IACV design for ITBs?

I'm in the process of CADing up an ITB manifold to mount Toyota AE101 throttles on a Mazda BP (how original). I intend on gun drilling a chamber across all four throttles to provide MAP, IACV, and ports for brake booster, evap canister, etc.

I originally measured up the OEM Mazda IACV and have been turning it every which way. I've now given up on that as being just too big. I'm leaning toward a GM IACV as they're ubiquitous.

I can't get to a salvage yard to pull a throttle body to take measurements and steal the IACV from until this weekend. Does anyone have measurements handy or happen to have a GM throttle body and calipers within arms reach of their keyboard?

Any suggestions for a more compact IACV which would be easier to implement? I'll be running this on a Megasquirt 3.

I'd be tempted to just tap each runner and run a hose to a small air manifold / box with the ports on it.  Yeah, you'll have to monitor the condition of the hoses, but it'll probably be easier to package (as it doesn't have to fit right on the manifold).  

I've done that on a BP - a small plenum box with the idle speed control valve attached. Worked a treat.

The Bosch units used on earlier CIS equipped cars is pretty simple and standalone.  It’s not controllable though as it is temperature based and just needs switched power and ground.

I used one on my ITB equipped car.

Getting enough vacuum signal to do much of anything was a huge challenge, even with the runners joined with a large vacuum canister and a restrictive on the MAP line.

I was under the impression that IACV are designed for throttles that close tightly, and which is something that most ITB's don't actually do. Any reason it wouldn't work to simply control idle the way motorcycles do, via minutely opening the throttle plates?

The OEM manifold for this application has ports near the head face joined to a common volume. This feeds the brake booster and IACV. I've run these throttles in their OEM application before and have not run into the issues people talk about with ITBs. I'd like this install to be reliable and have idle up for accessories and air conditioning and for that reason I'm basing this off the OEM Toyota manifold.

So the ITB's you're using are set up to use IACV from the factory? Sorry if this is a dumb question, but why not recreate that with the same IACV? 

Yeah, as burdickjp and Driven5 say, why not use the factory configuration?  It works really well.  I've run 2 of them, one megasquirted and one with the factory ECU.

Driven5 said:

So the ITB's you're using are set up to use IACV from the factory? Sorry if this is a dumb question, but why not recreate that with the same IACV? 

Sorry for the confusion. The OEM Toyota manifold has a large bung at one end with a large diameter hose connected to one port of the IACV. The other port has a hose which is connected to the air box. The IACV is mounted on the head just below the throttles.

I'd much rather have an IACV with all of the plumbing incorporated into the manifold itself. I want to minimize my external plumbing as much as possible, so incorporating the MAP sensor and IACV should get me most of the way there.

If you want this to be reliable and have the accessories work, then keep the original configuration and don't go drilling holes through the thing.

Dr. Hess said:

If you want this to be reliable and have the accessories work, then keep the original configuration and don't go drilling holes through the thing.

I'm really bad at this!

I'm building a new manifold to bolt the Toyota throttles to a Mazda BP engine. I'm incorporating a vacuum chamber similar to the OEM manifold. I'd like to incorporate as much as I can into the manifold itself, rather than having a spaghetti of vacuum lines.

Many Saabs have an iacv that is fitted with hose barbs on both ends, so you could mount it anywhere and just run hoses.

Look for 90s Saabs with the red direct ingition module (spark plug cover thing).

I intended to run IAC on my ITB's, but never did.  Going on 12 years now.  I "help" it along when it's cold, but it heats up quick enough driving that I've never needed it.  I'd probably just feed a vacuum line somewhere to each runner.

I'm already machining a manifold from scratch. I'm already machining it with a vacuum chamber to provide vacuum for stuff. Adding a boss for the IACV is no more difficult than barbs for vacuum lines. I just need the necessary dimensions for the boss.

If someone has a GM throttle body sitting to the left of their keyboard and dial calipers sitting to the right I'd greatly appreciate it if they'd put the latter to the former and provide some rough dimensions I can use during my prototyping before I get a chance to measure one myself.