1.6 Mk2 Link to 1.8 conversion

Conceived by Ray Ayala

This article explains how to convert a 1.6 mk2 Link to a 1.8 mk2 Link.  Off course, this also means that you can reverse the procedure should you want to convert a 1.8 mk2 Link to a 1.6 mk2 Link.


1) Remove R21A (330 ohms) adjacent to R21.

2) Add R21 (10 ohms).

3) Remove R23A (470K) adjacent to R23.

4) Remove R28A (2.2K) adjacent to R28.

5) Remove old R87 (4.7 ohms) from mounting hole wired to connector pin 2K.

6) Add new R87 (680 ohms) using alternate mounting hole wired to connector pin 2I.

7) Remove jumper from connector pins 2L and 2M.

8) Remove jumper from connector pins 2P and 2R.

9) Add jumper to connect Pin 1R to IC5-12 (between R9 and R11).

If anyone is interested in modding their ECU to prevent the potential flooding problem when the ECU ground is broken, it involves adding a 1N5817 diode to the ECU internally.  Doing the mod makes a different aspect of the problem more important though.  With the mod, the ECU will actually run with its ground disconnected but some of the sensor data (including O2) may be incorrect depending on where the sensors end up being grounded.  The manual should probably be expanded to include a sensor check list for users to run through to verify that all the incoming data looks reasonable.  The mod is very simple.  The banded end of the 1N5817 diode gets connected to the banded end of D16 (closest to TR6).  The other end of the 1N5817 diode gets connected to the farthest end of R91 (closest to R66). If you like, you can remove both D16 and R91 and install the new 1N5817 in the printed circuit board holes vacated by them. 

10)* Remove old D16 (1N400x).

11)* Install new D16 (1N5817).

12)* Remove old R91 (4.7 ohms).

13)* Install new R91 (zero ohms).


* These steps are not part of Link's conversion process but are to prevent engine flooding when the ECU ground is removed. These may also be performed on a 1.6 Mk2 ECU.

A preferred ECU ground mod that will work for both 1.6 and 1.8 and still not interfere with a stock ECU is to tap into the wire going to ECU pin 2C (about 3 inches from the ECU connector) and solder splice in a wire going to the body at one of the ECU mounting bolts.  Do not cut or break the 2C wire while doing this.  It is not essential to mod pin 2D on a 1.6 and it would be incorrect to do so on a 1.8.  When a 4-wire O2 sensor is installed in a 1.6, its signal ground (gray wire on some) but not it's heater ground should be be connected to the B/LG sensor ground wire going to the CAS and AFM connectors.  The heater ground should go to either a body or engine block ground point. 

 

If you want to use the 1.6 MAP sensor in a 1.8 car, you'll need to cut off the connector of the 1.8 stock MAF sensor and replace it with the connector of a 1.6 Air Flow Meter.  This is the layout of the pins:

1.6 MAP pin

1.8 harness pin

Description

1

NC

Fuel pump relay

2

NC

GND for FPR driver

3

4

MAP/KNK Ground

4

1

Vbatt

5

3

Knock signal

6

2

MAP signal

7

NC

FPR ctl from 1.6 ECU

and maybe

3

5

Another ground

 

Here are the mods required to support three new MK-I features so you can think about whether or not you want to implement them.  It's OK to do only the ones you want to use.  For mods like this I scatter-wire the parts on the surface of the board and then cover them with clear silicone rubber.

 

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