I simply connected the new hose to the end of it.

Attach one end of the new hose to the T piece you inserted and the other end onto the connector on the sensor. The hose should be tight enough without the need for grips.

Pressure sensor feedFigure 7 - Pressure sensor feed


Cut the new hose halfway along its length and insert the plastic air filter (Figure 8). Again, these connections should be tight enough without grips. Tuck the hose safely out of the way. Make sure its nowhere near the radiator fan!

Boost hose air filterFigure 8 - Boost hose air filter


Connect to wiring harness to the pressure sensor connector and pass it across to the solenoid side of the engine bay. I tucked mine tidily behind the brake pipes on the bulkhead.

Pressure sensor wiring harnessFigure 9 - Pressure sensor wiring harness


Connect the wiring harness to the boost solenoid wiring connector and thread it down the gap in the very corner of the engine bay as indicated in Figure 10.

Boost solenoid wiring harnessFigure 10 - Boost solenoid wiring harness


Jack the car up and remove the passenger front wheel. Remove the rear part of the wheel arch liner. You should see the wiring harness that was threaded down from the engine bay. Some S14s have a grommet under the liner that will allow the harness to be passed through into the cabin. Most, however, do not. This is where I needed to do the only bodywork drilling. Drill a hole EXACTLY in the location shown in Figure 11. The hole must be sufficiently large enough to pass the AVC-R control unit connector through.

Wiring harnessFigure 11 - Wiring harness


Before working on the ECU, disconnect the battery! 

Remove the plastic cover protecting the ECU in the passenger footwell and unbolt the ECU. There will be a gap in the bulkhead behind the ECU and soundproofing in approximately the location arrowed in Figure 12. You should be able to feel the harness that you threaded through from the other side. Pull the harness carefully through. You need to achieve a happy balance of tightness for the harness in the engine bay and enough slack in the cabin for the AVC-R control unit cable to connect to it AND be tucked away safely. For this reason, I would advise not putting the wheel and arch liner back on until you are completely finished.

The ECUFigure 12 - The ECU


You need to be aware that Nissan started fitting S14a type ECUs into S14s from November 1995. If you have a 1995/6 S14, you MUST check which ECU you have before touching the wiring. Remove the plastic wiring cover from your ECU and compare the number of pins with the pinout diagrams below. Once you are sure which ECU you have, proceed to the next stage.

S14 ECU pinoutsS14 ECU pinout diagramS14a & S15 ECU pinoutsS14a & S15 ECU pinout diagram


The appropriate coloured wires needs splicing onto the matching wires using the ECU pinout diagrams. As stated above, ensure both ground wires are spliced onto the same ECU wire.

Once each ECU wire is identified, VERY CAREFULLY shave a section of the wire's sleeve to leave enough bare wire to attach the relevant harness wire using the provided metal crimps and a crimping tool. This needs to be done for all six harness wires. 

This is, by far, the most nerve-wracking part of the installation! Take your time, don't rush it, and make absolutely sure you are connecting the correct wires. 

Once complete, bolt the ECU wire cover back on to the ECU and bolt the unit back in place. Reconnect the battery.

Wiring diagramWiring diagram


Where you want you control unit is entirely up to you. I found that mine was fairly unobtrusive over the gap where the ash tray was. Wherever you put it, you need to thread its cable down and attach it to the wiring harness. Tuck or tie the cabling safely away.

Fitted!Figure 13 - Fitted!



Once happy, replace the ECU footwell cover. Coat the wheel arch hole that the harness goes through with plenty of waterproofing sealant and reattach the arch liner. 

Put the wheel back on and lower the car. 

Tidy any stray wiring in the engine bay using tie grips. 


Right! Now you just need to read the instructions for how to set up your AVC-R!!

Christian Jull

During his 'car years', Christian owned, ran and modified a Nissan 200SX (S14) and Nissan Silvia Spec R (S15). He was an active staff member of the UK 200SX Owners Club and one of the founding members of the S15 Owners Club. He owned and administered the club for ten years. Over the course of five years of Nissan ownership, Christian wrote modification guides to aid others. These guides have proved very popular with 200SX/Silvia owners all over the world.

Included with the guides is a record of car ownership over a ten year period.

Christian is now car-less and lives in the public-transport-friendly city of Helsinki in Finland.