Boost Creep on Ported wastegate
05-18-09, 11:48 PM
#1
Boost Creep on Ported wastegate
So i'm getting some boost creep at the higher rpm range. (5-7k) I have a street ported motor and stock twins (non-seq.). My PFC is set at 8psi untill i get tuned. Rebuilt motor was recently broken-in and i took it up the other day on the highway and did a few pulls to see if everything looked ok before taking it to get tuned. Holds 8psi up untill 5k rpms, past that it will creep to about 10psi by the time it gets to 6k? Only got up to 7k rpms on one of the pulls and it the gauge was reading 12-13psi., so i quickly let off.
Why is it the boost creeping so bad? My exhaust is pretty open... 3'' dp, high-flow 3'' cat, and 3" HKS catback... but i dont think thats the problem. My wastegate is ported on the twins as well. Any thoughts would be accepted and greatly appriciated.
Thanks,
Zach
Why is it the boost creeping so bad? My exhaust is pretty open... 3'' dp, high-flow 3'' cat, and 3" HKS catback... but i dont think thats the problem. My wastegate is ported on the twins as well. Any thoughts would be accepted and greatly appriciated.
Thanks,
Zach
05-19-09, 12:56 AM
#2
1. Do you still have restricter pills installed?
2. What are the exact settings you have in the PFC? What are the boost numbers and duty values? Go into the "boost" screen of the commander and copy down exactly what is written there and what you have selected.
2. What are the exact settings you have in the PFC? What are the boost numbers and duty values? Go into the "boost" screen of the commander and copy down exactly what is written there and what you have selected.
05-21-09, 11:51 PM
#4
again, what are the exact boost settings you have in the PFC? What are the boost numbers and duty values? Go into the "boost" screen of the commander and copy down exactly what is written there and what you have selected.
you have all your vacuum hoses hooked up in the stock manner correct?
I think you are asking a lot from an internal wastegate. Trying to run less boost than stock on a street ported motor with full exhaust is asking waaaaay more than what the system was designed to do, even after being ported. For example, you can port the **** out of 2nd gen internal wastegates (single turbo) for example but there is only so much they can flow. Once you open up the exhaust it's hard to stay at the 6psi spring pressure on those cars even with a ported wastegate and no boost controller installed.
one thing you could try is essentially eliminating the wastegate and precontrol solenoids from the picture by capping off the second nipple on the actuator. Theoretically you should stay at spring pressure if your wastegate is flowing enough. The solenoids would no longer be venting away pressure from the actuators.
attached is a diagram of what I'm talking about. I used a simplified sequential diagram just so you could see everything better. You would have to cap off/plug the hoses from the actuator to the two solenoids in order to prevent a boost leak for this to work.
If the boost doesn't settle down without these solenoids hooked up you have insufficient flow from the wastegate or some other mechanical problem
you have all your vacuum hoses hooked up in the stock manner correct?
I think you are asking a lot from an internal wastegate. Trying to run less boost than stock on a street ported motor with full exhaust is asking waaaaay more than what the system was designed to do, even after being ported. For example, you can port the **** out of 2nd gen internal wastegates (single turbo) for example but there is only so much they can flow. Once you open up the exhaust it's hard to stay at the 6psi spring pressure on those cars even with a ported wastegate and no boost controller installed.
one thing you could try is essentially eliminating the wastegate and precontrol solenoids from the picture by capping off the second nipple on the actuator. Theoretically you should stay at spring pressure if your wastegate is flowing enough. The solenoids would no longer be venting away pressure from the actuators.
attached is a diagram of what I'm talking about. I used a simplified sequential diagram just so you could see everything better. You would have to cap off/plug the hoses from the actuator to the two solenoids in order to prevent a boost leak for this to work.
If the boost doesn't settle down without these solenoids hooked up you have insufficient flow from the wastegate or some other mechanical problem
05-22-09, 11:04 AM
#6
which one do you have selected? the first one?
Secondary boost setting ("Sc") is the one that really matters based on my testing. .70 kg/cm^2 = .70 * 14.22 = 9.954 psi . Your boost is set to about 10psi, especially since an untuned PFC reads a bit lower than a mechanical boost gauge usually does.
Try this.
Set #1 to
Pr .55 kg cm^2 56%
Sc .55 kg cm^2 56%
Then make sure boost setting #1 is in fact selected. That may drop your boost up top a bit by opening the wastegate earlier and decreasing boost control duty cycle. But there's only so much I can tell you since you don't have any way to save logs (Datalogit box) of what the boost controller is doing.
If needed, continue to drop both duty values (keep both % the same) on each pull you do, as low as maybe 20% . Keep both boost values at .55 . See if the boost comes down at all.
Secondary boost setting ("Sc") is the one that really matters based on my testing. .70 kg/cm^2 = .70 * 14.22 = 9.954 psi . Your boost is set to about 10psi, especially since an untuned PFC reads a bit lower than a mechanical boost gauge usually does.
Try this.
Set #1 to
Pr .55 kg cm^2 56%
Sc .55 kg cm^2 56%
Then make sure boost setting #1 is in fact selected. That may drop your boost up top a bit by opening the wastegate earlier and decreasing boost control duty cycle. But there's only so much I can tell you since you don't have any way to save logs (Datalogit box) of what the boost controller is doing.
If needed, continue to drop both duty values (keep both % the same) on each pull you do, as low as maybe 20% . Keep both boost values at .55 . See if the boost comes down at all.
