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

[thrlskr]

Going to be installing a new 6765 BB/Billet wheel w/ 4 bolt housing in the next month. To extend the Turbo life and protect against compressor surge should I go with the ported shroud or tial 50MM blow off valve...or both?

Also - This will be on factory shortblock so my boost levels will be modest (ie not TSM levels) until I can build a motor.

Thanks,

Bill

 

[bison]

Going to be installing a new 6765 BB/Billet wheel w/ 4 bolt housing in the next month. To extend the Turbo life and protect against compressor surge should I go with the ported shroud or tial 50MM blow off valve...or both?

Also - This will be on factory shortblock so my boost levels will be modest (ie not TSM levels) until I can build a motor.

Thanks,

Bill

Ported shroud is not needed. Blow off valve not needed. Chances are you will be running more boost than TSM.

 

[GNBRETT]

I went with the Tial 50 mm BOV for mine but im not really sure it does anything other then look kool. It does match my WG tho They are pricey. I think it's more of a novelty then anything.

 

[wickedtt]

Ported shroud is not needed. Blow off valve not needed. Chances are you will be running more boost than TSM.

Wouldn't that ported shroud help divert some of the air rushing back up against to the compressor wheel once you let off the throttle after a wot blast. I could be wrong but I thought it was easier on the turbobearing especially with that size turbo. Would it hurt anything to run the ported housing?

 

[bison]

Wouldn't that ported shroud help divert some of the air rushing back up against to the compressor wheel once you let off the throttle after a wot blast. I could be wrong but I thought it was easier on the turbobearing especially with that size turbo. Would it hurt anything to run the ported housing?

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.

 

[thrlskr]

Bison - Thanks for the response. Otto and I have been debating it as he is doing the work on my car and we are going to order the Turbo early next week.

Does the ported shroud impact spooling at all?

 

[GNBRETT]

Bison - Thanks for the response. Otto and I have been debating it as he is doing the work on my car and we are going to order the Turbo early next week.

Does the ported shroud impact spooling at all?

You need to get a Tial to match ur WG

 

[Royal-T-Ltd]

street or race car?

.... 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:]

 

[D's GN]

.... 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.


The midrange boost / part throttle bucking or surging will disappear with a ported shroud. The pic below is of my GTK turbo with the bullet ported shroud which works nicely, Precision uses a different type of shroud which works the same way (check out GNBRETT's turbo thread). As a bonus the air recirculating in the ported shroud will change the way the turbo sounds, mine "whistles" like crazy.

 

[bison]

Bison - Thanks for the response. Otto and I have been debating it as he is doing the work on my car and we are going to order the Turbo early next week.

Does the ported shroud impact spooling at all?

I doubt it would do anything to affect the spool but i cant see it helping power if running the turbo hard. Id expect it to actually hurt efficiency a little.

 

[QWIKWE4]

I just ordered a ported shroud compressor housing for my DBB 6265s. I'm also using a T4 turbine housing. Right now if I drive under part throttle acceleration (8-12psi) I experience compressor surging, only if the car shifts and the rpm drops though. It's quite annoying. Should get the new compressor housing Friday or early next week. I'll let you know how it works.

 

[2QUICK2B6]

ordered my billet turbo without ported shroud glad i did . BTW my 6768 is alot quieter than my TE-60 .... everyone usta think i had a monster turbo on my car by the sound of the TE-60

 

[S2V6RACER]

I folded in my throttle body blade last time out when I lifted after the pass. I checked the logs and there is no doubt a BOV will help make things easier on the parts. The other thing you need to think about is what happens to the throttle blade when you lift. Pressure outside it and vacuum inside. I feel as you turn things up it gets a lot more hostile on the parts and that is where it will come as the most benefit. I am going to a Procharger BOV next season and will be able to do some nice comparison data from this year with and without....

 

[TurboBob]

there was a big intercooler at BG a few years ago with a split end tank. In my opinion it most likely happened at the end of the run when the throttle was dropped. There is a large pressure spike in the intercooler and piping at that moment.

The big turbo v8 guys run BOV's, I asked one guy how they choose the valve, and he said they keep adding BOV's until the intercooler connector hoses don't blow off any more.

The car I was looking at had 2 BIG ones at the time.

Bob

 

[RUQWKNF]

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.

Ported Shroud 6262S

Straight inlet 6765S

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

 

[S2V6RACER]

Bob, I log my turbo out PSI and checked the boost spike when I lifted. about .8 psi for less than 1 second. I would be curious what others have found. The scary thing is for about 2 seconds there is a differential of 30+ psi on the blade (mine this would be different at different boost levels) and obviously that boost is pushing back through the compressor since is has nowhere else to go. It is relatively smooth drop not pulses.

 

[TurboBob]

i'll check with Matt and see if they have any logs from the red car.

Stenod Performance Photo Gallery - Tom's "Red Rocket" Turbo Camaro

the BOV is under the front fascia. there are a couple pics showing it.

Bob

 

[turbo nasty]

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:

 

[S2V6RACER]

Here is a snip of what happens when you let off the gas at the end of the track.

Bottom purple trace: Turbo outlet PSI
Light blue: TPS %
Green: RPM
Red: Manifold Boost
The spike in the purple was 8 psi not .8(error in above post)


Resolution 50 frames/second.

 

[TurboBob]

where are you measuring the pre-throttle pressure?

considering the speed of the airflow when the throttle is dropped, I would bet the pressure at the throttle blade is higher.

But, I don't have any data to back it up.

Note: I have a RFL blow-off valve on my car.

Bob