yes i checked that earlier, all is well, thanks. i did however find that my UIM IS CRACKED!!! pretty much all the way around the front nut that attaches the UIM to the LIM... i epoxied it for the time being (til i can get a new UIM) and it seems to be running smoother, idling smoother, etc. and i was thinking this was going to fix my boost problem, but it did not. owl is still "hooooing" under my hood.

 

ok update:

we removed all the intake pipes, resealed the UIM and all vacuum lines, problem still exists. we sealed up ALL possible boost leaks, so it must be a control issue.


i can boost up from 2500-7500 and the boost hits 8-9psi, then i hear the CRV release, then the boost drops to about 3psi. the boost pattern is like 8-5-3...
then if i let off and punch it again, as soon as i let off i get "HOOOO" coming from the passenger side/turbo area. if i let the engine cruise in vacuum for a few seconds and then punch it again, it will hit 8-5-3 again. its weird, if i punch it again too quickly after the bad boost pattern, it does the HOOOO owl noise when i let off...

 

Are you sure it's not your turbos themselves (IOW a hardware issue VS a control issue)? I still want to hear a sound clip BTW, if you have one of those little MP3 players (I have a Creative Muvo TX FM 512 MB) you can record sound digitally.

 

sounds like a job for a white T2 !!!

 

I intermittently get this owl noise as well.

 

Put a cat in the engine bay, maybe it will chase the owl out!

 

owl is still in the engine bay!! ahh!

 

No sound clip yet :/ Other than that, how's your car running?

 

maybe its chubaka

hes haunts me when i forget to connect vac lines

 

could the diaphragm on the actuator for the wastegate be cracked? When you reopen the throttle at high rpm, the flow through the wastegate will be a lot more and the crack in the diaphragm may open while the diaphragm is trying to pull the wastegate closed under the higher pressure. once the pressure drops with the rpm then it can pull it closed. that would explain why the boost pressure goes up some but not all the way. it's only strong enough to partially close the wastegate again.

 

if the wastegate isnt working (maybe due to a bad diaphram, bad signal, etc.) the flapper is stuck shut, not open, which would make boost shoot up too high, not too low.

also, the problem is after the transition. the boost is fine under 4500, then i hear the CRV, then i hear a turbo spool back up (probably the primary) and the boost drops and stays at around 3 til redline.

now i'm assuming that whichever solenoid controls the flapper on the y pipe is not functioning, because everything else seems fine: the primary spools up, the CRV blows off, i hear spooling again, then boost just drops. when i let off i hear "hooooo"

 

my car has this problem!

Sometimes it's fine WOT at high RPM and will make 10+psi, othertimes I get 7 no matter what and it makes the stupid owl noise during transition from vacuum to boost.

 

do you mean the transition from boost down to vacuum?

 

^ thaat made me LOL :]

 

My car is currently doing the exact same thing.

If I start out at a low RPM below say 2500 I get boost and a good transition. However once I let off and then apply throttle again at say 4500 I have about 3 or 4 pounds of boost followed by the owl sound.

On my car I won't hear the primary blow off when it's not working properly but when the system is good I can give it a little gas and hear the blow off. I'm convinced it has something to do with the Y pipe flapper not working properly but I've already replaced the CRV soleniod, the y pipe actuator solenoid, crv itself all the check valves and a few other things.

Click on the video link below and watch the video titled: BMW VIR skid pad and you'll hear the sound.

http://fritz.sysadmin-racing.com/

 

after doing a search I'm now leaning more towards the TCA pressure side solenoid.

 

i dont think it would be your turbo's themselves because my fd had the same problem and I had brand new 99 spec's. I tried to figure it out but got way to frustrated and eventually went to a gt35r single. my car did the exact same thing. primary boosted to 10psi then bogged to three and when I let off throttle it made that rediculous hoooo sound. never did figure out what it was so I'm gonna keep an eye on this thread. good luck with it.

 

i never figured it out guys, i went non-seq a few months ago.

 

Did you ever replace the turbo control solenoid in the rats nest?

 

i also went non-seq. a few months ago....but i still hear the owl every now and then....mostly after i let off from the first under-boost pull after it warms up. currently running the poor mans non-seq.

Drew

 

no sir i did not. replace yours and report back!

 

Will do.

I'm going to either set my car on fire or strangle the damn hoot owl but I WILL NOT go NON SEQUENTIAL.

 

Most of the time this is caused by the turbo control actuator. There are two lines that go to it....one on the side is for pressure and the one on top/middle is for vacuum. Apply vacuum to the top one and see if the actuator rod stays 'sucked in'. Normally the diaphram goes bad and you will see it leak back down which uses all the vacuum in the vacuum chamber. The charge control and charge relief lose their vacumm when this happens and those gates shut causing a loss in boost and also a surge on the secondary turbo. Since you are making boost only that is why when you let off you get your vacuum back and it starts making boost again only to fail. If that is fine look at the lines at the back ( underneath the connector ) of the charge control solenoid and charge relief as they are probably switched seeing that those connections are so close.

 

So far I've replaced these solenoids:
Both turbo control
Charge control
Charge relief
Purge for fun

All the check valves including the one between the fire wall and t-body. I have the symptoms related to the valve behind the t body being faulty. Improper boost unless the rpms go below 3k to 2500. It's obvious I have some sort of problem maintaining vacuum. It's probably the vacuum tank so I guess I'll be eliminating the PS as well lol

Removed the double throttle

Replaced the pressure chamber

installed a nice polished uim and new coils just for the hell of it

So when I get a chance I'll replace the turbo control actuator which doesn't seem to be leaking but I'll do anything before removing the pressure chamber hehe.

Apparently this Owl is a tuff little bird to get your hands on.

 

Fritz, et al:

There are two lines going to the butterfly in the y-pipe... try swapping them, and/or swapping where they are tapped into the nipples that go through the LIM... when I had this problem, it was because these weren't hooked up correctly, and believe me it's bloody irritating.

The TCA is a logical choice too... this sounds like it would be not transitioning to twin mode... mine had the opposite problem of not switching BACK from twin mode, so one run and the it sounded all farty... but not like an owl.

That owl sound is likely compressor surge... so something is pushing your boose back through the turbo, or restricting it from leaving... in otherwords, something ain't opening up where it should. That leads me to think it's the y-pipe, because if it was the TCA, it would just stop making boost in the first place.