PTE 6765 BB - Ported Shroud or Blow-off Valve?

[S2V6RACER]

Bob, I am measuring it right at the turbo outlet. I have a weld bung in the intercooler pipe after the connection. The intent was to measure pressure drop through the intercooler. It came in handy to try and get a idea what was happening to cause the blade to fail. After this pass, I noticed a little higher idle. The next pass it failed on decel. I overwrote the data on the return road messing around with the car. It would have been interesting to compare the two passes.

If I'm not mistaking the BOV should be open(ing) around the time the spike happens. Another lessen learned is maybe ease out of the throttle if you can, that might also help out, but who's thinking about that while you are worried about stopping.


The throttle body was a Holley with a billet AL blade. Not sure if it's a little more prone to bend than the other type of material, but the bottom line is it finished my year up a little early.

 

[HighPSI]

The graph would make more sense if the red and purple trace had the same scale. Either that or you have one heck of a restrictive intercooler The blowoff valve would open as soon as the red trace dropped. I think you might still see a slight pressure increase on the purple trace just before the valve pops.

 

[V6UnderPressure]

.... this would probably help to know too....

I know from personal experience, if i try to feather the boost on the highway [roughly between 10-15lbs] it will start to experience some surging....

low boost is fine, high boost is fine - just some times in the middle when i try to control boost with my foot....

i have not switched to a ported shroud hsg yet, but i will probably try it out just to compare.


HTH

[oh btw, i have a TiAL BOV with no ill effects, whether or not its saving my turbo, is negligible as i take care of my car and regularly maintain it..... but, it sure is purrrrrrdy:wink:]

This is a clear explanation on why a ported shroud would help. I had the same exact issue, and it is damn annoying. I even had it on my WRX when I had a larger turbo. While some may know 100 people that don't experience surge, theres a 100 that DO. My question would be...would the ported shroud eliminate enough surge thus decreasing the need for a BOV? People will sit there and say...BOV's are for manual transmission cars. Its because you close the throttle when you release it to shift in between gears and you need to relieve the backpressure. Just because we don't let off the throttle during accelleration, doesn't mean your foot is gonna stay there. It eventually has to come off, and if you are full boost and have to all of a sudden lift completely off the gas....guess what? You got surge. No matter how you look at it, its putting stress on the bearing.

However, if I could go with a ported shroud instead of a BOV, I'd love to go that route. Any turbo gurus in here available to provide feedback. Preferably someone directly from Precision.

 

[V6UnderPressure]

My general rule of thumb, when it comes to blow off valve on a Buick is this.
If the car runs a factory MAF sensor, a standard vent to atmosphere B/O valve could cause some driveability issues. When I have this question asked on a Buick application, my first questions are this.

- Will this be going on a daily driver application?
- Are we replacing a stock turbo with this new unit?
- What is your driving style, IE: do you do alot of partial or half throttle driving?
- Do you run a front mount intercooler?

Reasons:
A daily driver application will see more partial or half throttle driving behavior than a wham bam dragstrip only combination. With a stock turbo the air flow capabilities at 5-10psi are nowhere near as great, as say a 6262 at 10psi. And unless you have a built 235+ ci setup with good flowing heads and cam that can take the extra amount of air flow, you will see some surging issues. Especially on front mount applications. This was a very common issue with the old TE-44 and front mount combos back in the day. I personally saw it myself with my last car when I went from a TE-60R to a PT6776R straight S cover. Normal no boost or WOT was fine. But part throttle with a few 5-7psi would surge like crazy. I scored a deal from Don on his old PT6776R turbo with a ported shroud H cover and no more surging under the same conditions.

In some full race applications, (IE: high boost non daily driver style application) we have seen a slight loss in power on ported shroud comp covers vs straight inlet style comp covers. Exactly how much varies application to application. This is why we typically try to spec a ported shroud comp cover for street driven applications and a straight inlet style comp cover on a more race oriented application.

I personally do like to see a ported shroud comp cover on a street driven Turbo Buick, especially on a stock motor with a turbo sized from 6262 on up.
Hope some of this helps a little.

Patrick

Damn, Patrick, I need to read from the top down instead of the bottom up. Anyhow, that is good info. Could I get your feedback on my previous question? Would a ported shroud decrease the need for a Blow Off Valve?

 

[V6UnderPressure]

Hold on stop the presses...is there a thread here that really implys the use aof a BOV or that i may be an actual possibility??? LOL

:biggrin:

It's because most of all the buick guys (and all the rest of the american car guys) always wanna bash imports and don't want anything to do with the technology they are using, even though it may work.(It makes em feel like they are part of the "click" that hates imports) Kinda reminds me of Chicago Bears fans, they BELIEVE and BELIEVE that their team is good every year when they are naive to the fact that they really suck. Because HEY, its THEIR team! Anyhows, I got off topic. That's the whole reason everyone in the past got flamed for it in the first place. FTR, I am NOT one of those guys. I wouldn't drive an EVO if I was.

 

[turbo nasty]

Yeah I was Clowning. I for one have a Blitz SSBOV on my car. I had to do something the bucking post boost lifting was horrible.

IMO All Turbo buicks should have them..JMHO though

 

[RUQWKNF]

Damn, Patrick, I need to read from the top down instead of the bottom up. Anyhow, that is good info. Could I get your feedback on my previous question? Would a ported shroud decrease the need for a Blow Off Valve?

Yes, a ported shroud will decrease the need for a blow off valve, absolutely.

Patrick

 

[Quik Six]

I'm on my 5th turbo in 10 years and the changes were all due to upgrades and not failures. Until I saw this thread, I didn't know a ported shroud existed. I looked at some websites of Buick vendors and, in most cases, they are not shown in the pictures or shown as an option. Jack Cotton does display some with ported shrouds and I was very surprised to see there was no additional charge for the ported ones.

I haven't had any surge problems other than the noise and I do a lot of part throttle driving with an RJC controller and running 24# of boost. I used to use a KenneBell ram air setup for street driving simply to kill the noise.

I have to agree with Bison about use of BOV's on "mere mortal" Buicks but I will get a ported shroud next time for no other reason than looks.

Phil Engle

 

[Darkcyde]

Ive never ran a ported shroud or blow off valve and never had a thrust bearing problem. There are many pthers who have never run a blow off vlave and never had a problem. BB cartridge has a lot more thrust capacity than a journal. Guys with really large compressors (nothing TO3 style is large) run BOV to prevent the compressor nut from loosening. Imo those items are a big waste of $ and the $ could be spent elsewhere to improve performance.

funny thing is cars without a BOV are louder then cars with in my experience.

it is never a waste of $ to properly control the flow of air in a forced induction vehicle

a bov isn't bought to 'improve' performance but to make the process of generating, spooling, forcing, cooling, inducting, and exiting boost less stressful and thus it your motor is less stressed. another simpler way to put it is that I've never heard/read anyone say a BOV will increase their performance.

but then again I love tial more then precision, tial is one of the best products I know you can buy. never heard anything wrong with them other then dips not properly installing them or the springs, but as far as function wise, NEVER a peep from anyone negative about tial that I can recall.

$100-150 used for a tial BOV, a 15 second process just recovered a $100 tial BOV Tial Blow off valve BOV for $100 if its authentic is a GREAT deal Remember, ALL TIAL BOV's have serial numbers on them printed on the top, like in this picture. When searching for tial product always get this number and call tial themselves and verify its authenticity or product AND color. No matching numbers no sale.
http://s207.photobucket.com/albums/bb143/xXxDarksidexXx/?action=view&current=tial.jpg

step one: goto google
step two: type in 'tial bov craigslist'
step three: buy cheap and enjoy quality!

 

[Darkcyde]

I'm on my 5th turbo in 10 years and the changes were all due to upgrades and not failures. Until I saw this thread, I didn't know a ported shroud existed. I looked at some websites of Buick vendors and, in most cases, they are not shown in the pictures or shown as an option. Jack Cotton does display some with ported shrouds and I was very surprised to see there was no additional charge for the ported ones.

I haven't had any surge problems other than the noise and I do a lot of part throttle driving with an RJC controller and running 24# of boost. I used to use a KenneBell ram air setup for street driving simply to kill the noise.

I have to agree with Bison about use of BOV's on "mere mortal" Buicks but I will get a ported shroud next time for no other reason than looks.

Phil Engle

5th turbo? dude you can totally afford a $200 bov brand new, imagine if you bought one with your first turbo purchase, the SAME tial BOV would still be working on your 5th turbo today. A bov slide show of the same tial bov on 5 different turbos would be sweet.

 

[Quik Six]

PTE 6765 BB - Ported Shroud or Blow-off Valve

5th turbo? dude you can totally afford a $200 bov brand new, imagine if you bought one with your first turbo purchase, the SAME tial BOV would still be working on your 5th turbo today. A bov slide show of the same tial bov on 5 different turbos would be sweet.

Dude, you're right. I can totally afford a lot of things I don't need.

5 turbos in 10 years with no problems tells me it's not much of a problem for my car.

 

[V6UnderPressure]

funny thing is cars without a BOV are louder then cars with in my experience.

it is never a waste of $ to properly control the flow of air in a forced induction vehicle

a bov isn't bought to 'improve' performance but to make the process of generating, spooling, forcing, cooling, inducting, and exiting boost less stressful and thus it your motor is less stressed. another simpler way to put it is that I've never heard/read anyone say a BOV will increase their performance.

but then again I love tial more then precision, tial is one of the best products I know you can buy. never heard anything wrong with them other then dips not properly installing them or the springs, but as far as function wise, NEVER a peep from anyone negative about tial that I can recall.

$100-150 used for a tial BOV, a 15 second process just recovered a $100 tial BOV Tial Blow off valve BOV for $100 if its authentic is a GREAT deal Remember, ALL TIAL BOV's have serial numbers on them printed on the top, like in this picture. When searching for tial product always get this number and call tial themselves and verify its authenticity or product AND color. No matching numbers no sale.
tial.jpg picture by xXxDarksidexXx - Photobucket

step one: goto google
step two: type in 'tial bov craigslist'
step three: buy cheap and enjoy quality!

To follow up on this, it was addressed that many people who never used a blow off valve have never had any thrust bearing issues. I truly don't think its a valid point as how many of us have changed turbos within 25k miles due to us changing our minds or wanting more power. Id be curious to see how many people on here have run a single turbo 50k to 100k miles without a blow off valve and no issues. Im sure we wouldnt have alot of people fall in that category. Hell, I have owned 4 turbos in the past two years and have put ZERO miles on my car.:biggrin:

 

[Darkcyde]

a bov isn't bought to 'improve' performance but to make the process of generating, spooling, forcing, cooling, inducting, and exiting boost less stressful and thus it your motor is less stressed. another simpler way to put it is that I've never heard/read anyone say a BOV will increase their performance.

is the point but o well what do I know

 

[Eticket]

I put almost 40k on a PT52 in a street car running high 11's in street trim. Those were 40k in what I would consider "hard miles". 100mph each morning onto the freeway. This is for real, I'd put my lead foot against anyones.

Patrick (who is a turbo dealer) and S2v6racer layed out scenarios when a BOV would probably be necessary. Those haven't changed over the years. Although S2V6Racer and turbobob are talking about probably 8 sec cars when the poster is probably talking about the airflow of a 11 sec car.

If a person hasn't needed a BOV for the 10k miles that he/she used a turbo, then he/she didn't need that BOV. This is the cheap-finance guy coming out.

To each his own.

 

[Quik Six]

Good answer, John.

I remember that car well, you were always just a step ahead of me and liked to remind me of that.:smile:

Phil Engle

 

[V6UnderPressure]

I put almost 40k on a PT52 in a street car running high 11's in street trim. Those were 40k in what I would consider "hard miles". 100mph each morning onto the freeway. This is for real, I'd put my lead foot against anyones.

Patrick (who is a turbo dealer) and S2v6racer layed out scenarios when a BOV would probably be necessary. Those haven't changed over the years. Although S2V6Racer and turbobob are talking about probably 8 sec cars when the poster is probably talking about the airflow of a 11 sec car.

If a person hasn't needed a BOV for the 10k miles that he/she used a turbo, then he/she didn't need that BOV. This is the cheap-finance guy coming out.

To each his own.

That's a good point. I think everyone is diving into this too deep. Everyone who has a GN/T-Type experiences or has experienced the "flutter" when lifting off the throttle under boost. It's evidence that surge exists. This puts stress on the bearings. It's a FACT people. A BOV reduces the chances of this. As RUQWKNF has said, this is more pronounced on a street car with the stop and go driving. If people think a BOV will not reduce the stress, they are in denial. Just because your turbo didn't break in the 20k miles you used it doesn't mean you didn't NEED it.

I do disagree with the last statement of the 10k miles not needing a BOV though. How many times have you seen a 10k turbo go out. Hell, that thing's just getting broken in.

 

[bison]

To follow up on this, it was addressed that many people who never used a blow off valve have never had any thrust bearing issues. I truly don't think its a valid point as how many of us have changed turbos within 25k miles due to us changing our minds or wanting more power. Id be curious to see how many people on here have run a single turbo 50k to 100k miles without a blow off valve and no issues. Im sure we wouldnt have alot of people fall in that category. Hell, I have owned 4 turbos in the past two years and have put ZERO miles on my car.:biggrin:

I had one of the first 5 PT54 turbos Precision sold back in the late 90's. I had over 40k on it and never ran a blow off valve. Boost was over 22psi the whole time and the car ran 124mph in the quarter with it. It was driven hard every time i took it out. Thrust bearing failure is much more prone to happening from debris than from compressor surge.

 

[Eticket]

I do disagree with the last statement of the 10k miles not needing a BOV though. How many times have you seen a 10k turbo go out. Hell, that thing's just getting broken in.

I think you missed the point about the statement.:frown:

 

[V6UnderPressure]

I had one of the first 5 PT54 turbos Precision sold back in the late 90's. I had over 40k on it and never ran a blow off valve. Boost was over 22psi the whole time and the car ran 124mph in the quarter with it. It was driven hard every time i took it out. Thrust bearing failure is much more prone to happening from debris than from compressor surge.

I agree totally. I myself will probably just go with a ported shroud instead of a BOV as I need to use the money elsewhere. (pinching pennies to finish this car). However, if I had a turbo used for 100k miles with a BOV and one used for 100k miles without a blow off valve under the same conditions, I'd gladly put a years salary that the one without the BOV would show more bearing wear whether it be minimal or not.

 

[V6UnderPressure]

I think you missed the point about the statement.:frown:

Not at all.