Blow off valve, compressor surge, turbo problem, need advice.
 

Blow off valve, compressor surge, turbo problem, need advice.

First some history:
My stock HT-18 turbo locked up and trashed the hot side blades and compressor blades wile doing 120 mph 6 weeks ago.
Turbo had 76,000 miles on it, is stock with stock blow off valve. Car is a 87 rx7 turbo all stock except for cats removed, 3" down pipe to dual racing beat exhaust, fuel cut defender, and cone air filter. When I pulled the turbo off there was some rice size metal peaces in the exhaust side of the turbo. Sent the turbo to Kevin at Majestic Turbo in Waco, TX. Turns out the metal came from the hot side turbine housing, not my engine, so a new housing was used and the turbo rebuilt. It had new garret wheels installed and new internals. Slight upgrade recomended by Kevin- both housings were turned/enlarged to acomadate slightly larger wheels, the compressor wheel was a .57 trim- thats' what Kevin said, the turbin side I dont' know but it is larger than stock. Got the turbo reintalled and had only drove it a few times, 120 miles when it made a odd nois when I shut the car off. Next day start car and a odd noise from turbo, so pull air intake hose off and the bullet nut holding the compressor wheel falls out of the intake. The blades of the compressor are trashed. Shaft looks like no lock tite used. Sent it back to Majestic. Kevin thinks the .57 trim was to big and I got compressor surge when I closed the throtle, causing the wheel to spin backward. He thinks there was to much pressure cusing the surge, power wise it seemed the same. He is now rebuilding it with a .50 trim, still larger than stock.
It seemed like the stock blow off valve was not sounding the same and the turbo sure sounded differant.

I tested the blow off valve by puting 12-14 pounds vacume on it and it opens- could not find specs for how much vacume is requred.
My question- is there a better blow off valve that would release more pressure or release if faster than the stock 3/4" blow off valve or is enough? Do I need to up grade the BOV to prevent compressor surge? Is Majestic messin up my car?
I do not want to do major up grades.

what kind of "odd noise" are we talking about?? take your turbo back to majestic. tell them it fell apart while driving.
check out www.fc3spro.com ted has a section about noises coming from your turbo. that should help you alot.
If your hearing surge... how many lbs are your running and how hard do you drive it? A new BOV cant hurt especially if your hearing surge. They're adjustable and not tooo expensive $50-$250 depending on how much you want to spend.

It all really depends on the BOV you currently have, and how the spring pressure is set. What BOV did you use?

And the next question would be.. How did surge trash a turbo in less then 120 miles?

I don't think either of yall read the post very well, lol!

indycrpr: he did take it back to majestic and it is getting a .50 trim wheel now because the turbo guy thought that the .57 was to big.

j-rat: he wrote in his post that it is the stock bov.

Has the Stock BOV that came on 87, 3/4" dia. valve, hose and connection at riser pipe off turbo- reculates back into the air inlet duct. It opens under vacume when I put a vacume tester on it- takes about 15 pounds to open it fully. With the orginal turbo working I could hear the BOV working when I let off gas, but with the rebuilt and larger turbo from Majestic it seemed that the BOV was not working- could not hear back pressure being released. Is there a larger dia BOV that could fit the existing riser at the turbo and reculate into the air intake? Any place that sells a riser off the turbo with a BOV attachment? I just have the stock boost gauage so I don't know the psi at boost. Also I noticed the vacume hose from the upper intake manifold to to the boost sensor has a ristictor in the hose- could that affect pressure surge?

The noise from the turbo must haaave been the compressor blades rubbing the housing, tthen the nut knocking around. I drive it WOT sometimes- not redline though. Not sure what compressor surge sounds like

Thanks for the clarification.....

Then thats the problem...

The stock gauge can sometimes get you in trouble.
A mechanical boost gauge would really help you.
Even the cheap $15 ones work very well.

A minor point - Vacuum is usually stated in mm or inches of mercury (HG).
Boost is usually in PSI or KPA or Bars .

IF you weren't running high boost (over 12 or so) then the stocker should have been adequate...I've run full t04b hybrids on the stock bov before without issue, and they certainly move more air than the turbo you had built.

This just adds credibility to my theory that it's a real crapshoot getting a turbo rebuilt regardless of who's doing the rebuild. I had 10 in a row bad ones built by a turbo shop in Nashville, several of which had the compressor nut come off, several others leaked oil internally and externally. It seems that about half the time you get a good turbo rebuild, and the other half the time something is messed up, usually it's one of the 2 things mentioned above.