Airbox Question - B5 RS4 vs. C5 4.2L A6

[BRSFour]

I am piecing together the intake upgrades for my upcoming stage 3 build, and am looking for the top half (outlet to MAF) of a B5 RS4 airbox...

I recently read a post where someone said that the top half of the B5 RS4 airbox is essentially the same as the top half of the airbox from a C5 4.2L A6. All that's missing is the plate for the ICMs which I won't need anyhow after converting to the TFSI coils.

Can anyone confirm this? It seems to good to be true, but if so, it's definitely the way to go!

Thanks for your time. Any thoughts on the subject are greatly appreciated.

[gmdiluca]

In for info this would be so ideal considering the RS4 airbox is stupid expensive

[BRSFour]

Here are a few pictures that I think best show the variations between the airbox designs. In the top picture, the airbox on the right is from a RS4, left being from a S4. The bottom picture shows the 4.2L V8 airbox. There are definitely some subtle differences, but as long as the outlet dimensions are the same, then one should be able to make this work...





I might bite the bullet and buy an airbox just to measure it. Anyone with a RS4 airbox willing to post comparison pictures of the outlet if I do?

[zipdoa]

Bump - has anyone established this? I've heard an S6 airbox flows same as an RS4 airbox, it just doesn't have the flapper port.

Relevant info - RS4 airbox is 93mm:


http://myaudis4.com/rs4-maf-flow-test/

[zipdoa]

Well... My D2 S8 has the same maf as a B5 RS4. I'll pull the airbox to investigate...

[jbain2]

The way the MAF housing interfaces with the air box is differ. The B5 S4 stock box has clips. The RS4 or 4.2L version attach via screws. I can tell you that the MAF housing ID for the 4.2L is 83mm so just off what is often used in the B5 S4 world for tuning which is 85mm. I suspect that this would be an easy work around. I have played with several airbox setups for my 2.7 swapped B7.


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[mauromj]

There is not a lot of info on this, so I will share. This was one of my best kept secrets…

As mentioned, the C5 4.2 airbox is very similar to the B5 RS4. It uses a bolt on style Bosch MAF, with an 83mm ID. This means you can cut the Bosch MAF housing and simply use the end of it as a 3.5” flange. This setups allows for a true 3.5” setup all the way through (well, 89mm OD, 83mm ID).

I’m using a standard B5 S4 lower airbox with the bottom cutout for more flow as well. In theory, this should be a better setup then a B5 RS4 box, and is significantly cheaper. You really can’t beat the OEM look in my opinion.

IMG_2357.jpg


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[Ronny_Nordstrom]

I picked up a A6 C5 4.2L V8 Air box with maf today, if anyone need any info about it then feel free to ask. Can measure if needed

[zipdoa]

There is not a lot of info on this, so I will share. This was one of my best kept secrets…

As mentioned, the C5 4.2 airbox is very similar to the B5 RS4. It uses a bolt on style Bosch MAF, with an 83mm ID. This means you can cut the Bosch MAF housing and simply use the end of it as a 3.5” flange. This setups allows for a true 3.5” setup all the way through (well, 89mm OD, 83mm ID).

I’m using a standard B5 S4 lower airbox with the bottom cutout for more flow as well. In theory, this should be a better setup then a B5 RS4 box, and is significantly cheaper. You really can’t beat the OEM look in my opinion.

IMG_2357.jpg


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Awesome info, was hoping I could avoid the RS4 airbox and keep it OEM.

I'm doing a full RS4 intake tract, I would assume the RS4 MAF will mate directly with the upper C5 4.2 airbox? No cutting required in this scenario?