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Primary Turbo Operation - What controls pressure after 7PSI? Strange Boost Problem!

Primary Turbo Operation - What controls pressure after 7PSI? Strange Boost Problem!

 
 
 
 
Old 06-10-04, 03:06 AM
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Primary Turbo Operation - What controls pressure after 7PSI? Strange Boost Problem!

*PLEASE READ CAREFULLY*

I have not tested all the solenoids....

but.. here is my understanding of how pressure flows through the engine (without all the details)...

Primary Turbo spools, building pressure. It then flows through the y-pipe, through the crossover pipe, down to the IC, then from the IC to the elbow, to the TB, to the UIM, to the LIM.

I understand the pressure tank holds pressure for the primary turbo, does it also hold pressure for the secondary turbo? What if my Check Valve was bad (the one leading to the pressure chamber?)

Now at 7psi the wastegate becomes active, slowing down the primary, and the secondary is preparing to come online (prespool).. this transition yeilds roughly 8psi stock. Once the wastegate has closed boost from the primary, the secondary will then boost the desired amount.

As far as the 'hardware' is concerned. Leaks could be caused at: Y-Pipe Coupling (I have efini, it has a flange), Intercooler Piping, Throttle Body, UIM, or LIM gaskets. All of these are good and I have finished a complete vacuum line job, so there are not any leaking lines.

If I am wrong, please let me know.

**HERE IS MY PROBLEM**

My boost is strong up TO 7PSI on the primary, and anything above 4500RPM when the SECONDARY is boosting. My SECONDARY turbo is strong at all levels, but my PRIMARY IS SHITTY after 7PSI. The turbo itself is fine though.

Now, what controls the PRIMARY turbo after 7PSI? Is there a solenoid that could cause rough laggy boost after 7PSI? Perhaps the Wastegate door is being gay and not doing it's job. Perhaps the WG Control Solenoid? But if it was this solenoid, the 2nd turbo wouldn't boost at all correct?

I need to know which solenoid would control primary turbo operation Above 7 PSI

Please look at my signature and note my modifications (exhaust, etc).

I have checked the gaskets, replaced all vacuum lines, checked intercooler hoses, and crossover from ypipe flange. Made sure the TB, UIM, and Elbow were all seated properly and torqued to spec. My Wastegate is ported!

I'm going to post this in the advanced tech section also... perhaps somebody knows the engine operation well enough to located a problem such as this.
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Old 06-10-04, 11:17 PM
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Aside from a boost leak, if either the pre-control or the wastegate solenoids decide not to vent air, you're going to be stuck at 7psi.

You can check the solenoids are working by pulling the electrical connectors off them and testing them with a 9V battery. It doesnt matter if the return hose is blown off, and if the actuator to solenoid hose is off (for either the pre-control or the wastegate) you're only going to see a lot more than 7psi.

Having said that, if all is good on the second turbo, it's got to be your pre-control that's stuffing up. Either the arm is locked open, or the solenoid isn't doing it's job. Also check there is the inline restrictor, (94 = turbo fitting, 93 = in hose). If that's missing, the soloid won't be able to dump enough air to keep up.
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Old 06-11-04, 12:01 AM
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So we're looking at the precontrol solenoid? I get up to 12psi on the primary, but... anything over 7 is crap, boost gauge is reading above 7, but the car is really running like crap when it's going over 7PSI.

And when you say Inline Restrictor, and you talking about the pills? If thats the case, I have the bleeder valves installed for boost control and precontrol, which I've adjusted accordingly.
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Old 06-11-04, 06:03 PM
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Alright well I elimated the precontrol and wastegate solenoids and I am using the manual valve to control them both. The electrical connections are connected, but there are not any lines going to the solenoids. I've adjusted my boost spike to where i want it to be, but I cannot get my turbos to boost under 14-15psi. I have the manual control valve fully open and I am stioll hitting 14+ psi. Maybe my primary turbo housing is cracked? or some crap. I am still getting that crap *** leak at 7PSI, the leak is stronger if I am WOT, if I am 1/2 way and slowly press the throttle in 2nd gear and raise the boost past 7PSI, it is not as noticable.

I really do not have a clue at this point.
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Old 06-11-04, 10:51 PM
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put my cat conv back on, and I bypassed my WG control solenoid and my precontrol solenoid. I thought by putting my cat on that I would get rid of the creep. Nope... turbos are still hitting 16 psi, and it's strange...

I'll get up to 7psi on the primary SLOWLY increasing the throttle and I can't really feel the leak or whatever it is at 7PSI, but if I floor it (WOT) then it goes all the way up to 16PSI. I have my boost controller **** all the way open which should be giving me a minimal boost and yet I am still hitting 16PSI, how the hell is this happening?

I replaced my restrictor pills with bleeder valves, I replaced all my vac lines, and I removed the precontrol and wg control solenoids from the equation. I made sure the flow of pressure from the turbos to the manifold were all sealed well, and reset my ECU and put my CAT back on the exhaust.

I do not have a single clue what could cause these problems, and it seems that nobody on the forum has experienced any of this, or has any clue what is going on.

I'm real close to selling it. I do not have the money to pay somebody $60/h at the shop to try and figure out the problem, nor do I have the cash to go single, and nobody seems to know what the hell to do.

If anyone has any ideas, throw them my way.

THanks

Last edited by dhahlen; 06-11-04 at 11:06 PM.
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Old 06-13-04, 03:44 PM
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^bump
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Old 06-13-04, 05:03 PM
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1) Get yourself a pressure tester. Like this

2) Stick it up your ...........oh wrong forum

Test your actuators and solenoids. Applying electrictity to the solenoids is an extremely POOR test as the motor in them may still be functional but the diaphram may be leaking. One of your actuators may be leaking or sticking, too. OR you may have to manually adjust them.

The prespooler acts as a miniwastegate. If 1st turbo is getting FULL exhaust, then the time comes to start prespooling the 2nd turbo, obviously, some of that exhaust is going to be redirected from the 1st turbo.

These threads may help show how the system works:

https://www.rx7club.com/showthread.p...r&pagenumber=1
https://www.rx7club.com/showthread.p...ool+prespooler
https://www.rx7club.com/showthread.p...ool+prespooler
https://www.rx7club.com/showthread.p...light=prespool
https://www.rx7club.com/showthread.p...light=prespool

This one is just for comedy relief
https://www.rx7club.com/showthread.p...light=prespool
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