Variable intake to ITB conversion - is this too crazy idea ?

[Bubba Zanetti]

Lately I am doing rebuilding of a 2.0 16V Lancia turbo engine for my daily driven megasquirted Delta - it first started as perfectly normal rebuild, but as you all probably know from your own experiencie - as time passes, every day you get some crazy idea that you " just have to try on your new engine" .

While gathering some parts that are missing, I found variable intake manifold ( V.I.S. system ) from Lancia Thema on nearby junkyard - I took it mostly because when removing fuel rail and/or injectors it's much, much more easier to do then with std manifold.

This varibale intake is in fact very simple designed - it has 4 longer runners for lower RPM area and 4 shorter for higher RPM.

Vacuum actuator rotates 4 throttle plates inside manifold that are controling airflow between 4 short & 4 long runners.

This is pic from above - here are short runners :

http://img.photobucket.com/albums/v358/ ... take_0.jpg

And here are longer runners:

http://img.photobucket.com/albums/v358/ ... take_1.jpg

I carefuly looked at this manifold in garage one day and suddenly I've got idea - hm, I have 4 throttle plates inside manifold ... and what could I get if I remove remove 4 longer runners.... hey, then I am practicaly left with plenum + 4 ITB's

And then suddenly one more idea came - if I remove 4 longer runners I then have to close 4 holes on plenum - so instead of just closing them permanently why not make that 4 big holes little more useful - for instance I can put big 1" one-way valve on each hole - so I can use them as diverter valves, they can suck air when not on boost , and should automaticaly close on boost...this pic should make it more understandable:

http://img.photobucket.com/albums/v358/ ... take_2.jpg

So what do you say - is it again time to visit my psychiatrist or not

[FiatFreak]

Hi there,

I'm wondering what you are hoping to gain by going to ITB's? I would think the variable intake design would give enough advantages of its own that you'd just keep it. Also, if you to the ITB route, you need to get a "clean" MAP signal that MS can use. This means you'll need to run a vacuum line to each runner, then have those 4 vacuum lines go to a large vacuum resovoir which will then connect to MS. The resovoir helps to dampen the fluctuations in the MAP signal. Also, I would think you'd get some weird behavior with the valving that shuts of the open air intake from the turbo charged intake.

So, in other words, you are going crazy and you need to see your doctor! Just kidding man, I think your idea has some issues, but probaby none that can't be solved. Good luck!

-Patrick-

[Bubba Zanetti]

2 FiatFreak:

I don't expect to gain anything special with such ITB setup - only maybe to experiment with such intake system - hey, what can I do - unfortunately my whole life I am always trying to complicate simple things , that's why I went Megasquirt route in the first place, but I guess if you're on this forum then probably you also aren't exactly "plug'n'play" type of guy he, he

Yes, I am aware of problems with weak MAP signal ..especially after I measured throttle plates inside manifold - they are huge - size of one plate is about 68x34mm

So one plate has larger area then std throttle body plate mounted on plenum !


But if such ITB setup can't work ok on my setup , I can always go back on std varibale intake idea - I can then connect vacuum actuator via solenoid that will be controlled by one of MS output - so I could program it to open/close only under some conditions : for example use longer runners only under 4500 RPM and under 100Kpa , else route air through short runners...or something like that...

Hm, I guess that with turbo such intake system isn't really necessary at all, but it can be interesting experiment.

[FiatFreak]

Hey Bubba,

It definitely sounds like an interesting experiment, let us all know how it goes.

-Patrick-