SAI and coolant hose delete

A5/S5/RS5
#1

I’d like to know a few things about the extra coolant pipe that tees off the manifold as well as the routing of the SAI pumps and actuators.

Where does each SAI draw its air from? I see the lines that transport the air are those ugly ones strewn across the valve cover…they enter the exhaust through that silver bottle/tube that’s bolted to the back of each head. When we delete the system, do we remove the entire silver tube and bolt a block off plate to the back of the head as well as each exhaust manifold?

Regarding that coolant pipe, I see how it’s typically removed and blocked off. Is anyone having long term issues from plugging the lines?

#2

As far as the Coolant pipe to heat the air going into the intake manifold there is no reason why there would be long term issues.
The SAI lines come off a fitting attached to the back of each Head and go through a one way vacuum operated cycling valve and over the top of the valve covers and to the SAI electric Air pumps in the lower corners of the front bumper, technically it is front to back and the air enters the back of the Heads and down a drilled passage with an outlet into each exhaust port.

#3

Wow that’s different than I thought. So the special passage in the head is used only for that purpose and doesn’t access any crankcase air? If that’s the case do most people leave it open and only block off the exhaust?

#4

For the SAI system, which has been around in vehicles in various forms since at least the early 70’s, Air is pumped into the upper (exhaust ports in the head) to mix with the hot exhaust to promote a fuller secondary combustion before the exhaust is released into the environment, also before entering the Catalytic Converter, if installed. The SAI system can be unbolted right off the back of the head and flat aluminum blockoff plates can be fabricated or purchased (JHM is one Co. that sells them) to cover the SAI passage. You will get a check engine light with the system removed unless you also run a custom tune that codes the message out. The system only runs for maybe 1 minute on a Cold start so it’s night like the world will end if it is removed but the CEL will remain if not coded. I do not need an emmissions test where I live so I have never checked with Vagcom to see if the SAI systems readiness tests pass.
Crankcase air is a mixture of gases of oil, fuel, and air, which by there nature of being unburnt are pumped back into the intake system to be burned in the combustion process in the cylinders. They are also what causes the majority of the deposits on the backside of the intake valves in all earlier designed Direct Injection System vehicles. Old Carbureted and Port injection vehicles had fuel dumped into the Intake manifold or Intake Ports which helped wash that oily crankcase mixture and carry it into the combustion chamber. With DI cars you get that crankcase vented gases burning onto the backside of a hot dry valve and intake port because the solvent like fuel is being directly injected into the cylinders.
I say earlier DI cars as most newer designs from most manufactures have greatly solved this issue by installing a smaller injector into the intake port or manifold in addition to the main injector in the cylinder, problem mostly solved.

#5

I know how the systems work for the most part after reading up on them. The BMWs I’ve had in the past didn’t have any SAI system and I also know the SAI is separate from the PCV. My question now is, after the complete removal of the SAI system including the valve attached to the back of the head, does that hole have to be plugged? The exhaust manifold hole is separate and obviously must be blocked off.

#6

There is no hole on the Exhaust manifold, the port is on the back of the head and there is an internal passageway that goes from the back of the head to each exhaust port in the head. The passageway on the back of the head is then blocked off with a plate when removing the SAI valves. https://jhmotorsports.com/block-off-plate-kit-for-sai-secondary-air-injection-plates-jhm-for-b8-rs4-and-rs5.html
Most BMW’s I know of also use a SAI system. E39’s, E46, E60’s, etc… I work on a few different BMW’s for friends since I’m the only one in our circle that has a shop with a lift. I know of a few old '70’s/80’s BMW’s that used a mechanical belt driven pump but most everything since the early 2000’s at least uses Electric pumps.

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#7

Thanks a ton for the info. I tried YouTube and no one really explained it for the Audi 4.2. I always worked on BMW turbo inline 6 but they don’t have SAI. It’s a new concept for me.