Outside air

[Craig Hoskins]

I was wondering if anyone has found a good way to use outside air for the TBI which is not direct ram air?

I have been through both the Sonex AeroVee TBI, and the Rotec Mk1 and Mk2 TBI's to get the performance and reliability I'm happy with. All three recommend against using ram air because it can result in going lean or improper performance. I have found cowl air gives the lowest CHT and EGT spreads and reasonable performance compared to direct ram air. However, I would like cool outside air if I could get it without the extra ram pressure.

If anyone has found a solution or has a good idea I would appreciate hearing about it.

Thanks.

[vigilant104]

Would a conventional air filter or an even less restrictive foam "sock" in the intake plenum do what you want (eliminate dynamic pressure while allowing cool air into the TB)?

FWIW, the cooling of induction air by vaporization of the fuel does present the theoretical possibility of induction icing, even without the pressure drop/cooling caused by the venturi in the throat of a conventional carb. IIRC, the use of slightly warmer under-cowl air is assessed to make up for this evaporative cooling effect and, in practice, eliminates concerns about carb icing if there's no venturi. Obviously, if this is correct and a user deliberately avoids the use of this warmer under-cowl air, the potential for carb icing goes up. And once icing is evident, I doubt that switching to the slightly warmer under-cowl air would be very effective at melting it, it would take "real" carb heat (heat muff around the exhausts, etc).

[bvolcko38]

I too have thought about ram air, a poor mans turbo, and heard about all the downsides.
What if you were to vent your fuel tank to the same area (pressure) as the ram air? That would tend to eliminate running lean, I would think.

BV