I decided to fit a performance air filter purely for the induction note. Some years ago I worked with K&N to develop a cone air filter for a FIAT Tipo 16valve twin cam, which was a highly underrated car and motor. Anyway, the new air filter was phenomenal and sounded exactly like a pair of 40s. I hoped for the same on the Z3 but it doesn't sound as throaty.
After removing the OEM airbox (easy to do, no pics needed) the new air filter was fastened directly to the MAF by a suitable jubilee clip.
I ran it without a heat shield for a while and the sound was a good howling noise at high revs, and with the exhaust I have (tubular manifolds, new late diameter down pipes, cats, twin 2 1/2" pipes to a single straight-through silencer) it sounded good from the cockpit and turns heads from outside. From inside the car it's particularly noticeable above 6000rpm when it sounds fantastic - though only for the last 500 revs before the red line.
Fitting the flower pot means the noise starts at about 5 1/2 and is louder than before - the pot acting like the bell mouth of a trumpet amplifying the sound.
I don't recommend you running an open air filter without a heat shield as heat soak from the engine bay will lose you power. The flower pot does a good job of shielding heat and guiding cold air from the standard air intake beneath the nearside headlamp to the new filter. After fitting the flower pot my Acceleration Redardation System Evaluator records an increase in performance noticeable above about 5500rpm where the car definitely hauls better than before.
A Pipercross foam cone air filter about 180mm long and 150mm O/D was bought from eBay for around £20. The mounting diameter was chosen to fit directly onto the inlet of the MAF. I don't remember the diameter, 72mm perhaps? Let me know if you want the details and I'll dig them out.
The flower pot used to make a CAI heat shield was black, 250mm long, 200mm diameter at the base tapering to 230mm at the mouth. It cost 99p in Tesco.
A hole is cut in the bottom of the flower pot and petals bent at 90degrees. The air filter fits through the hole and the assembly pushed over the MAF inlet. A jubilee clip fits over the petals and fastening it all together.
To cut the hole scribe a circle in the base of the pot which is the outside diameter of the air filter mounting flange. Scribe another hole about 20-25mm smaller in diameter. Use a hole cutter to cut the smaller diameter hole. Make radial cuts every 15mm or so to the larger scribed circle.
Bend out the petals as they'll form the mounting flange to hold the MAF/air filter/CAI together. A heat gun made the bending easier and more consistent.
You can see three of the petals here
The flower pot I bought was too large to fit in the space vacated by the air box. It was made shorter by trimming the top flange off which also reduced the diameter. It fouled on the alternator so I made a cut, folded the two parts over themselves, and pop riveted the join. This also remove the circular shape of the pot and helped it fit in the complex shape between inner wing, front panel and alternator. It's easier to do than it sounds, and the pot costs less than a pound if you need a second attempt.
Here's the finished job. I've lightened the image to help show the detail. The existing bracket that held the OEM airbox has been utilised by adding a cotton reel exhaust mount and a steel bracket pop riveted to the CAI. Without it I was concerned the assembly would fall into the clutches of the alternator belt.
The small diameter plastic water pipe connecting the rad to the expansion tank has been reformed, assisted by the heat gun, to its new position following the slam panel and along the inner wing, behind the strut mount to the tank.
Exhaust heat wrap is used on the top hose to lessen heat transfer to the CAI.
Without lightening the photo I think the black coloured pot fits well in the engine bay. A terracotta pot might look a bit Bill and Ben.
My exhaust is fecked - advice please
Linear Mode
