Does anyone know if the 3 vacuum outputs on each side of my 89 TII intake manifold just after the throttle body are just plumbed straight in so they receive the same pressure? I am using one on each side with 2 blocked off, then T fittings on the one... If it is all the same I'd like to dump the T fittings and just plum each vacuum hose to its own nipple..
~Jeremy

 

They all get the same signal.

 

Actually they don't...those things are depending on if they are before or after the throttle body.&nbsp Before the throttle body will only see 0 to + boost.&nbsp After the throttle body will see both vacuum and + boost.&nbsp I used to know which one was which, but I forgot and didn't bother to write it down.



-Ted

 

Come on Ted I know you can read better than that

Does anyone know if the 3 vacuum outputs on each side of my 89 TII intake manifold just after the throttle body

 

Uh, yeah I do...

Ever trace those passages?&nbsp Some of those nipples go through the upper intake manifold, through the black plastic spacer, through the throttle body to the front of the throttle plates.




-Ted

 

I knew that some of those passages snaked from a NA manifold I took apart once. Any way to test? Just hook up a pressure gague to each? If I get - and + pressure then Ill assume those are equal.

 

The reason I found out the hard way, was I plumbed one into my boost gauge, and it never saw vacuum.&nbsp It only moved under boost, and off-throttle it went downt to "0".

The only way I found out which went where was to use a length of hose and BLEW into it.&nbsp With the throttle body still bolted onto the upper intake manifold but the upper intake manifold unbolted off the engine, you listen to whether the sound was coming from the upper intake manifold (after TB) or from the front of the throttle body...



-Ted

 

...So are the ones that plum to the front of the throttle body and only see 0 and + boost ok to hook to the (SX) fuel pressure regulator? Does it only adjust under pressure or also vacuum?
~Jeremy

 

That's an interesting question...

When under vacuum, it's all going to be set at whatever base pressure you adjust the FPR, all the way up to 0 manifold.&nbsp What does matter is that it start to increase fuel rail pressure when you go into boost.&nbsp Oddly enough, in this case, it shouldn't matter if you take before or after the throttle body.

As a side note, you cannot do this with the STOCK FPR, since the stock FPR runs at 30psi of fuel rail pressure under vacuum and 35psi of fuel rail pressure anything above 0 manifold.&nbsp What this means is that the engine will run rich under all vacuum condition, including idle.

Did all of that make any sense???



-Ted

 

A stock fuel pressure regulator, with the engine at a boost pressure of 8-10 psi, will put out 50psi. Know it to be so because I attached a fuel pressure gauge to my windshield wiper and drove the thing at full boost while observing the fuel pressure gauge. Duplicated the same in the driveway using a Mittyvac on the fuel pressure regulator and putting 10psi on it while observing the patched in fuel pressure gauge. On the vac lines on the throttle body, I suggest taking it off and apart, lighting up a cigarette and blowing into the nipples to see where the smoke exits. The path from the oil injectors goes to the front of the throttle plates along with the path to the air bleeds for your primary injectors. Don't own a 90, just a 87 so I can't tell you where each goes, just that they ain't all vac coming out of the throttle body. Some are just looking for filtered air with no vac.

 

Well next time I take it apart I'll let you know which is which...

 

For what its worth....on a 87 turbo, there are four vac nipples on the back of the throttle body. The top three are all connected together inside the body and go to a approx 1/4 inch hole in front of the throttle plates. There is no vac on these. They are being supplied filtered air from the afm. The only one of the four nipples that has a vacuum , is the bottom one. Its source is behind the throttle plates, and it ends up servicing the double throttle diaphram on the front side of the throttle body. Of the ones that do not draw a vacuum from the body, the large one goes to the spider for the oil injectors. One of the other two smaller ones, feeds the primary air bleeds. The third gets capped off.

 

Also be careful with some of the hoses. I was only expecting to find one restrictor pill within the hose running to the pressure sensor, but have found others...specifically in the hose between the Tee and the wastegate actuator.

Some of the vacuum hoses have the restrictor pills purposefully to send accurate pressure information.

/F/

 

remember guys NOTHING is stock except the actual manifold...

 

ANSWERS!

Of the 3 nipples pointing to the FRONT of the car, the TOP and BOTTOM receive pressure and vacuum while the MIDDLE gets pressure only. Of the 3 nipples going to the REAR of the car, the TOP and MIDDLE receive pressure only, the BOTTOM I didnt test. The rear middle BTW is the one that goes to the oil injectors.

For my SX fuel pressure regulator, it does need to get a line with vacuum and pressure. I pulled the hose and set it at 55 psi. Then at idle with the hose re attached the fuel pressure is at 46 psi.

~Jeremy

 

Archive it!



-Ted

 

For the MAP sensor, would it matter if the vacuum hose is routed from the nipple on the back curve of the intake manifold pointing at the passenger wheel VS coming from one of the nipples just after the throttle body?

 

As long as it gets a the full range of manifold pressure, it doesn't matter.

 

I'm not so sure about that. As I understand, all fuel pressure regulators set fuel pressure at a certain pressure above absolute manifold pressure. With linear rate regulators (i.e. stock) the difference between manifold and fuel pressure is constant, in rising-rate regulators the difference rises as the manifold pressure rises, hence the name.
But in either case, if there is vacuum in the manifold, fuel pressure will be lower than if the manifold pressure was at atmospheric pressure, and the fuel maps will be set around this. If the FPR can't receive a manifold pressure signal below atmospheric, then whenever the engine is running with the manifold under vacuum, the fuel pressure will be higher than it is supposed to be, resulting in overly rich mixtures.
I hope that made some sense!

 

The problem is with your assumption. The stock FPR is only a two-stage FPR and can only run at two discrete fuel rail pressure levels.

At vacuum, the FPR runs at around 30psi of fuel rail pressure.
If you still have the stock FPR system (i.e. "orange" FPR solenoid) still active, the ECU switches the FPR vacuum lead to vent to atmosphere, effectively letting te FPR vacuum lead see "0" manifold.&nbsp This switches the FPR to run at 35psi of rail pressure.

The stock FPR is NOT anything close to a rising-rate FPR.

The TeamFC3S.Org guys (Gary Walker in particular) figured out that you can run boost on this line, so you can eliminate the solenoid and supporting vacuum hoses.&nbsp It still runs at around 35psi of rail pressure even if the FPR vacuum line is pressurized from + boost.



-Ted

 

RETED and heck, GARY WALKER. I really do disagree with you very much on this. That fuel pressure regulator is very much a variable one. I've proven it too many times on two different cars. Here's the deal. I have a fuel pressure gauge tee'd in the fuel line. Start the engine. Pull the vac line off the regulator. Put a Mittyvac on the regulator. Apply 10psi to the regulator. The fuel pressure WILL go to 50 psi. I can do this on a turbo or a n/a. Both do the same thing. With the turbo, I can drive it and go full boost and the fuel gauge goes to 50 psi. Its NOT a two stage regulator. Its variable b/t 28 to 50psi.

 

...time for the gloves

 

Dunno, my SPI fuel pressure gauge shows that it doesn't go over 40psi...



-Ted

 

I'll redo my little project using another fuel pressure gauge today. I've done it at least four times on two seperate cars with the same results. Gauge is two months old. Mechanical. Forty five bucks. Fuel pump jumpered. Read gauge. Apply 10 psi pressure to the nipple on the fuel regulator. Pressure rises to up to 50 psi. Not jump to 50, but rise to 50 depending on pressure applied. Like I say, I'll try another gauge. Not starting an arguement. Just that I see something different than what I am seeing in print. Both turbo and na do the same.

 

...why don't y'all just get a -10 an steel braided fuel line system with an SX fuel pump and regulator like me? you know you want that 1000 HP potential... hehe

For real though, anyone know where I can get a replacement filter element for my SX fuel filter?