jester125

I just got a TH tach and I'd like to know how to tell what the optimal rpm is on this engine/prop combo or on any for that matter?
I never took tach readings before so I have no idea what kind of performance I should expect, should all engine/prop combinations have the same RPM for maximum performance?

Please explain
Thanks, Chris

jester125

Well I just got finished taching it, with a 11X6 prop I got 13,230. Does this sound off or too high? The engine still isnt running smooth yet so I'll have to wait to get some help tuning it when I get to the field when the weather improves.

Chris

seanychen

My Feedback: (4)

That's real good for Super Tigre 51. That's what OS 50SX would do on a stock muffler.

Optimal setting should be just a few hundred rpm richer than the peak rpm setting.

Tigres take a little longer to break in. So run it 1000 rpm richer (lower) for another 1/2 gallon and don't worry tuning for optimal yet.

jester125

Thanks for the reply, I wish I could say it was running ok but I tried again to run it but it sounds terrible. It wont idle correctly and it smokes a ton at high rpm. For fuel I'm using SIG Synthetic Plus 15% with a stock muffler. Its not a new engine but it has a new ring on it from the guy that sold it to me. I'll have to research a lot more to get this engine running right.

Thanks, Chris

WMB

My Feedback: (1)

I never tached mine, 4*40 and 11x5 APC is an awesome combo- fast and fun. 11x6 a little slower.
APC 12.25x3.75 gave incredible non ending climbs but a lot slower.

Jack Hyde

My Feedback: (1)

If it has a new ring it should be broken in again. Read:
http://www.rcuniverse.com/forum/m_25...tm.htm#2576729

jester125

Thanks for the link but it will take time to figure out what he's talking about.

Chris

Jack Hyde

My Feedback: (1)

The link has posts from several fliers that have experience with breaking in ringed engines. It is interesting how much they differ. The post from Downunder is very complete and clear, and according to Flyboy Dave way conservative. Both of these guys have broke in many engines that worked well for them. I would lean toward the conservative approach, it only costs time and fuel and wont hurt your engine. If you have more questions ask and someone will help you.

DarZeelon

Chris,


This ST is actually putting out 1.21 HP, which is very good.

Some other threads were started in this forum, where users were trying 11x7 props and only getting a measly 10,700, or so RPM.
This engine's torque curve must have a very big dip, preventing it from exceeding that low number with the slightly heavier 11x7 size.

The 11x6 is, respectively, the largest prop size ST recommended for this engine.

Most engines of this size, or even smaller ones, like the OS.46AX (and the defunct FX), which cannot be considered 'torque paragons', can spin an 11x7, or even a 12x6, or 12x7 at respectable RPM levels.

jester125

Yeah I think I'll stick with the 11X6, if I now could just find the time to run the engine and adjust it.

Thanks, Chris