1991 S5 N/A Header install
 

Goodmornig Gents! I have purchased a Racing Beats header used from a seller on Facebook. At the moment what is being included is;
1. RB Exhaust Header as seen in photo
https://cimg4.ibsrv.net/gimg/www.rx7...951b80466a.png
2. Manfold Hardware.
3. Extended 02 Sensor

To properly install this on a S5 I want to make sure I have the proper items in my RB cart for order. I would like to use the factory Y Pipe-back, so I will be purchasing Prescilencer as well as the gaskets.
I've put together this cart currently:
https://cimg1.ibsrv.net/gimg/www.rx7...55a5bac68e.png
Do I need a air control valve block off plate as I do have an S5? What is the install like these are the steps / cart items I know, please fill me in on what im missing;
1. Spray all studs/nuts with PB/WD40 to loosen.
2. Remove factory O2 sensor
3. Remove factory exhuast manifold.
4. Remove exhaust back to Y-Pipe
5. What do I do with RATS nest? / AVC here??
6. Install hardware/new RB header to keg gasket
7. Install header with copper anti seize and evenly tighten bolts
8. Place Prescilencer gasket on rear of prescilencer put copper anti seize on hardware, evenly tighten
9. Install rear side of prescilencer onto factory Y-Pipe and tighten evenly.

Is this all there is to it? Please give insight on rats nest block off and any sugestions welcome.

if you want to keep the 6 ports working you need to keep the air pump and air control valve, you might as well keep the rats nest too. its a lot of work to remove it, and benefits are questionable at best.

also you can leave the original O2 sensor in the original manifold, if you have a new one for the header

Good shout yes, ill disconnect the o2 and just leave it in as I have the extended one coming. So removing anything from the ACV is not needed for a 91 S5? Or just a block off plate for the recirculation delete "Emissions Delete"

Since you have a S5 you need the Air Control Valve for your aux(5th & 6th) ports and your VDI to work. If yours is currently working IIRC you don't have to touch anything to do with them after the header install and they will continue to work. So unless you are disabling them and wiring them to their high RPM position, or they are already non-functioning you don't need the ACV block-off plate. Everything else looks correct.

Is there a way to know if they are not functioning currently at the moment (Stock) don't know why they wouldnt be. So removing the factory manifold doesnt expose anything or open any hoses that need addressed? Sorry for the probably redundantly seeming questions, but I daily my vert just do not want to have downtime. Does this mean I do not need a block off plate for the ACV?

Nope. Just install the header and leave the rats nest intact and don't touch anything to do with the ACV. IIRC it's been a while since did mine (1998) and I did have functioning Aux and VDI when I first did it. Only thing I ever did to the rats nest is replace all the vacuum line with silicone ones and have never had an issue from keeping it.

Got it, so my cart above should be solid for header - Y pipe?

Not sure on the best way. One way is go for a drive and redline it. The disconnect the hoses to the 5th&6th port actuators and repeat if you notice a definate decrease in power on the top end they were working. No change they probably aren't. They should be open above 3800rpm. Do the same for the VDI. It should be active above 5500rpm. Not sure how noticeable a non-functioning VDI is. Maybe someone else does.

Yes. The header presilencer combo bolts to the stock Y-pipe or and aftermarket cat-back. Sound with the stock mufflers is interesting. Kinda deep at idle and below 3k then switches to something resembling a KX85(small two-stroke dirt bike) and a can of rocks above that. I'd recommend getting different mufflers as soon as you can afford it. The Racing Beat's sound nice.
Kx85 power band🫣 - YouTube

I hope it sounds decent i’ll get some mufflers soon really want something throaty, keeping stock parts as i’ll keep the am when i sell the car. Any idea why it sounds so airy stock, this is my third s5 na and my original 91 sounded so much better stock than my 89 and this 91

Muffler design mostly I think. The stock mufflers are chambered similar to a turbo muffler. thrush turbo muffler cutaway - Google Search Most aftermarkets. like the RB is a straight through style.

Bump, need insight here. Do i need a block off for the acv or do i just cap off the line ran to the factory cats and leave the acv alone for the 5/6th ports to continue to work properly ?

It looks like the on the S5 the 5th/6th are controlled by a solenoid which is directly hooked to the air pump which is pressurizing the line. . . .As long as you keep the air pump and solenoid, the ACV can be removed. . . .The caveat to that is the VDI also gets powered through that section of the air pump prior to the ACV.. . . And the VDI is controlled primarily through a solenoid located on the rats nest I believe. . . Check that... . Go to foxed.ca to see a larger view of this to see what I mean.

Air pump has to stay and ACV can get blanked off assuming the air pump still powers the VDI and 5th/6th through their respective solenoids.. .. .It should be noted that I think one of those solenoids is on the rats nest.

I know you can't see it, but the line past "Solenoid (6 P1) also goes up to pressurize the VDI solenoid. (rats nest?)

Go to foxed.ca fuel and emission section page F1-6 1989 S5

Now that I think about it. .What stops a S5 from working like a S4?. . Which is simply using the side port on the main cat to pressure the line to the 5th/6th actuators.. .(or in your case welding a port connection to the header if you have no cats) . . . Probably use the existing check valve... . Interesting. .You can find that S4 diagram on Foxed.ca in the 1988 section.




https://cimg1.ibsrv.net/gimg/www.rx7...7fd3978588.jpg