I'll order one of Van's pre-made NACA ducts tonight as this will eliminate downtime for fibreglass work, and tomorrow I'll phone a few rad shops.

    Do you usually run with both FI pumps on while climbing? As I didn't have this problem to this extent previously, it reaffirms your theory that most fuel is consumed at full power with less being recirculated when a single pump is used, but with both pumps running, I still had allot of fuel being recirculated, while picking up full power heat.

    It seems that running with both pumps on for extra safety may in fact, have contributed to the problem?  Just another theory.

 

S. Todd Bartrim
Turbo 13B RV-9Endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

   "Whatever you vividly imagine, Ardently desire, Sincerely believe in, Enthusiastically act upon, Must inevitably come to pass".

 

I take and land with both EFI pumps and my boost pump on.  I have found that on the few occassions when I did detect perculation , even though turning on the boost pump brought it undercontrol, it took it a few seconds to do so- with attendant engine sputtering.  Keeping boost pump on during take and landing seems to preclude the perculationg from starting in my case.  By the way, I may have misspoke on the size of the hose to the fuel cooler,iits either 2 or  its 1 1/2" diameter rather, just can't recall.  May be best to wait until you get the naca duct before getting the hose {:>).

I am not certain whether two EFI pumps on affect the perculation problem either way.  It might -with two pumps trying to "suck" fuel may lower the pressure in the header tank more making it more conductive to vapor forming.  On the other hand, I really like having two pumps running during take off.  Should one suddenly fail, you might not have a lot of time to take dianogistic and corrective action {:>).

Ed