comments in the pictures. I am prepared to tap additional ports for manifold reference if needed. I also have an auxiliary little log manifold but I知 not at ease with that solution. Anyhow, I知 hoping that I can get manifold pressure from one ore more of the nipples. It was pointed out that one nipple goes to the plenum, but it痴 on the secondary side. I知 concerned that it would give false readings, especially at early tip in to the throttle.



I知 hoping I can get manifold pressure off one of these nipples. I壇 like to run FPR and BOV.

What I知 working with. I do have the nipple near the IAC that I have designated to the ECU.

 

you'll have to do a little testing. its easy with the stock T2 setup to pick a nipple that only sees vacuum, and not boost, which is a problem for the fuel pressure regulator.
or maybe more to the point, not all of the nipples see vacuum AND boost, some are one or the other.

 

It's very easy to divine this by looking at the TB gasket/integrated vacuum block. Also your ECU source should be plenum'd to both rotors, not just one runner as is the case with the IAC nipple.

The quick and dirty - and I believe accurate - is the rear most nipples are all pre-TB and of the front side nipples that see both vacuum and boost the bottom most nipple (if memory serves, been a while since I've fiddled with stock TBs) feeds from the primary portion of the plenum.

 

Thank you, and great point on the nipple near the IAC.

 

Hi,
I have a 88 GXL with a N/A engine. I am trying to figure out where the crank case blow-by gases enter the throttle body from?

Here is a picture of the back side of the throttle body.


Notice the varnish deposits only on the secondaries!

I examined the black plastic piece that goes between the throttle body and the dynamic chamber, but I am unable to determine how the blow-by gases enter and coat both secondary ports?

The only opening in the black plastic piece that can feed both the secondaries at once is the one that is centered. Maybe?

The chamber has only two ports on the outside facing the rear. Both attach to the purge valve, the connection on the top of the valve hooks up to the lower nipple on the chamber. I understand this to be the vacuum port to pull against the spring in the valve. Idle's hi-vacuum will allow just a small amount of gasses through. Low vacuum at load will allow more gasses through.

This leaves the upper nipple on the dynamic chamber to pull the gasses into it! This connects to the small, centered nipple on the bottom of the purge valve.

How do the gasses entering through this one connection get into both secondaries at the same time? I cannot figure out how the above-mentioned center hole does that?

Anybody have any ideas? Just curious.
Thanks

 

Short answer: The varnish on the back of the secondaries is there because the air coming out of the diverter block isn't moving very fast. Crank vapors can't reach the primary throttle plenum.

Long answer: The diverter block routes a few different "vacuum" sources. The three air bleed sources; primary, secondary, and oil injector all route to that hole that runs straight through. This pulls pre-throttle air straight through and meters it in via the different bleeds. The PCV system works a little different. The diaphragm of the PCV valve is controlled via the upper throttle plate. The diverter block routes vacuum from right behind the primary throttle plate to provide the vacuum source to open and close the valve. You may also notice a tiny pinhole before the primary plate. This is routed to the diverter block so that the PCV valve doesn't encounter max vacuum and pop the diaphragm. No crank gasses can go through the diaphram into the primary intake plenum. The actual air movement for the PCV system is taken care of on the secondary intake plenum side. Crank case air is sucked through the PCV, then through the diverter block into two little notches behind the secondary throttle plates. This is how crank case vapors are ran through the intake. The reason it is on the secondary plenum is that the secondary plenum stays under vacuum longer if you are only using partial throttle. It also closes sooner when the throttle is released, giving it a much larger window to apply vacuum. When the crank case vapors reach the secondary plenum, you have a full speed vapor that disperses into a large, dead air chamber. The vapors are moving slowly and then start sticking to stuff. They don't evacuate the plenum until the secondary throttle plates open.

This is somewhat related to the port polishing post we had on here a week or so ago. The air bleeds provide velocity to the air around the fuel and oil injectors so they don't spray into a static intake. If there was another air bleed right behind the secondary throttle plates, you wouldn't see the varnish build up like that, but that would be another thing to worry about.

 

Thank you very much, I noticed the air passage that goes all the way through the throttle body. This has to be the source for supplying filtered are to the oil nozzles through the spider lines. The air adjust screw for setting the idle speed seems to go into this passage also, so it does more than one thing.

The deposits you see in my picture built up over 150k miles, I was concerned that the deposits were clogging small openings somewhere, but I did not find anything closed up.

Here is a picture of the diverter block, I noticed a pinhole in the same area on both sides.


front

back

You are looking at two different blocks side by side, both have the same pinholes!

On my block, you can see what appears as oil coming out.
It's a mystery to me how it got in there, the space under the gasket is full of oil!
There is nothing on the mating surfaces of either the throttle body or the dynamic chamber that would make these pinholes.
They were made during manufacturing, wonder what they are there for?
It must be something internal to the functioning of the block?
Any ideas?

Also, I can't seem to find these notches? (Crank case air is sucked through the PCV, then through the diverter block into two little notches behind the secondary throttle plates. This is how crank case vapors are ran through the intake.)

Thanks again, you are a hugh help!

 

Those pinholes are likely ejector pin holes from the press to keep it from sticking and tearing when the press separates. They are not part of the routing and are all covered when the plenum and tb are assembled.

It's got oil in it because that's where the PCV crank case air comes through. Under full throttle, there isn't any air movement in the pcv line, so like I said before, the oil starts to drop out. Some amount of oil will be present in any used diverter block.

The notches are in the plastic barrel sides in the diverter block.

 

I'm trying to learn what the five vacuum ports on the dynamic chamber are for, so I can make sure all the lines all go to their correct locations.

It seems to me that the side with three ports are all pre-throttle filtered air passages.
Top port supplies air to the four oil nozzles, the air must be needed to allow the oil free passage through the jets into the airstream for the primary intake. Kind of like pre-mixing!
The secondary oil nozzles allow oil directly into the intake cycle of the rotors.

The next port down draws air into the primary air bleeds under the injector tips to help atomize the fuel into the airstream. It needs this because of the relatively slow velocity in the primary intake. This is the line that connects to the single nipple on the lower intake manifold.

The bottom port seems to allow air for three of the four solenoid valves on the vacuum piping. I might have these two bottom ports reversed?

Here is a picture of the throttle body side of the block.


You can see the three separate air feeds at the top, it's the one opening centered between the three barrels that I want to figure out!

Here is the other side.


You can see the three separate air feeds on the left side,

Did you notice that there is no air bleed needed for the secondaries!

Now onto the two ports on the other side of the dynamic chamber.

The top port supplies vacuum to the top of the Purge Valve, at idle (high vacuum) a little bit of crankcase blow-by gasses and carbon cannister gas vapors are pulled from the oil filler neck into the rat's nest pipe going into the bottom port. The top port only connects to the centered hole between the barrels!

At 2000 rpms a lot more gasses and vapor flow through the purge valve into the bottom port.
The bottom port only pulls through one notch in the block in the primary barrel.


It connects to only the notch on the left

There are three notches on the primary barrel and none on the secondaries

Do I have all five dynamic chamber ports correct? Or am I missing something?

The oil in the block is a concern, all the passages seem open, but should I make an effort to remove the oil?

Your explanations are great, sometimes the most minor detail makes a world od difference.
Thanks!