Originally Posted by
Pylonracr
I got the 10mm carb option since I wanted top speed. This airplane has the engine mounted upright, and with the header in place I can not get the tank high enough. Mine has fuel draw problems.
Scott,
there have been others who confirmed that the 10 mm carb on this engine does not have enough suction to draw fuel consistently unless the carb/tank relationship is finely tuned beforehand on a stand and then matched in the model. The obvious and best solution with that carb is to pump it like you have.
That said, given you are running it in a speed model, I suspect you are probably using a straight or angled header rather than a fuse top style header. Given the low exhaust port location of the Speed/13, the mid-line of your tank is probably quite a bit below where it should be. Two solutions to this: 1) use a the low rise 1" fuse top header (or higher) and 2) use a shallow draft fuel tank where the fuel is distributed sideways rather then height wise. Tanks like the Hayes 12 and 16 oz slim (you'll probably want a 16 if you're aiming for max RPM) work well as others of similar geometry. A long cylindrical tank such as the Sullivan 16 oz "shampoo bottle" tank also work well although there is a longer fuel draw. This latter might suit your model better as it is likely narrow. Several folks have used this engine/9 mm carb/tank combination in the GP Dirty Birdy ARF albeit with the tank mounted sideways.
The obvious solution is to side mount the engine, or use the smaller 9mm carb which would be a better choice for a pattern plane. I put a pump on mine, which also works. The next plane I build around this engine will be side mounted.
I haven't tried the engine side mounted but others have with good results but a similar carb/tank relationship is still required. I suspect it is harder to design an effective speed plane around a side mounted engine though. The advantage of the 9 mm carb is that it allows you to meter the fuel in flight as the fuel level changes and this helps too but you want get max RPM out of the engine. IMO, the 9 mm is best suited to pattern while the 10 mm to speed.
I'd be interested in hearing what pump you're using and how you have it installed.
I have about a half gallon of break in fuel through mine. 10 to 15% fuel is fine. I would not use less than 20% oil, but that goes for all of my engines.
Omega 10% fuel with 3 oz of castor added (to bring it to ~20% oil content) has worked well for me - with pattern. For speed, I'd likely try Omega 15% nitro 4-stroke 17% 50/50 oil blend.
The 50400 pipe is very quiet, but good god is it heavy!! When I weighed one (a while ago) I think it was 5 or 6 Ounces! Yikes. I made a carbon fiber pipe for mine, but I think a Macs quiet pipe will work at half the weight.
The Speed/13 is a generally heavy engine setup as the engine itself is heavy too (~620 g). Model weight should be adjusted accordingly. I tried using a current Macs 10 cc QP but wasn't pleased with the results. I believe the pipe doesn't allow the engine to breathe properly. The NR pipe works much better on a 9 mm carb and I suspect even more so on the 10 mm. However, there are other wider bore pipes which allow the engine even better performance than the 50400. The old Macs flat back 10 cc pipes work well as reported by Robert on the RCG classic forum. I suspect an OPS 10 cc pipe works equally well and perhaps better than the NR. I will try one this Spring.
I am setting mine up to run in the 17K range, but other projects have been pushed in front of this one so I don't remember what props I was using. Since I am going for speed, they are small diameter and high pitch. I will dig out my notes if anyone is interested.
That would be great. I'd be interested in hearing its performance on 10" (9"?) props as the smallest prop I considered was a wood 11x7 (again, for pattern). Max engine power should be just about at 17-18K and I imagine you would get there on the 10 mm and 15% nitro on a light 9x9, 9x10,10x7 or thereabouts.
Power of the engine on a 9x10@17K would be approaching 2.30 bhp. On a 10x7@17K, 2.46 bhp which is just about peak performance. It's just a matter of finding out how to get the engine there...
David