TB Ports

[belize1334]

I'm hooking up a Dejon-Mod 1G BOV and I need another reference port that is pre-throttle plate (i.e. charge pipe pressure). I'd like to avoid drilling another hole in my charge pipes and I don't want to T into the line coming off of the turbo-outlet if I can avoid it. Is there a port on the throttle body (A or E) that will accomplish this? I tried searching but it seems like we all just cap them off and there's no discussion about what they actually do. I know that the P port is just plenum pressure making it ideal for a boost reference. Does anyone know what all of the other TB ports reference to?

 

[atc250r]

The throttle body is a terrible place to get a boost or vacuum signal from, I know first hand (at least the "P" port) is. The problem is that the passage that feeds it is only a few thousands in diameter so you very little volume there. For something like a boost gauge it would probably be OK but when I ran my BOV off of it I had a terrible flutter when shifting. I moved my source to the intake plenum and the problem went away. I'm sure the other ports have similarly small passages.

John

 

 

[belize1334]

Is that diagram suggesting that the A and E ports are both pre-throttle plate? The text also seems to imply this since the E port vacuum is low during idle conditions which is consistent with behind ahead of the throttle plate which acts as a restrictor. I'm not sure I understand the bit about leaking to the A-port but I have my FIAV blocked off which I image means that the "thermo" valve will never open.

I'm not too worried about the size of the lines since this is only for a reference signal to control a vacuum switch. It shouldn't have to move any air at all (unlike the main BOV line which has to move the diaphragm).

Edit: I checked the A and E ports (only A1 since the n/a tb has no A2 port) and determined that, at idle, only the A port actually sees vacuum. I'm not sure if it's because I have the FIAV blocked off or if it's something to do with using a turbo tb gasket on a n/a tb. Still, the A port seems to read pipe pressure rather than manifold pressure which makes it ideal for use with a Dejon-Mod bov.