jsenicka
Key Veteran
Location: Hampton VA
| Thought I would share my experiences this far with the CarbSmart on my Raptor Squadron.
Let's start with the R90SE. This one has a OS91SZ-H with OMI/Cline 60M carb, and a Hatori SB18 pipe. The HS-81 servo is mounted in a modified TREX 600 mixture mount I picked up from www.readyheli.com part number CHP-A205N. I used RTL fasteners servo screws to mount the servo frame to the forward gear leg on the 90.
I started with the carb at my default settings. Mid at 5/8, idle to center and high at 1-1/4. The CarbSmart midpoint/failsafe was set at 1-1/4, and allowed adjustment from just under 1.5 to just over 1 turn open. Gain was set at 50% and target temp was set to 110c.
Starting was a bit harder, as the carb was pulled close to 1 turn on the main, so idle was a bit lean. Still no major issue. Getting in the air was another issue. Every time I tried to spool up to hover RPM the engine flamed out. After 3 hover attempts with plenty of warm up, I started trying things a bit different. My assumption was the high end was too lean, so I reduced the total throw on the lean side. I also richened up the bottom end mixture valve. No joy here during 6 more flame outs. The only way I could get it close to airborne was with the governor off and sneak up on the needed RPM in manual curve mode. So I walked back to the truck and warmed up for a while. And the answer came to me.
The CarbSmart was trying to heat the motor to 110c at idle and hover by pulling the high speed needle as lean as possible. In all 9 flame outs, I checked the needle arm, and in all cases it was full lean. This means it could not get the motor hot enough at mid range throttle positions, and in trying to heat it up, has the high end leaned all the way. When I punched up the throttle to near WOT, it was way too lean to run, and died like a car with a bad accelerator pump. The secret was to get the carb to operate more like a 2 needle carb. Jim O'Neal at OMI told me an SZ can run with the mid range needle closed, and adjust all with just the low and high end needles. He said this resulted in a fat run at WOT to get midrange rich enough, so in reality some mid range was needed. He mentioned normal was 5/8-1/2 turn, but could go as low as 5-8 clicks (around 1/4) on some engines.
I stepped back and made some major changes. I reset the CarbSmart for full range adjustment with 1-1/4 turns open on the main at at center. I then closed the mid-range needle to 1/4 turn open from full closed. I pulled the idle mix back to factory center, and finally I dropped the temp setting to 100. This time it came up to hover power after a brief warm up with no issues. With the mid range almost closed, the majority of my temp control is coming via the main needle. So it does not have to lean the main needle way out to compensate for the rich midrange.
I did a tank of hovering and goofing and it ran great. What surprised me was punching collective and the heli just leaping up, with no real sound change or bog at all. After a tank hovering I got brave and topped off and went and flew. Nice and smooth. Good, but not yet great power, as I still get a little bog in monster loops and long climb outs at a full 12 degrees of collective, but I am running at 100c rather than 110 right now. It was the smoothest, cleanest run I have ever had on a 90 size ship. I did continuous rolls into the wind from one end of the field to the other, a few tic-tocs, and some funnels and it all sounded great. And I landed and still had lots of fuel left! Next step is to take it to 110c on the temp and fly again. I had a throttle servo start acting funny before I could get in any more flights.
====================================================================
On to the the Raptor 50's.
The 50's benefited from the lessons learned on the 90. I used an ST-15 JR sport servo for mixture control. I mounted using two TT servo mount plates bolted to the front gear leg with 2.5mm bolts and nylon lock nuts.
The 50's both run an OS50SXH with a 60L Hyper carb (These are the old style non hyper head engines with a hyper carb). I went with the hyper carb to get a single needle to worry about with the CarbSmart. Both have MP5 pipes and RL10 revlocks.
One has a brand new engine, so I set it up with 1.5 turns on the main as the full rich setting based on that being the recommended run in setting in the manual. I then set temp to 90c and just went out and flew. I put in 3 tanks at 90, then kicked it 100c and started to beat on on it a bit harder.
My second R50 engine has just completed break in with about a gallon on it. This one is set with just under 1.25 turns as mid point (sensor fail position) and as close to 1 turn as I can get with servo throw on the lean end. Low speed mixture control is set to just lean of center. I set the temp to 110c and 17,750 on the RL10 governor. It is fantastic. I spent 6 flights getting it dialed in. The first 4 flights were making really inconsistent power. I determined the idiot mechanic that works on my birds appears to have been drinking with my wife and did not have the glow plug tight... The last 2 flights got it spot on. I did some monster size loops, continuous flips and rolls, a few funnels. No bogging, and super consistent power. I am running +/-12 on the Kasama head and it just pulled. The secret is getting the engine close as far as tuning, and using the "always runs decent" needle setting as your midpoint. I know that between 1.25 and 1 turn on my 60L carb will always make decent power, so I set close to 1.25 as my middle of adjustment.
My observed results on my Raptor 50 at 110c was I was making about the same power I would when I used to get a "great run" on the engine, consistent from top to bottom of the tank, and probably 25% longer run on the same fuel burn.
Sorry for the book!!!
Jim Senicka
2x R50V2/OS50 - 3x R90/OS91
Futaba12FGH 2.4g |
