DBB 6776 & Boost Creep

[BMF_Racing]

Well just did the first tuning session after installing the DBB 6776, 62mm hemco w/62mm TB and big FMIC. The engine is stock unopened, other than valve springs.(may be another reason for overboost with small head/intake) I was very happy with everything but cant contol the boost from creeping.

The boost is 21 to 22psi in 1st & 2nd and in 3rd it creeps higher and higher (boost gauge is only 20 psi for now). The car has THDP with 1.5" puck. Before the install, I did machine and ported the a/r housing's wastegate hole out to 1.375" to try to help with boost creep that I read about on the forums. I do have the MAFT Pro on the car with Boost Controler but not hooked up, just a vaccum line to the WGA with no preload on the WG arm (arm is loose and can giggle with your fingers). I can loosen it more but it just causes lots of turbo lag and still eventually gets over 20 psi in 3rd. The WGA is the low pressure one from Full Throttle. Is there anyway to control the boost to lower it in 3rd?
I would like to run arount 19 to 20 in all gears, but don't know if I need to take the A/R off and machine it bigger and get a different puck for the THDP to accomplish that or if theres something else I can do to help?

 

[BMF_Racing]

Lots of lookers, no opinions? Does anyone else with a 6776 have stock motor and have or has had similar issues?

-It spools up very fast, with the wastegate arm just slid on the flapper arm with no preload, it almost hits and passes by 20psi at just 3000 rpm.:smile:


Anyone ?

 

[Brer Rabbit]

OK, Ill try..

Not really what ur looking for but I run my 6776 BB with an external wastegate that is fed by exhaust before the turbo. 0 boost creep with this set up. However I would not be concerned with a lil boost creep--U have alky and that turbo is crazy at 26lbs. anyway. So I say let it creep.

 

[TKGN1]

I had/have the same issue. I could not get boost below 30 lbs before porting the wg hole. After porting the wg hole lowest I can get is 23. It will creep from 23 lbs to around 24-25 lbs. 93 oct with alky (and FAST) I get no knock so, gonna leave it at that level. The 6776 moves a ton of air, so without going external wg I believe 23 is gonna be the low limit on my car.
I also have the vac line going straight from the turbo to the WGA to get max opening.
HTH

 

[salvageV6]

No issues at all with a DBB p-trim 70 on a stock motor and a BSTC with 2 solenoids and a HD stock type wastegate system, THDP.

About 19 to 27 psi. control.

No front mount stock location V4, 62mm T.B.

About a 1.080" hole in the turbo housing. Garrett I believe.

I think there may be other issues there, not quite sure what however.

 

[BMF_Racing]

I think there may be other issues there, not quite sure what however.

I'm going to re-do my vaccum to see if that is it. Where is the best place ? (on the compressor housing?)

 

[power6usa]

Had the same problem with boost creep. You have to port the wastegate hole. I left between a 1/8 and a 1/16" around the edges so the puck seals. Use the carbon marks as a guide many pucks are not centered.

 

[BMF_Racing]

Had the same problem with boost creep. You have to port the wastegate hole. I left between a 1/8 and a 1/16" around the edges so the puck seals. Use the carbon marks as a guide many pucks are not centered.

The wastwgate hole was just over an 1.0" when I got the turbo and I did machine & port it out the wastgate hole before turbo was installed. Final hole size is 1.375" and the DP has 1.5" puck, giving only 0.0625" of sealing area around the hole.

I would like to get the boost down to 19 ish because for now the trans/converter is stock and I have the feeling they will not last too long with 22 + psi of boost from the 6776. :frown:

I'm going to redo the vaccum line going to the WGA this weekend to see if that helps? Where is the best/strongest source for the WGA?

 

[BMF_Racing]

Well after picking at Patrick's mind and some helpful suggestions from him, I found out that Lo-pressure WGA that I ordered was delivered as a HI-pressure WGA. I changed it out to a stock actuator and sure enough 14 psi of boost in 1st & 2nd and 15 psi in 3rd gear. Even at those boost levels the car is very impressive, not sure that stock trans is going to like all this new found power. Guess we will see, just hope it lasts till the GS nats.

Brad

 

[Big Turbo Scott]

Well after picking at Patrick's mind and some helpful suggestions from him, I found out that Lo-pressure WGA that I ordered was delivered as a HI-pressure WGA. I changed it out to a stock actuator and sure enough 14 psi of boost in 1st & 2nd and 15 psi in 3rd gear. Even at those boost levels the car is very impressive, not sure that stock trans is going to like all this new found power. Guess we will see, just hope it lasts till the GS nats.

Brad

Hey Brad, what kind of mileage you get from that srt4?

Scott

 

[BMF_Racing]

Hey Brad, what kind of mileage you get from that srt4?

Scott

Well it depends. I have a DTEC fuel controller on that car that I use with a gameboy to tune the car. With that I have had 28.8 mpg highway. The best before the FC was when it was stock with just the stage 2 kit (came with stage 2 from factory) was 27 mpg. But when I'm beating on it, mpg drops to the 22 mpg area, never less than 21mpg.

 

[conn84gn]

What stall converter are you using?
I know you said stock tranny but I didn't catch the stall

 

[BMF_Racing]

What stall converter are you using?
I know you said stock tranny but I didn't catch the stall

its all stock, including TQ converter. Once it gets spooled up to 5 psi @ 2900rpm it takes no time to get to 15psi @ 3000rpm. (traction control) :biggrin:

 

[conn84gn]

Interesting I have two convertors
ProTorque 2600-2800 stall and
Precision 3200-3500 stall
I was thinking the 3200/3500 was a little much for the street

 

[BMF_Racing]

Interesting I have two convertors
ProTorque 2600-2800 stall and
Precision 3200-3500 stall
I was thinking the 3200/3500 was a little much for the street

going with a tighter L/U one from Dusty, somewere around 2800 to 2900 rpm due to the limited track use and better street behavior.

 

[KWIKR 1]

Not really what ur looking for but I run my 6776 BB with an external wastegate that is fed by exhaust before the turbo. 0 boost creep with this set up. However I would not be concerned with a lil boost creep--U have alky and that turbo is crazy at 26lbs. anyway. So I say let it creep.

how fast do these 6776BB REALLY actually spool up . I have a TR sitting on 4 stands with a new stroker and 6776BB in front of a TH400 w/3300-3400 stall waiting to be "stepped on" when the weather clears up . I hope these 6776BB turbos are all they are cracked up to be .

 

[BMF_Racing]

how fast do these 6776BB REALLY actually spool up . I have a TR sitting on 4 stands with a new stroker and 6776BB in front of a TH400 w/3300-3400 stall waiting to be "stepped on" when the weather clears up . I hope these 6776BB turbos are all they are cracked up to be .

Well my girl freind's T-type has the DBB 6776 on a stock un-opened 109 block, with 3" charge tubes and big FMIC (12" x 27 " 4 1/2") and this turbo fills this displacement with 20 psi around 3000 rpm. We've even seen some amounts of partial throttle boost, thats crazy with a 67mm turbo. With a stock convertor I was able to brake boost 3 psi (only tried it once just to see). We went from a stock turbo to this 67mm and I was surprised on how little turbo lag it had, even with a stock tq convertor. I'm definetly happy. You will have instant boost with a 3300 to 3400 stall. should be fun. :biggrin:

 

[KWIKR 1]

Well my girl freind's T-type has the DBB 6776 on a stock un-opened 109 block, with 3" charge tubes and big FMIC (12" x 27 " 4 1/2") and this turbo fills this displacement with 20 psi around 3000 rpm. We've even seen some amounts of partial throttle boost, thats crazy with a 67mm turbo. With a stock convertor I was able to brake boost 3 psi (only tried it once just to see). We went from a stock turbo to this 67mm and I was surprised on how little turbo lag it had, even with a stock tq convertor. I'm definetly happy. You will have instant boost with a 3300 to 3400 stall. should be fun. :biggrin:

thanks for the info BMF Racing . I have at least another month due to weather before I can roll onto the street and test your info . it's driving me crazy . Thanks .