aspeed

Just ran most of my .40 to .46 motors for something to do, and for comparison. New house is in a settled area, so I wanted to get it over with. I used a Master Airscrew 10-6" prop, 10% Ritches brew half Castor. Pretty hot humid day. Sweat was dripping on the tach. I ran most with open exhaust and mufflers where it was easy to do that. Not sure how to set margins OS SF .46 14,600 RPM powerbox muffler, 15,600 open exh.; OS FSR .40 13,800, muffled (9-7 prop was 14,800, as that was on my little combat SPAD) ; Thunder Tiger Pro .40 14,400 muffled; Old cross scavenged K&B .40 13,500 muffled; LA .46 14,000 slightly opened muffler, 14,600 open exh. OS LA .40 12,600 stock muffler, 13,800 open exh.; T Tiger GP .40 open exh. 13,400; OS FP .40 13,000 opened muffler to only 1/4" and 13,400 open exh. Royal .46 (INC) 14,000 with muff.; FX .46 15,000 with opened outlet and baffle, 16,000 open exh.; Supertiger .45 15,300 and 16,000 open exh. I suppose a pipe might get all the numbers over the open exhaust readings, or Jett muffler maybe. These were just the random motors I picked up out of the drawer. I have doubles of some like the LA .40s which may be better or worse. I guess my fast planes need the Supertigers, or the newer OSs with maybe a pipe or mousse can of some sort.

1QwkSport2.5r

I'd put money on the SuperTigre over the OS in a high rpm environment... The ST will hold up...

I have a NIB 45ABC in the drawer (made in Italy even) that I'm waiting to fire up for a special occasion. Good to know it should run 16k or better on a 10x6 and Jett pipe. Should spank my TT .46 by 500rpm or better.

aspeed

All my stuff is old, so it would be Italian. Just thought that I still have a .51 ST and an AX .46 in planes still. Oh well, another day. The pistons seem pretty thick on the ST, a bit of lightening could help with the revs, and longevity/shaking too. Maybe I am just used to the smaller motors.

1QwkSport2.5r

I have a .51 Italian, but the spraybar was modified. The flat milled spraybar from the .90 woke the .51 up quite a bit so I shaved the round spraybar down from the .51 carb... I'll have to pull my 45 apart and look at the piston - I don't recall it being all that bulky/heavy...

If you're used to the small guys and run big ones, they do seem to shake more... Ever run a big Jett? If your tank isn't bubble-free, you have essentially whipped cream in the tank running at full power. My biggest Jett is a .56 and even with a perfect balance on the prop, it'll still shake things up and I'm only running that one at 16,500 since it's still pretty new and a bit high strung still.

aspeed

We used to put the heavy blade on the counterweight side of the old Fox .35s so your hand wouldn't tingle at the end of the flight.A cheek cowl was needed too. The newer LA .25 does not need this at all. Of course it was not designed in the 1950's. It is a bit windier at the new digs, so I have to use the bigger planes, or I miss the whole season. The carb shook loose on the FX .46 in the test and the screws fell right out.

1QwkSport2.5r

Ouch on the screws falling out... Sounds like the prop was out of balance.. Never have screws shake loose albeit I've recently changed prop balancers which made a significant difference on vibration problems. Dubro balancers = the shiz! Top Flite balancer = junk. Tried new shafts and new cones from hobby services and those were worse than the ones that came with the balancer.

Hobbsy

My Feedback: (102)

Do you gents mind if I post Fox .46 ABC numbers here. I will use the black prop pictured here, the red one has huge blades but still turned 13,089 on a Fox .50 ringed engine.

aspeed

The black Master Airscrew if 10-6, it is the same as the prop in my tests, ya, the more the merrier. I would like to know just how much greater the Jett is as well as pretty much everything that size. Especially with no muffler, as the results vary so much. A Jett muffler can make any strong motor even stronger too. Using a pipe is so variable, that the results would not prove much, but a Jett pipe would be good. Wish I had one.

1QwkSport2.5r

I have a .46 sized Jett muffler (tuned range 15,500-17,000) that I use on a few engines. Some engines get a greater benefit from using it than other engines do of course... They are much more versatile than full-wave pipes because they don't behave "peaky-like". One thing I did notice using a ST G51(Italy) - it ran better and faster on a 10x6 APC using a stock ST "Silent muffler" than it did using the Jettstream muffler. My TT Pro .46 gained about 1k rpm but the carb is a tad small to really open up. I think it peaked around 15,700 using the APC 10x6.

In this size class, I have the TT Pro .46, ST GS45 ABC (Italy), ST G51 (Italy), Fox .46 ABC, Fox .50, and Jett 56LX (Piped). The GS45 will probably run like a scalded cat on a Jett muffler or tuned pipe - it has a huge blowdown period. I haven't checked the port timing on it yet though. The Jett 56 probably won't run very well without a pipe on it due to its high pipe timing. If I get around to it, I'll round up some of these engines and run them. I rarely run my engines without a muffler so it'd be nice to see how well they run and what "real world" power they produce.

aspeed

I wore ear plugs. Anything over a .10 is pretty loud with an open exh.

1QwkSport2.5r

I know. I have some nice 3M earmuff hearing protection I wear whenever I run anything on a test stand. My K&B .65 was probably the most obnoxious of the engines I've run open faced thus far. The others were smaller than .40 displacement.

Hobbsy

My Feedback: (102)

I hope you don't think I'm weird but I never run engines in a configuration that I would not fly them. The difference between the pictured props is way more than I would have thought. I took the ringed piston and sleeve out of a .46 engine that I converted to a .50. I installed a little used .46 ABC sleeve and piston.

Engine===Fox .46 ABC circa 1988/later lower compression head button.
Fuel=====Wildcat 2/4 10% with 18% full synth.
This engine was super rusty when I bought it from a guy out west. It has BOCA Ceramic bearings which are still glass smooth. They have only been run in Diesel conversion mode.
Exhaust==MVVS .49 sized muffler
Plug=====Ancient Fox Idle Bar
Prop=====Robbe 10x6, red in the picture
Prop=====Master Airscrew 10x6 pictured
RPM with Robbe======12,990
RPM with MA=========14,790, astounding to me and a pleasant surprise. When I fly it I will use the Robbe though, it created the most wind and the least noise.
I guess that makes it about 99 rpm less strong than the .50. With the Robbe.

1QwkSport2.5r

I'm not surprised you saw the differences that you did. The blade profile of the Robbe is wider and probably pitched closer to its advertised pitch much like APC. I've often encountered very different rpm figures when comparing MAS to APC. I will say that MAS props are more durable, but they're known for having more blade flex, make more noise, and the actual pitch being a bit less than advertised. Not nitpicking here, just making observations and repeating what others have said. Nonetheless, the Fox ABC .46 makes respectable power which is good to know since I have a new one sitting in its box in my engine cabinet. It's a shame it didn't have the spinner with it - just the spinner backplate.

Personally, I like to know what kind of power the engine can produce (open exhaust) and then try to find an exhaust system that will allow the engine to run close or better than that power figure. Then again, I currently only run my engines on boats so I'm not confined to the same restraints aircraft are limited by/to. Some engines I have will never fly or be run on boats which are the examples I'll run "for the heck of it" on days I have time to burn.

aspeed

I like to know what an engine will do with no muffler as a starting point. A muffler normally slows it down 1,000 rpm, and a pipe raises it 1,000 or much more rpm. A bad muffler kind of spoils a test for what could otherwise be a good motor. I am thinking specifically of a Norvel .15 and an AP .15 which are really quite good, but have bad mufflers. I can easily open up the stinger of a muffler to get some power, but if it is not going much faster with an open exh, there is no point. Maybe I should just mount my motors and go flying, but I got a tach to play with :-)

aspeed

Just got in. Tried a new to me Picco .45 side exhaust with the MA 10-6, and 10% that I used before. 14,900 with a muffler, and 15,700 open exhaust. Really loud with no exhaust, and seemed louder with the throttle opened the last little bit. It did not really seem faster when opened, Just louder. It was not really as good as I thought. The Supertiger and OS FX are still the winners. Even the LA .46 was pretty good, considering.

1QwkSport2.5r

I'm surprised the Picco didn't do better... Maybe it needs a few more runs to wake up? My Picco buggy engine is a sick piece of Italian art, though I ported it out a bit.

airraptor

My Feedback: (66)

qwk the Italy ST 45 have lower timing and make better power down lower where the china made ones have higher timing but worse port matching. The china ones perform better with the Jett muffler than the Italy ones in stock form.

1QwkSport2.5r

And they're "supposed" to be made the exact same.. My last reply was in relation to the Picco .45 which is said to be a fairly fast engine. I'd certainly expect more than 14,900 from one using a nominal prop and muffler.

FWIW, my ST S45 ringed turns 14,700 on a 10x6, 5% nitro, stock silent muffler. GS45 ABC (Italy - stock carburetor) did 15,250 on same muffler, fuel, prop, and plug. This is a well used engine too. The trick to the .45/51s (at least stock) is to thin the spraybar like they did in the .90s (.45 up to .90 uses same carb but .90 has narrowed spraybar). This frees up a lot of breathing. Mod the timing and bore the crank and you have a killer sport engine. The ST crank leaves a LOT of room for improvement alone.

aspeed

I think my ST .45 was the S with the old type noisy muffler. I don't have one of the new ones. The Picco does not need any more breaking in. It looks well used, but good shape. I have a couple smaller newer Piccos, and the .12 is much better than any .15 I have. On a Supertiger .40 and many others, I often fill the front radius with solder especially when it looks like it has been drilled too deep. I also grind a bit on the window to smooth things out a bit. I have not measured more than 300 rpm on anything, but normally do it if I have the motor apart that far. I think I will start to widen the exit hole to the sides like a Fora does. I am not convinced the "turbo" cuts at whatever angle, is the way to go. Just a bit wider to get the air around the rod and give the impression of a bigger crank hole. I noticed a pic of a Jett crank which has pretty much a cut straight across the centre of the back face of the crank. I guess that is to direct it to the ports, maybe it was on a rear exh.? I have not got a new chinese ST, but do believe them when they say that they have not changed much. I think the ring is maybe a couple thou. different, and the cat's eye cutter got a bit dull, and pushed up a burr. The operator likely got reamed out for that and smartened up. Too bad no one wants to carry the ST brand any more. I guess there is more money to be made on a million drones than with us old farts toys.

1QwkSport2.5r

By more time on the Picco I mean just a couple tanks to "clean it out" so to speak. I've noticed engines I've had in storage don't usually turn the rpm they had in the past right away. Usually after 3-4 tanks they do.

As as to the porting I mentioned - what makes them make more power is reading how they're setup to start with and adjust from there to make more power. Increasing the bore of the crank, changing the open/closing times of the induction port, boost port, exhaust port, and in some cases transfer ports. Changing the shape of the exhaust port, radiusing the bottom of the liner at the boost port, clearancing and smoothing the ports in the crankcase, among other things. It's a "package deal" if you will. I did this package to a Picco .28 buggy engine that is clearly the most powerful buggy engine I've ever run. Thr scallop cuts on the crank allow smoother passage of the inlet charge and also "stir it up" a bit in the crankcase. The crankpin has a bit of a wind vane pump action too and those cute may aid in pushing the charge towards the boost port. The fang cuts on the ports are pointless. Backfilling the front of the crank is really aimed to smooth out the idle and transition quality, doesn't really do much for top end power.

airraptor

My Feedback: (66)

The ports on the Italy ST are better matched to the case and have more detail in them. The transfer and boost ports are lower than on the China STs. I had thought they were the same also until I picked up 4 used st 45s that were made in Italy. Two have the "S" on the side and the other two have 45 where the "S" is. stock so far we saw 14,000 open exhaust with a APC 10x7 on one of the engines.

1QwkSport2.5r

Both of my Italian .45s are GS series engines. I have been trying to get my hands on an S45 ABC piston and liner myself to make my S45 more appealing to sell. The S series engines are timed lower than the GS series engines - one of the primary changes they made when they discontinued the S series and came out with the G series. Some engines got more than a cosmetic exterior makeover. S series piston/liner sets do not fit GS series engines. The OD of the liners are completely different.

airraptor

My Feedback: (66)

Thanks for the info. I havent played with many normal two strokes lately. Most of my time has been racing. I am racing Q40 and figuring out these engines as far as timing and head clearance goes. so far looking at about 29,500 in the air on a 7.4x7.5 carbon APC prop. almost 8 pounds of thrust on the ground too lol.

1QwkSport2.5r

If you want the information, I can get you the timing differences between an S and GS .45 (Italian only). I'm gonna hop the GS up. I have a new one, old one, and a spare P/L that's near new. I am gonna go to RPM city.

aspeed

What kind of abnormal two strokes are you playing with? I am guessing Jetts. Maybe MB Profi? I was always impressed with Rob Metkemeijer's stuff since i was a kid. Only met him a couple of times. He was into Team racing, and Speed then. I have not seen the APC carbon fiber stuff at the local hobby shops yet. I should get out more. I have been thinking of a pipe on the Supertigers, as I have a header and a few pipes around. Not really to go faster, but because the old mufflers are heavy and loud. I would think a higher exhaust port may be better for that. At least if faster is the idea.