VEMS on a Subaru Impreza Engine

I have a lot of spare Subaru parts. It would be silly to not make the most of them, so I am about to start experiemnting.

Triggering Options

I will be using the standard Subaru "short gap" trigger.

The config I plan to use is as follows: (Translated into MT later)

I would appreciate a sanity check!

crank_minper=x75  (1872 usec - not sure this is right)

"TDC after trigger" will be determined by timing lamp.

Since the native Subaru trigger now works with VEMS, the 36-1 tooth trigger is left here for historical reasons:

An has made a crank trigger wheel that is a direct replacement for the Subaru one. (Barry from Janssen Tuning & Training Netherlands asks if that wheel is available. Send him a quote if you have them. 2009-01)

It was originally for an acquaintance to use a Pectel ECU, but it'll work just as nicely for VEMS. It even allows reuse of the standard Subaru VR crank sensor.

The cam sensor signal can either be ignored or the wheel modified to give a single pulse per rotation.

[Large!] Pic of wheel - note that it includes the cambelt cog too.



Standard injectors on my old engine are side feed 380cc HighZ.

This type is rare & more expensive than top feed HighZ, so may well be replaced by something more standard in the future...

My new Subaru has side feed 440cc lowZ, but with a different fitting into the fuel rail.


Coils are a passive COP system on the old engine and a wasted spark coilpack on the newer car. Either way, the amplifier unit is external to the ECU, so may be removed in favour of the internal IGBTs in VEMS.

Airflow meter

Will be removed at the earliest conveneince as it is redundant

MAP sensor

Standard old Subaru MAP sensor is good for 1.1 bar of boost. New Subaru is good for approx 2 bar. Both have 3 wires - GND, +5 and signal.

I am re-using a VEMS unit with internal MAP fitted, I'd like to use it as-is. The ECU will most likely be located in the engine bay on this installation, so no problem with pipe lengths & accel enrich.

Is there a high boost internal sensor option for VEMS?

Loom Adaptor

The development of the loom adaptor for the older Imprezas is now complete. I have built the first prototype and this is due to be fitted in a car this week.

Do you happen to have a diagram for the old impreza wiring and the new loom interface? Also, by saying the OE trigger is supported, do you mean the 6/7 style cam+crank trigger as fitted to the EJ20?

[add pic of prototype!]

The car was progressing nicely over the past couple of months. A bit slow due to family commitments, but progressing all the same.

I tried 1.1.44 on the TVR and found some useful new features so tried it on the Subaru. Now it won't run at all.


I suspect the H[1] table is not correct, but putting in h[1] = 0 3 0 3 or h[1] = 0 3 6 9 did not make the car run.

Does Subaru trigger still work on the 1.1.xx firmwares?