Today I took great pains into removing the "factory CAI" - that is, the trunk which brings air from the front to the airbox.
My reasons had been the following: factory intake is rather well designed, with the scoop behind the headlight sucking from a high-pressure area, neatly tucked in the space behind battery, and yet airflow at high rpm was not quite the best, acceleration at highway/motorway speeds was not brilliant, and despite my 1.3-1.5bar remap, the dyno (rolling road) test indicated a whopping 9-10hp difference between running with airbox and without it (keep in mind I've said without
airbox, not filter). The most likely culprit had to be the absurdly small duct.
It took me a long time and plenty of scratches on my hands, but I've managed to remove it and leave the airbox in place.
I've fitted in the same place a flexible rubber hose, 105/110mm diameter, with hard plastic coil reinforcement inside. I have chosen it for it was smooth inside, no ribs or fins, and it was very elastic. Unlike a hose with metal reinforcement, the hard plastic allowed to squeeze it to pass through the small space behind fender and battery, and expand to its real size once inside, unharmed.
Kept the scoop behind headlight, cut the snout on which the original duct had fit. The snout is roughly triangular and it's barely 65x45mm!!
Cut a bit into the airbox to fit the hose, ended up with a large hole with rough edges. Made a gasket out of foam-insulation sheet and glued it around, it's very light and yet is has a bit of rigidity which allows the gasket to stay in place until the glue hardens.
The inside of the airbox was
not smoothed yet. Panel filter is the factory type, and quite dirty (11000kms old).
The results had been quite amazing.
For the first test, slow driving around:
- rpm raise slightly quicker, but the difference is very small, had I not paid attention I couldn't tell;
- engine noise is slightly changed;
For the second test, motorway run up to 180km/h:
- turbo spools up slightly quicker;
- acceleration at high speeds and high rpms, 5000-6000, is much better;
- slow raise of rpms in the 4000-6000rpm range is gone for good;
- continuous driving in 4th, 5th, and 6th gear at high speed, which felt a bit restricted before, like "not breathing enough" now it's perfect. 100% perfect. From 130 to 140, 150, 160, 180 km/h and back, no flat spots, no problems. It takes off in 5th gear just like it did before in 3rd gear... amazing
- engine noise at high rpm has changed, no longer a screech but a deep rumble, like a small V8... music for my ears
All these without any sort of bucket-sized cone filters, EUR 300 induction kits, airbox drilling, smoothing, not even a sports panel filter. Just a no-good, ratty piece of rubber hose, which is available at the hardware
store for the immense price of EUR 7.66 including Romanian VAT.
Right now I sip a well deserved shot of brandy and smile like crazy. Maybe nobody believes me, poke fun, or think I'm crazy. I just know it works
Regards,
~Nautilus