|
|
Specialists
in |
|
|
ExtraEFI.co.uk |
|
2 Wired Valves
These valves are wired between an ignition switched 12V and the Megasquirt
Idle Valve wire in the loom. (The MS ECU switches ground to make them work.)
Make sure the 12v is switched off when the megasquirt is off. Many looms contain
a protection diode, leave it there.
Some valves will have a spring return
mechanism to shut them, others have a spring to open them, so the duty cycle
at high and low temps depends if the MS ECU has to drive it open against the
spring or shut against the spring.
If the ECU has to shut the valve down against the spring to reduce air going
through it as temp increases then the duty cycle will need to increase with
temp, so the value at low temp will be around 0 and the duty at higher temp
will be 100 or so. The opposite if the MS ECU has to force the valve open
against the spring to increase air flow.
3 Wired valves e.g. Bosch Valve
0280 140 505
Three wired valves can also be made to work via the IdleValve output from
an MS1 or an MS2 (Note that all ExtraEFI.co.uk ECU's are modified during the
build process so they can drive a valve, standard ECU's can not drive them
directly!) The centre pin of the valve goes to an ignition switched +12V,
one of the other 2 pins will hold the valve shut when its connected to ground
(0V). This pin needs to go to earth via a resistor (30-40Ohms 50W), the other
pin goes to the Idle valve output in the wiring loom from the MS ECU.
On a 3 wired valve there are effectively 2 windings that fight against each other, one opens the other closes it. So we put a resistor in line to ground with one winding, this shuts (or opens it depending on what winding you use) the valve, so its like having a spring holding it one way. The MS ECU then forces it either shut or open, it can do this as the resistor in the other winding limits how much it can force it one way.
4 Wired Valves
If you have a 4 wired valve then its a stepper motor, these can NOT be controlled
with MS1-Extra, only MS2 can drive these. BUT if you want to use the stepper
outputs on the MS2 ECU as a programmable output or Boost or NOS, etc, then
you may lose the stepper function as there is a limitted amount of output
pins that can be used. See HERE for more details.
Options are then to fit a suitable 2 or 3 wired valve from an older vehicle.
This is the route most people take for MS1 anyhow.
Base settings for a bosch valve in Warmup Only mode:
Other Idle Valves
There are valves that need no control other than a 12V supply when the ignition
is on. These heat up a bi-metalic strip that rotates a plate inside the valve
and shuts the air down as the engine heats up, these are known as Extra Air
Valves. They are becoming rare and hard to get hold of, they were fitted to
various engines, like the Flapper type RV8 EFI's. The Idle Speed has to be
controlled with the throttle stop when using these type of valves, as the
valve is only used to add air when the engine is cold.
Here is a Bosch example:
