I recently bought the unit listed above by Lex3. Below is my inital review.

I thought I would share my experiences with my latest test of a new (at least to me) gizmo - the EFR-801 from PC/RC Products. EFR stands for Electronic Fuel Regulator.



I bought mine second hand - the EFR-801 is no longer being produced by PC/RC, but may still be available elsewhere. MSRP - $159.95

I think this was originally developed for use with rc cars, but I've put it on my Raptor 50. Basically, the EFR-801 is an electronic needle valve. The unit includes a thermocouple, solenoid valve, and a control box. The thermocouple is mounted in the muffler mounting flange and measures the exhaust temperature. The solenoid valve is placed inline between the fuel tank(s) and the carburetor, and meters the fuel according to the engine temperature. The control box has a small processor which calculates the modulation of the solenoid valve based on the exhaust temp and the throttle setting. The throttle servo, receiver, thermocouple and valve solenoid all connect to this control box. Everything is powered via the receiver from the existing flight battery.

The manufacturer claims "No more manual engine tuning, no more guessing, no more temp guns. The EFR-801 reads engine temperature off of the header and via a small computer processor, changes your engine settings for you automatically!" and "It automatically tunes your motor resulting in dramatically improved low end and mid range power. It also helps save fuel. It's like having a pit man inside your car tuning your motor on every turn!"

-Sounds like just what I've been looking for. I had to try it to see if it was too good to be true. Is it a winner, or just another gimmick? Read on!

Below are some pics of the installation in my Raptor 50. I decided to put this gizmo on my R50 because I have quite a bit of time on this particular model, and am pretty familiar with how the engine runs (TT-50 heli engine with stock R50 muffler, drinking Cool Power 30% heli fuel, Jo-Z glow plug). This familiarity will give me a better indication of what the EFR-801 is actually doing.



Pictured below is the thermocouple, which is factory affixed to a 6-32 muffler pressure tap, mounted in the muffler flange. I added a bit of high-temp silicon to prevent leaks.



Pictured below is the thermocouple layout on the model.



Pictured below is the solenoid valve, attached to the raptor frame with an eyelet cable tie and black fuel tubing.



Pictured below is the control box, showing the servo and solenoid connections. No, this isn't yet readied for flight in this picture - I added electrical tape to secure the servo and solenoid connectors, tiddied up the wiring and secured the control unit >before< flying. The tri-color LED indicates which mode the EFR is in, and the 5 DIP switches determine the programming, run, cold start, and performance mode settings.



Initially, my EFR settings (cold start = 3 and performance = 12) and my high speed needle valve settings were wrong and I could not keep the engine running. It would lean out and die almost immediately after spooling up the blades. I frowned and scratched my head. I tried different settings. I also couldn't figure out if the thermocouple was working, and why it would lean out. I wondered if the solenoid valve was working correctly as sometimes the characteriestic valve clicking would stop. Later I found that the clicking sound of the valve changes once fuel lubricates the valve innards. I also learned to let the engine warm up fully before trying to fly. By slowly increasing the throttle and letting it run for 15 or 20 seconds at increasing speeds (up to about 40% throttle - the heli is still not airborne yet), the temperature rises slowly and the valve can keep up with the changes. You can actually watch the smoke density change as the engine warms up and the valve reacts. After letting the engine warm up this way for about a minute or two, the EFR is ready to rock.

So far, I'm pleased with it's operation. I can fly my whole routine without worry - the mixture settings are reliable. I can't tell any power difference with the engine under control of the EFR versus a well tuned manual mixture setting, so that's good! My current settings for the EFR-801 are : cold start value = 3, performance setting = 1. I'm not sold yet on the EFR-801, but am impressed with it's ability to maintain a steady mixture throughout the tank - right up until the last teaspoon of fuel! Without the EFR, my TT-50 will begin to lean out when my main tank is down to about 1/4" fuel level (roughly 3-4 ounces remaining). With the EFR, the mixture doesn't lean out, and the engine happily puffs out a steady smoke trail from the beginning of the tank until it leans out from fuel exhaustion.

My normal high speed needle valve setting (without using the EFR) is 2 turns open. The instructions tell you to richen the high speed needle enough so that raw fuel spits out of the exhaust. So I initially set it at 4 turns open. I wasn't able to get satisfactory results this way. My current high speed needle setting is at 2.5 turns open. This gives good performance with the EFR. If I disable the EFR and try to fly at this setting, the engine is way too rich. With the EFR operating, the mixture is just about right, and never leans out even when the fuel head pressure drops. I've kept my low speed needle as it was before (as recommended in the EFR instructions) - 7 turns out.

So, what's the verdict? The EFR-801 works pretty well. It doesn't totally eliminate the need to adjust a carb, or negate knowledge of how to tune an engine, BUT it does a good job in regulating the mixture throughout the run of the tank. So, once setup, the claims of a steady, adjustment free mixture are true, but I haven't seen any increase in fuel economy.

My next experiment will be to use it with an OS .91. My hope is that it can eliminate the mid-range tuning problems of the stock .91 carb. I also want to borrow a temp gun and check the temp differences between manual tuning and EFR-801 tuning.