ok, i know that there have been a billion threads written on this but i keep finding contradictory information everywhere so i wanted to get a final answer. i borrowed this pic from a thread and believe Njgreenbud created it, please correct me if im wrong or confirm if im right (HAILERS, RETed, NZconvertible, this is for you). THIS CONCERNS A US SPEC S4 TII throttle body:

1) Vacuum
2) Metered air
3) Metered air

4) Metered air
5) Metered air
6) Metered air
7) Vacuum

 

What is the difference between vac & metered air? The vacuum must be metered, since it's being generated by being drawn into the engine. I think a better way of describing it would be pre-throttle and post-throttle. Pre-throttle is subject to atmospheric pressure & higher, and is used for injector air bleeds IIRC and switching/emissions controls, while post-throttle is subject to the full range of pressures that the engine will see (vac & boost), and is needed for the fuel pressure regulator, wastegate, ECU, brake booster etc.

 

The rear of the jpg of your is correct. Only the bottom nipple is vacuum, the others are metered air (not vacuum is metered air).

On the front the top nipple is vacuum as shown in the attached decal off a series four TRUBOII. The bottom two are for the purge valve.

And it appears I've been wrong about the bottom one on the front of the throttle body in the past. It too should have vacuum if you look at the second jpg I attached. It shows the small hose on the bottom of the purge valve is connected to a nipple located after the primary throttle plate. So top and bottom on the front are vacuum according to the diagrams. This is for a turboII and not a non turbo engine.

I'm not sure how I went wrong in the past. I always thought the top one was the only one on the front that had vacuum. Sorry 'bout that. Makes me want to put the PVC piping on the engine and take off the intercooler and check it out and see where I went wrong in the past.

 

toplessfc3sman: correct, what im talkin about is pre- and post-throttle plates.

HAILERS: so it should be:

1) Vacuum (Post-throttle plates)
2) Metered Air (Pre-throttle plates)
3) Vacuum (Post-throttle plates)

4) Metered Air (Pre-throttle plates)
5) Metered Air (Pre-throttle plates)
6) Metered Air (Pre-throttle plates)
7) Vacuum (Post-throttle plates)

correct?? thanks again for the quick response

 

Yes. I KNOW the rear is like that and the front should be as you just listed. I think I'll just go out and put a piece of PVC on my truboII and make sure about the front.

On a series four NON turbo the ones on the front are from top to bottom........air......air.....vacuum. I KNOW that to be a fact. I'll post again later.

 

Interesting....I definitely have my boost gauge hooked to the top nipple on the rear of the throttle body (4) and it see's vaccum... Ironically, when it was hooked to the bottom nipple (7) it would only read boost.

 

Well I owe everybody an apology. On the front the top one is vacuuum..........second one is air (no suction when at idle) and the third is vacuum.

I put pieces of PVC pipe on the turbo car in lieu of the intercooler. Ran a vacuum hose to each of the three nipples and idled the car. Pulled the stopper out of each hose one at a time. Had vacuum on top...........no vacuum on the middle one...........bottom had vacuum.

Then I went to the shed and got a spare turbo throttle body out. PUt a hose on the top nipple and filled my mouth with water. Pushed water thru that top hose while holding the primary throttle plate open and the sun shinning into the body. Water came out after the primary throttle plate. Did the same to the bottom nipple......water came out after the primary throttle plate.........did the same to the middle nipple........water came out prior the the primary throttle plate.

So on the front number one is vacuum.........number two is air..........number three is vacuum. No doubt about it and you can bet all your money on it.

Like I said earlier, the rear four are as in your picture. The bottom one is the only one with vacuum of the four nipples back there.

And yes, all of my cars/stuff is USA series four TurboII. With the exception of the 86 non turbo which is different and is a change in driving style when driving it vs the others.

 

you're the man HAILERS, i appreciate the trouble you went through. i would have went out and blown smoke threw mine but its pouring here in SE VA. thanks again dude, now someone archive this so it NEVER has to be discussed again haha.

 

No apology needed. I thought everyone knew this though.

The back though always had me confused. I used to search and found people saying 3 nipples. I had 4! Then I bought a UIM from the parts section and got 3.

I use the front top nipple for my pressure sensor and gauge, then the bottom for BOV. Only one on the back I use is for OMP.

Too many damn places for vac/boost leaks on this car

 

I have used the middle nipple on the front of the UIM for secondary injector air bleeds on s5 turbo (s4 does not have secondary injector air bleeds). Bottom nipple is a good vacuum/pressure source for a boost gauge, MAP sensor, etc.

 

************************************************** *************************

ON the back.........on a series four TurboII that has four nipples, only ONE is vacuum and that is the very bottom one. ON a stk car it's used for the water thermo valve just inches to the left of the nipple. The others are used for oil metering pump spider and the primary injector air bleed. The top one is capped off, but even it is just air and not vacuum.

ON a non turbo ..........of the three on the front........the top two are air and not vacuum and those two are used for the oil injector spider and the primary air bleed feed. The bottom one is the only one on that non turbo that is vacuum and it feeds SOME of the solenoids. Not all the solenoids.

Somewhere in the past I lost my way on the front of the turboIIs three nipples. Matters not to me 'cause mine are all run to stk locations. There's too many other choices for boost gauges and the like.

 

Does anyone have any input to the S5 Turbo nipple configurations. I have the front ones all capped off the the back ones I'm not quite sure about. I know there are 3 back there, but I'm not sure what's what.

Can anyone fill me in on this? I think one is for the OMP spider connector, one is for the injector bleed, but not sure where exactly everything goes...

 

i think you must have a jspec mani. what the difference is is that jspec UIMs have only three since one of the 4 on the USspec goes to something that jspecs dont have... thus it doesnt exist on the jspec UIM. i know that was vague but i cant remember what exactly it is... and im not 100% sure that this is correct haha, just what ive heard....

 

My S4 TII manifold only has 3 nipples sticking off the firewall side (and I suspect its a JDM UIM), and they are connected to:

Top - Pre-throttle (metered air)
Mid - Post Primary Throttle (vacuum)
Bot - Post SECONDARY Throttle (vacuum)

The bottom doesn't go through the black spacer between the throttle body and UIM, instead it is just drilled straight through into the secondary runner plenum. This means that it will have slightly more vacuum than the post-primary throttle nipples at idle & low throttle openings. What the benefit to this is, or what this had been connected to originally, I don't know. Does anyone have a copy of the japanese FSM so that we could check?

The nipples to the front seem to be the same as for USDM UIM, and they are:

Top - Post Primary Throttle (vacuum)
Mid - Pre-Throttle (metered air)
Bot - Post Primary Throttle (vacuum)

 

I was just playing around with it on the car instead of in pieces on my lap, and it looks like I got two of the back ones wrong. So, this is the correct version, disregard my previous post.

Firewall Side:
Top - Pre-throttle (metered air)
Mid - Pre-throttle (metered air)
Bot - Post SECONDARY Throttle (vacuum)

Radiator Side:
Top - Post Primary Throttle (vacuum)
Mid - Pre-Throttle (metered air)
Bot - Post Primary Throttle (vacuum)

The middle one on the front (radiator side) is technically pre-throttle, but it connects to a hole that is drilled right in front of the primary throttle plate, so that at idle is it definitely pre-throttle, but at part-throttle openings it is behind the leading edge of the primary throttle plate and could be seeing vacuum

 

note this is a cut shut from a reply i have made on an aussie forum
it indicates the differences in jap s4, US N332 and aussie s5 N370
( which also has four nipples firewall side )
aussie N370 and US N332 appear very similar

if you have 3 or 4 holes on the firewall side for vacuum then you may just have a vacuum into the secondary mezzanine
the bottom most is normally the one



s4 ( jap ) will have only two on the firewall side,, one bigger than other ,, both connected via the phelonic spacer to IN FRONT of the TB ,, secondary plate ( turbo side of TB )
these are PURGE PORTS


of the three on the water pump side ( for both s4 and s5 ) , top and bottom go via the phelonic spacer to engine side of primary throttle
( TRUE VACCUM PORTS )

and the middle port always goes to just in front of the shut position of the primary throttle blade
and is thus considered PORTED VACUUM PORT


s4 ( jap ) and s5 ( aus ) UIM, showing the different vacuum ports


same same this side