Pressure Carb

[blaplante]

maybe I'm just inclined to 'do my own thing' sometimes... but I'm thinking about putting a Bendix pressure carb (i.e. PS-5) onto an o-320 or o-360.

Pros:
Less prone to carb ice
Less expensive than a full FI conversion
Independent of electrical system (except for boost pump - but still have mechanical engine driven pump)
Works inverted

So, some questions... would a cold air sump be appropriate / advisable?

Electric boost pumps for more than carb pressures are horrible expensive. Which is crazy when automotive FI pumps put out much more pressure...

How about this for a boost pump (spec for PS-5 seems to be 14 psi)
http://aerospacecomponents.com/index...0:fs&Itemid=66

Would it make sense to plumb the two pumps in parallel? [with check valves?] That would seem to be more reliable in case some pump became clogged.

Thoughts anyone?

[rocketbob]

Rotec TBI would be a better choice.

[Don at Airflow]

There is probably no operational problem with this set up. It should work on a cold air sump also, but I have no personal experience installing one on a cold air sump.

Cost to overhaul one of these PS-5?s is getting very expensive. Upwards of $2500.00 to $2700.00. If your PS-5 has the flurosilicone (red) diaphragms then you should be good to go assuming the internals are not worn out. You may have to recalibrate the PS-5 for a 320 engine depending on what part number PS-5 you have.

You will need the 12-15 PSI mechanical pump for the engine. The race car pump would work for your boost pump if you plumbed it in parallel with the engine driven pump (it will probably not free flow through the pump when it is off) and put a check valve on the outlet of the mechanical pump (to protect against a mechanical pump check valve failure) and a check valve on the outlet of the electric boost pump (to keep the mechanical pump from back flowing the boost pump). This seems overly complicated when you can normally plumb an aircraft type boost pump in series with the mechanical pump. Spending another 100 bucks will get you the correct electric boost pump.

So while this system is feasible you have to look at the benefits of spending a bit more and going to a multi point fuel injection system. If the PS-5 needs an overhaul I would just go ahead spend the extra bucks and put fuel injection on the engine and know that it will operate correctly plus have better fuel distribution than the PS-5 set up.


Don