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post #1 of 16 Old 7th October 2016, 01:35 AM Thread Starter
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Cold Air Feed Mod

Hi everyone, just a little mod I have recently carried out to my A5 3.0tdi Quattro. I have carried out similar modifications on most of my vehicles always with a positive outcome. The mod works best with larger turbo'd engines (as you would expect by increasing airflow efficiency) but some factory airboxes are more efficient than others to begin with. As it happens the A5's offering is pretty decent however I've never come across one I haven't thought could be improved!

This modification basically provides a forced cold air feed to the hole located at the bottom of the airbox. This has a butterfly valve covering the hole which opens at 3,000 rpm which I have removed. It un-clips from the mechanism quite easily and can be put back if desired. The hole takes its original feed from a trumpet on the other side of the airbox towards the headlights which is also removed by twisting and pulling out of the airbox. The trumpet is just drawing ambient air from behind the headlight so a feed of fresh moving air will certainly improve flow.
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post #2 of 16 Old 7th October 2016, 01:44 AM Thread Starter
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You will need an appropriate sized hose to run from the new intake to the hole in the bottom of the airbox. Luckily for me I had a spare hose left over from a K&N kit which happened to fit snugly in the hole of the airbox. The grooves on this hose acted as a thread to screw into the hole making it nice and air-tight.

APOLOGIES - MY WORK FIREWALL WILL NOT ALLOW ME TO POST ANYTHING OTHER THAN THE ORIGINAL POST - SOON AS i AM HOME I WILL EDIT AND POST FULL WRITE UP AND PICTURES!

CHEERS
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post #3 of 16 Old 9th October 2016, 10:32 AM
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Just dont through any puddles!
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post #4 of 16 Old 29th October 2016, 11:59 AM
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I thought my commute was a bugger but this guy is already on day 22 and no update?

Agree with the last post that any small flood could force water into the engine ala BMW style.

Like the butterfly valve removal though!

PS - Good luck on that return from the Amazon delta. LOL

His - A5 3.0 TDI Quattro Sportback, stage I map, RS5 pedals & Grill, 19 inch alloys, LED Interior light pack, Folding Mirrors, Auto dim rear mirror, Transmission mount, rear spoiler, de badged.
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Hers - A1 2.0 TDI Sportback. Every extra apart from Sat Nav and panaromic roof.
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post #5 of 16 Old 12th November 2016, 05:04 AM Thread Starter
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I'm back . . . glug glug glug . . .

Just resurfaced from my trip to the bottom of the M25 basin.

Apologies all round but since my last post my DPF has completely blocked after the cars failure to regen even after a forced one it was still too blocked to save. Also the clutch is on its last legs and juddering like crazy so have also decided to have that replaced seeing as the car is in pieces anyway.

Unfortunately due to the fact my car is the early (and frankly stupid) "long" downpipe DPF design it is rare as dodo teeth and as a result rather that getting an after-market replacement I am having it cleaned whilst the clutch is going on.

Appreciate the advice regarding the air intake, indeed it would be a concern about getting water into the engine but due to the bend in the pipe (its kind of an "s" shape) behind the fog light cover, the water would do very well to get anywhere near the airbox so fingers crossed no problems.

I actually hadn't realised anyone was paying attention to this thread, if so I would have written up more quickly but like I say its been a bit of a nightmare trying to sort out my DPF woes.

Anyway here's the write up!

Cheers,

Chris
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post #6 of 16 Old 12th November 2016, 05:09 AM Thread Starter
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Next choose what kind of air intake you want to fit into the fog light grill. I chose a rectangular tapered feed but I have had large trumpet types which work well also. I just felt this intake went well with the design of the bumper.
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post #7 of 16 Old 12th November 2016, 05:11 AM Thread Starter
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Remove the grill and have the hose attached to the hole of the airbox at one end and leave it ready to attach to the new intake at the other. You will want a little bit of "wiggle room" so the hose is not too tight that you yank it out of the airbox every time you remove the grill but not so slack that you have miles of unnecessary hose (after all we are aiming to improve efficiency).
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post #8 of 16 Old 12th November 2016, 05:12 AM Thread Starter
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Now draw/score the shape of the new intake on the rear of the fog light grill to make a template of where you will be cutting. Then cut out with a hack saw/jig-saw or whatever you feel comfortable using. Remember to cut on the inside of the template, especially if like me your intake has a lip which you wish to fit snugly to the face of the grill. My cutting is not the neatest but remember you can always remove more material, its difficult to add more on!
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post #9 of 16 Old 12th November 2016, 05:14 AM Thread Starter
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Then secure the intake with araldite (superglue) from the rear making sure none drips through whilst drying. Don't worry if there are a few small gaps at the edges, it is unlikely you have cut the shape so perfectly that there are no gaps (congratulations if so!) you can use black putty to fill these in.

I have used some extra tape from behind the intake just to make sure it is as secure as possible, however if you have glued it well it should be rock solid by now anyway.
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post #10 of 16 Old 12th November 2016, 05:17 AM Thread Starter
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Extra tape just to be sure
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post #11 of 16 Old 12th November 2016, 05:19 AM Thread Starter
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After everything has dried you can connect the hose from the airbox to your intake, again the hose was a decent (but not perfect) fit to just rest on the back of the intake as I secured the grill back into position. You can use a hose clamp or tape to secure the hose onto your intake, I may do this at a later date.
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post #12 of 16 Old 12th November 2016, 05:19 AM Thread Starter
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Finally once the grill is back on and looking decent you can use putty (or whatever you like) to mould the air intake for a flusher and more professional look. Mine actually looks a lot better in reality (the photo's make the putty look shiny, its now duller and blends in a lot better). The putty also helps more air enter the intake but smoothing the edges.
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post #13 of 16 Old 12th November 2016, 05:22 AM Thread Starter
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To be fair if I did it again I'm sure I could make it look a lot neater but I had never used this type of putty before and it takes a few go's to master!

Unlikely to see massive bhp/torque gains from this mod (although possibly a few) but the throttle response improves as there is always a direct supply of fresh cold air to the engine.

Hope you get the same results I have from this mod!

You can also drill the slightly restrictive "scoop" that is located inside the airbox from the primary air supply coming from the front grill. From what I can work out all it does is slow the air coming into the airbox. As mine is an early model "07" it also has blanking plates in the top left corner of the grill (right where the airbox draws its air from!). So I have drilled holes in these also. It's not the prettiest but I believe it makes a further improvement in air flow. As I will soon be replacing the front grill I'm not particularly fussed about the cosmetics of that particular part.

Always interested in other peoples cars and experiences so let me know how you get on!

Cheers,

Chris
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post #14 of 16 Old 28th November 2016, 11:48 AM
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I like what you've done here... I currently have one of the Volante intakes on my 3.2 A5 and there is a bottom "intake" on the airbox that draws from beneath along with the grill entry.. could see putting a hose on that bottom intake and route it to an entry point at the foglight area... good call.

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post #15 of 16 Old 14th December 2016, 11:23 PM
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I'm looking at doing this on my 08 pre facelift over chirstmas.

did it make but more induction noise or power?

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post #16 of 16 Old 16th December 2016, 08:29 AM Thread Starter
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Hi there, I would say there is a tad more induction noise but could well be in my head. Main advantage is that the air should be slightly colder and therefore a little denser. Throttle response seems improved although my MAF was playing up so replaced that and now is a lot Sharper. Unlikely to see much power gain but a colder supply of air to the engine is never a bad thing!

Cheers
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