S13 200Sx SR20DET + Gearbox Fitting Guide

SR20DET Gearbox Fitting Guide for UKS13 200sx

John Bennett

Additional research: Marty_T3 and Fry1

This document considers donor engines from the UK 200sx S13, S14 and the S15.

It assumes you are experienced in engine removal and fitting, concentrating on the main ‘difficulty’ – electrical wiring.At the back of this document a more detailed mechanical fitting guide is included by Fry1.

Air-system is not considered in detail, as factory service manuals show this for you, and it is open to re-arranging anyway.

I take no responsibility for you blowing up your ECU/engine etc due to errors in this document, or your own cack-handedness. This is just a guide, read the service manuals if you’re not sure (that’s where I got all the info from).

Engine/Mechanical Fitting Overview

S14S14a

• Straight fit on engine mounts and gearbox.
• Use original S13 propshaft.
• Speedometer may require speed sender from S13 box to operate correctly?
• Throttle cable to plenum mount sits further forwards than CA18 so fixing cable is not possible, - use either SR20 throttle cable, or alter/recreate a new mount.
• Wing Intercooler can be used as a temporary solution. IC Pipes may need to be crossed over.
• Exhaust will not fit. Custom, or combine S14 downpipe, decat pipe and S13 rear.

S15

• Straight fit on engine mounts.
• 6-speed gearbox requires S15 mount as it is bolted in a different place along the gearbox. Also the 2 holes on flexible section of mount require filing to oval them by about 5mm as the 4 gearbox mounts holes will be about 5mm out otherwise.
• 6-speed requires splines from S15 propshaft to be spliced onto the original S13 propshaft (propshaft specialist will charge about £60). Unconfirmed rumour that S13 automatic propshaft may have the correct splines. Rear section of propshaft must be from an ABS S13 as ABS differential is required for speedometer (ABS diff is 2cm longer than standard diff). ABS diff is identifiable by sender unit by the mating face to the propshaft
• Speedometer signal is generated by the ABS computer from the magnetic sender on the rear differential. ABS sender is present on S13 and S14 ABS diffs, so S15 diff is not essential. Signal is unipolar square wave and will not drive S13 dash. More info later.
• Throttle cable to plenum mount sits further forwards than CA18 so fixing cable is not possible, - use either SR20 throttle cable, or alter/recreate a new mount.
• S13 PAS pump can be adapted to fit with additional metal on bracket, but belt angle is precarious, so not recommended.
• Wing Intercooler can be used as a temporary solution. IC Pipes may need to be crossed over.
• Exhaust simply requires rotation of the downpipe flange to fit. Stock S13 system severely restrictive however.
  Wiring

Fitting an SR20 should have no effect on the ABS system (in UK cars), but this has not been verified yet (all cars tested didn’t have ABS), so if you get an ABS warning light flashing, please contact me.

ALL ENGINES

Remove the starter/alternator loom from your CA18DET.

Fit it to your SR20DET.

All the starter/alternator/oil pressure plugs should be a straight fit, although you may need to enlarge the ring terminal for the alternator with a circular file.

I don’t know if the 3 gearbox connectors are the same for SR and CA 5-speed boxes. If they don’t fit, hack the CA18 gearbox plugs off and solder in the SR20 plugs.

The 6-speed box has different plugs for neutral and reverse sensors, so I attached them to the wires of the corresponding plugs on the S13 loom. 6-speed has no speed sensor.

If your S13 loom is tatty, remove the black tape (keep the plastic protection bits though), wash it in soapy water, dry and re-tape it.

Your SR loom may be nicer looking, but using the CA loom allows you to plug it straight back into the engine bay connectors by the fuse box without any serious rewiring.

Take your S13 main engine loom (the one with the ECU on one end).

There are 2 plugs (F8 and F10) that go to sockets by the passenger headlight, under the airbox (there’s a black relay/fuse box there).

These sockets provide power to the ECU, as well as the signals from the gearbox.

You need to extract the 2 plugs from the harness along with their wires, as they are going to be attached to the SR20 main loom to provide power etc.

Extract the wires as far back as you can (to within 20cm of the ECU connector, if possible).

This will involve removing lots of tape, and cutting any wires that branch off to other parts of the loom (don’t worry – if it’s not going to the ECU connector, just cut it).

An alternative would be so just hack off F8 and F10 and solder on a couple of meters of wire to each pin, but I didn’t want my CA18 loom and I couldn’t be arsed to source and join more wire.

Also there’s a plug (F3) just next to the ECU connector (see right). Lop this off with about 5cm of wire as we’ll graft this plug to the SR20 loom too. This provides 4 connections (start signal, speedo, tacho and water temperature).

Ok, now you need to take the main ECU loom of your SR20:

On the previous page you saw where we would be adding wires to the SR20 loom.

We now need to look at the wires we’re adding.

Here is the pinouts of those 3 plugs & wires extracted from the CA18 loom:

Take note of the numbers, they’ll be referred to later.

Connector F10

1: N/C

2: 12V when Fuel Pump activated

3: N/C

4:12V when ign on/start (via 10A fuse)

5: Neutral switch signal from gearbox

6: Signal wire to enable fuel pump

7: Signal wire to enable air-con Relay

8: Signal wire to enable ECCS relay

Connector F8

9:12V when aircon is activated

10: N/C

11: Knock sensor shield

12: IGN coil 12V supply

13: 12V from battery

14: ECU power (from ECCS relay)

15: Knock sensor

16: 12V when IGN on/start

Connector F3

17: Output from speedometer

18: Tachometer

19: Water temp gauge

20: Start 12V signal.

Fortunately we’ll only need a small selection of these wires for the conversion.

The wires from the S13 ignition coil and ECCS relays won’t be used, as the SR20 loom has its own relays built-in (as you’ll notice when you have to unplug them to push it through the bulkhead).

The knock sensor is built into the main SR20 loom, so we can forget about joining those wires too.

Basically you take a selection of wires from the previous page and splice them onto connector F4 Connector F4 is connected directly to the ECU connector , and is a leftover plug after you’ve plugged all the SR20 sensors and ECU onto the ECU loom (see page 4 for a diagram of where it is on the SR20 engine loom).

F4. Pins 1 to 32 are the little pins on the grey side. The pin diagram is‘Terminal Side’ – meaning that’s how they’re numbered when you hold the pins/sockets to face you. To be sure, Pin 40 is the thick black wire in the far left hand side of this photo,

Ideally, if you’re getting your SR20 from a breaker then try and get the corresponding interior connector to F4– slice it off a few cm from the connector, then you can join onto its wires instead (as opposed to T-ing off / or slicing the wires to F4) and plug it in.

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When joining wires, I then wrapped the S13 wire around the exposed SR20 wire, soldered it and taped the lot up.

Those horrid blue clip things people over-use when fitting car stereos would do the job. I guess.

In the following pages, tables are provided to tell which S13 harness wires (page 7) are connected to which wires on F4. A schematic diagram is also given to help you see the purpose of the wires that are actually being joined – this is mainly for reference.

If you can get a couple of in-line fuse holders (basically a fuse in a plastic socket with 2 wires coming out of it), then it may be worth fusing some of the new wire links, as they should ideally have 10A fuses. Where a fuse should be added, I’ve put a Y in the ‘fuse column of the tabkes’. If multiple connections have to be spliced to one wire and all require fuses, just use one common 10A fuse for them all.

ECU pins have been given too. These are to help you double check you’ve wired stuff in correctly (see the testing page near the back of this document). When finding a wire pin on the ECU connector, notice that pins above 100 are thicker with larger housings. Also note the locator on the top middle of the plug. This should help you avoid getting it upside down/miscounting.

The ground connection to the ECU is provided by two ring terminals that bolt to the plenum. The plenum is then connected to the battery ground with the earth strap. Do not attempt to connect the loom to earth anywhere else, and do connect the ECU without a proper ground connection. Likewise do not do any soldering with the ECU in place, or the battery connected.

S14 loom connections.

S14 loom connections

Attach a 10k ohm resistor between pins 3 and 40 of connector F4 to operate an S13 CA18 tachometer from this ECU.

*not-verified – please check this is correct, using instructions later on in this document.

S14Aloomconnections

S14A loom connections

Attach a 10k ohm resistor between pins 3 and 40 of connector F4 to operate an S13 CA18 tachometer from this ECU.

*not-verified – please check this is correct, using instructions later on in this document.

S15loom connections

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S15 loom connections

NATS (S14a europe)

You need these 2 units.

One is the halo unit that goes around the key barrel.

The other is a little black box – the IMMU amplifier, with a Siemens sticker on it.

The original key is also essential.

You don’t need the interior wiring harness – grab the aforementioned units, but try and get the harness plug and a few centimetres of cable as it gives you something to join onto.

The ‘Antenna Amp’ is the halo unit. It has 4 wires.

I forget the colours, but one of them is black. Solder that one to the wire from the NATS IMMU box on pin 10 (Green + white stripe). The IMMU pinout is at the bottom of this diagram (M59). Join the other 3 wires from the antenna amp in the diagram order (again forget the antenna amp colour codes).

The IMMU needs a ground connection, so join the wires on IMMU pins 8 & 9 to the ECU connector (either wires 39 or 48).

It also needs a power supply on pin 4 (red), so take this off wire 13 (red) on S13 connector F8 (see page 5).

Likewise connect IMMU pin 3 (green) to S13 wire 16 (black+red) (see page 5 again).

A security indicator is an option, but just bung in an LED if you want it, as above.

Join wires from pins 5 & 6 to the ECU harness on pins 8 and 25. Colour codes should match up in this case.

Put the key in the halo, and the NATS will do its stuff. Start the car with your normal S13 key. The NATS unit can be positioned anywhere – you could even permanently tape the key in the halo and hide it all in the footwell.

Additional Stuff (all engines)

Tachometer:

The signal to the tachometer needs a 10k ohm pull-up resistor to make it work. You can do this at the ECU end (put the resistor between the tachometer pin on F4 and a IGN ON/START wire (splicd to black + red). Where to do this on the wiring loom, on connector F4 is listed in the earlier tables. Alternatively pull out the tachometer and attach the resistor between the signal and ‘IGN’ screws on the back.If you happen to have a KA24 tachometer (I do), contact me as I’ve written up how to adapt these to CA18’s (easily), so all you do is add the 10k resistor to make them work with the SR20.

Water temperature gauge:

You’ll need to transfer your CA18 water temp sensor over to your SR20, as its resistance is matched to the gauge on the dash. The wires to splice are in the table, but to double check I’ve got them right, measure the resistance between the given F4 pin (4) and the bodywork. It should be about 600 ohms when cold.

Speedometer:

Unconfirmed here, but if your speedometer doesn’t work with an S14/a SR20, swap the speed sender on the gearbox for your CA one. SR20 sender does not appear to operate the CA18 speedometer correctly (reads too low).

S15 owners need the S15 gauge cluster, ABS computer (part of ECU loom) and a rear diff with an ABS sender unit to get a speed signal (S13 ABS, S14 or S15 diff will do). The ABS computer calculates the vehicle speed and tells the dashboard (which in turn tells the ECU for boost control, speed limiting etc).

The speed signal is not compatible with S13 speedometers.

I’m working on a home-made unit to allow you to drive an S13 speedometer (analogue or digital) from any ABS diff (without need for ABS computer). Will update the guide when it is completed.

Diagnostics lamp:

As in the NATS section, there is a driver in the ECU do operate a bulb to indicate electronic faults. Wire this to a spare bulb on the dash if you wish (one pin goes to the ECU, the other to 12V IGN signal). An LED could be used instead, with a 1k ohm resistor in series.

To put the light into diagnostics mode, wire a switch between 12V IGN and pin 23 on the check connector for S15/14a or pin 47 on S14. Shorting the pin to 12V for 2 seconds puts the LED into diagnostics mode.

Consult:

Wire a consult to RS-232 converter board to the pins on F4, listed in the pinout tables. S15 does not need a clock connection.

If you’ve purchased one of my boards, beware that the RX pin on the board goes to the TX pin on the ECU, and TX on the board goes to RX on the ECU (I swapped the labels by mistake).
Testing

Before connecting the ECU, it is advisable to test your handywork

Firstly, using the tables provided, check each wire you’ve spliced to exists on both F4 and the ECU connector (use a continuity test). This will help you check you’ve connected to the correct wires.

Put the multimeter on the current setting, put one probe on the body ground, and with the aid of a pin/needle, short-circuit any pins that operate relays to ground. You should hear a click from various places in all cases (or a whirring noise for the fuel-pump relay pin). The current may be up to 1 amp. The ignition may have to be on for this to work, depending on how it is wired. Also be aware of any aftermarket immobilizer you have fitted, as this may stop the fuel-pump from operating, unless it is disarmed. ECU relay is the most important to check.

You can check injectors with this method too, but leave this for troubleshooting if the engine refuses to start, as it’s unlikely they’ll not work as you shouldn’t have touched them when splicing looms..

Also use the multimeter (on voltage) to check all 12V connections work, and switch on/off depending on how the key is turned. Don’t forget to check the start signal (orange wire, number 20, page 5).