The Definitive 1990-1997 VVT Swap Megathread.
I've made several posts on this topic, but I've never consolidated all of the information into once place until now. This thread will outline all of the mechanical and wiring tweaks necessary to install a 2001+ engine in a 1990-1997 chassis. This method relies mostly on OEM 1990-1997 wiring, and assumes you will be using a standalone ECU (either an AEM or a Megasquirt of some variety).
There are other ways to complete the same task, but this post will outline the methods I've used successfully. I believe that this is the easiest way to complete this swap with the least cost and headaches incurred.
In some places, I have added info that is 99-00 specific, but this thread is largely VVT-specific. If you are doing a 99-00 BP4W swap, you'll need to fill in the gaps yourself.
VVT = Variable Valve Timing
VICS = Variable Intake Control System
VTCS = Variable Throttle Control System
EUDM = European Domestic Market
TPS = Throttle Position Sensor
IAC = Idle Air Control
CAS = Cam Angle Sensor (refers specifically to the 90-97 sensor)
Motor mounts, transmission, clutch, flywheel, starter motor
Any 1994-2005 motor mount will bolt up to the 2001-2005 block. The 2001-2005 engines used a unique 4-hole mount, but any 94-05 3-hole mount will work in place of these. All 1.8 mounts (94-05) will bolt into the 90-97 sub-frame.
All 5 and 6-speed 90-05 transmissions will bolt up to the 99-05 block. You can use any clutch (1.6 or 1.8) as long as you use a matching flywheel (1.6 clutch with 1.6 flywheel, 1.8 clutch with 1.8 flywheel).
The starter motors are functionally identical. The NB starter is lighter, so if you have the choice, use it.
Alternator and pulleys
Use a 1994-1997 alternator and pulley. The 1.6 alternator has a different shaft diameter, so a pulley swap is not possible - the entire alternator must be swapped. It may be possible to use the 99-05 ECU with wiring changes and an ECU with alternator control, but few/no PnP ECUs for 1990-1997s will have this feature, so it's easiest to simply use a 94-97 alternator with onboard control.
Intake manifold, throttle body, and throttle cable
Use any 1999-2005 intake manifold (VICS, VCTS, or EUDM Squaretop). There are three OEM intake manifold options. The 99-00 "VICS" manifold will produce the most low-end torque (assuming you are controlling the VICS butterflies). The 01-05 "VTCS" manifold is the most common and the cheapest, but it makes slightly less power than the other two options and requires very slight modification to clear the 99-00 fuel rail. The 02-05 JDM/EUDM "Squaretop" manifold was available overseas and makes more power than either US-market intake manifold, but slightly less mid-range torque than the 99-00 VICS manifold. The 1994-1997 intake manifold will bolt up, but the ports on the 99-05 heads are significantly higher and the 94-97 IM ports are misaligned by 3/4". All three intake manifolds are EGR compatible. The EUDM manifolds came with an EGR valve in Europe, while Japanese market cars were shipped with block-off plates on those ports.
All three intake manifolds have the same throttle body location. Any 1994-2005 throttle body can be used, but the 99-05 TB is more desirable for its internal idle valve routing, which makes plumbing for custom 2.5" cold air intakes or intercooler piping much simpler. Using the 99-05 throttle body will require that you change the TPS and IAC valve pigtails, but this is a fairly simple modification. The 1990-1993 throttle body cannot be used on the 99-05 manifold without an adapter, and you lose the benefits of the linear TPS on all 94-05 throttle bodies.
Use a 1999-2005 throttle cable. It will bolt directly into the NA chassis and fit perfectly with the NB engine. The NA cable is too long.
Exhaust manifold and exhaust
Any header from 1994-2005 will bolt up to the head. If you are using a 1994-1997 header, you will need to delete the EGR tube and EGR valve, but you will be able to use a cat and catback exhaust from a 1994-1997 (the exhaust hangar locations are the same for 90-97). Using a 1999-2005 header will allow you to retain the EGR tube, but you will need to have a custom cat pipe built to jump from the 99-05 header flange to your 90-97 catback (you cannot use an NB catback without changing several of the exhaust hangars). If you use a 99-05 header to retain EGR, the 2001+ headers flow much better and are significantly more desirable.
Use a 1999-2000 fuel rail and a 1990-1993 fuel pressure regulator. No other combination of OEM parts will work. The 90-93 fuel rails are too short, the 94-97 rails have incorrect mounting tabs, and the 01-05 rail places the fuel pressure regulator in a spot which interferes with the cylinder head. The 94-97 FPR places the pressure reference in a spot which interferes with the cylinder head and the 99-05 regulators do not have a return line.
You will need to retain one of the fuel injection fittings from the 01-05 fuel rail to use as an adapter on the 99-00 fuel rail. I prefer to use a 90* adapter instead of a straight adapter to aid fuel line routing around the alternator. Do not simply slip a fuel hose over the end of the 99-00 fuel rail - it will not stay in place. Use 5/16" fuel hose to run from the feed line to the 90* fuel injection adapter and into the fuel rail. For the return, install the 90-93 FPR upside down in place of the OEM 99-00 fuel damper (fuel outlet facing up). Use 5/16" fuel line to run around the back of the intake manifold and into the return line on the chassis. The fuel pressure will be 43psi with a pressure reference, just like the 1990-1993 fuel system.
Alternatively, you can use an aftermarket fuel rail and aftermarket fuel pressure regulator.
Use the 2001-2005 coils and wires. The VVT oil feed line interferes with the 1990-2000 coil mounting location. The 01-05 coils are fairly reliable and easy to wire up.
You must use the NB cam and crank angle sensors if you want VVT control. There is no way to control the VVT if you use an NA-style CAS driven from the exhaust camshaft.
The OEM 1990-1997 CAS has 4 wires. One wire is +12v, one wire is a sensor ground, and there is a signal wire for the crank position and a signal wire for the cam position. You will need to cut the factory plug off and extend the +12v and ground wires to each of the NB sensors. The cam signal wire will get routed to the camshaft sensor on the top of the valve cover, and the crank signal wire will get routed to the crankshaft sensor located near the harmonic damper. This will bring the appropriate cam and crankshaft patterns along the OEM harness into the ECU, and all of the other changes necessary will happen in the firmware/software of your ECU.
12v (extend 90-97 wire to both 99-05 sensors):
Cam (extend to Cam sensor only):
Crank (extend to Crank sensor only)
Ground (extend to both 99-05 sensors)
90-97: black/light green
If you are swapping to the 99-05 throttle body to upgrade to the internally routed IAC valve, you will need to swap the pigtails for the TPS and IAC wires. The IAC valve wiring is not sensitive to polarity, so you can simply swap the pigtail without worrying about which wire goes where.
The 90-93 manual chassis did not originally come with a 0-5v variable TPS. To use a 94-05 0-5v throttle position sensor in a 90-93 chassis, consult with your ECU supplier to confirm the wiring changes that are necessary.
The 1994-1997 chassis did come with a 0-5v variable TPS. It is a standard 3-wire TPS with an additional fourth wire (red) which serves as a wide-open switch. Your standalone ECU will likely not use this fourth wire, so if you are changing the pigtail to a 99-05 style, simply heat-shrink over this unused wire. If you are using your 94-97 throttle body, there are no wiring changes necessary. If you are using the 99-05 sensor, wiring colors are listed below:
94-05: Light Green/Red
The VVT solenoid is a 2-wire PWM solenoid, just like an EBC valve. There is no polarity on the wires. Connect one wire to +12v (the injector harness is very close and has plenty of extra current room on its fuse) and the other wire directly to your ECU's VVT control pin.
The wiring modifications for the coils are chassis-specific.
You will need to delete the ignitor first. The 01-05 coils have on-board ignitors. Connect the wires as follows:
Route 1 (white) to 2 (brown/yellow) (trigger for cyl 1/4, the text in the pic above is wrong, see post #156)
Route 7 (brown) to 8 (red) (trigger for cyl 2/3, text in pic above is wrong, see post #156)
Route 4 (yellow/blue) to 5 (black/white) (connects ECU directly to tachometer at gauge cluster)
Terminate 3 (blue) (unused +12v)
Terminate 6 (black) (unused ground)
At the 90-93 coil connector, there are three wires (+12v and two triggers, no ground). Connect as follows:
Trigger cyl 1/4:
Trigger cyl 2/3:
99-05: black (ground to intake manifold)
The 01-05 coils have no provisions for a tachometer output. The AEM Series 1 (30-1710), AEM EMS-4 (30-6905), MSPNP2, MS3-Pro, and all 94+ MSPNP1s have a tachometer driver which will run the factory tach in lieu of the factory coils. For 90-93 MSPNP1 owners, you will need an aftermarket tachometer driver, which can either be added to your ECU or purchased and wired separately. See posts 44 and 62 for more details.
trigger cyl 1/4:
trigger cyl 2/3:
Injectors (90-93 only)
Most people elect to switch to sequential fuel while doing this swap. The factory 1990-1993 cars (except for California-emissions 1993 cars) have fuel injectors wired in pairs (1/3 and 2/4). I typically elect to run new trigger wires for injectors #3 and #4 and leave the OEM trigger wires in place for cylinders #1 and #2. Simply cut the trigger wires (Yellow and Yellow/Black) at the #3 and #4 injector pigtails, heat-shrink the loose ends on the harness side, and attach/route two new wires directly from your ECU to the trigger wires for injectors #3 and #4. Terminate all loose wire ends.
Injectors ('93 California emissions and all 94-97):
Use your factory 94-97 injector harness. No modifications are necessary.
The 90-93 cars have two coolant temp sensors and a thermo-switch. The two-wire sensor on the back of the head is the sensor that provides the ECU. The one-wire sensor on the back of the head provides signal to the gauge cluster. The one-wire switch on the front of the engine switches the fans on and off. The 1994-1997 cars have the same two sensors on the back of the head, but the OEM ECU controls the fans instead of a separate thermo-switch.
Install your 1990-1997 2-wire ECU coolant temp sensor and your one-wire gauge coolant temp sensor in the 2001-2005 engine. This will allow you to retain your OEM CLT sensor pigtails. The 01-05 engines have a small plug in the hole used by the one-wire gauge sender - simply remove the plug and install the sender in the 01-05 engine. The front thermo-switch (90-93) is no longer necessary, as your ECU will control the fans.