Disappearing Boost Trick

[zeppenwolf]

I'm losing my boost.

The vacuum part of the dial seems completely normal, but on the boost side I'm down to a maximum of about 4 lbs, stepping on it like bigfoot. I've tried every bit o' advice that I could find this forum:

1) Wastegate arm: it takes a fair bit of force, but I can push the arm towards the wastegate and it will snap back by itself, making little whoosh noises out of the hose, (which I disconnected at the orifice to do this test). Guess that's ok.

2) Hoses: Took them all off and looked at them hard, and I don't see even the tiniest crack. The outlet hose looks like crud, (it's that smooth gray one, not the black weave one), and it looks kinda like a witche's face, but no holes or cracks.

3) Turbo: With the inlet hose off, I stuck my finger in there and spun the turbo wheel around-- completely smooth and easy.

4) Solenoids: Took em all off, and they all pass air from the middle inlet one to the bottom one, (if it exists), and they click and pass air to the top one by applying 15 volts, (I couldn't manufacture 12 easily). I think they're fine.

5) Vacuum Leak: I've just about completely replaced the entire emissions-hose business-- you know the story. It's not exactly stock, but pretty close, and more to the point, there ain't no way there's a leak in that part of things. I went spraying ether all over the place anyhow, and to the best I could I tried spraying on the manifolds gasket, but I can't find anything.

6) BOV: I can't blow up through the bottom to save my life. But with the eraser end of a pencil I can push (gently) the diaphragm up a bit. Anyway, guess that's ok too.

I'm running out of things to test or try. Um.... HELP!?!? I don't know how to test the MAP sensor itself, for one. And I hope nobody tells me to do a compression test, because if I'm losing that much boost through my rings then I guess I'm in some serious doodoo!

?!? Ack!

[Screamin4banger]

Here's a thought, did you check to make sure the throttle is opening all the way? Get a buddy to look under the hood (with the car off) as you "step on it like Bigfoot". then have your buddy make sure the throttle is open all the way.

[Sittn86]

When you replaced the vac/boost lines, did you run the wastegate directly off the intake manifold, or did you leave the solenoid & restrictor in place? Connecting it to the manifold will make it boost real low or not at all. Air may move through the wastegate solenoid, but does it block it properly? A leaky solenoid will do it, too.

[zeppenwolf]

Quote:

Originally Posted by Screamin4banger Here's a thought, did you check to make sure the throttle is opening all the way?

Ok, I did the Bigfoot Test(tm). With the pedal to the metal, the throttle plate is as level as I can tell with my fingers. In other words, it's completely open, as near as I can measure.

Sittn, my wastegate solenoid hose circuit is basically stock. For some ironic reason, the hoses connected directly to the turbo are the only ones I haven't had to replace-- I guess it's actually cooler down there than above the fuel rail area. (!) And those hoses have those nasty 'one-time-use' clamp things I didn't want to deal with. I replaced the nylon going across the engine to the solenoid, but the orifice down there, and the 2nd orifice at the Tee joint... it's all original, and just like the diagram.

Anything else I can try? I'm starting to get just a wee bit worried here...

[Screamin4banger]

Quote:

Originally Posted by zeppenwolf my wastegate solenoid hose circuit is basically stock. it's all original, and just like the diagram. Anything else I can try? I'm starting to get just a wee bit worried here...

I just want to double-check with you. Alot of people disagree on what is stock. Your lines are hooked up like this?


Just double-checking. It may be T'd differently, but as long as all the parts are where they should be and the solenoid isn't capped off.

P.S. I am not an artist

[shadetreeshop]

just run the line from the turbo port to the wastegate and be done with it.

[Sittn86]

^Uh, I think he wants his turbo to spool?

[zeppenwolf]

Quote:

Originally Posted by Screamin4banger I just want to double-check with you. Alot of people disagree on what is stock. Your lines are hooked up like this?

Yes, that's it exactly. Just like the underhood decal.

The orifice next to the turbo is orange; the one between solenoid and Tee is blue. I mention that because I think they're color coded.

The hoses directly on the turbo seem fine, but I haven't pulled them and inspected them, as I think I mentioned. Could *they* be the problem? I know from experience, (at the JY), that any mucking around with the orifice by the turbo will shatter it in a second, so I've held off on that so far.

Quote:

Originally Posted by Screamin4banger P.S. I am not an artist

Pshaw! The picture is great; it seems you must have a tablet.

[crusty shadow]

when my boost control setup was still stock, i had to replace the lines from the turbo wastegate and boost control solenoid- all were wasted.i ran a line from the nipple on the turbo( theres 2 i used the smaller one thats closer to the inlet where it was originaly) to a 'T' from the T i ran another line all the way to the solenoid, no orifice. and from the remaining nipple on the T i ran a line to the wastegate can with an orange oriface inline between the T and the wastegate can. the second oriface may be hurting you. the way the stock boost control works is like a bleed. when the solenoid is open and allows air to flow thru it you will get boost when it closes, air flow from the turbo goes to the wastegate can causing the wastegate to open , limiting boost. the extra orifice between the T and the solenoid will restric airflow, causing pressure to act on the wastegate can sooner. this may limit your boost as you are experiencing. the orifices are there to smooth out the action of the wastegate solenoid by restricting airflow and preventing the wastegate can from opening too fast. any clog or restriction between the T and the solenoid will kill boost. try running all new lines with just the orange orifice inline between the T and the wastegate can. you should be able to blow thru the lines fairly easily from the solenoid end, with most of the air coming out of the turbo nipple hose. if you think the solenoid may be the cause, then try using another solenoid- the EVAP solenoid will work fine, just swap em, and make sure they are both plugged in to avoid any codes.
if all that fails, and you're sure the turbo to throttle body hoses are all good and sealed and blow off valve doesnt leak, then try a manual boost controller. theres a guy selling manuals much like the "G" valves talked about on here, they are only 20 bucks and work great, very simple to install and adjust, probably easier than the G valve if you ask me. NSX motorsports on ebay. if you get one of those and still dont get boost, then shyt, um do a compression test.......lol

[scott_s]

I seem to have the same issue. I could only boost to 8psi, then 6 then 4-5 seems to be the max. I ruled out my BOV, and most of the hoses. Though I do not hear anything out of the ordinary when in boost.

[Screamin4banger]

I'm starting to think maybe the spring in the wastegate can could just be losing its strength. Leaky lines to the can or the solenoid wont cause under-boosting. I would reach down and try to pull (with the car cooled off) the wastgate arm out to open the wastegate. It should not be easy to pull out.

[Moparbishi]

if all this fails and you want to get dangerous, you can run the wastegate to open air!!:P
this will make max boost from the WG. just be careful. if it hits boost watch and make sure it don't go above 15.

i tke no promises on this advice....

[zeppenwolf]

Ok guys, I didn't manage my time very well last weekend, so I wasn't going to post until I had more to offer, but I also don't want to seem like I'm going to blow off (hee) all the help here, so... I'll just mention what I managed and what I hope to do next weekend.

Quote:

Originally Posted by Screamin4banger I would reach down and try to pull (with the car cooled off) the wastgate arm out to open the wastegate. It should not be easy to pull out.

OK, well that was already entered into evidence as Exhibit #1 in the first post, but I did it again, just for greater accuracy:

I can pull the arm, from the can towards the gate, and it will travel maybe a half inch, and of course it snaps back. It takes considerable force; it's hard to be really accurate with just my fingertips back there, but I'd guess it takes between 5 and 10 lbs.

While doing that, (since I'm leaning over the pass side fender), I can stick the hose-boot at the solenoid in my ear and hear it going Whoosh! / Shooow! as I go back / forth, so I've confirmed at the same time that the hose stuff works, at least mostly. Of course the orange orifice side could be all plugged up, but clearly the can to solenoid side is whooshing just fine.

****

The other thing I managed was what someone suggested above, swapping solenoids so that for the wastegate function I hijacked the usually purge canister solenoid. (The purge business I just plugged up for the day).

That was clever, but it makes no difference at all.

Next weekend, I guess I'll do all the digging necessary to replace the hoses around the turbo to the Tee, but honestly I don't have much faith in that; I'll do it just to completely eliminate the possibility of something funny there.

I also hope to somehow do a more meaningful test of the BOV. Is it possible for these to open up at 5 lbs instead of the 15ish ? Beyond that, the other options mentioned so far seem kind of desperate to me. Is there a way to test the MAP sensor?