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!

 

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.

 

so the car hits boost pretty easily but then falls flat?

 

How does it boost with the WG line disconnected? (BE VERY CAREFUL!!!)

 

kane i believe ngo may have disconnected that wg line already and it climbs pretty high..ill let him chime in

 

yup, I can set the boost controller to hit higher boost but it still drops off. on street set at 7 psi with the b/c I may hit mid 6 psi and it drops off to about mid-to-low 4's by around 8000 rpm.

 

Yea, it boosts fine with the line disconnected. I never went completely full throttle but my boost was hitting 7-8 psi easy.

 

And you got a new actuator.... hmm; have you tried a pill in the WG signal line?

 

haven't tried a restrictor pill, but I've put it inline with my boost controller (HKS EVC6) and have gotten the same issues. would the pill be any different?

 

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.

 

I thought you were having problems with the actuator bracket bending on extension.
Did you fix that? Is it solid now?

 

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.

 

bump. I'm going to be diagnosing more tomorrow. Any one else have any ideas I could try or look into?

 

Leak down test?

 

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

 

bumpety bump to get this boosted beauty fixed.

 

can you also post up the dyno and a log of your mass air flow . This may help with the diagnosis ............

plus maybe a pic of what your actuator/wastgate setup is ..........

 

also what is the turbine size you have - similar to 3071 ?
Do you have a cat ? What condition is it in ?

 

what if you cruise at 7000 then nail the throttle - will boost climb above 6psi .

You can use your overboost warning buzzer to tell you when to back off ........

 

Turbine is an 84 trim with a 56.5mm Inducer and 51.8 mm Exducer. Same as the 3071. A/R is .86

I ran catless racing beat dual resonated at the time of these dyno runs.

 

is it a low mount with internal wastegate or top mount ?

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 .

 

he has a low mount with internal wastegate

 

he's running an HKS bov, venting to atmostphere.

team effort ftw.

 

I believe the peak boost will hit initially whether at a lower or higher rpm, and then will drop off. I will check it again tomorrow. I'll get a pic of the wastegate tomorrow as well.

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.

 

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.