'Kay I searched and this must be another one of those "everyone but me knows already knows this" type of things...but what exactly is a rats nest? What does it do and why does everyone remove it?

 

For a short answer... it's a **** load of vacuum lines all "rats nested" together... remove them cause if you get a vacuum leak it's a pia to find... sometimes... and make the engine look cleaner and easier to work on.

 

where would this be located on an S4 TII

 

everywhere :P

 

It refers to the assembly of metal lines and solenoid valves on top of the engine. Some are for emission controls, other are for functions like hot-start assist, twin-scroll control (S4 Turbo) and 6PI and VDI control (S5 NA). The fuel lines are in there too.

Most people remove them to clean the engine up a bit in conjunction with emissions removal and to eliminate actual or potential vac leaks. Unless you actually have a vac leak somewhere in there, there's no performance advange to removing it (assuming you fix the vac leak in the process).

 

i dont have a vac leak, but id like to avoid them...im also removing emissions when i do my rebuild so is there a writeup for removing the rats nest?

 

well here soon i am going up to Ft. Wankel to drop off my car to get some work done on her and if you want gimme a call and ill talk to him and see if he will help you out. if you want me too. and hey how does greenwood sound either friday night or saturday night

 

You should really understand how the rats nest works before you remove it. Some of the devices such as the air controll valve are routed through the nest to particular selenoids. Not all of it is for emissions like icemark said.

Personally, I should have kept mine now that I know what it does. If I were you, and were having vacuum leak issues, I'd just rebuild the entire intake with a gasket set and a good 20ft or so of vacuum tubing for the rats nest.

thats me tho.

 

There are literally dozens of threads covering it. Search for terms like solenoid, emissions, AVC, UIM, air pump, rats nest, vac rack, twin-scroll, etc. Don't just rely on one thread, look at a bunch of them. Thorough reseach will mean fewer mistakes (yours or repeating someone elses) and a much greater chance the car will actually run afterwards.

 

i removed mine way back and you have to have a visual reference to see where those lines go before removing them. most of them can be removed entirely but some must have vaccum on them somewhere. i just used the vac diagram in the haynes manual and the FSM to see what went where. before removing stuff though you need to know what each component does. some of those solonoids and lines and all the other stuff youll still need

 

The "Rat's Nest" is a common term accross all generations of RX-7 referring to the assembly on top of the engine block that holds most of the vacuum hoses, fuel/vacuum pipes and solenoids. It looks like a big mess so that's how it got the nickname. If you loook at a later carb'ed 1st gen you really start to get the idea.

Most of the time people remove it because they are confused and don't know how it functions, are under the impression that it will make the car better in some way, or have a problem with it that they cannot solve due to their lack of knowledge.

Other times it is removed on upgrading to a standalone engine management system since it's functions are no longer needed.

 

Ain't that the truth.