Moving to ITB, vacuum doubt

For discussing injector selection,manifold modifications, throttle bodies, fuel supply system design and construction, and FIdle valves and IACs.
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pb81
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Joined: Tue Oct 14, 2014 11:59 pm

Moving to ITB, vacuum doubt

Post by pb81 »

Hello, as the topic title i'm moving to itb's on my Vw ABF engine with large cams, and i have to feed with vacuum brake servo, FPR and maybe one day an idle valve. Last one maybe in a very boring day :D
Most of setups provide vacuum by installing nipples on tb then a vacuum hub with xx outputs but i dont like the idea of intake runners sharing pressure between eachothers during vacuum pulses
What if i put one-way valves on evey tb vacuum output then a vacuum reservoir with all the outputs needed? Is there something durable and fast enough to close and open with air pulses?

Thanks!
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EWflyer
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Posts: 40
Joined: Thu Jul 30, 2009 12:00 pm

Re: Moving to ITB, vacuum doubt

Post by EWflyer »

I'm working on a small motorcycle fuel injection project. It has a bank of four small Mikuni carbs that I've turned into throttle bodies. I'm going to build a SyncroMAP circuit for these throttle bodies. The SyncroMAP circuit has a dedicated MAP sensor for each cylinder and it uses diodes to deliver only the signal that currently has the lowest kPa reading.

This means no "sharing" of actual intake vacuum between the cylinders.
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hberwald
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Joined: Thu May 23, 2013 2:38 am

Re: Moving to ITB, vacuum doubt

Post by hberwald »

I have this setup on my flat 4....I was getting a very unstable MAP signal so I tied all 4 vacuum ports to a fuel filter and inserted a mig .028 orifice into the line to the Map sensor. This smoothed out the signal much better. Added a little filtering to the signal and now all is good. With the large throttle bodies, as soon as I crack the throttle I loose vacuum very quickly. I needed this set up for part throttle under load...You could just add 4 Map sensors and average the readings....much more work and I don' think there would be any benefit. my motor is a 2.7 L flat 4, 103 by 80 with a split duration cam....idles at 65kpa
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