DIY Intake Manifold Flapper Mod | Piggy Pipe Install | Audi S4 B6 B7

I remove the OE downpipes and show how to install piggie pipes, plus a step by step tutorial on the flap mod for the 4.2L V8 intake manifold found on the 2003-2008 Audi S4.
Featured Shop Tools and Project Materials (Amazon)
DEI Under Hood Acoustic Lining: geni.us/DEI-underhood-lining
DEI 12"x12" Gold Reflective Barrier: geni.us/DEI-reflect-a-gold
Vibrant O2 Sensor Spacer Kit: geni.us/vibrant-O2-spacer
Intake Manifold Cleaning Brushes: geni.us/bottle-brush-set
Mini Wire Brushes: geni.us/mini-wire-brush-set
Centering Punch: geni.us/centering-punch
Deburring Tool: geni.us/deburring-tool
Skip to chapters
00:00 - Intro
01:07 - Under hood insulation fix
03:46 - Piggy pipe downpipes install
11:27 - How oxygen sensors work
14:34 - Oxygen sensor spacer demo
16:32 - How the intake manifold flap works
26:08 - Flapper mod DIY steps
35:17 - Flapper arm repair mod
35:47 - Goooold!
36:29 - JHM intake elbow coolant bypass

[@north49innovations28]

Enjoying the series. I'm a B7 S4 Cabriolet owner from Lethbridge. I feel like I've replaced/modified 50% of the car over the past two years. Fun, addictive and expensive! Thanks.

[@FigureItAudi]

Thanks for tuning in, fellow Albertan. Hope you're getting in some good driving this summer - while it lasts...

[@jjonathan3828]

You should always remove the insulation and never put it back. You don't need it. Let the fresh air be there, let yourself hear the rev notes better, even your hood is painted from underneath and looks super, think about weight reduction. But your channel is great and thank you very much for sharing your knowledge.

[@janvlcek7167]

wow i just found you and i gotta say your videos are great, really educational and im really thinking about doing some of these upgrades on my B6 S4 avant. Thanks man looking forward to new episodes with this build

[@FigureItAudi]

Thanks Jan, appreciate it - lots more in the works right now.

[@215djt]

Yesterday I took a stapler to my hood insulation to stop it from leaking foam! I needed this!

[@peekaboo4390]

I am reso modding an 03 A4 3.0 convertible. The manifold on the AVK engine is a one piece abs plastic with two flappers so cleaning it is very difficult. I soaked the unit in industrial degreaser for two days and the amount of blow by was incredible. I did a full top rebuild and the timing belt water pump and all that stuff. After mounting all back and trest driving her I had a noticeable increase in low end torque and throttle response. I will also be mounting a catch can this spring.

[@jerbear2199]

Keep up the videos. Love it

[@wgfvideos3768]

The down pipe 3 bolt flange that’s on driver and passenger bank all six Is actually a 12mm nut. great video dude keep up your vids !

[@s4_murph]

Here from Matt's post on Facebook. Was not disappointed.

[@bathc0198]

Amazing video

[@maxallen9012]

You could have bought a spark plug gap or this also called a spark plug spacer and also can be used for the auction sensors

[@glenbjack]

I think some of that sludge is partially from audi's internally egr solution. Through the intake valve. Exhaust/intake Timing overlap for just enough exhaust for next intake stroke, helping pass emissions. I read it in a audi ssp on the 4.2l 40v. Ahead of their time❤ great video

[@XXSkunkWorksXX]

As an S5-V8 owner with p2004 error (flaps stuck in open pos) inside the intake I am trying to learn as much as I can because I'll be damned if I want to pay £3500 to have a new one fitted. Mine is the magnesium intake with electrically operated flaps and is slightly different but I found your video to be most informative. Kind of like a friendly study class. One of those _I-think-I've-bitten-off-more-than-I-can-chew_ classes! - but hey, nothing ventured and all that. Subb'd and Liked. Thanks again.

[@FigureItAudi]

Granted, I'm not familiar with your intake setup but I doubt anything is wrong inside the intake and it has more to do with how they're actuated. Failure is usually related to 1 part (ex. a solenoid, or wiring) than the whole system. If I'm to assume your S5 is your daily car, you're practically better off looking for a whole intake (on the B7, you can find a fully plumbed one for $250 CDN) to purchase from a part-out car, use that as your learning model and spare parts source, then fix yours when the moment is right.

[@FigureItAudi]

I've also learned a lot on my own projects when I'm jammed up on a lack of understanding how something works by reviewing the system in it's schematic form. You can find yours on www.ilcats.ru/audi/.

[@DOMS4.]

I got longtubes while I had everything out, definitely one my favorite mods. Completely different sound. Edit: Also I've driven my S4 through 3 Toronto winters and have had no issues with cold throttlebody sticking

[@FigureItAudi]

Good to know x 2. Jealous of the headers.

[@DevJB]

Probably because the crazy heat near firewall keeps it warm, just above a pre-cat. ; ) p.s. First winter I drove my S4 b6.. It got a stuck open fuel injector and ruined the alusil block.

[@kevins4155]

You got a link for the long tube headers?

[@bluemoth1879]

Brilliant…:) 🥂🤙

[@ThorinJames]

Hey Steve, Could you speak to why you chose UHMW poly vs Nylon or another material? Some plastic vendors I have spoken to are noting the 200-212F limit of the UHMW might be an issue.

[@FigureItAudi]

My choice was largely based on chemical resistance knowing it'd be in contact with oil, unburnt fuel and whatever else might contaminate the oiling system. I hear you on the temperature range. My thought was that although the engine bay can reach temps that could theoretically put the material at risk, the flap isn't exposed to those temps directly. In fact, it's exposed to a cooling source (intake air!) that's well below its threshold. Is there a more optimal material out there? Yeah, probably. After putting a few thousand KMs on this modded manifold I took it apart for an inspection and the components were holding up great. No loose fasteners, flap hasn't misshapen, nor discoloured. My hope would be that as more people DIY this mod and make alterations in material, flap design, etc., they can add their own data to the conversation too.

[@paradox5087]

i gotta question for my 4.2 squad anyone done motor swap to new chassis how hard are they to re wire i have a massive plan and its to take gods motor and pop it into another chassis its not been done before or at least where I come from please help

[@ThorinJames]

Any recommendations for getting the spring housing (flapper rotation) out of the body? I have everything disassembled to the point of removing the rod and housing. However getting the housing to come out is proving rather difficult.

[@FigureItAudi]

You might just have to give it a little whacka whacka from the back. Once the spring and arm were removed from the front, mine more or less just fell out. The rod is truly just sitting in a hole in the manifold with nothing else holding it in place.

[@DOMS4.]

To anyone doing this mod I'd recommend using Teflon or Nylon for the flapper due to high temps. UHMW isn't really recommended over 100⁰C.

[@RCeolim]

Hello From Brazil. We have a touareg 2008 4.2 v8 with the same engine as your video. I suspect that the diafragm (inside pcv valve) is perforated, because there is a lot of air suction on oil cap and when i acelerate a lot the EPC failure warms up in painel. My doubt is: Can I substitute only the diafragm (i found the diafragm on internet) but i didnt found all pcv valve to buy. Bests reguards. Rafael

[@FigureItAudi]

Hey Rafael - My guess....as long as you can open the PCV without breaking all the tabs and get it back together so it doesn't leak....yeah, swapping out the diaphragm could work. The whole unit should be pretty cheap though (it's like $12 USD); do you have the ability to buy from American websites? Suction in under the valve cover is a good thing, though so the PCV may not be your problem. I would check the fault codes store in your ECM if you can get someone with a basic OBD2 reader to do a scan for you.

[@RCeolim]

@@FigureItAudi I read that suction through the oil cap may be the pierced diaphragm. It also fails after 5,000 rpm and takes a long time to change gears when it accelerates strongly.

[@RFaggioli]

Great videos. Not enuf people making vids for DIY'ers to correct factory design flaws. Us V8 guys have timing chain guides, intake camshaft adjusters, oil leaks, motor mounts and 20+ hoses that will burst @ some time and cost an arm & a leg to purchase, if even available. I will enjoy her while she's still in good shape. (how many times have we all said that?) My one critique on this video was the scene showing how to remove the collar holding the flapper into lower intake must've gotten left on the cutting room floor. Good grief it's a chore. I got the clooar to come out with some sensible prying, but getting the shaft to free up from that collar is proving difficult to say the least. The visual aides were priceless nonetheless. Thank you!

[@2nsane2005]

How tough should it be to move the pivot arm. I have my b6 s4 manifold on the work table and I can move the pivot arm back and forth but it does take a bit of strength to move it. Thanks

[@FigureItAudi]

That's a good call out. So, I too was surprised at how much tension the spring applies to the arm in its default state. To me, it's way (WAY) more pressure than I think needs to be applied to the flapper arm to counteract the vacuum in the intake - but neither of us are german engineers (right?). I'm always amazed to see the actuator pull back the pivot on start-up, but it works under the vacuum provided so what can we say? That said, having the pivot assembly nice and clean will ensure no additional stress is applied to the actuator.

[@2nsane2005]

@@FigureItAudi I guess it is what it is ha.

[@davidzicch2820]

did you notice any performance difference after you installed these downpipes? I have read and heard that with the B7 RS4 installing downpipes and or gutting the pre cats on the OEM Downpipes. Can cause a loss of low end torque / power. Did you experience anything like that or anything at all after the install?

[@FigureItAudi]

No, I didn't notice a lack of power, but to be fair, I couldn't feel the gain either. I think anything in the 10ish HP range is essentially unnoticeable to the butt dyno. I also don't really understand how the removal of the pre-cat (which causes the largest, earlier bottleneck of exhaust gas flow) could reduce torque. IMO, this is one of those claims that has to be dyno proven, otherwise it's just more armchair mechanic hearsay, kind of like my guess here :)

[@davidzicch2820]

@@FigureItAudi appreciate your assistance and feedback. I agree with you on all. I just gets confusing when you hear so many conflicting opinions / experiences. Last thing I want to do is spend the time and money on downpipes to loss low end torque and gain it in the top end.

[@davidzicch2820]

@@FigureItAudi What is your experience with intake spacers with port dividers removed for the B7 RS4? Any real noticeable benefits? Again, something I hear conflicting opinions and experience with.

[@FigureItAudi]

Keep in mind my manifold (S4) is different than your RS4 one. The spacers and modifications to the intake manifold are definitely another butt vs. real dyno situation, but I do believe in the science behind runner length, air flow and of course heat management. In that sense, the spacers are a great little investment. I subscribe to "more (smooth) air in, more air out = good".

[@hossein3867]

@@FigureItAudi I can assure you that you don't lose torque from removal of the pre-cats. when mine got hollowed out and before my JHM flash, the moment I drove away, with out any doubt I had way more torque than before.....no way that was in my imagination.

[@charlesr4325]

where is the video of the sound of the exhaust ?

[@Martijndeboer_]

Iam working right now on this mod, any recommendations on how to apply any sort of pressure to the spring? Mines loose and I can’t seem to get it tightened

[@FigureItAudi]

That probably means it needs to be compressed another full rotation before you start installing it. The spring pressure is insanely high for what it needs to do. I can't recall my installation trick exactly but do whatever you can to coil up and hold the spring prior to seating it. You may be able to zip tie the ends to one another then cut it when it's ready to release.

[@Martijndeboer_]

@@FigureItAudi actually that’s a pretty smart idea! How dit I not came up with this 🤣 Thanks a lot for your answer 👌 Loving the series btw 👊

[@anthonyriccitelli4852]

What size nylon bolts /washers did u use

[@FigureItAudi]

1/4" for all hardware associated to the flapper mod.

[@polygon9176]

where did you get that type of material for flapper mod?

[@FigureItAudi]

Although I did find options on Amazon for it, the reviews mentioned that the size and quality was questionable, so I searched for commercial plastic distributors in my city and found a place that had a variety of plastic options in different thicknesses and would only charge to cut a piece to my dimensions. Worst case, you might be forced to buy a sheet and fashion the flap yourself. You probably just need to call around.

[@EGEIS9]

i also have a b7 s4, I honestly dont exactly know what the flaps purpose is i did a lil research and its suppose to help with the proper air to fuel mixture etc. but my question is why not just delete it entirely?

[@FigureItAudi]

Did you watch the video though? Lol, I literally explain how the flap affects low and top end torque by shaping runner length. Fuel isn't a relevant part of the intake manifold flap and definitely don't delete your flap - you will notice the (bad) difference.

[@EGEIS9]

@@FigureItAudi at first i skimmed through out and thats when i made my comment but i did indeed watch the video after. Im currently doing the timing on my s4 and possibly might have to rebuild bottom end so i was looking for some mods to do while everything was out.

[@EGEIS9]

@@FigureItAudi i finally got my s4 to run and she is running pretty strong. do you know what the performance numbers are like with the flapper mod? any hp increase?

[@SlowwS4]

Any downsides of gutting all 4 cats?

[@FigureItAudi]

Yeah, the car smells terrible and the exhaust pipes and muffler tips get quite dirty. And you know, the environment.

[@SlowwS4]

@@FigureItAudi yea

[@NoDayz0ff]

why not just remove the intake manifold flap all together? similar to the cats, less restriction and more air flow

[@FigureItAudi]

The flap is super important to maintain low end torque. If you were to remove the flap and shortcut the runners, your car would actually be slower for the majority of the rev range. And even though I'm saying that long runners are good for lower end power, it's not like creating ultra long runners with - let's just say a theoretical, 6 inch intake manifold spacer between it and the intake ports - is a good thing either. Good engineering is happening in the manifold; this mod just attempts to make the air move a little smoother.

[@NoDayz0ff]

@@FigureItAudi thanks, appreciate the response, i have a b6 3.0 and the manifold runners were shot and instead of spending few hundred on flap and diaphragm, i just removed it =/

[@calebbay8372]

the only thing I needed to see was how to get the flapper out of the intake and he didnt show that. Why would you put all that nonsense in there. It just going to break. The engineer that made it certainly knew about the airflow requirements. flapper mod is hack mod.

[@MikeFico998]

Broseph just rip the whole thing out