Skip to content

Dinan Cold Air Intake

    A previous owner added a Dinan exhaust system, Dinan cold air intake (CAI) with a 3.5″ Hot Film Mass Airflow Sensor (HFM), and Dinan “Stage 2” engine management software; the car runs quite well with the set-up and tune, but the CAI installation was a little too much of a hack job for my tastes.

    Most obvious was the adapter and hose clamp party that mated the HFM to an OEM intake boot, and the plastic zip tie mounting of the HFM to a bracket bolted to the strut tower.  Zip ties? Really?  Sure, they work, but I suspect the 3.5″ HFM was a very expensive Dinan modification and I’m of the opinion that a better mounting scheme should have been developed.

    I found the Dinan CAI air filter positioned above a hole hacked into the top of the driver’s side brake cooling duct, it had obviously been a long time since it had been serviced. I selected an AEM 21-204DK dry filter as a replacement:

    Dinan vs. AEM 21-204DK Air Filters

    The crudely modified left brake duct was on par with the plastic zip tie HFM mounting; :

    Hacked Brake Duct

    I suspect the installed Dinan CAI carbon fiber-ish tube (I’m not convinced that actual carbon fiber fabric was used, I think it’s black fiberglass cloth) was not specifically designed for a Z3 or an M Roadster; no matter how I clocked the tube it just didn’t seem to fit correctly, so I lopped off a chunk, trimming it back to the marked line:

    Dinan Intake Tube Modification

    I went with a silicone boot from Cosmo Racing to connect the throttle body, (actually, the Anti Slip Control + Traction (ASC+T) assembly) to the HFM, replacing the OEM boot and adapters. I would have preferred another rubber boot with a flexible accordion section to prevent engine movement and vibration from being transferred to the HFM, but the Cosmos boot was the only one I was able to find that was the correct diameter, had a barb port in the right place for the idle control valve hose connection, and would work with ASC+T:

    Cosmo Racing Intake Boot

    A trial fit indicated that the Cosmo Racing silicone boot needed minor trimming to clear the strut tower:

    Cosmo Boot Trial Fit

    After removing a wedge-shaped slice from the ASC end of the Cosmo boot, everything fits fine; much cleaner with plenty of strut tower clearance:

    HFM Installed

    After modifying the tube, the AEM dry filter is positioned behind the bumper opening for the left brake duct; I’m not a big fan of the carbon fiber look under the hood, so I removed the Dinan decal and treated the CAI tube to a coat of semi-gloss black:

    AEM Filter Installed

    I left the hacked brake duct off for now since I plan to go back to an OEM-style airbox at some point and will need a new left brake duct to connect to the airbox inlet ducting.

    As an update, I replaced the Dinan Cold Air Intake with a BMW Z3M S50 airbox assembly, which works with the 3.5″ HFM.