Why no blow off valves?

Berman

New Member
Joined
Mar 24, 2002
My only previous turbo car was a AWD Eclipse. It came with a BOV from the factory, and everybody upgrades the BOV on it. Why do I rarely see modded GN's running BOV's? Is it had to get tuned right? I don't see how, it was easy as hell on my dsm. But the GN is a different beast obviously..

Thinking that some turbo sneeze would be cool :D What bov's do you guys use when they are used? Use the jap ones like HKS or Greddy? (i had a greddy and thought it sounded really cool, the hks sounds like more of a phhhhhh than a sneeze).
 
How does one work anyways? I am :confused: on the inner workings of the unit. Would there be a downside to it on a TR?
 
Originally posted by Berman
My only previous turbo car was a AWD Eclipse. It came with a BOV from the factory, and everybody upgrades the BOV on it. Why do I rarely see modded GN's running BOV's?

While accelerating a GN your throttle blade is open all the time....most of the factory BOV equipped cars are standards and you close the throttle blade (lift the go pedal) with each shift. The sudden stop of the charge air is very hard on the turbo.

Over the years I've gotten into the habit of lifting slowly at the top end of the track. Easier on the turbo but harder on the brakes. :)
 
Re: Re: Why no blow off valves?

Originally posted by ChrisCairns


While accelerating a GN your throttle blade is open all the time....most of the factory BOV equipped cars are standards and you close the throttle blade (lift the go pedal) with each shift. The sudden stop of the charge air is very hard on the turbo.

Over the years I've gotten into the habit of lifting slowly at the top end of the track. Easier on the turbo but harder on the brakes. :)

Doh. My dsm was a stick car. Don't know why I didn't think of that. It still seems like a BOV could help for when you are under boost and totally get off the gas..

So do you guys get compressor surge? It sounds funky on the dsms anyway (I had a 16G turbo). My GN needs some more work before it's ready for street duty.. (need to fix the brakes. i figure that's kinda important)
 
a Problem i have seen with my bov, is at around 0 boost or 1psi when im merging on to the highway the valve starts openeing and closing rapidly, kind of fluttering and making a ton of noise. I might be able to adjust this, i just havent had the time to play with it. I have a turbo XS valve.


Mike
 
By-pass valve

The valve has a diaphragm inside which is sealed from the outside air (bottom half vented) when you attach a vacuum/boost hose on top of it, so when you are on boost , the pressure will keep the valve closed, but when you lift off the throttle and you go to vacuum , you pull the valve open releasing the boost .............. When you back off the throttle (close) at high boost you still have pressure in the intercooler and pipes . This pressure tries to go in reverse back out the turbo inlet, stopping your compressor (the hissing , coughing sound you hear), the by-pass valve releases it :) alan
 
Re: Re: Re: Why no blow off valves?

Originally posted by Berman

So do you guys get compressor surge?

Running mid 11's and quicker in a car originally intended to run mid 14's is the main reason some of us get compressor surge. A T-R makes so much torque that sometimes you don't feel like you need full throttle to do what you need to do. When you don't use full throttle, you open yourself up for compressor surge.
 
Seems like a Blow Off Valve would be a good idea! How come not many TR owners use them??? If you spend money on an upgraded turbo...,then a BOV sound like it might extend the longevity of the turbo.
 
I have a blow off valve installed on my buick with the pt54. To the one that had the problem about it opening and closing rapidly at 0 or 1 psi, you just need to tighten the screw. mind was doing it at idle and making it run rough. I run an HKS. I have the screw all the way down as far as it goes and it finally fixed the problem. now at idle it stays closed and under pressure it stays closed, of course due to the fact it runs off the vacuum line. then once you let off the gas the vacuum sucks that valve open and lets out all the boost pressure that would have gone back to the turbo and driven the shaft against the bearing. But as someone stated its mostly for sticks, but could save money even on gns. some people see no use, and others swear by em. Guess its your own choice.

Scott
 
I run a 1st Gen Mutsi BOV on my GN.
With a 60 series turbo seems like a good idea.
I did the mod of adding the extra port to it so that it doesn't open at 16 PSI. I run 21-28 PSI of boost and it seems fine.
As for making sound effects, I couldn't care less.
 
If you spend money on an upgraded turbo...,then a BOV sound like it might extend the longevity of the turbo
My stock turbo has 180,000 miles, and is still Ok (knock on wood) So, how much benefit would I have gained from spending several hundred dollars on a blow-off valve? There are folks with turbo Buicks and blow-off valves, but for most of us, there are many, many other things that provide more benefit for the dollar. (Bang-for-the-buck doesn't sound good when your talking about a turbo Buick- something about head gaskets?) A blow-off valve, in some installations, helps to maintain boost between shifts on a stick shift car. That function isn't needed on the Buicks, either.
 
A blow off valve probably isn't going to prolong the life of a smaller stock turbo. Step up to a 66 or larger and the sheer weight of the rotating assembly is rougher on the thrust bearing under compressor surge, even the later 3 bolt thrust bearings won't handle it if abused. That's why there are better bang for the buck improvements for stockers, they don't need a BOV.
 
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