ORIGINAL: Ilikebipes

Konrad,

Thank you for the time you are taking to explain this so plainly so I can understand. If you will allow, I would like to try and see if I understand what you are saying.

It would be best, just to begin, to stay with the stock carb because:

1. Even though there is power loss due to a smaller venturi, the overall run will be more consistant because there will be less differential in atmospheric pressure. This will actually maintain a pressurized tank more efficiently and keep fuel pressure to the spray bar. Less change in total pressure differential as a result of changes in fuel head preasure. Pressurized tanks are another issue, look up YS engines.
2. Because of the above, a pump will not be needed to compensate for the difference in atmospheric pressure at the different nose attitudes. Again changes in fuel head pressure
3. Due to the smaller venturi in the stock carb, a pump may not make a large change in power, but may actually complicate a well tuned engine. No change in power and makes any engine set up more complicated
4. A larger carb will give more power, but it takes a lot more to accomplish this job. Starting out, I will have more enjoyment with a stock set up by eliminating all this extra work. (I can always change my system in the future as I progress.) BINGO

It would be best, just to begin, to run a tuned pipe because:

1. Better fuel economy. No, but while a pipe might make the engine more efficient as a result of a higher dynamic compression ratio, really no.
2. It will help move fuel past the baffle on my particular engine. This will keep fresh fuel over the cylinder and add power. (It will also harm fuel economy though-won’t it?) It will help any engine scavenge the cylinder. Fuel economy needs to be thought as CC per HP. More HP will need more fuel
3. It keeps with the overall reason for the purpose I am building the Model. I want to fly a classic Ballistic Patternship- the UFO.

It would be best, just to begin, to run a bubbles tank behind the firewall, not CofG because:

1. (regarding to tank location) A stock carb will not take a pump well. (not true, it just won't make more power) This ties my hands as far as tank location. However, the closer to the carb the tank sits, the less work load there is on the carb. This will keep a more consistant operation. Even creating more power in ratio to headaches.
2. The tank, pick-ups, and fuel delivery system to the carb are the probable cause of my headaches in the past. By installing equipment that will ensure good fuel delivery, I will have more success without the headaches of the past. Yes, 80% of all engine problems are fuel and tank related

You are correct to determine my goal with my UFO is for creating a classic ballistic pattern flying airplane. I am tired of simply throwing the sticks every which way. If I have a reason and a goal to accomplish I keep my interest and actually learn something. I like the way you termed it: “a weapon for carving pattern out of the sky.”

In relation to the pump conversation, it seems as though a regulating pump is a better choice over the other pump.

Perry offers a regulating pump that maintains a constant .25 psi to the carb. Is this the choice to make regarding fuel pumps?
Brian

[link]http://www.perrypumps.com/prod02.htm[/link]