Eganwp

My Feedback: (1)

Hey guys,

Wondering if anyone here has some experience with this engine, and if so, what kind of RPM do you see on a specific size/brand of prop? Did some searching around but can't find a lot of info and mine seems weaker than what others are reporting.

I bought the engine the other night from an older guy leaving the hobby in an Ultra Sport 60. He said the engine was pretty new and just broken in very rich. I fully tuned it on 10% Omega and can only peak 11,800rpm on a 12x6 APC. The engine itself runs just fine after fully tuning and transitions perfectly, but it just seems to be weak to me @ under 12k on the 12x6. Before I ran it I opened it up and all looks good, the engine has good compression, and looks to be broken-in. Is it just me, or should I be happy with these numbers? Seems odd, as I pull 12,800 RPM on an 11x7 APC on both my OS 55ax and ASP .52 which seem like they're more powerful than this .75! I mean I know I'm a bit spoiled and like to overpower my planes, but you kind of need it for taking this plane (7 lbs) through the IMAC sequence.

Or maybe I'm just expecting too much of a ringed engine? It's possible it's just not a revver as I haven't torn this one down yet to measure the intake/exhaust and boost port timings, but before I do that I figure I'd ask to see if anyone has any tips or info. I'm going to toss on a 12x8 and see what she'll do as a test. I'd run a 13x6, but I don't really have enough prop clearance for it. Might try removing a shim as well. The engine definately isn't overheating or anything as it maxes at a cold ~190*F. I've tried 2 new fuels (both 5 and 10% Omega) and added a bit more castor oil to bring the total up around 19%. Completely reset both needles and ran it up again today and it's still exactly the same RPM fully peaked. If this is all she's gonna do, I think I'm going to toss on a .91-.95 2s instead. At this rate my .55's would be much more practical, turn better RPM's on the same prop and are nearly 40% lighter!

Thoughts?

Edit: stock muffler.

estradajae

Looks like the engine may be timed for bigger props, and a 12x6 won't give the engine justice... My tower 75 turns apc 12x6 at about 13000+ but won't do much on bigger props, but it's because of timing.


Try a 13x6/7 just to see how the engine works...and then worry about clearance...

High nitro won't do much on the Supertigres...with 5% nitro you'll be just fine.

bkhart

My Feedback: (6)

My ST .75 turns a MA 11X8 at 13,200 rpm on 5%. I'm using the old style swing muffler. This has been a great engine in my Killer Chaos.

Bill

c550

My Feedback: (16)

I have four of these and I really like the APC 13x6 I think I was getting around 11000 or sow but I haven't taken a reading in years, but they haul around my heavy top flite warbirds very well. I would go for a bigger prob than what you are useing. Just my 2 cents.

Regards,

Dave

Eganwp

My Feedback: (1)

Hey guys, thanks for the replies. Just an update. I pulled the engine this morning and bought a 13x5 mas and a 13x6 apc yesterday. Upon pulling the engine I was suprised to see that the muffler and the block were both stamped with "Made in Italy". From the pics I've seen, I thought the old Itialian versions looked a lot different than the chinese ones, as this looks like the newer chinese versions... Hmm... Anyway, I'm going to check the timings on this engine later today. The exhaust duration does look quite limited upon first inspection, so I probably take the dremel to the sleeve and open up the exhaust duration 10* or so to start with. I'll check the crank intake and modify it as well if it needs it.

Eganwp

My Feedback: (1)

Just wanted to give a quick update to any of you engine modders out there. I just pulled the engine and did the timings. Here's the results:

Exhaust duration: 146*
Intake duration: 163*
Boost ports: (didn't bother checking)

So suprisingly, this engine is actually timed pretty well and there isn't much room for improvement on the either the intake or exhaust. I could up the exhaust another 5-10*, but from other engines I've modded, it's not much of an increase; at most 200rpm I'd say, depending on exhaust. I'm suprised to see these timings actually. I'm not gonna bother cracking out the dremel to mod the sleeve/crank on this one.


I'm out to test a 13x6 apc on this beast!

Egan

daveopam

My Feedback: (9)

I am late on your question but, I ran a MA 13x6 on mine for many years. On 10% nitro, it would tach 10,800 on the ground. I am at 2,000ASL so it might do better at a lower alt. I did port the exhaust stack on mine to match the block. It was good for and aft but narrow top/bottom.

David

Gizmo-RCU

My Feedback: (27)

They take at least a gallon or more to really start to show their stuff!

Eganwp

My Feedback: (1)

Well today I went out and ran a 13x6 APC as suggested. Turned 11,170 peaked which is reasonable I guess. It's enough for sport flying (and yes she's pretty fast, but I'm used to 100+mph fast in my glow planes) and all the aerobatics, but it's not enough for the IMAC sequences. I took her though the sequence 4 or 5 times today, and it just doesn't have enough vertical for manouvers like the humpty bump or anwywhere you need really long uplines. Anyway, I guess that's what my 30% Edge is for. I'll probably just leave the ST 75 on for now, possibly try a 13x5. But when I finish my own Ultra Sport 60 kit build I've now confirmed I'm gonna need a 91 2s or something like a Saito 1.00 4s to pull enough power to be satisfied.