Audi S4 - Carbon Fiber Hood

This is a review of the Aerofunction B7 AF-1 Hood in carbon fiber which can be found & purchased from Aerofunction directly. Email them at info@aerofunction.com to place an order…alternatively, it’s available on Amazon here for $879 plus shipping.

I had been looking for a carbon fiber hood for my Audi S4 (and my A4 before it) for quite some time until I found a link to this hood posted on Audizine when I was up browsing late one night. Previously, the only manufacturer who made a vented hood for the B7 Audi platform (2005.5-2008 A4s, S4s, and RS4s) was Vorsteiner, and that hood had been discontinued well over a year ago. When I heard about this hood I was thrilled, and I contacted Aerofunction immediately. Aerofunction explained to me their fitment guarantee and three year warranty on all parts, and assured me if I wasn’t happy I could ship it back and get a full refund. The price seemed very fair, so I went ahead and made the purchase. I couldn’t find any firsthand reviews of the hood before buying it, so I took a ton of pictures (and even a video!) to show just how nice it looks. I’m really excited to be one of the first people to buy this hood and share pictures of it, and I have a feeling a lot more Audi owners will be buying this soon as it’s a really good product at a really fair price, and offers both performance & aesthetic benefits…

Audi S4 Carbon Fiber Hood by Aerofunction

The hood offers great looks, OEM-like fitment, and the vents can be drilled/cut-out to be functional. When you order the hood, you can choose either fiberglass or carbon fiber. The carbon fiber doesn’t offer a ton of weight savings over fiberglass (which is also very light), but I thought it was well worth the extra price for the carbon fiber version to match my other carbon accents (like my interior trim and B & C pillars). The hood comes from Aerofunction without the vents cut-out so that if you do not wish to have them functional you don’t have to (some people worry that water may get into the engine bay). I indeed wanted the vents cutout, but luckily I have a great body shop, Phoenix Collision & Custom Paint, to help me with that. My hood came within a few days of me placing the order and I had it shipped directly to my body shop so they could paint it.

Audi S4 Carbon Fiber Hood

The only downside to the hood is that if you want to cut-out the vents to make them functional, it will take your body shop some extra time and expense to do so. My shop told me it took about 10-15 hours to complete the hood, which included time to paint and install it as well, although most of that time was spent cutting & filing each vent to make sure they were cut-out perfectly. It was time well spent, and I’m really happy with the paint scheme we chose that exposes some carbon fiber but not too much and blends nicely with the rest of the car’s carbon fiber accents. My body shop said that the hood fit very well and didn’t need any major adjustments or anything like that – they reused the stock hood latch and used a small shim underneath the latch to make it fit absolutely perfect. You can see the fitment really well in the video below – I am very impressed with how it lines up with the body lines, I have seen a lot of carbon fiber hoods in my days and very few fit this well:

The Aerofunction website advises you to use hoodpins. When we first installed the hood, I was seeing the hood lift and move at high speeds (80 mph) more than I liked. We had cut out all of the vents to be functional, and our theory was that the top layer and bottom layer of the hood was separating at high speeds due to the air pressure. We decided to take the hood off and fill any gaps between the top & bottom layers by injecting an expanding foam into it. The foam may have also added 2-3 lbs, but the hood felt a lot more solid and best of all, no lifting or movement at high speeds (I’ve tested it up to 100 mph so far). I feel pretty confident without hoodpins, so the plan is to run without them permanently. Here is a picture of the underside of the hood after we injected foam and painted the underside black:

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The only other modification we made was to remove the factory hood strut, as I worry it is too strong and may crack the hood. It is pretty common advice to do this on carbon fiber hoods as the OEM hood struts are intended to raise something that weighs 5x as much and therefore may be exerting too much force for such a lightweight object. To replace it, you can either buy an RS4 hood strut (the RS4 has an aluminum hood so the strut is softer) or buy an aftermarket hood prop like this one I ordered on Amazon. While I’m waiting for the hood prop to come in, I’ve found that a Swiffer broom/stick does a pretty good job as a temporary measure.

Carbon Fiber Hood Vents - B7 Audi S4

I originally meant to try to do some data logging and find the before & after of the intake temperatures with the hood installed. I never got around to that prior to having this installed, but you can feel hot air venting out of the engine bay from the two side vents, and given the placement of the middle “scoop” I would imagine that is also helping keep things cool. I think it definitely offers performance advantages in terms of airflow, and weighs about 50 lbs less than a stock hood (the stock hood weighs in around 70 lbs for reference, and this hood is about 15 lbs) so the weight savings is very nice, especially in a front heavy car like the V8 powered S4. The hood is designed to have a cover underneath the vents to collect any rain or condensation which is great so that you don’t have to worry about taking your car through a car wash or rain storm and having too much water come in contact with the engine through those vents – it’s already taken care of…

B7 Audi S4 - Top View

I have quite a few more  pictures that I’ve taken, and I’ve got to say I’m very pleased with the hood from every angle. It did exactly what I wanted it to from an aesthetic standpoint – wake it up, give it a little contrast, and make it appear more aggressive without being too over the top – and the functional benefits of it are great too. I’d definitely recommend both the hood and Aerofunction if you’re in the market!

B7 Audi S4 with BBS Wheels and Carbon Fiber Hood

You can check out the rest of the pictures below:

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