Engine Air Induction


A warning to those that contemplate going “off the reservation” when making non-standard engine and fuel injection choices: without knowing it, you are probably adding 1-2 months of building to your schedule as you fabricate custom cable brackets, finesse clearance issues, and generally re-invent the wheel to make those choices work.

My engine order included a 7 degree up-tilted ECI intake manifold and an Airflow Performance FM200A injector. These choices meant (although I didn’t know it at the time) that the standard Van’s throttle and mixture brackets would not work, that the standard Van’s induction would not work and that I would have to fit a ram air scoop to the lower cowl.

The Airflow Performance FM200A injector is a wonderful piece of machinery, but it is very long in comparison to the Bendix/Precision Silverhawk injector which is normally furnished. I chose this injector because I believe(d) that it will add performance. After spending two months and a lot of money to figure out a way to make it fit in the cowl, I’m not sure it was worth it.

In the end, I fitted a Spectre 9833 Inline Air Box to the injector using three AN525 washer head screws (#8) with lock nuts mounted to the outside for easy inspection. The inline air box is constructed of .063 aluminum with a cone filter mounting inside. The halves of the air box are held together with a wide stainless steel clamp. The air box installation is very secure with nothing in the air path that could come loose and enter the engine. The filter (HPR9833) is rated at 450 CFM, so that ought to be more than adequate for this engine, even expecting less than optimum air flow. I mated the air box to one of Rod Bowers’ scoops, so it’s a straight shot directly into the injector.


This air box setup did not allow for alternate air, but I had decided not to install that anyway. The decision of whether or not to include alternate air on experimental aircraft is, like many others, almost religious. Some swear you need it in case of the plastic bag blowing across the runway on take off and others are firmly of the belief it’s more trouble than it’s worth. I tend to belong to the latter camp and after flying for more than 35 years, I’ve yet to have a case where it was needed. It is not required, and therefore I elected to not install it.