Ok I have a 90 TII. I dont quite understand whats happening,but I only get 3lbs pretty much redlined. I take off the vacume line to the boost control actuator and plug it with a bolt and bam! as much boost as I can handle....well went to 7psi and backed off. I dont get it. How can the boost actuator open with 3psi. I cant open it by blowing into it. How retarded. How hard is it to get a new one? What else could it be?

 

where is the boost control actuator by the way?

 

I actually dont know what its called. Its the actuator under the compressor. It has an arm that goes to the wastegate.

 

I wonder if that's my problem.. my boost runs right up from like well below -200 mm HG to just over to 0 and sits there all the way to about redline. It doesn't seem to be making full boost. Any ideas?

 

Try unpluging the hose to the actuator and stick a 12 or14 mm bolt in it. Just becareful about boost. Itll just keep on climbing

 

do you have a picture of it? I'm wondering exactly what this thing is.. man, never worked on a Turbo before.. this is a friggin' job.

 

There is a solinoid valve on the oil filler tube that is supposed to bleed off part of the pressure signal to the waste gate actuator. I think it is called the "duty cycle solinoid". If this is not working you won't get full boost.

Rob

 

I've been having the same problem for almost two weeks now. Mine is intermittent, though. I'll take off for work and it'll be sluggish and I'll stop at a light and take off and all of a sudden I have full boost. WTF???

 

are you guys running aftermarket boost gauges, or are you reading it on the stock gauge.

The stock gauge can get pretty messed up and read completely wrong.

 

Autometer Phantom Series

 

my stock gauge reads about 1 psi, while a pressure tester read 5.5 psi at full boost.. still not full boost, I wonder why I'm not getting it?

 

The waste gate is sprung to open at 5.5psi. The Duty Solinoid bleeds off a portion of the pressure signal so that you get full boost. Essentially what it does is delay the opening of the waste gate by reducing the pressure signal that the actuator sees.

If unplugging the pressure line to the waste gate solves your problem your intake, exhaust, and turbo are probably ok. Look at the duty solinoid.

rob

 

what is this duty solenoid? Any pictures of it or can you direct me to it? I reference my other post here:

https://www.rx7club.com/forum/showth...threadid=94483

 

You’ve just run your turbo uncontrolled! This is a stupid, dangerous thing to do, and could easily result in a blown engine. The wastegate is rarely the cause of low boost problems and should never be tested like this. It’s clear from these comments you know very little about turbos and how they work. No offence here, but you should learn a little more about turbos before you start pulling things off randomly or you may make a very expensive mistake. Don’t take my comments personally, I’m just looking out for the health of your car.
The wastegate isn’t opening a 3psi, there’s an airflow restriction somewhere. You don’t mention any mods so I assume you’ve still got a stock exhaust. Clogged cats are the most likely cause of low boost, same with a dirty air filter. Check all of the hoses and connections between the turbo outlet and the TB for leaks.

 

Actually all Im looking at when I have the WG disconected is the boost gauge. im not trying to see how quick it is, just how the boost is responding. I thought it also was a cloged cat. The exhaust was welded as one piece when I got it. Turns out the first is punched out and the second is intact, not anymore though. Also I have a cone filter. I only disconected the WG to determine if I could even build beyond 3 psi. I dont think Turbos are rocket science. More complicated than my NA but I did most of my homework. Dont assume people are idiots just by brief posts. Next time Ill try to include every detail and thought I had before posting. And my 90TII was $1500. Im not gonna cry if it blows. Good reason to street port.

 

If your as knowledgeable help me figure this out then.
My turbo is very responsive with the WG diconected and builds to 7psi, before letting off the throttle.
With the WG hooked up the turbo spools up quickly, just like before. BUT it only builds 3 psi? What else could it be. I dont think its a restriction, if so why would it build boost so easily w/o the WG. It has to be a faulty WG. Even if the duty selenoid wasnt working the car would atleast goto 5 psi. Im still diggin though the FSM on this one.

 

If you disconnect your wastegate it won't open to release any exhaust gasses from the system, therefore FORCING 7 PSI to occur as a result (which is going to cause MASSIVE backpressure in your system, not healthy).

Your Exhaust has got to be the culprit, with the wastegate opening as it should if your system is clogged you will only see 3 PSI until you unclog the exhaust. Main Cat is probably very badly clogged.

I was pushing 5 PSI until I got rid of the main cat, now I push 8-8.5 PSI. (just replaced the cat with a mid-pipe the same diameter as the rest of the exhaust to prevent boost creep and overboost...which worked nicely.)

And per your "blowing won't open it" Have you ever tried to blow into a boost gauge and read it, barely 1 psi before you feel like your cheeks are going to explode.

 

Yeah I can blow about 2 1/2psi. I have a diagnosis gauge. Sorry if I didnt make this clear in the last post. My exhaust is completely empty. Im not concerned about boost creep. This car is a project and Im fixing/moding until I can confidently run the car. I totaly thought the cat was to blame but its no diffrent from before I punched the cat out.

 

Do you have any leaks in your intake? Once or twice I forgot to tighten down a main intercooler hose, and while the turbo was EXTREMELY loud, I only got to about 3 psi. After I tightened it down, it wasn't so loud, but the turbo was there. It wouldn't result in a vacuum leak because it would seat under vacuum, but under pressure it pushed the hose out.

 

What kind of cone filter? Do you have a cold air box? A el cheapo cone filter will last an amazing 5-7K miles, then you start loosing boost.

 

its a KN.