At least, I hope these are some new ideas .

Hopefully in the not too terribly distant future I'll be in the position to fulfill a dream I've had for a LONG time and buy my first FD. I've been HEAVY into the RX-7 scene since about '95, have owned a number of 2nd gens, and have a 10th Anniversary that's modded to the hilt that will be for sale in the very near future. That said, my goal when I acquire my FD is to make the car Mazda should have made - engineer solutions to the various compromises they made, while keeping stock-like driveability and better than stock reliability.

Anyhow, one thing that I've been curious about are the various vacuum solenoids that control the sequential control system. Believe it or not, those solenoids have been on EVERY RX-7, from the 1st gen on up. It's a design that was way overdue to be re-engineered - they're bulky, have bulky connectors, and get quite brittle with heat.

As you may or may not know, in Japan for MY 96 they fixed a LOT of stuff on the 3rd gen - this was the equivalent of the '89 model year update to the 2nd gen. One of the big things Mazda did was fix the "rat's nest" - there is a sizeable black box under the upper intake manifold that handles a lot of the vacuum solenoid work. I know next to NOTHING about this, though. I've seen a pic of one WAY back in the Big RX-7 list heyday in the '90s from a guy in the UK with a '96 Japanese import.

So, in a roundabout way, this is what I'd like to figure out.

1. What is the deal with the "Japanese Black Box"? Does it replace and simplify the vacuum solenoids, as I am led to believe? What is its purpose? Does anyone have any better pictures of it?

2. Is the JBB (yay! new acronym) usable on a US car? If it is simply a collection of 12v switched vacuum solenoids, that shouldn't be too hard to wire up - 12v and ground to each. But, a lot of this depends on #1.

3. Is the JBB possible to acquire somewhat easily? I imagine with the influx of JDM engines there should be some of them in the US. Is it available from Mazda? How much new?

4. If the JBB is a total dead end, are there better solutions out there? For example, a 3-way switching vacuum solenoid that's designed for high temp operation and is small and compact? Maybe from Grainger or Mcmaster-Carr et al? Maybe from some other vehicle with vacuum switches?

A lot of this is, at the present, an interesting thought experiment. This isn't something I'm looking to immediately implement or anything. Let's see if we can't pick this idea apart and get some answers.

Thanks!
Dale

 

We explored the JDM "Black Box" question here:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/99-rats-nest-replacement-block-315993/

Making the system easier to work with depends on what you are keeping on the car. Most of the lines are between the sequential and emission systems. If you elminate emissions, you'll knock out half the lines. However if you need to keep emissions and you want to keep the sequential setup, you are basically stuck with the "rats nest".

I haven't heard of anyone finding/using a stronger solenoid. Honestly, add a vented hood or other mods to aid in reducing the underhood temps will help keep those solenoids from roasting. Also, someone here on the forum add some insulation under the nest to help protect it from heat. I don't know if that helped or not..

 

Thanks for the link, Mahjik! Seeing pics of it shows me a few things.

1. It is greatly simplified from the '93-95 rats nest. Instead of having multiple vacuum lines carrying a certain "signal" (vacuum, boost, whatever the source is) there's just a few inputs, and it's distributed internally to the solenoids.

2. It appears that there are multiple solenoids in the black box, and they're just good ole 12v switched solenoids. Each has 2 plugs - power and ground, just like the solenoids on the '93-95 cars.

With one of those boxes, it wouldn't be terribly difficult to map out the vacuum patterns, find the equivalent signals on the '93-95 ECU/harness, and wire it up.

The thing to remember about the solenoids is they're the vacuum equivalent to a relay. No power, vacuum is blocked or routed a certain way, apply power and vacuum passes through or is routed another way. It's quite simple but the layers of the system can make it tricky.

About an hour with an air compressor, a spare battery, and some test leads and I could easily sort the whole thing out. The next question is whether or not it would actually FIT under the upper intake manifold, and whether all the solenoids in the '93-95 US spec are represented.

Thoughts?

Dale

 

Here's an archived version of an old forum thread with all the pics and descriptions of some of the differences.

http://filebox.vt.edu/users/coanders/Rx7/RX-7%20Forum%20-%20japenese%20and%20american%20engines%20differenc es,%20take%20a%20look%20(pics).htm

BTW, the black box is incorrectly believed to be a '99+ feature, but it actually appeared on the '96 model year.

Has anyone ever sourced a '96+ vacuum diagram from the later shop manual? Maybe one of the Aussie guys?

Dale

 

The coils are moved to make room for the "Vacuum Box" as well as I believe changes in the LIM. The wiring connectors are different, so you would have to rewire the stock harness to make it work. Assuming that the solenoids operate the same (12v) on and off (and you can relocate the coils to make room as well as the other changes that I'm sure are more), I'm really not sure what type of benefit it would be.

Adding silicone lines is really more than adequate (I've yet to have a hose pop off with them). The problem with the solenoids actually failing will still be present with the box as it will with the standard setup (you still have the same heat beating on them).

 

I just think the true benefit of the BB is that it makes troubleshooting easier if you have less vac hoses to worry about.

 

Which was my point about the silicone lines. I don't know if you've tried to remove some of the silicone lines when working on your car but I nearly have to rip it off the nozzles (zip tying them is really redundant at that point). The stock rubber hoses are a different story.

The BB could actually make troubleshooting and repair harder. If you have a solenoid fail with the stock setup, it's fairly easy to trouble shoot. However, if you have the BB, you have to pull the entire thing to start testing instead of a single solenoid.

Using silicone hoses really makes the "reliability" part of the hose system a non-issue (as long as you don't have corrosive liquids splashing all over them).

 

Ive already done the silicone upgrade but as you can tell Im all about making my mechanic's and my respective minds intact and somewhat on the sane side and the FD doesnt help the situation much.

 

When I got my 93 I saw that load of vacuum lines under the intake and the coils as well. I removed them and mounted them on their respective fender wells. I have each solenoid in clear view and can handle them anytime I need to. There was no way I was going to own a car that was set up that way. Since I have 20 years of tune up and drive-ability working at large G.M. dealers I was able to engineer the new lay out. I also removed the coils and put then where the battery was. I wont lie it was a lot of work laying out all the lines and electrical connections. I used solid plastic line, the thin one on modern systems. The system works fine. I didn't set it up exactly like the factory but it preforms great with all the emission systems up and running for a Ca. engine.

 

any chance you can take a pic of your set up?

 

Yes I will see about posting some today.

 

This is a pic of the first run, its changed a bit but gives you a basic view of the work involved.

http://members.***.net/stdotjohn/NEW...7.NEW%2050.jpg

 

Pretty cool! Any more/higher-res pics?

I wonder how those plastic lines will hold up over time. I helped a buddy's dad pull and replace a motor in a late '80s Econoline utility van, and ALL those plastic lines were brittle and snapped off. But, it does make a large hose run like that much more compact .

That's a neat job you did there!

Dale

 

That looks good. However, I wonder what effect the lengthening of the lines will have. Seems like it would slow the reactions of the system.

 

I will say theres something a skew because I only get 7 psi of boost, but otherwise it works fine. Honestly I am good with the power and the lesser pressure put on the engine. I have a cheep photo re sizer and it skews up the pictures. I try to send out a better pic.

 

If you are using INTERNET explorer and the picture is huge, turn on the "auto re-size" check box . Click top of page, Tools - Internet options - advanced. Then close the pic and re-open it. "If you don't know this

http://members.***.net/stdotjohn/New...0ons%20028.jpg

 

Thanks for the bigger pic! Much easier to see all the details.

Dale

 

If you have full exhaust and no air pump why not just do the seq simplification? Its gets rid of the rats nest and makes things much nicer under the uim. I ran my car like that for a year or so and really liked it.

 

If you add an IC fan that hooks up to a thermostat at the IC (in addition to being tied to teh radiator fan via diodes and relays) then you will push cold air into the engine compartment even after the car is turned off - until the temps fall below a preset temp - such as 180 degrees.

I forget the specifics, but when I put termometers under the hood, and then parked the car after driving on a hot day - boy did that engine compartment heat up.

 

Sometimes I daydream about replacing the main actuator with a stepper motor, remotely mounted and using cables to prevent heat problems. Use a pic/stamp to control it. Then I can remove the pre-spool stuff. Then I wonder about removing the charge control and replacing it with a simple flapper valve, maybe a couple of 2-stroke valves.
The result (not the primary goal) would be elimination of all the sequential control solenoids except for the waste gate control.

 

i'm considering doing this, however i would like to keep the air pump and idle cam. you didn't have any problems with boost control, idle... ?

 

I dream about being 35 again. I am 49 with a back injury and am not able to run and cycle like I used to. When I was 30 I started running before work and built it to 10 miles a day. That I miss the most. Now I will shut the **** up.

 

The "sequential simplification" certainly takes away a ton of crap and makes things far easier, however, for us guys that need to pass emissions, it's kind of a dead end.

My "somewhat sequential simplificaton" was to eliminate:

1) Double-throttle control
2) EGR control
3) Fuel pressure regulator control
4) PCV valve

The solenoids are still physically there and hooked up (to avoid getting a check engine light), but the vacuum lines and check valves that were attached to them are gone. It doesn't sound like much, but those three solenoids use a lot of hose!

You cannot pass visual without a PCV, but putting one back in is a 10 min job. I have a 1995 ECU in my car and the 95 cars did not have an EGR valve, so I feel safe in leaving it unhooked.

The above simplification eliminates 2 sources of boost leaks, too: the double throttle control check valve and the PCV. Both of mine were leaking.

Sonny