ECU to VEMS Harness

4A-GE Trigger

The connector is described at 4A-GEPinOut

These have a potential market for Corolla (AE86 and newer) and MR2. These engines are used in Mk1&Mk2 Ford Escorts as they are very similar to the Cosworth BDA engine, powerful and light.

Some decent scope traces.

http://www.jamesmccombe.com/tube/Cars/MR2/ImageLibrary/Thumbnails/Drivetrain/EngineManagement/DistributorTesting/ContactSheet.shtml

Information on the Toyota 4a-eg timing system - distributor driven.

http://www.autoshop101.com/forms/h23.pdf

Sensors

IAT Sensor

CLT Sensor

Injectors

The early Toyota 4A-GE engines came with Low-Z 2.3Ohm injectors wired in parallel pairs with two 2 to 3Ohm resistors in series with each pair, for some reason these pairs are connected in parallel which ends up giving a 1ohm value when measured.

Is it possible to use two FETS to share the load of switching the injectors?
- it is very easy to fill in h[] table to switch more than one (up to 8) injector outputs simultaneously. See GenBoard/Manual/DigitalOut/Table. However, connecting several injector in parallel is a bad idea. The FETs share the load fine (and they are spec-ed to >10A anyway). On the other hand, the flyback does not share the load well. In the worst case only one channel bears 95% of the whole load (the channel with lowest flyback voltage), the other channels only flowing marginal current (because the diodes have -2mV/K temp coefficient, so if one diode-set gets more current, the break-voltage will drop -2mV/K because of the heat, so it will get even more and more until it will bear all current). One channel can bear appr. 4A if PWM is not used, and 2A if PWM is used.

Timing

Here's a diagram of the type of trigger found in European and JDM Toyota 4A-GE engines.

In its simplest form we can use the G trigger and set VEMS as a Coil type ignition

Next step will be to modify the 24 tooth signal wheel to be 24-1, which will give us the ability to run fully sequential injection and coil on plug. The downside is that cranking may take longer (one rev!)

== Config - Coil type ==\n

# config using primary multitooth wheel only
# still using distributor based ignition, or wasted spark ignition
# depends on igchmax and h[2] table 
# CAMSYNC #####################################################################
cam_sync_f_edge_phase=FF
cam_sync_r_edge_phase=FF
reset_engphase_after=FF

## trigger and tooth wheel setup ###################################################
# tooth wheel, angular width of tooth
# For Toyota fitment we have a 24 tooth wheel revolving at 1/2 engine speed
# Two teeth must be ground 180degrees apart 360 / 12 = 30 (0x1E)
tooth_wheel_twidth1=1E

# tooth wheel, angular width of missing tooth
# 12 - 1 wheel, 2 times tooth_wheel_twidth1 = 60 degrees (0x3C)
tooth_wheel_twidth2=3C
tooth_wheel=0B  # 11 teeth between the missing tooth

# trigger1, bit0 0:falling/1:rising, bit1 0:toothwheel/1:coil, bit2 0:no filtering/1:filtering
# Toyota  G trigger:   primary_trigger=FE
primary_trigger=FE

# trigger2, bit0 0:falling/1:rising, bit1 0:toothwheel/1:coil, bit2 0:no filtering/1:filtering
#disable camsync use multitooth wheel on primairy trigger only
secondary_trigger=02

# tooth wheel, active trigger tooth
# after the missing tooth (00: right after missing tooth)
# so that trigger tooth is ~60 degrees BTDC
# Toyota with its 30 degree tooth width = 1
trigger_tooth=01

# The amount of degrees after the trigger till tdc
ign_tdcdelay=3C # 60 degrees

# you probably want 4 trigger event per cam rotation with the 2x 12-1 wheels you will have to trigger twice per
# crank rotation, that what another trigger tooth is for, trigger again after 6 teeth (180 crank rot)

another_trigger_tooth=6

crank_minper=50  # for std. coil tach signal

## Ignition setup
# crank advance = 10 degrees
ign_crank_advance=2E

# EDIS:0x0? dummy: 0x7? disable:0xff bit0: invertout
ign_out=70     

# i assume it is a 4 cyl ?
ignchmax=03

Config Notes

When setting up up timing keep mda28 fixed at 10 degrees

Adjust ign_tdc_delay until the timing is at 10 degrees during cranking as verified by a timing light.

Later Trigger types

Toyota have developed sensors for their later engines (such as found on MembersPage/DanielHenriksson page). These use either a single tooth G trigger:

Or a twin tooth G trigger: