Jenvey throttle bodies on an Alfa V6 24V photos.

[Sando]

I was wondering, where do you pull a vacuum for the pressure gauge. Normally it would come from the intake, but I don't see anywhere on these throttle bodies to attach a vacuum line.

Not quite sure about vacuum for a pressure gauge?
But I drilled and tapped just one inlet runner for the servo (booster) take off. Works just Fine. No issues at all, ( it was always common practice for multi carb set ups back in the day too) it does run through a standard non return valve, but you would be using that wth any servo take off.
If you needed vacuum for anything else, I'm sure it would work just as well, however you would most likely see the pulses on a guage unless you dampened it out. (A piece of threaded rod in the hose may do the trick...Early Turbo boost fooling trick to bleed pressure or vacuum slowly)
Rob

[strat24v]

All bike throttle bodies have vac Lines from each body that are all the same length. All run to a common connection then on in a single line to the fuel pressure regulator. Been as bikes are by far the biggest users of throttle bodies, I figured they'd have done the most r&d so followed that lead.

[tipo158]

Here is a diagram of the Jenvey pressure regulator, as you can see, there is a vacuum port. Sorry, I meant pressure regulator, not gauge.

[LM mic]

To my knowledge this port is never connected to anything when using a separate jenvey throttle bosy and watever specific ECU ( Emerals or any )

[STR_Strat]

I think its up to you whether you use it or not. The fuel map will be written to take account either way, just make sure that you don't alter it after its been mapped. If you don't connect it to vacuum then it should be left open to atmosphere and not blocked off.

Dave

[Sando]

With an aftermarket ECU the mapping will (should) give you the correct mixture at all times so can't see why you would connect the vacuum. That's for sudden throttle openings with a standard ECU to richen the mixture.

You need a constant pressure at the regulator for the Aftermarket ECU to work with.

.....could that be the cause of you bad fuel consumption Dave?????

[Jeff]

You need a constant pressure at the regulator for the Aftermarket ECU to work with.

.....could that be the cause of you bad fuel consumption Dave?????

I did discuss this with the chaps at Emerald (basing fuel pressure either on atmospheric or manifold pressure). I was told that the ECU could work either way (ie mapped for one or the other) but that using manifild pressure as a reference was better.

I have fuel pressure set relative to the manifold, but i wonder if this doesn't add another factor making things unnecessarily more complex.

[STR_Strat]

.....could that be the cause of you bad fuel consumption Dave?????

No Rob, mine is not connected.
I think the reason not to block it off is to make sure the pressure remains constant, blocking it off would create a sealed vessel so the pressure would vary dependant on temperature.

Dave