spooledUP7

Well, I have preached the gospel of turbo troubleshooting for over year now, and I still admittedly have turbo issues. I still however feel confident that I can help solve other people's turbo problems. Go figure. Actually, I have been aware of my problem for quite some time now, but I have been too damn lazy to get around to fixing it. Turbo control solenoid (Vacuum side) fails when hot. Knowing this, I have relocated the solenoid from off the ACV and wrapped it with heat shield out in the open. Sounds good on paper, however, it did not work.
For laughs and giggles, I hooked up my boost vac/gauge to a T-fitting on the turbo controller side of the solenoid to see what is really going on when it gets hot and at what point.
With the motor relatively cold, I did a few 2nd-3rd gear burst above 4500 rpm. What I saw was as predicted, vacuum would instantly appear just before 4500 rpm, but what was not anticipated was the vacuum hold after deceleration (1st sign of malfunction), which in essence leaves the turbo control wide open. (This explains why I would still have slow primary boost up to 4500 rpm when getting back on it.)

So, cutting to the chase, I pull the solenoid and check the ohms. I get nothing. I throw it in the freezer, and suddenly bingo, 35-37 ohms. This solenoid is made by Mitsubishi (part no. k5t48171-n3a1), again, go figure, but it does have one cool feature that goes beyond Mazda...It is modular.
By modular I mean, the unit is comprised of a metal end unit (the nipple a cage), a center coil unit (the fried part), and the end split nipples.
It's a pretty cool little valve, but worthless broken.

The cure is easy, replace the solenoid, but if you are like me, $60 for this valve is a tight fit up the ol' keyster. Granted, I will be buying a new solenoid, I feel there is some experimenting to be done with this cool solenoid and in the mean time I am going to perform a little transplant surgery from my friend the purge control donor.

The shop manual says that the purge control solenoid basically is there to prevent any unbalnced fuel ratios during idle. So, to compinsate for this when I remove the solenoid, I will insert a restrictor pill to simulate a duty cycle at idle. During boost (which is most important) the check valve will prevent the gastank from filling up with boost as per normal.

I have taken the end metal portion of the T/C solenoid and afixed it to the purge control solenoid, and so far bench tests prove compliance.

Now on to the road test, I will keep you all informed of my little frankinstine.

spooledUP7

It's ALIVE! It's ALIVE! I believe is most appropriate to say.

My little Frankenstein seemed to have worked, and seemingly without any compromise to the idle.

Like I said before, I will be replacing the T/C solenoid, but for now my creature will get the job done.

That's satisfaction on a budget!

So, secondary turbo is back online, however, I still have slow boost build-up, 9 pounds boost, and a funky change over of 5 psi with a quirky flutter for a few seconds. But, on the bright side, one more problem checked off, and now I can concentrate on the low boost.


My best guess is that there is similar troubles with the precontrol solenoid, and I will be pulling it to test soon.

spooledUP7

It looks like I had my boost pill backwards, primary on the secondary and so on.

Happy boosting!

spooledUP7

I'm still pretty stoked about this mod working so I have done up a drawing for future archiving.

The drawing shows the two solenoids coming together.

As for the restriction pill, I used a welding tip with a hole of around .1625.

KZ1

congrats on that success. but the TCA shoudl hold vacuum in it on deceleration, until the point it goes back to single mode. I haev similar problem, 99 out of 100 times mine comes out fo dual mode at 3000rpm, but sometimes it doesn't. it will just stick on non-seq like I had it wired there. I can even go to idle, adn won't switch to primary. Has only happened few times, and I think my most recent find of a leaking EGR valve thus leaking vacuum tank fixed it.

good luck

spooledUP7

Good point, and in fact I have been thinking of building a dual chambered aluminum tank with solenoid mounts and mounted right next to the TC. My hope would be to lessen the time that it takes to actuate the TC as well as create a dedicated vacuum, pressure source without scavangers like the EGR.