Just recently I have been getting 18-19" vacuum as usual at idle when starting the car but then it slowly drops to 11" as the car warms up over a couple of minutes. The boost needle doesn't bounce, the idle seems normal, there isn't much exhaust smoke and the car runs strong. I haven't done anything that should have blown the motor. Any ideas?

Also since doing research on this problem I realised the car has probabely had another problem as well since I got the car...

On hard acelleration I only get ~10 lbs of boost on the primary turbo. Hiway acelleration results in whatever I have primary boost set to in PFC.
When I floor the gas in neutral I don't build any boost all the way to redline.

The 2nd turbo stuff all works great and I get whatever my boost is set to. Some power is there since I just ran 12.8@110.6@12psi at the strip. I'm going to pull the UIM and check hoses, valves, solinoids, actuators, etc. but If someone can narrow my search I would greatly appreciate it.

My mods are...

PFC, Pettit stage 1 turbos
intake, DP, HF cat, cat back
Crooked Willow IC, pulleys
4x850cc injectors, Supra pump
Autometer boost guage
silicone hose job, Fluidyne Radiator with NPG+
Homedepot manual valves for precontrol and wastegate

 

So, are you having primary turbo issue.. I would check on the manual valves for the pre-control and wastegate..

I had primary turbo problem.. in your case you are getting 10lb on primary.. I on the other hand got 0.. I believe it was my AVCr..

Other thing could be your actuator to open the secondary flap by the y=pipe.. If it opens, than your primary boost might be leaking thru..

Also, check your BOV's and the hose.. small crack could lead to boost leak on primary.. and when secondary kicks it, the secondary turbo might compensate the small leak..

Good luck..

 

> herblenny said...

> So, are you having primary turbo issue.. I would check on the manual valves for the pre-control and wastegate..

Yes, the 2nd problem does look like something to do with the primary turbo. I've tried the manual precontrol valve in many positions including all the way closed and still no change in boost. I even took the valve out and blew through it to make sure it worked. The wastegate valve is adjustable and works fine.

> I had primary turbo problem.. in your case you are getting 10lb on primary.. I on the other hand got 0.. I believe it was my AVCr..

That had to suck. Is the AVCr a boost controller?

> Other thing could be your actuator to open the secondary flap by the y=pipe.. If it opens, than your primary boost might be leaking thru..
> Also, check your BOV's and the hose.. small crack could lead to boost leak on primary.. and when secondary kicks it, the secondary turbo might compensate the small leak..

I'll check those. Thanks.

 

It could also be the fact that ur running 850cc primary injs.

I had a friend that ran that and had symptoms like u described.

He went back to 550cc primary and upgraded the sec to 1300cc and that fixed the problem.

 

> BATMAN said...

> It could also be the fact that ur running 850cc primary injs.

> I had a friend that ran that and had symptoms like u described.

> He went back to 550cc primary and upgraded the sec to 1300cc and that fixed the problem.

That's the first I've heard of this. I wonder how that could be. Maybe air is pulled in through the injector holes lowering vacuum? I did add the lower O-ring and checked my changed PFC injector settings.

I searched the forum for 850cc injector problem and didn't find any info on this. Has anyone else heard of this problem? Does anyone have a thread or know a web site that talks about this problem? Thanks.

 

I think I found my primary boost problem. It was a small slit/hole in the short rubber line (not silicone) from the precontrol actuator to the metal line that leads to the precontrol solenoid valve. It must have leaked enough pressure that the actuator didn't work (always diverting to 2nd turbo). This problem was easier to find than I thought. It's also nice to know my primary turbo can make 10psi while diverting to the 2nd turbo. Thanks for the help.

Now the only question is why my vacuum drops after warming up?