HELP=Blow off valve popping hose off!

[Guest jjohart]

Hi, I've an 83 280ZXT 5 speed 2 + 2, with a NPR I/C, the usual K and N intake, a Greddy Profec B controller, a DSM generation1 blow off valve, as well as a modified pop off valve.

The plumbing system was "designed" and installed by Custom Tubes in Woburn, MA. I'm afraid the installer gave somewhat short shrift to the blow off valve, apparently using clear plastic 3" heat resistant tubing to tie the output of the turbo to the blow off valve: I don't have my digi cam, but when I get one I'll post the pic, but to illustrate in words, the damn hose has a slight kink where it comes out of the turbo, then it turns around and up in a letter C/90 curve and reverses direction to go over and around the other devices (e.g intake pipe) and connects to the BOV above the intake.

Whenever I get into the upper rev band, with my boost setting on hi and the dial at 3 o clock, IF I push in the clutch too fast, I can hear the pressure of the turbo litterally pop this hose off! Usually the car dies after that, and I go underhood and try to reattach it (it has popped at the turbo outlet, and at a plumber's joint that I created to lessen a secondary kink with a plumber's 90' copper piece and those plumber's clasp rings (that tighten with a screwdriver).

Oddly enough, the hose has never popped off the BOV fitting. My initial suspicion was that this crappy hosing is too constricted by the bends/kinks/connectors, so whatever PSI is going to the BOV must be not overly serious (I seriously doubt anything's wrong with the turbo, but with that hose popped, it sure runs like crap on or off boost!).

I am now wondering if I should replace the BOV, for perhaps it isn't opening fast enough in response to this sudden blast..I did have it tested for leaks, with a smoke machine, and it was fine, but IS THAT THE SAME AS IT BEING TOO SLOW TO OPEN? Are all BOV's the same in this way? I have noticed a Greddy type that has a "soft-hard" dial on the face of it, and two different sized fittings...is this a better option for me if I'm going to replace it, versus the DSMs that are all over Ebay..I doubt any of those are new!

Back to the plastic tubing, I was going to have my local shop try to find positive lock connector fittings and braided anodized "racing" application hosing...does anyone have any links to such stuff. I don't know how the mechanic would make threads or cleats for the fittings to connect on...any suggestions? The BIG THREAT to this is, hey, suppose it's my BOV and not the cheap hosing..if I put some kind of hose (or other metal pipes-custom of course) which are almost guaranteed to not break off, wouldn't that stuck BOV actually potentially cause turbo damage if the gases can't go out of it?!!!?

Can anyone suggest an order in which to go about replacing the items above? I don't have a non-stock boost gauge, but I am pretty sure I am in 14-15psi tops with this set up when I put the hi-boost dial up....I have tried living with it at a lower setting (12 o clock hi position) but I find there is a hold-back of boost once 12-13psi is reached, so accelleration suddenly becomes linear regardless of throttle position or gear selection...almost like a slingshot suddenly turning into an electric elevator, if you can imagine....)

Please give me some hints, as I can't believe the biggest problem I'm having with this whole set-up is over stupid plastic tubing and/or a BOV....I would think this would have been bulletproofed by the installer, but he seemed like he was ready to put everything together without a BOV at all! (BONUS QUESTION:I've heard of certain I/C'd turbocars not having blow off valves!? How do they get on without them, and should I start thinking about this, or will I be again risking turbo damage w.o?

Thanks

John

[SleeperZ]

I'm using the same (unmodified) DSM valve and running 16psi with no problems, either leaking or compressor surge. I suspect your problems are related to your plumbing, and it sounds shoddy the way you describe it. My plumbing is all hard lines, except for a rubber hose where the valve dumps back into the turbo inlet.

[Guest jjohart]

Ummm, not really sure about which rubber hose you are running...would you possibly be able to submit a pic?

Yes, the tubing is shoddy, but I still wonder if something else would blow up if it were tighter! Is that possible, when the turbo spools when the clutch is quickly pressed in at high revs, that if the gases weren't being allowed out of the BOV at all, wouldn't that force the turbo to crack up? I mean, as it is, when that hose pops, the sound is like a dentists drill suddenly turning into a high speed drill through Eddie Van Halen's Kramer guitar pickups....whathehellisthat!?!?!?!!!!!!!

John

[Cody 82 ZXT]

Sounds to me like your BOV is working perfectly and venting excess air into you clear hose the proublem is that your getting so much pressure build up in the hose that it is blowing off your connections. In my experience every place that there is a hose connection there must be a small ridge in the metal tube to make a mechanical obistical (sp) for the plastic or silicone hose to go over and the clamp to have something to help it hold onto the connection.

 

Check out this link and you'll see what I'm talking about.

http://www.roadraceengineering.com/eclipsetech/icpipebead.htm

 

Also quality clamps make a big differnce also check these.

http://www.roadraceengineering.com/hoseandclamps.htm

 

The clamps are down at the bottom of the page and can also be found at Napa. The hardware store stuff can be made to work but, the stuff that is purpase built for this is much better and easier to use.