I really shoudl not be goin aboove 4k righ tnow seeing as how i am only half done with breaking the engine in but I have to knwo what swrong. When I boost from 3-4k rpm and shift my boost keeps just fine at 11 to 10 psi. But if I shift while the second turbo is on past the 4500 poitn the turbos fall flat on their faces 3 or so psi and I hear a hi pitch squeel that sound liek the turbos trying really hard to spool or something? is this a turbo control solenoid problem? Searched and read....

 

I experienced something like this once, it was a loose hose underneath the pressure tank.

 

Good luck, man.. I'm dealing with the exact problem. Let me know if you find out what's wrong, and I'll do likewise.

 

No problem Saner, I'll update you guys with my progress.

 

your wastegate is being kept open. I have the same problem since I put my manual boost controller on. for me...it is because there is no way to vent the wastegate line pressure when you shift (have to drill a 1/32" hole in the controller to vent pressure correctly).

what kind of boost controller are you using or stock? most likely a selenoid is acting up or a hose popped off of a pressure tank or somewhere in the rats nest.

 

I'm using a home depot made boost controller

 

I'm experiencing the same problem, I'd like to know if you guys find the squeel turbo sound problem too. Mine just happened after I fabricated and installed my version of James Paventi's factory cold airbox mod with shield (thanks James for the great info and pics). I took a test drive and man you can hear the turbos whooshing, then I heard a pop pisssss sound. I thought it was all normal sounds till I started hearing the squeel at 4k and power dropping off. I am thinking it might be in the rats nest. I will let you guys know what I find. My car is basically stock just the air box mod and Apexi Ni Dual Muffler.

 

2 valves.....thats it.....it probably is my MBC.....becasue if I let up and go back down on the pedal a couple of times it seems to work it self out.....Hmm where do I drill the whole in the MBC? before the lines go to the turbo or before the lines go to the MBC from the acutators?

 

I'll check my vac hoses just incase as well. And update as well, if someone finds a solution this seems like it should be made into a sticky.

 

well, mine is a ball and spring controller. if you just have the needle valves, then that shouldnt cause it to do it. I switched from the needle valves to the ball and spring style. although, it is most likely a hose popped off or a tear in one of the hoses in your case. even if the hose looks ok, double check it...I ran around for a couple weeks thinking mine couldnt be the boost controller line...turned out the line had a tear in it that I didnt see before.

 

Alright well if it is a line why is it that I can get back boost when a play with the pedal in gear?

 

What he said!

 

The reason you can get it to work if you play with the accelerator is that the ball (or something else in the line to the actuator) is not sealing perfectly, and eventually the pressure in the line to the actuator will drop off. The small hole (I used a 0.020-in hole) does that automatically.

Drill the hole anywhere that it's convenient in the air passage between the controller ball and the actuator.

 

Yes.

and if you have a needle valve type controller, you shouldnt need to drill a hole in it. You may need to check to make sure nothing is periodically blocking the line/controller.

 

Remember that a needle-valve controller works in conjunction with the stock solenoid valve(s), so what you are doing is balancing orifice sizes, and the bleed is not necessary.

With a ball-spring controller, the WG (and PC, if you have a ball-spring controller on it) actuator exits must be blocked off to isolate the actuator from the solenoid valves so that the controllers can control properly. If the small hole is not there, the ball-spring then acts as a check valve and traps pressure in the actuator line, causing this response problem.

 

when that happened to me it was because one of the smaller hoses going to the intake was cracked.

 

could it be the turbo control solenoids are causing this problem?

 

Yes.

I had the same problem that took a while to diagnose, but was easy to solve. I would get boost from 0-4,500 (where the transition would occur and go into non-sequential mode). After the transition, it would fall flat on its face and only build up to 3psi while also fluxing in boost from 0-3psi from transition to redline. It would keep boosting this way even after I shifted and maintained my rpms above 4,500rpm. Once I went below 3,000rpm (back to sequential), it would do full boost again.

The problem turned out to be an issue with the TCA not getting any pressure to actuate the arm. The turbo control actuator uses boost pressure to power the actuator that opens, and holds open the gate bringing the second turbo online. One side of this actuator is connected to the pressure system and one side is connected to vacuum. I had a bad hose that I was not able to tell whether or not it was damaged or not at first glance.

I would start with small things like check valves first. Use a handheld vaccum pump to see that they maintain the checking direction up to at least 25in/hg. Although some say that it's your wastegate, I think it sounds like it may be an issue with your TCA. Check the various turbo troubleshooting guides and follow the various procedures of diagnosing the TC related stuff. If you need any further assistance, feel free to message me on AIM.

Good luck with your quest for working sequentials; it will be worth all of the cursing and broken knuckles when you see that you can make full boost @ 2,800RPM.

 

Update...I took off the two solenoids at the front of the UIm and di what Damian did just to see if I could get my waste gate to work with out the stupid solenoid....well it turns out it didn't work...it actuall ymade the **** boost to 12 psi with the first turbo with the manual Boost controller all the way open but didn't help the the secondaries at all....made them a bit worse actually...like they wouldn't boos tproperly at all ad start to lose 10 psi by 6000 though I might just eed ot readjust the secondary controller. It didn't help my shift through gears so I am going to go through all my vacuum hoses now and check....These are brand new silicone hoses so that why I doubt it is a broken one...and none of them are popped off.........

 

I would check and re-check to make sure that the correct lines are going into the TCA. After that, it's time to check the TCA to make sure it's working (KOKO test).

If that is working, then it might be your solenoid. The solenoid+rack is under the UIM, which is a hassle to get off and test. Be sure to test them with a 12V source (an old computer power supply works well for this test). I have seen many cases where solenoids will function well at room temp., but fail when they are heated. Placing them in a oven for a bit before testing will eliminate this possibility. I think it was DaveW that also found that solenoids tend to not function properly when more than 10PSI is applied. Let us know when/if you make any progress.

 

Thanks, but that wasn't me that noted that - maybe Dave Geesaman?

 

I might have foud my problem...the two hoses on the LIM that go from the turbo control solenoid were squeezed down.....pinched at a 90 degree angle....I remade the hoses to be longer so they wouldn't squeeze down the way it was squeeze it wasn't l;etting much air by at all.....if this isn't it I will go mad.....

 

I might have foud my problem...the two hoses on the LIM that go from the turbo control solenoid were squeezed down.....pinched at a 90 degree angle....I remade the hoses to be longer so they wouldn't squeeze down the way it was squeeze it wasn't l;etting much air by at all.....if this isn't it I will go mad.....

 

Update....I enlraged the nipples into my needle valve MBCs and now i have a good 10 psi on the first turbo. And it holds and starts to die with the second turbo at like 6000 rpm which what it is supposed to do right? Hold 8 or 6 psi I think it was till the end? Well I'm still having a problem with getting boost from a shift....I get around 5 psi and even when I jiggle the pedal now it won't boost higher I will try to sort out the MBCs.

 

problem solved. Well my problem has been solved let this be a sticky....Here is what I did. I took off my UIM....I noticed that my turbo control solenoid (the one on the LIM) vacuums hoses were being sqeezed off becasue they had a 90 degree bend in them. going from the solenoid that sits on the LIM to the rats nest. So I took em off and replaced them with somelonger ones that bent in such with out squeeziing the air off. I then proceeded to make my boost controller nipples a bit larger becasue I wasn't able to let enough air pass through last time around to get the primary turbo down to 10 psi. After a couple of test drives I adjusted my valves to a pervfect 10 -9-10 pattern. When I shift the PSI now keeps at 10 psi with the second turbo.