Low and Fluctuating Boost Problem
#1
Low and Fluctuating Boost Problem
Hey guys, some of you may have heard of my problem back on the dyno day the Sunday after Sevenstock. We assumed the problem was a 6 psi wastegate actuator getting blown open and a flimsy actuator bracket
I have replaced both with a 10 psi actuator and a 4mm thick steel bracket, but the problem persists.
Here's the problem with my boost:
1. boost limited to about 5 psi at the engine using a 10 psi actuator (tightened 7 full rotations of arm (wastegate opens about half way with rod extended))
2. boost dropping off almost immediately after hitting peak boost
3. target boost varying almost 1 psi at times
What I've checked so far:
The problem is present both with and without the boost controller hooked up.
There are no major boost leaks in intercooler piping
Vacuum is a solid 18 in-Hg at idle
Tested boost with pressure line to actuator disconnected and it rises fine
Had a boost gauge hooked up to a Tee with the actuator and compressor outlet and boost was shown to be limited
The turbo is an HKS GT2835, which is equivalent to the Garrett GT3071R.
I've been trying to figure out the problem since October with what appears to be no luck. Currently I'm slowly shortening the rod length of the actuator to increase the tension, but I'm looking for ideas on what else to check. Thanks!
I have replaced both with a 10 psi actuator and a 4mm thick steel bracket, but the problem persists.
Here's the problem with my boost:
1. boost limited to about 5 psi at the engine using a 10 psi actuator (tightened 7 full rotations of arm (wastegate opens about half way with rod extended))
2. boost dropping off almost immediately after hitting peak boost
3. target boost varying almost 1 psi at times
What I've checked so far:
The problem is present both with and without the boost controller hooked up.
There are no major boost leaks in intercooler piping
Vacuum is a solid 18 in-Hg at idle
Tested boost with pressure line to actuator disconnected and it rises fine
Had a boost gauge hooked up to a Tee with the actuator and compressor outlet and boost was shown to be limited
The turbo is an HKS GT2835, which is equivalent to the Garrett GT3071R.
I've been trying to figure out the problem since October with what appears to be no luck. Currently I'm slowly shortening the rod length of the actuator to increase the tension, but I'm looking for ideas on what else to check. Thanks!
#2
Administrator
iTrader: (7)
Jeff sabotaged your car so you'd dyno lower then his Garett 3071. that bastard!
I'm fresh out of ideas as to how to fix this.
I'm fresh out of ideas as to how to fix this.
#3
Administrator
iTrader: (7)
so the car hits boost pretty easily but then falls flat?
#10
Illudium Q-36 Space Moderator
iTrader: (1)
I know some smaller turbo's need them to help prevent boost fall off and speed spool time.
If you are sure it is not a boost leak; and you have already replaced the wastegate; and your sure that you aren't over breathing your turbo.... the pill would be the next test IMO.
Lower the volume of boost and smoothen the signal to the wastegate.
If you are sure it is not a boost leak; and you have already replaced the wastegate; and your sure that you aren't over breathing your turbo.... the pill would be the next test IMO.
Lower the volume of boost and smoothen the signal to the wastegate.
#12
I thought so too, Jeff. Had one fabbed using 4 mm-thick steel and it's solid, but the problem is still there. It is not as bad as when you ran it on the dyno, since it still holds boost above the 1 psi we were getting then. Then again, could be a load thing with being on the dyno.
#15
Bumping this thread back to see if anyone else has any ideas or input. Been a while but I still would like to eventually figure this out.
I have tried a boost pill and it did not fix the problem.
My varying peak boost isn't a problem anymore but the fluctuation and boost drop still is.
Problems:
1. boost limited to about 5 psi at the engine using a 10 psi actuator (tightened 7 full rotations of arm (wastegate opens about half way with rod extended))
2. boost dropping off almost immediately after hitting peak boost
here is a post of some of my boost curves from my last dyno tune.
Note: my boost responds in a similar fashion without the boost controller active (at a 5 psi peak).
Any ideas would be appreciated. Thanks
I have tried a boost pill and it did not fix the problem.
My varying peak boost isn't a problem anymore but the fluctuation and boost drop still is.
Problems:
1. boost limited to about 5 psi at the engine using a 10 psi actuator (tightened 7 full rotations of arm (wastegate opens about half way with rod extended))
2. boost dropping off almost immediately after hitting peak boost
here is a post of some of my boost curves from my last dyno tune.
Note: my boost responds in a similar fashion without the boost controller active (at a 5 psi peak).
Any ideas would be appreciated. Thanks
#16
Administrator
iTrader: (7)
bumpety bump to get this boosted beauty fixed.
#21
Boosted Kiwi
iTrader: (2)
How about the BOV - what do you have and how is it set up ? Have you tried holding it shut to see if it is allowing boost to escape ?
sorry for the basic questions but I have no idea of your setup .
Last edited by Brettus; 01-26-2010 at 09:44 PM.
#23
Administrator
iTrader: (7)
he's running an HKS bov, venting to atmostphere.
team effort ftw.
team effort ftw.
#24
Here is my dyno and the airflow for that. If you need the excel file for the air flow I can post that up too.
#25
This is weird...wish I could make a helpful post on this...
The only thing I have experienced with my setup is I had fluctuating boost and spikes due to a leak at the wastegate actuator nipple....
I thought it had to do with the actuator arm needing to be preloaded....turns out I didn't put zip-tie on the vac line to the actuator nipple. I loosened the actuator arm since and I get 9-10 psi to redline with my boost controller on. 7 psi with it off.
Hope you get this figured out man.
The only thing I have experienced with my setup is I had fluctuating boost and spikes due to a leak at the wastegate actuator nipple....
I thought it had to do with the actuator arm needing to be preloaded....turns out I didn't put zip-tie on the vac line to the actuator nipple. I loosened the actuator arm since and I get 9-10 psi to redline with my boost controller on. 7 psi with it off.
Hope you get this figured out man.