Thaddeus

I am sorely tempted by the 'Forge' thread, but I don't want to spend 140 bucks if the mod does nothing. Pros? Cons? Skip? Danno? Anyone?

Thaddeus <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />

*WiZaRD- 951

I think it IS worthwhile, I do not remember where, but someone did a test with various blowoff valves, and his 1/4 mile was as much as .75seconds different from one to the next!! That's amazing, if it holds the boost for each shift better, sounds bitchen, and has a noticeable effect I'd say it's worth it ;-)

IanM

If you've got a notoriously tear-prone 951 BOV, vacuum test it and see if it holds a vacuum. If it doesn't, replace it with either a 993 BOV, or an aftermarket one like a Forge BOV. If yours works, then it works, and it's doing it's job. I don't think the stock Bosch BOV's are terribly undersized or anything, it's just that they're prone to fail.

Dave Bouzaglou

We concur with Ian M- the stock BOVs do fail with surprising regularity in performance applications.

Luke

seems that mine tore (really bad) just to shortly after I installed my LR wastegate. Man Are these car's ever sluggish with a torn blow off valve. Im' gonna get a forge unit (007 hopefully) I think the 006 looks to big.

Renntag

If there is boost pressure available more immediately between shifts...that is worth it alone.

Sounds good to me.

lou951

It's not a mod that will give you great performance results like a MAF or bigger turbo ect.. But it is a mod that will give you a seamless power delivery between shifts and will once and forever eliminate the tearing problem that plagues the stock BOV. It will give you crisper throttle response (to a point) and eliminate some of the "jerkiness" when coming off throttle at mid rpm's. That alone makes every other mod work better and in harmony. The fact that this piece is servicable makes it a life-long investment. Plus the simplicity in installation can't be beat. You can upgrade to bigger intercooler tubes and still use this piece. No need to upgrade and spend more.

Luke

I wouldn't even call it a mod. It's more like an "update".

John Anderson

My motto.....drive it til it breaks, then upgrade the hell out of it, waste gates, blow offs...if they work, they work...when they break, buy better :-)

I used my stocker wastegate on my older engine (2.7 liter) it held fine, boost was strong, remember, with a manual controller, if your waste gate is working, your telling it when to open.

I was also using the stock blowoff, at the time I was running 24psi on my stock lower end block laying down 371 at the tires...

I say, save your cash, and spend it on HP!

Danno

John got my kinda attitude! I hate upgrading perfectly working parts just to have them sitting uselessly around. That's why I drive like a madman in hopes that something will break so I can upgrade!

aka 951

I haven't said anything about this blow off yet as I'm not sure that it is really an upgrade. The most effective blow-off valve is one which prevents pressurized air from reverberating into the compressor's high pressure side when the throttle plate is slammed shut.

As you guys know the pressurized air coming back into the turbo can stall the compressor wheel and wreak havic on the turbo's bearings (bushings). It seems that the factory blow-off valve does this admirably by completely venting the pressurized air into the intake stream. As a matter of fact, the Porsche blow-off valve is ocnsidered an upgrade to many turbocharged Japanese imports.

A stiffer spring in the blow valve would tend to prevent all of the pressurized air from releasing from the intercooler and intercooler tubes in the manner described above. While this is advantageous for boost response as there is still pressurized air in the intercooler and intercooler pipes, it would seem to be a trade off as at least some of the pressurized air would reverberate back to the compressor and therefore stress the compressor wheel more so than the factory BOV. I think this would lead to decreased turbocharger life.

In reality the main reason why the blow-off valve fails is because the rubber diaphram ruptures and as a result pressurized air tends to escape into the intake via the BOV. If this happens then you do in fact need a new BOV. A tighter wound spring though - I'm not sure that's the best way to go. My car (turbo S) chirps the tires all the time. Boost response seems to be immediate when changing gears - therefore I don't see how potentially quicker boost response in between gears would make any difference - I've got all I want.

Luke

I guess there was enough difference between my stock wastegate and the LR unit to DESTROY my blow off valve on installation. <img src="graemlins/jumper.gif" border="0" alt="[jumper]" /> (if there are still people out there saying the LR's are no better)

Renntag

[quote]Originally posted by John Anderson:
[QB]My motto.....drive it til it breaks, then upgrade the hell out of it, waste gates, blow offs...if they work, they work...when they break, buy better :-)

QB]<hr></blockquote>

Yes, but upgrading early, you can sell your good parts to recover some of your upgrade cost.

I was able to afford new rubber more often when I was racing fulltime by selling my tires after a weekend to the street guys. I got money back, they got a deal....

lou951

AKA 951, I totally agree w/ you on the function of a BOV, but I think that you are missing the point. The Forge unit does not have a stiffer spring. It works at a correct preasure. The main benefit is that it will not tear. Since we agree that the stock ones tend to tear, that is where you can potentially cause damage to your turbo as it will have less control to keep it from spinning backwards. The Forge piece is just a better quality product which enables the preasure differential between the wastegate and throttle body to remain at a more controlled level when the throttle is slammed shut, hence better boost quality and more of it available when shiffting. The stock valve tends to leak preasure which is bad for both boost and the reason it is there in the first place, to prevent reverse rotation. Since I had to replace my BOV anyway, I invested in a better piece which is like a cheap insurance policy. It would be safe to say that there are many 951's and 952's out there w/ damaged stock BOV and the owners don't know it. It became apparent to me when I installed my MAF. The design of the MAF enables the turbo to be more audible. I would hear a horrible grinding sound when I got off the throttle. This led me to believe that my BOV was not working properly and the turbo bearings were suffering because of reverse pressure. Upon installation of the Forge BOV, that noise disappeared, replaced by a wonderful "FSSSS"-like sound.

aka 951

The stock 951 BOV's do tear - you are correct. The 993 upgrade (which is cheap - $30?) has a metal diaphram, does not tear and is a direct bolt in.