ct-26 popping/screaching

[Harley]

Alright, first off if anyone knows of a thread or answer to this, PLEASE link me to it, i don't want to waste anyone's time if i'm too dumb to have missed a thread on this!


Now for the problem, my dad and i just finished installing a turbo 7m into my originally non-turbo MA70.
we replaced all the heater hoses, vacuum hoses, pcv hoses, oil lines etc. but did not touch IC pipes, or anything "big", as such.
I originally had a 57 trim ct-26 from driftmotion to put on it, but for some reason the shaft has come loose and the compressor wheel started scraping on the housing, fortunately i cought it before it was too late. now i'm running the standard ct-26 which is exeriencing some problems of it's own.

We first took the car out the other day, we drive it for nearly 2-4 kilometres to get out of suburbia with no boost, changing at around 2-2500 rpms.
i put my foot down and it spooled up beautifully till 5-6 psi through third, fourth and fifth. i drove for about five minutes more and tried again and it made a loud "pop" noise and won't spool up.
We had a few vacuum hoses pop off/leaking which have all been fixed, the accordian pipe is secured, the intake "3000" pipe and all surroudingpipes are tight, new couplers put on etc. and i have double checked this to make sure there's no leaks.
Now whenever i drive it, the turbo starts to spool, makes this "pop" noise, (almost like a vacuum hose sucking in and stopping airflow) then it sounds like a turbo running a screamer pipe and sits on -4 vacuum and won't even reach 0, let alone a positive boost number.
Any ideas? hopefully it won't be an engine/turbo to the bin.
Once again thanks for any help/ideas anyone has.

 

[airhead04]

Is the bottom coupler that attaches to the turbo attached with a clamp on it?
I know my BOV clamp cam loose and would cause a nice POP then hiss really bad. And I could only make -5 vac.

 

[paradox616]

does it start to run rough when this happens? any black smoke out the exhaust? Reminds me of the noise when i forgot to tighten a hose clamp and metered air was venting before any pressure could build.

I'd go over every inch of the cooler piping, Are you still running the stock blow off valve?

 

[Bri7man]

Have you checked the fin condition after that?

 

[Harley]

Is the bottom coupler that attaches to the turbo attached with a clamp on it?
I know my BOV clamp cam loose and would cause a nice POP then hiss really bad. And I could only make -5 vac.

Yeah i made sure to double check that when the engine first went in, plus i have recently checked it too.
I bought a new clamp for it, as the old one was stuffed, so i know thats all good.

does it start to run rough when this happens? any black smoke out the exhaust? Reminds me of the noise when i forgot to tighten a hose clamp and metered air was venting before any pressure could build.

I'd go over every inch of the cooler piping, Are you still running the stock blow off valve?

Nah, it runs strong as ever, runs better than the N/A engine actually.
No smoke, got dad to follow me and it hasn't blown a single cloud.
Intercooler piping has been checked countless times, so as far as i can tell it's not the cooler piping.
Yeah i'm still using the stock BOV, but i disconnected it, blocked off the hoses (accordion hose, 3000 pipe and the vacuum hose) and it still did the exact same thing.

Have you checked the fin condition after that?

The fins on the compressor wheel are still fine (on a visable inspection), but i haven't checked the impeller wheel. There is slight shaftplay, but that was there before i put this old turbo back on, and it hadn't worsened, so i ruled that out.

My next step is to see if there's any oil getting to the turbo, because i put new suprasport braided lines on it, although when i took the 57 trim off there was plenty.
So we'll see how it goes, i'll post up results if i find anything.
But keep the help and feedback coming/thanks for all the help so far supramania!

 

[airhead04]

Yeah i'm still using the stock BOV, but i disconnected it, blocked off the hoses (accordion hose, 3000 pipe and the vacuum hose) and it still did the exact same thing.

So you ran the car without having anything connected to relieve the pressure??

 

[hvyman]

Dont take things off if you dont know what they do.

You prolly have a boost leak somewhere. Check all your ic pipes and make sure the lower hose at the turbo doesnt have a crack in it. Check all the plastic ic pipes for cracks around the seems.

You could also make a boost leak tester to make things easier.

Edit: i bet if you checked codes you would prolly have a 34.

 

[Harley]

I only ran the car without the BOV only long enough for one change of gears, and when it did the same thing i hooked it back up.
I know it causes compressor surge without it and ruins the turbo, so it's back on there, i just wanted to rule out the BOV creating the problem.

I did however get under the car and found alot of oil leaking out from somewhere, i'll investigate further tonight.
I'm thinking maybe there isn't enough lubrication in the turbo? Although when i took the 57 trim off there was plenty.
I'll see if thats the problem, hopefully it isn't too serious.

 

[airhead04]

I only ran the car without the BOV only long enough for one change of gears, and when it did the same thing i hooked it back up.
I know it causes compressor surge without it and ruins the turbo, so it's back on there, i just wanted to rule out the BOV creating the problem.

One change in gears is all it takes to completly destroy a turbo.

Anywho, find the oil leak, because you may have roasted your turbo if there isnt enough oil in it. Please for you turbos sake NEVER run it again without the bov/bypass valve. There is another way to test the bov, blowing air through it (off the car) is one way.