Worth upgrading??? PT 67..

[ThatDamGoldCar]

I have a PT67 P-trim Journal bearing turbo. It only has about a hundred miles on it along with a new motor.Ive never pushed it passed 20 lbs..yet. The car is an animal,spools pretty good. What can i expect if i upgrade to a new Billet 6766 Journal?? Is it a waste of money? ALSO.. I was told ball bearing is unnecessary in these cars...
Ive been messing with these cars for 20 years and have had 8 Turbo Buicks and 1 Turbo T/A. This is the one i really wanna dial in..
Someone enlighten me on the newer turbos..Thank you

 

[NyBlankets]

I've been researching turbos for the past 3 months for my particular combo. Thats something you should post, your combination of parts would help some of the more experienced to sound in and determine with better accuracy what would work with your setup. What your goals are would help as well.

Precision rated your turbo @780hp and the 6766 @935

 

[ThatDamGoldCar]

updated sig..

 

[Major Nutz]

Subscribed. Your build is similar to mine and I've thought about going to a newer turbo but not sure if it is worth the $$$.

 

[JP112_89]

If it doesn't say billet next to it, nobody wants it anymore?

Keep your 67. Your good.. and looks nice.

Joe

 

[Slow91z]

Don't think you'll see a gain until the boost is WAY up...like 30+

 

[jasjamz]

I think you wll be impressed by your current turbo at 24/25 psi and it will shock you at 28/30 psi! That should hold you over for quite some time. Also I'd lower that A/F target to 10.3/10.4 before you crank it up. Also make it so the translator can only pull 5% of fuel.

 

[tsm3089]

I find it interesting that the 67/66 is rated at the same hp as the 67/68 hpq. Is the new 66 wheel as good as the old 68.

 

[SHADOWII]

If the 67 is enough for your goals, I say keep it. Use the money for the supporting mod' s such as C-clip eliminators, etc.

 

[Ttype6]

Again,you'll love it at 28 lbs of boost. You haven't used it to it's potential yet.

 

[NyBlankets]

The import guys make ridiculous hp with the 67s, they run 40+lb of boost though. The newer turbos are more efficient but one would probably have to push it beyond 30lbs to see any kind of benefit over the older style 67s. I've seen dyno charts where the new billet turbos make over 100hp vs the old designs. Again these guys run well over 30lb of boost.

 

[jasjamz]

The turbo Buick crowd typically runs between 20-30 psi. There are some that use more but it's not a large percentage. One should state their performance goals, ET,horsepower, and boost level when building their combinations.

 

[bison]

The import guys make ridiculous hp with the 67s, they run 40+lb of boost though. The newer turbos are more efficient but one would probably have to push it beyond 30lbs to see any kind of benefit over the older style 67s. I've seen dyno charts where the new billet turbos make over 100hp vs the old designs. Again these guys run well over 30lb of boost.

The newer turbos aren't more efficient. They support more mass flow than older designs of the same inducer size and typically spool faster. Peoples engines haven't kept up with the compressor technology so they shouldn't expect more power. If you have a 6776 and have gone 9.8@138mph then you are ready for more turbo if you are looking for more power. You will need more engine and or a higher pressure ratio to increase mass flow to make more power. There's no magic parts. You want to get the most out of a newer 67 compressor then build an engine that can support 90+lbs/min and run the boost needed to get there. Not happening with a small hyd roller and 25psi unless the engine is 300+ci. You need to increase the operating rpm.

 

[NyBlankets]

"They support more mass flow than older designs of the same inducer size"

Trying to grasp the concept Brian, please bear with me. Lets say for arguments sake I'm running a 6765 JB cast wheel turbo on an engine that could easily handle 90lb of air. I then upgrade to a 6766 JB billet and keep the boost level the same (as an example, 28lb.), would they make the same HP or would the 6766 show a noticeable gain? Am I correct to believe that unless you move out of the 6765 turbo efficiency range they would make the same power?

 

[bison]

"They support more mass flow than older designs of the same inducer size"

Trying to grasp the concept Brian, please bear with me. Lets say for arguments sake I'm running a 6765 JB cast wheel turbo on an engine that could easily handle 90lb of air. I then upgrade to a 6766 JB billet and keep the boost level the same (as an example, 28lb.), would they make the same HP or would the 6766 show a noticeable gain? Am I correct to believe that unless you move out of the 6765 turbo efficiency range they would make the same power?

I can't say for sure what the 66 ex wheel will flow especially in a 3 bolt housing with the small volute. What will happen is the cast wheel will probably hit a certain point like 78-80lbs/min and it won't move anymore air. You probably wont be able to get to 28psi across the engines otherwise useful power band. The 67 cea and other forged milled 67mm compressors will potentially flow quite a bit more than the old t04r cast wheel. So with all that you can keep running the pressure ratio higher or increase the cam profile (or both) to get more mass flow. You won't hit a wall where the compressor just flattens out. I'm speculating that the 66ex wheel will flow about 3-4 lbs/min more than the old 65. So it will support about 50hp more. If your engine is 250+ci and has enough head and cam to flow
90+lbs/min you would be lucky to see 25psi in really good air even wiring the wastegate closed 100%. As rpm increased past the peak mass flow of the compressor you will typically see the boost start falling off or it will just heat the hell out of the air and mass flow will be stagnant or go backwards. Power will fall off really fast. It's
Still possible to hit peak power with the smaller wheel and then have it crap out a few hundred rpm later where both may show the same peak power. The newer wheels won't crap out and will continue to make power. The drive pressure is less and the compressor wheel is taking a larger bite of air for each rpm of shaft speed. You can increase the CR and play with the cam to force more of the inert gasses out of the cylinder in a high back pressure situation to make use of a better compressor. There's a balance between ex pressure and manifold pressure and mass flow required if you want to have a decent spooling combo and make a lot of power. So the 6766 should show a pretty big gain there since the mass flow on the compressor wheel and the ex would be more. Increasing the CR and purpose building with the 6766 to run at say 2.8:1 PR will likely net even more. Even though the 66ex is probably choking it the piston is forcing out the inert gas and the cam profile and timing are opening and closing the valves to reduce backflow. This is like adding duration under power. The first few degrees of crank rotation after tdc there is not much going on as far as mass flow. The ex pressure will be the lowest pressure you will ever see there so positive flow can't occur till the cylinder pressure is lower than the intake manifold pressure. Squeezing that crap out and closing the ex valve fast will add power if the compressor is capable. Hope that explains it kind of. There's other things that can jam things up like running the wrong compressor cover. It could increase the drive pressure prematurely so the compressor can't reach a speed where it's able to hit it peak potential.

 

[Jerryl]

I can't say for sure what the 66 ex wheel will flow ....................

Not only are you very knowledgeable, but have the patience and ability to explain the physics behind it. Well done as usual!


Clarification:
You ever read something you posted and say . . . That can easily be taken the wrong way . . . hence the clarification.
I was not judging the content . . . . I actually understand very little of it and was merely commenting on how well written and explained it is so noobs like me can understand it.

 

[ThatDamGoldCar]

Wow..thank you for the insight..i guess even a new billet wheel is better than mine..even if i dont go ball bearing.which i was told by a major turbo name is not necessary for our cars...
I feel people were going plenty fast before alot of the latest billet/ball bearing hype..
This 67 was all the rage when it came out...

 

[Mr.Spool]

you have a good turbo on the car now only running 20 psi,turn the boost up and the car will wake right up,that 67 turbo has been real fast.

 

[Blazer406]

If you aren't going to push it past 20 psi, you might be happier with a 44.... it will get up on boost quicker. These larger turbos will need bigger boost on an engine built around more airflow to let them shine..... back at only 20 psi boost.... 80% of these aftermarket turbos IMHO are just eye-candy..... because someone is going to come along with a much smaller combo and clean your plow.

These smaller combos are also going to be much more fun to drive......

 

[ThatDamGoldCar]

One of my best combos on a street car was blue top injectors,a te44 and homemade alky before anyone knew what alky was..