Black51

So a couple weeks ago, I installed a wideband, and mounted the gauge, along with a boost gauge and the MBC under the radio. Since then, it seems like the boost is not coming on like usual. What I mean by that is in 1st and 2nd gears, no matter how far I turn the MBC **** one way or another, it seems to have no effect on the boost level. It just goes to about 12-13psi, and seemingly more laggy than usual (although that might just be because it's warmer now).

On the other hand, when in 3rd gear, the boost will go up to the set boost level, and 4th will go higher. I've seen it spike up to 20psi in 4th and hold there until letting off the throttle. Yet in 2nd, it would still only be going to 12-13psi...

Does this sound like a MBC problem, a vac line problem, WG, or something else? I haven't done anything else since installing the wideband.

onspeed

MBC or vac line issue I think. Stock wastegate? If it's a LR or Tial unit, be sure you've got the MBC hooked up right. If it stock, then that's idiot proof.

Paulyy

yes ,check your vac lines to the wastegate

Black51

It's a LR dual port. The line is hooked up to the WG, I checked. Now, the line from the WG, does it go to the nipple with the arrow or the other one?

Paulyy

This is how the LR dual port should be connected

Black51

Thanks Paulyy. Where'd you get that vac line diagram? It's a gooder.

Paulyy

No problem
i got bored so i drew one for my self when i took all my vac lines off to replace.

I've got 2 that one and another one for the TiAL WG setup which the 2 vac lines at the WG are swapped around.

i got most of the info from the lindey diagram and added more myself.

Black51

Well, it 'seem' to want to get into boost a lot sooner now. Still only goes up to about 13psi in 2nd. I'm assuming that is because it's only an MBC, and not an electronic controller past that. 3rd goes higher, and 4th higher yet. I can't remember how boost came on in 2nd in previous years if it was like that, but either way, it appears the lines were backwards.

I noticed my my line that feeds into the boost system is attached at the manifold, rather than on the boost pipe, but I doubt that matters. I guess an advantage to having it on the boost pipe would be that the WG would open earlier, mechanically preventing boost spike.

Thanks Paulyy.

onspeed

If im not mistaken, the boost pipe is never under vacuum. Having the top diaphragm port hooked to the intake would cause the wastegate to be open when you're under vacuum. Might contribute to your boost issue. Fix that and get the lines sorted and you should be in good shape.

Black51

So how would I hook a line up to the boost pipe? I've never seen a 951 with a vac line attached to a boost pipe. Isn't stock setup with the line attached to the manifold?

EDIT: Ohh, I see what you're saying. The top port is hooked directly to the MBC now. The side port is hooked up to the manifold IIRC.

Black51

K wait, now I'm confused lol. I'll have to go look at it to see what's hooked up where...

onspeed

Your vac line for the wastegate should be coming from the turbo to intercooler pipe. You should put a vacuum T along this line, sending one end off to the top port of the LR wastegate unrestricted, and the other end to the MBC then to the side port of the LR wastegate. Refer to Paulyy's diagram if it doesn't make sense in words.

If it's a Tial wastegate, then it's reversed. MBC goes to top port on the Tial and the unrestricted line from the IC pipe goes to the side port. Just in case those with a Tial were confused.

There shouldn't be any line going from the intake manifold to the wastegate, in a typical configuration.

Paulyy

I think you should double check what you've done. The top port goes to a T which 1 goes to the ice pipe and other goes to the mbc

Willard Bridgham 3

Go back, start again and follow the LR diagram.....it's pretty fool resistant.

Black51

The only thing that is confusing me is that I've never seen a WG line hooked up to a boost pipe. Now I'm being told that if the line is hooked up to the manifold, the WG will open under vacuum...

I can't see why it is necessary to hook up a line to the boost pipe, since either way, air under boost or vacuum is passing through both systems.