I put an FP 40 on my rebuilt Vector which seems to run great except in the outside stuff. At the transition from outside to inside on the horizontal eights it tries to die and again on the third corner of the outside squares which makes square eights real interesting and the four leaf is something to behold. Any ideas on what could be going wrong with this? I am running pressure with an 11x5 prop at about 9600 rpm on the ground the motor seems real happy there
Would appreciate any ideas as I am totally lost right now. And also on the outside of the hour glass and vertical eights its the same thing

 

what lap times,
 what brand of prop,
what fuel, and oil content.
what tank setup
I run an FP  in my vector as well as several other planes.
is this an iron piston or newer FP? toungue muffler or tube? just on  a first guess, it sounds like it is overpropped. I run 4 and 4.25 pitch props on mine usually 11 or 11.5 diameter
fill in the blanks I am sure I can help you out some

  I put an FP 40 on my rebuilt Vector which seems to run great except in the outside stuff. At the transition from outside to inside on the horizontal eights it tries to die and again on the third corner of the outside squares which makes square eights real interesting and the four leaf is something to behold. Any ideas on what could be going wrong with this? I am running pressure with an 11x5 prop at about 9600 rpm on the ground the motor seems real happy there
Would appreciate any ideas as I am totally lost right now. And also on the outside of the hour glass and vertical eights its the same thing

 

I had one that did that so I gave it away for the last time it happened It quit on me. Unless iknow the cause I don't want an engine that threatens to quit.

My OS S30 running on Powermaster GMA 10/29 straight castor fuel would quit like someone threw a switch. Changed to home brew 10/20 straight castor and it was fine.

The cause can be a combo of effects. A number of things that are little off. If you go to a smaller prop with slightly less pitch, for instance, you can lean the engine up a bit, keep the same lap time. The rpm you're running is a tad low for an unmodified FP. I've done it. 11x5s can keep an FP from hitting the runaway zone, by loading the engine up. (At least I've used them in at least one plane, did avoid a bad resonance.) But maybe in this case you need the extra RPM of the "sweetheart" 10 1/2 x 4 1/2 apc. Something of a mythic prop for FPs. If the issue is related to slight flooding, such as a fox burp, this will help. A hotter quality plug, (Enya #3), will also help burn off excess fuel. Reducing oil content can also help the burn. Repositioning the tank slightly, can lean things out some where you need it. Another thing you might try is seeing if the engine richening is worse or better at the beginning of the run. You're problems seem to be in the later maneuvers of the pattern. Granted they are more demanding on the engine system. Try the late maneuvers early in an engine run, see what you get. Lowering the tank slightly will lean the engine in outside maneuvers. This might be what you need. Then you get into the type of tank used. Conventional vent or uniflow? Unhooking the uniflo in a given combination can tell a lot. Some combinations of tank, engine, fuel etc. don't like uniflo. FPs can be particularly sensitive to this. But usually uniflo issues present themselves as engine runaway...

I'd start with the plug, fuel, prop, in that order. The Vector 40/FP 40 can be a dynamite setup. Good luck.