Throttle body

[totta crolla]

Does anyone know if there is a throttle body (or attachment to) that will fit a 4age plenum and allow electronic idle control?

[jondee86]

Lots of ways of getting there. This was one way I used with a smallport and smallport factory ECU.



The smallport has a PWM controlled idle valve built into the airbox. I found the same valve with
in and out connections on another Toyota in a junkyard. Plumbed it between the air intake after
the filter and to the OEM connection on top of the throttle body. This only supplies a small amount
of air to "trim" the idle, with the idle air bypass providing most of the idle air flow.

To use a system like this on a bigport you would need to block off the AAV. I'd only use this setup
if using a near stock smallport with the factory ECU.

If you want a valve to supply ALL the idle air you can use the IACV from a 20V (requires two PWM
outputs, one inverted) or a two wire bosch valve and plumb it directly into the intake manifold.

Cheers... jondee86

[totta crolla]

Really interesting stuff.
I might look into that Bosch valve and try to find an ingenious way to feed it into the throttle body via the existing port.
Any ideas on this?
Thanks for the info.

[jondee86]

You should be able to pick up a Bosch valve for next to nothing from a junkyard. Be a lot
easier to just drill and tap a fitting directly into the inlet manifold rather than be trying
to hook it up via the throttle body



The Bosch valve is used on a lot of engines larger than 1600cc so if you are wanting a
stealth installation you can probably find a smaller valve and plumb it it in underneath
the inlet manifold.

Cheers... jondee86

[totta crolla]

Junkyards here seem to be a great thing of the past.
H&S covid and "climate change" have ensured they are nearly all closed.
Never the less the Bosch valve looks just the job.
I guess if l blocked a few ports l could do away with all of the standard cold start/idle gubbins too?

[jondee86]

I guess if l blocked a few ports l could do away with all of the standard cold
start/idle gubbins too?

Exactly. The valve is capable of passing all the air the the engine needs for starting and
idling. There is no need for any other idle air source... electrical load, A/C load,
starting, stall saver etc. These functions should be controlled by tables and settings in
your programmable aftermarket ECU.

The primary function is water temp vs % open to raise the idle when cold and taper it
down as the engine comes up to operating temperature. Secondary table settings add a
few % opening to take care of A/C load and electrical load. I used a factory 20V IACV for
my individual throttle body setup and it worked fine once the correction tables were
calibrated correctly. Just check that your ECU has the tables and a spare PWM output
with a suitable power rating (pulls 12V to ground).

Cheers... jondee86

[totta crolla]

I'll use some smallport rocker covers that have had AN fittings fitted for breathers, this will free up the original breather inlet in the plenum.
As it is a smallport inlet l have already modified the internal air passage to suit.
I guess at idle the engine is not fussy about where it gets its air from?

[jondee86]

The crankcase breather usually exits in front of the throttle body which would not
work for idle control. Your modification would need to dump straight into the intake
plenum after the throttle body. The volume of air required to maintain idle is quite
small, so the crankcase vent tube should be OK.

When removing/blanking off the AAV I would recommend leaving the idle air bypass
screw operative. You can screw it down to close it but if at any future time you need
a little more air, the bypass would come in handy. Where the idle air enters the plenum
is not critical... in the side about halfway down is fine,

Cheers... jondee86