setting up Q40 engines
05-05-2007, 02:39 AM
#1
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setting up Q40 engines
want to know how to set up a q40 Nelson
how do you know which prop is best suited for it
i have the short stroke Q40 i am using APC carbon props 7.4*7.8 and 7.4*8.0 also the 8.2 pitch aswell
what rpm should i be getting on the ground?
how do you know which prop is best suited for it
i have the short stroke Q40 i am using APC carbon props 7.4*7.8 and 7.4*8.0 also the 8.2 pitch aswell
what rpm should i be getting on the ground?
05-05-2007, 07:20 AM
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RE: setting up Q40 engines
With the short stroke I like to see 23,000 rpm (minimum) peak RPM on the ground, in which I will richen up to about 22,500. Use whichever prop it takes to get there. The 8.2 is probably too much, the 7.8 and 8.0 are what I used predominately with the SS.
You do not want the motor to sit on the ground very long at these rpms as it will get hot. It is best to find peak RPM as quickly as possible, back it off 500, and have your helper either launch the plane quickly, or CAREFULLY put their finger over the venturi to limit the airflow into the motor as the pilot gets ready.
There are a couple newer props available, the 7.4 x 7.5 and the 7.4 x 7.6. You may want to give these a try also.
Lastly, not all props are exactly the same. If you have a pitch gauge, you can check the pitch of your props, or just run them and notate their rpm.
Personally, I always ran my Short Strokes at .196 and .016 (sleave and head spacing), although many others ran them in the 193 and 13/14 range.
You do not want the motor to sit on the ground very long at these rpms as it will get hot. It is best to find peak RPM as quickly as possible, back it off 500, and have your helper either launch the plane quickly, or CAREFULLY put their finger over the venturi to limit the airflow into the motor as the pilot gets ready.
There are a couple newer props available, the 7.4 x 7.5 and the 7.4 x 7.6. You may want to give these a try also.
Lastly, not all props are exactly the same. If you have a pitch gauge, you can check the pitch of your props, or just run them and notate their rpm.
Personally, I always ran my Short Strokes at .196 and .016 (sleave and head spacing), although many others ran them in the 193 and 13/14 range.
05-05-2007, 08:29 PM
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RE: setting up Q40 engines
Izzy:
As Dave says you need at least 23K+ on the ground with the SS engine. Anything less makes them tough to needle. I believe they actually run better (quicker times) if they are 24K+ on the ground. While I ran the 7.8 or 8.0 prop (the only ones available) last year. I would probably would run the 7.6 or 7.7 this year if I was still running the SS. In general a smaller prop will make the engine much easier to run. A lot of guys get into trouble trying to run to much prop. The original 8 pitch APC would turn almost 25K on the ground and it ran really well. I would start off with a 1k pinch up and tune from there. On the SS engine the plug should show almost no color after a run. If you are running 15% you should have about 15 thou head clearance no matter what the liner is set at.
Any Q40 racing in your part of the world?
Barry
As Dave says you need at least 23K+ on the ground with the SS engine. Anything less makes them tough to needle. I believe they actually run better (quicker times) if they are 24K+ on the ground. While I ran the 7.8 or 8.0 prop (the only ones available) last year. I would probably would run the 7.6 or 7.7 this year if I was still running the SS. In general a smaller prop will make the engine much easier to run. A lot of guys get into trouble trying to run to much prop. The original 8 pitch APC would turn almost 25K on the ground and it ran really well. I would start off with a 1k pinch up and tune from there. On the SS engine the plug should show almost no color after a run. If you are running 15% you should have about 15 thou head clearance no matter what the liner is set at.
Any Q40 racing in your part of the world?
Barry
05-05-2007, 08:34 PM
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RE: setting up Q40 engines
Barry,
23+ wasn't too hard to hit in your neck of the woods. Up here in Minnesota, and at the Nats in Muncie, that wasn't always easy.
Probably why I settled on a little higher settings, as it made it easier to needle.
D
23+ wasn't too hard to hit in your neck of the woods. Up here in Minnesota, and at the Nats in Muncie, that wasn't always easy.
Probably why I settled on a little higher settings, as it made it easier to needle.
D
