Secondary air delete?

[ExspRS]

Hi all,
I've heard something about a secondary air delete?
I have no idea what this is.
And something about removing something plastic in the Inlet runners?
What is this all about?
And should I do this to my car?

[IanH755]

I have had both of these done so I will try to explain why/what but very long story short 99% of the time No it's not worth it

Secondary Air - The Secondary Air Injection (SAI) system is used to help with emissions after the engine is started when cold. So for about 30 seconds after the engine started the (SAI) Pump will activate to add extra air into the exhaust to get the 4 OEM Catalytic Converters (2 on the back of the turbos and 2 at the bottom of the downpipes) to heat up faster as they work better when hot and not as well when they are cold. I don't have these 4 OEM converters fitted, I only have 2 aftermarket "sports" cats fitted far away from where the extra air is injected so the SAI system is virtually ineffective on my car so I asked MRC to remove it. It's not done for performance but just to remove "unused" items which can occasionally fail.

Inlet Runners - These reduce the size of the gap in each air inlet to help increase torque a little bit at low RPM. They can stick in the wrong position and cause maintenance issues but usually thats more common to the NA engined RS4 than the RS6. I had mine removed during my 900+ conversion as I wanted to remove any potential restriction/failure point in the inlet system and the amount of torque lost by removing them at low RPM is negligible for my car. Again it's not about gaining any extra performance, it's mostly about removing a potential failure point.

Should you do this to your car - Unless your car is (or becomes) highly modified I would say "No, there's no need". Even if you do modify your car heavily these two mods are still not going to increase performance so at that point it's up to you to decide whether the extra cost to remove these items is worth the "potential" reduced maintenance on them (which is already very rare anyway).

Hope that helps.

[ExspRS]

Hey Ian,
Thanks heaps for taking time to explain both.
I'm trying to make last minute add ons of obscure mantainance items or modifications to do when my engine comes out and apart in a few weeks time.
So I'll probably ask my engine builder to do the secondary air delete and Inlet runner piece if he isn't already doing them from your advice
Cheers.

[welwynnick]

A stage 3 upgrade sounds interesting. Care to share what work you're having done?

Cheers, Nick

[ExspRS]

Hi,
2009. Just clocked over 100k kilometers

Main bearing seals
Oil pump seals
Re-sealing engine
Coolent hoses along firewall and in wheel arch
Carbon clean
New spark plugs
New coil packs
Replacing upper and lower control arms
Suspension bushes
Gearbox service
Re-gas air conditioning
Secondary air delete (because this forum thread, cheers!)
Intake runner modification(^^ same as note above)

Stage 3 Upgrades:

Gearbox tune
Ecu tune

[IanH755]

Looks good so far! 2 extra things I'd consider with the fuel system -

The in-tank fuel pump upgrade - Just because you'll demanding more fuel at the engine (uprated injectors/HPFP's), even something like a Walbro 255L/hr pump would be sufficient.

HPFP - These are directly driven by a little tappet in each Head and these can wear-out, reducing the pressure the HPFP's should be running at (approx 5BAR) so I'd consider replacing them - Part No is 07L109311 - item No 4 below

[ExspRS]

Hi again Ian,
Thank you so much for your suggestions, diagram and even part numbers!
Like your last suggestions; I will defiantly discuss with my engine builder on Monday morning.
Thanks heaps.
Steve