Why is a BOV ( blow off Valve) so improtant

[Air TGP]

why should i have a BOV , will it really heart my turbo ? will it give me better performance? will someone please tell me the the cold hard facts of the BOV and what they do?



dan
89 TGP red
stock but planning a lot

[RareGMFan]

I borrowed this excellent and simple description from www.turboste.com.  He also has nice directions on how to install them.  Go to his site, click on "Performance", then "Blow off valve".

"The idea of a blow off valve is to relieve boost pressure when you let off of the gas. This pressure is normally forced back through the intercooler and to the turbo when the throttle plate is closed (when you let off of the gas after flooring it). This almost brings the turbo compressor wheel to a stop (from 100,000 RPM), which means longer spool up time when you get back on the gas. It also causes un-needed wear and tear on the turbo. Since the Turbo STE is a MAP sensor operated vehicle, I don't have to re-route the blown-off air back to the turbo (not to mention, I have a cone filter on the turbo itself, so I'd have no easy way to route the air to the turbo anyway). If the Turbo STE was a MAF sensor operated vehicle, I'd have to route the air to the turbo. On the Turbo STE, since it has an automatic transmission, a Blow Off Valve is merely preventative maintenance, as it is not a requirement for normal vehicle operation. But after I installed it, and put my hand over the blow off port and felt the pressure it relieved, I'd never own a turbo car without one."

So, as you can see, is it essential?  Maybe not.  But it will definitely extend the life of your turbo (I can't imagine bring the compressor to a screaching hault from 100,000 RPM  :shock: ), and will improve your performance because the compressor doesn't have to start spooling up all over again from a complete stand still.  Definitely a beneficial feature to have.

[Air TGP]

thanks for the Info. i never really under stood how they work, now i do .



Dan
89 TGP red

[The Burning Rom]

eclipse5302's site isn't there anymore!  :shock:  :shock:  :shock: :(

BTW, does anyone know if you need a gasket between the BOV and the flange? I was thinking of actually working on installing my BOV this weekend..but I didn't know if I had everything needed.  :oops:

[god910]

I don't think I have the gasket on mine, but I can check tomorrow.  Damn I love that sound.  I've been thinking of going w/ an aftermarket BOV (I friggin swear mine is leaking a little up high)  But I can't see spending sooo much damn money on something that does little more than make a neat sound.  I know I need it, but I have one that does what it's supposed to.  The only reason I want to change is to get a better sound.  (NOT a good reason to spend over $200)

[Invasion1]

i just took my GEN I DSM BOV off the flange and there was no gasket  :)

dave

[Mick]

Well, that's not a good thing...  In its stock application on the turbo Eclipse/Talon's they DO use a gasket.

One could forego the use of a gasket with a very careful application of automotive grade RTV sealant.  However, if the small reference port is blocked by the sealant, the valve could be rendered inoperative.

The use of a BOV on an automatic trans equipped application offers very little performance benefit.  The throttle body plate that typically closes between shifts of a manual trans, does not close when an automatic shifts.

I used the GEN I BOV for my applications at one time.  I first purchased a slightly used one on ebay, but it produced a very obnoxious metalic squeak during valve operation.  Thinking it may have been defective, I decided to purchase a brand new one direct from Mitsubishi.. It had the same obnoxious squeak. :(
This probably has more to do with the fact that in a Fiero, you can hear just about any noise emitted from the engine bay, as the engine it is pretty much right behind and approx 1 ft. away from your ear.

[Invasion1]

so it is supose to have a gasket? in original applications?

mine will be going on a 5-speed 3.1

[Mick]

It does need to be very well sealed, however, when given the choice of doing so thru use of a gasket, or attempting to seal it with RTV, I would chose the gasket. :)

I mentioned the auto trans applicability, as I did not see any clarification of it on this thread.  We certainly would not want to encourage the stock transaxle (i.e. automatic) TGP owner's out there into needlessly buying and installing a BOV.

[Mick]

Jay :
Many of the conditions I have heard you describe could be an indication of either boost creep or surge.
What diameter exhaust are you running? With a cat or without? Any porting done to the exhaust side of the turbo?

One should optimally obtain max boost quickly, and this value should hold very steady.  If you overshoot the max specified (compressor surge), or if you are dropping from the max value without a corrsponding decrease in either load or rpm  (boost creep), then you may need to review the turbochargers flow charateristics, and possibly even make a few changes.

One or both of these situations can easily occur when increasing boost levels on a stock turbocharged system.

[The Burning Rom]

It doesn't have much of an impact on an automatic when shifting, BUT it still helps when you let off the gas completely.

And thanks for clarifying that it does indeed need a gasket. I have a brand new BOV from Mistubishi and a laster cut flange to install.  8)