Fact or Fable?

[Dus10R]

Having read many posts and blogs on numerous forums regarding modifying TT's, I keep coming across a common recommendation to change out the stock diverters valves, hereby referred to as BOV's. Most topics on the subject claim that the stock BOV's either leak or fail if running higher boost applications. After consulting a friend of mine that works for a very well established Porsche tuner and repair shop, races a 993TT Cup car and is teamed with a friend that races a 996TT cup car, I came away with the impression that our stock BOV's are more than capable of doing their job. Matt's 996TT makes around 700hp and he still uses the stock bov's and said that he thinks the rumor was started by parts suppliers just wanting to sell some of their parts. Not knowing enough about it to argue either way I figured I'd post this poll to see if there is any legitimacy to the claims.

Edited February 6, 2008 by Dus10R

[Dus10R]

Another question... does anybody know if the stock BOV's are "pull" or "push" types.

[Chuck Jones]

I switched just kuz....and I got a good deal on a set of EVO diverter valves. After I switched, I noticed that I got more or less the same boost numbers that I got before I switched...which is about .9 to 1.0 on my X50. Since the stock DV's use a diaphram, it can tear and will show up as lower boost output. Apparently, the cheap plastic stock ones are prone to failure, hence the recommendation to replace them. The billet DV's can be disassembled periodically and cleaned/lubricated for continued service. Since they come apart, you can also either change the springs or shim them for more boost pressure. I won't mess with the spring pressures.

Just remember that whichever you choose to buy, make sure that the vacuum hose attachment on the top comes off at a 90 degree angle....much easier to install. Some of the replacement DV's are larger and have little or no clearance between the top of the DV and the engine housing.

[wross996TT]

DV's are not blow off valves (BOV).... So the deal is the stock DVs are fine for performance...the issue is that when they go the pieces go into the turbos...that can get expensive. My tuner has seen the effects of DVs disintegrating into the turbo (he builds and rebuilds turbos). So it is just not worth the chance.

Edited February 10, 2008 by wross996TT

[Dus10R]

DV's are not blow off valves (BOV).... So the deal is the stock DVs are fine for performance...the issue is that when they go the pieces go into the turbos...that can get expensive. My tuner has seen the effects of DVs disintegrating into the turbo (he builds and rebuilds turbos). So it is just not worth the chance.

Okay, a matter of symantics I guess... a BOV vents to atmosphere and a diverter recirculates the excess back into the intake track. As far as them comming apart; that's why this poll is here. I'm told that it is a myth among Turbo owners, so i wanted to see how many owners have actually had a problem with the "Diverter" valves. Don't you think that if a $100 part was causing catastropic failure of a $3,000 part (turbo) that Porsche would issue a TSB or a recall so as to save themselves from expensive warranty repairs? Like I said, I have a friend that runs the stockers on his race car with no problems.

[wross996TT]

Okay, a matter of symantics I guess... a BOV vents to atmosphere and a diverter recirculates the excess back into the intake track.

That would not be symantics.

As far as them comming apart; that's why this poll is here. I'm told that it is a myth among Turbo owners, so i wanted to see how many owners have actually had a problem with the "Diverter" valves. Don't you think that if a $100 part was causing catastropic failure of a $3,000 part (turbo) that Porsche would issue a TSB or a recall so as to save themselves from expensive warranty repairs? Like I said, I have a friend that runs the stockers on his race car with no problems.

If you want some real information, why don't you just ask some of the folks that do repairs (rather than owners). The DVs probably do not fail under warranty with stock systems (hence no concern from Porsche for warranty repairs). The problem is with modding (boosting 1.2 plus). This the stock DVs do not handle as well... I'm glad your friend runs his "race car" and is willing to redo the turbos...that of course is his choice. Most folks that actually have "race cars" rebuild their engines anyway so who cares what they run?

[Dus10R]

Okay, a matter of symantics I guess... a BOV vents to atmosphere and a diverter recirculates the excess back into the intake track.

That would not be symantics.

As far as them comming apart; that's why this poll is here. I'm told that it is a myth among Turbo owners, so i wanted to see how many owners have actually had a problem with the "Diverter" valves. Don't you think that if a $100 part was causing catastropic failure of a $3,000 part (turbo) that Porsche would issue a TSB or a recall so as to save themselves from expensive warranty repairs? Like I said, I have a friend that runs the stockers on his race car with no problems.

If you want some real information, why don't you just ask some of the folks that do repairs (rather than owners). The DVs probably do not fail under warranty with stock systems (hence no concern from Porsche for warranty repairs). The problem is with modding (boosting 1.2 plus). This the stock DVs do not handle as well... I'm glad your friend runs his "race car" and is willing to redo the turbos...that of course is his choice. Most folks that actually have "race cars" rebuild their engines anyway so who cares what they run?

The guys that I'm talking to ARE Porsche mechanics; they also race. They both work for a shop called Sport Haus; one is the head tech and the other is the parts guys. The shop has been around for over 30 years, so yes they know Porsche's pretty darn well. And although there's only 14 votes, I don't even see 1 that says failure or leak...

If you have a turbo please vote...

[wross996TT]

The guys that I'm talking to ARE Porsche mechanics; they also race. They both work for a shop called Sport Haus; one is the head tech and the other is the parts guys. The shop has been around for over 30 years, so yes they know Porsche's pretty darn well. And although there's only 14 votes, I don't even see 1 that says failure or leak...

If you have a turbo please vote...

I'm sorry, I was not meaning to be derogatory. My point is you can not conduct a survey with any legitimacy using your current poll. This is why I suggested you actually talk to a number of folks that work on these cars (not just the ONE shop you deal with). If you search on Rennlist and 6speed, you will find plenty of folks that have had problems with their DVs.

Post #49

Bad DV

another

More with pics

yet another