I have a 1990 NA-Turbo build and was reading up on a rats nest delete and I just want confirmation, can I just delete this whole thing, cap it all off with a banzai racing kit. Tune it and be set?

 

Yep.

 

Yes. When I did my 6 port turbo build i removed the entire assembly. It's sitting on the shelf..

Have fun!

-M

 

This is good to know as the JSPEC S5 TII motor I bought a couple years ago was missing the rats nest. I got it local pretty cheap because it had low compression on a couple faces of the front rotor. It was mostly intact other than having a S4 throttle body and no rats nest.

 

Hi everyone,
I am installing the third engine in my RX-7 and decided to delete the EGR, Sub-zero starting assist, and the Secondary air injection control system.

Are there any issues with drivability doing this, I heard of open loop and limp mode?

Here is a picture of my rat's nest as I want to install it, after spraying it all with clear satin engine paint.



After looking everything over, am I correct that only the fuel lines and the purge valve will be functioning? Along with the fuel pressure regulator and the air bleeds on the primary diffusors. Which vacuum hoses can be capped off? These capped lines will be one less thing to cause a vacuum leak going forward. There's only 13 connections!

The reason for the deletion of these parts is to limit the introduction of carbon into the engine.

Here is a picture of my last engine.



Quite a mess!

Your help will be greatly appreciated!
Thanks!

 

I am putting together some videos on this very subject. I found someone who can edit what I have recorded, and we should have it out this summer. My hope is that it works as a complete guide for how the vacuum system on an S5 TII works.

Gsmith, there are a few unrelated things mentioned in your post. These systems look complicated until they are broken down to the fundamentals. First off, deleting the sub-zero, egr, and air pump assemblies is ok and won't effect much. The only thing you should notice after a completed delete is that your stock ECU will show fault codes 30 and 33 whenever you read them off. These are not critical enough to throw a check engine light when normal driving.

The rats nest is actually a pretty good way of organizing a lot of different vacuum routings into one unit. The more I got into it, the more I thought better of it. With the deletes you have completed, you will only be using one solenoid, the orange one, for your fuel pressure regulator. You can leave the other solenoids on the rack and use them as backups in case your fpr solenoid breaks on you going down the road. If those rubber hoses aren't new, I'd upgrade to silicone hoses that will maintain pliability. Other systems you should leave still hooked up are the PCV system to ventilate the crank case, the evap system (charcoal canister) to relieve your fuel tank pressure, and the 3 air bleed systems. The 3 air bleed systems are for the primary, and secondary injector diffusors, and the oil injectors. These 3 air bleeds carry air directly from the throttle body ports to the lower intake manifold. They supply the majority of your idle air, with adjustment coming from the idle adjust screw on the side of the BAC valve. Don't touch the screw on the throttle body if you haven't already.

As far as keeping carbon out of the engine, the only carbon sources into the engine are the oil and fuel systems and the EGR (unless you haven't changed the air filter in decades). You have removed one of these. The oil and fuel issues are addressed by having good fuel mixing and atomization at the injectors. This is done by keeping all of your injector air bleeds working correctly, as well as the oil injector vacuum lines. These 3 air bleed systems give the fuel and oil enough velocity that it mixes and goes in with the intake air instead of dribbling down the intake. If fuel or oil is just wetted to the side of the intake runner, thats where you're going to get carbon build up. When its mixed and moving, it gets burned and sent out (more so for the fuel than the oil). Also, making sure you don't have vacuum/boost leaks ensures correct fuel mixing.

Once you get everything put back together, remove and cap the line for your MAP sensor so you don't damage it, and test the manifold pressure with about 10psi. You should hear any leaks and be able to fix them. When you start your engine, you should notice a lower idle than before, because you are not receiving air from the pump, nor the EGR. You will have to go through the factory procedure and adjust the idle with the screw on the side of the BAC. Then you should be good to go.

 

this one time, i had to put the emissions stuff back on a car, but without the rack as it had been thrown away.
so i ran hoses instead and it works, but its a huge mess, vacuum rack is way cleaner

 

Thanks for your reply, this is the information that makes it work!

It is an amazing engineering thing, the hardlines tee into one another, loop back and seem to defy logic! It is a thing that it all works together.

Which hoses can be removed and capped off with my deletions? Any help will be appreciated.

 

Sorry to bring this thread back from the dead. I am in a similar boat, just rebuilding my system. I am running an emissions delete removing ACV, Air Pump, EGR, relief and switching solenoids. My OMP has also been removed. Was wondering if you had any input on how you finished up the rest of yours?

I assume without the OMP, that air bleed line that goes to that can be capped off as well? Ideally I would like to make a step by step guide to this once I am done because it has been a chore scouring the forums.

 

If it were me, I'd keep the air bleeds to the oil injectors. They supply a large portion of idle air. It might be difficult to get the idle right after capping those off.

 

Hi, at cold or hot idle the oil metering pump is practically shut off. Only when the throttle is opened does the rod lift to allow the oil to flow.
I am not an engineer so I am assuming that the air entering the top of the nozzles keeps a vacuum from forming that would stop the oil from leaving the nozzles
To me, even when the rod is lifted into the MAX oil flow to the four nozzles, the amount of air entering going into them would not amount to much.

That being said, at idle is when the intake manifold vacuum is highest and the OMP is flowing its minimum amount of oil, there should be a strong vacuum pulling on the nozzle openings.
Is this when the nozzles are allowing the extra air into the manifold?

Perhaps someone can do a quick test for this! Directly after a cold start, pull the hose off the dynamic chamber and put your thumb over the hose end.
If you feel a vacuum on your thumb, this shows that some air is getting through at idle. If not, this means that not enough air is bleeding through the nozzles to affect the idle quality.
You can alternate taking you thumb off and on every few seconds and see if there is any change to the idle speed.

Now for the real reason for keeping the OMP system installed and working. Upon deceleration the computer does a semi or full fuel cutoff. To help emissions of course.
If you do just a pre-mix, that wonderful 2-stroke oil mixed into your fuel will never enter the engine, you would be surprised how much of the running time of the engine is under deceleration!
Keep the OMP working and the engine receives the oil it needs at all times. What do you think of my reasoning behind this?

 

My ports for the Injectors are capped with freeze plugs, so I'll end up capping them.

As per the other post about the OMP; that does make sense. Overall, with a newly rebuilt engine and trying to keep things as simple as possible, I'm not super concerned with it. The level of care I will give the car versus what it got its first 30 years will be quite different. That is an interesting point about the vacuum and I may have to test it once everything is back in the car.