As of March 27, 2017 when I purchased them, the cost of all 4 OEM solenoids that control the sequential turbos was $245.29 cents before shipping from Ray Crowe. Viton check valves aren't much, so you could be under $300 total, and you're going to do new vacuum hose anyway, so that doesn't even play into this equation because it's not optional.

For so little money, why would you go through the trouble of waiting until the solenoids and check valves fail one by one? I think changing all the check valves is a common thing, but the amount of headache people put into figuring out which of their $60 solenoids just crapped out on them is absurd. They ALL fail, just like all your brake pads wear out. So get new ones. They will fail again too, just like your brake pads will wear out again, but that will be years from now. The OEM solenoids fit right in there and they don't cost that much.

$300 isn't a ton of money in the scheme of things. That's like 1 tire for a lot of you.

Ray Crowe knows about this stuff, but FYI the part #s from Mazda are:

1480-13-240A - Quantity: 2, Charge Relief and Charge Control
N390-18-741 - Quantity: 1, Turbo Control (Solenoid Rack)
N3A1-18-741 - Quantity: 1, Turbo Control (by the ACV)

The other rats nest solenoids can sometimes break while servicing the vehicle, but those 4 are the main ones you need to fix your boosting problems.

 

plus, the old ones are good spares for the emissions solenoids, or if one happens to break when you're in there

 

I bench tested mine before putting them back in during a rebuild, but that was several years ago. If I have issues...and agree that's likely at some point, I'll replace them all.

 

I hope one day to reach the point where I refer to 300$ as "such little money"

 

seriously though, people get so frustrated with the sequential twins having one boosting problem after another, that they go non sequential and aren't happy with the low end torque, or they go single turbo and spend thousands and thousands of dollars.

New OEM or OEM replacement parts (ie, viton check valves which are cheaper and better than OEM) go a long way. Considering most people on this forum use their FD as a second car, putting 5000 to 1000 miles a year on the car, new solenoids are going to last 10 years and you won't have to worry about them for the rest of the time you own the car.

 

I guess I've gotten super lucky... only solenoid that ever went bad was the TCA under the UIM. I was able to reach it with a 10mm socket and replaced without taking off UIM.

The rest of my ~25 y/o 150+k mile solenoids are still sending vacuum and pressure to my turbo bits just like they should. Go figure...

 

Good info. I will prob do this soon.

 

Also, note that there is the pre control solenoid and there is the wastegate solenoid on the front of the intake manifold. Those do not have a reputation for failing. I would consider changing them optional/unnecessary, and a lot of you aren't using them anymore due to some other form of boost control.

 

Thanks for the PNs. I'll be picking up a set.

 

I would be curious if you get a smoother or quicker transition if you swapped all the solenoids out. It would be a good case study of before and after.

 

Arghx,

All of the solenoids under the UIM (rats nest) are literally the same right? except for the sticker on them?

 

I'm not sure. They are 3 port solenoid valves that are configured in different ways. Whether they are physically different inside, I don't know. Also, Mazda may have changed suppliers since 25 years ago, so who knows if that has affected it. Based on the part numbers the charge control and charge relief are probably shared wih other Mazda engines.

I wouldn't be surprised if there is a different specification for the turbo control. Mazda went through a lot of trouble to make the valve open and close quickly and seal. It's detailed in the SAE paper about three sequential turbos. The charge control and charge relief are more likely off the shelf .

 

the 1480/1481 solenoids are the same except the direction of the air passage. (one goes from A to B without power, and then A->C with power, the other is A->C without power, and A->B with power)

these are the ones that are shared with 81-91 Rx7's and some other Mazda's (and since its a Mitsubishi part, probably other stuff)

the N3A1 and N390 solenoids are going to be specific to the Rotary in some way, either the connector, color, or mounting.

 

https://www.rx7club.com/3rd-generati...noids-1083984/
https://www.rx7club.com/3rd-generati...o-help-677221/

In these two threads it's described that all of the rats nest solenoids are the same. Im I reading this incorrectly or has new information come up regarding the rats nest solenoids?

 

First we have to clarify what the definition of the rats nest is.



This image from Mazdatrix shows the different solenoids in the rack. Notice that it excludes the additional turbo control solenoid by the ACV as well as the precontrol and wastegate.

For turbocharger control, the charge control and charge relief are the same part numbers. All the other solenoids with filters on them are similar, except the turbo control.

The turbo control has a unique part number even though it should be similar to the secondary air bypass and EGR. I don't have any hard data to back this up but I suspect there is something special about the turbo control solenoid. Why would it have a unique part number if has the same configuration as those two emission solenoids?

It seems silly to use anything but brand new OEM for all 4 parts I mentioned at the top of the thread. Emission solenoids are less important.

 

The only solenoid problem my car has ever had (as a first run 1992 model FD) is when I clumsily broke the barb off the double throttle control solenoid about 2.5 years ago because it was brittle.
I capped that line off and one day I may fix it but have had zero issues. My solenoids are 25 years old.

I've probably jinxed it now.