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Th pro .46 and others, 3000 rpm drop from 9x6 to 10x6

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Th pro .46 and others, 3000 rpm drop from 9x6 to 10x6

Old 11-22-2023, 06:34 PM
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rcbence
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Default Th pro .46 and others, 3000 rpm drop from 9x6 to 10x6

Hello. I picked up a new tower hobbies pro .46 with purple head for a pretty good deal on eBay. I'm not sure when they stopped making them exactly. Was it 2009? My box has copyright 1998 and the manual has copyright 1999 but I don't know that that tells me the year for sure.

But anyways I started with a 9x6 apc not knowing exactly what to expect for a break-in for RPMs. To my surprise it was peeking out around 16,500. I ran it in a rich 2 stroke of course. After some running on that I put a 10x6 apc and was getting 13,500 RPMs. I didn't go crazy on finding peak but that should be close enough to accurate. I ran it in rich 2 stroke to drop RPMs a bit more than that.

Now was my tach not reading right with the 9x6 apc? I wasn't expecting about 3,000 RPM drop for a 1 inch bigger prop.

I'm asking because what concerns me is it unloading in the air a few hundred RPMs and just enough to maybe get on the pipe? It's completely stock. This must be what is happening as 3,000 RPMs doesn't seem normal for 1 inch prop change? Does anyone have experience and know exactly what RPM the engine might come on the pipe? I did some research and found that other .46 engines like the thunder tiger pro .46 that people are getting close to 17,000 RPM with a 9x6 on those engines too. I'm assuming thats on their stock TT mufflers also. What's so special about the tower hobbies tuned muffler at 13,500 with a 10x6? I only have a litre of fuel run through it so far. Now the TH engine is new but my old TT pro. 46 was getting 14000 RPMs with the same apc 10x6 on 10% nitro.

My concern is that it unloads and makes a bunch more power and RPMs when it's in the air and leans out. Is that going to happen if I were to put it in a plane eventually with a 10x6 or even 10x7? I'm wondering if there's anything different with the tower hobbies tuned muffler compared to other stock mufflers for how it behaves.

It must be that at a certain RPM there is a significant power boost on these engines to be 3000 RPMs higher with a 9x6 over a 10x6?

Right now I'm just running it in on the ground to get some fuel through it. Same 10% nitro.
Old 11-23-2023, 02:03 AM
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1967brutus
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Those numbers are not anywhere extraordinary, albeit a bit low for a .46... I am completely unfamiliar with the TowerPro 46, no idea if it is a mere sports motor or more performance oriented.

According to my propcalculator, on the 9 x 6 your engine is doing about 1,15 hp, and most .46 engines should do better at that RPM.
Maybe your break in is not yet completed, or maybe you're still on the rich side, I don't know. Wrong plug perhaps?
Be that as it may, the 3K drop in RPM represents about 0,95 hp @ 13500, and that is, in relation to the 1,15 hp @ 16500 a "to be expected" number.

I would say, give it time. Most engines need at least a gallon of fuel to be fully broken in, fair chance the numbers will rise significantly still.
Old 11-23-2023, 08:01 PM
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you bought 1 of the most cheapest, lowest tolerance engines on the market! my friend bought one straight from Towers. it was a monster to tune until it had 2 gallons run threw it. he pulled the back plate off and you could see that it's lower Rod bearing was way too lose.
I hope you didn't pay much for it, causse you could have bought a nice OS 46AX on RCG for $75.
I say, you bought it. it's an overpriced $80 engine. don't compline about it, just fly it for what you get out of it. if you get 5 gallons out of it feel lucky.

Jim

Last edited by the Wasp; 11-24-2023 at 07:34 PM.
Old 12-02-2023, 08:53 AM
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13.5k on a 10x6 is a little low, but not by that much. The Tower muffler is not a tuned unit. It’s hollow with no tuned chamber. It is good for about 500rpm over a normal OEM muffler because of the larger volume.

What I am curious about is why on earth would you peak the break-in prop long enough to get an rpm reading? The whole idea of using a smaller prop is to allow the engine to run close to unloaded rpm while still being rich. 20-30 minutes n the test stand on the break in prop set rich is all that’s needed. Mount the flight prop, set the needle for 500-700rpm rich of peak and fly it. It’ll get a little better with time. My TT .46 on a Jett tuned muffler turns a 9x6 APC above 17k. On a 10x6 APC it will run 16.5k on all castor 5/20 fuel. With a bigger throat carb, it’ll run a little faster. The best budget type sport engine IMO is a Super Tigre GS45 with a flat spraybar. It’ll do 17.5k on a 10x6 on 5/20 all castor fuel. The flat spraybar and tuned muffler is good for a 1k rpm boost.

I would put a Tower .46 slightly above an OS .46 in quality only because of the chrome liner. The SuperTigre crushes the OS in every respect IMO.
Old 12-05-2023, 05:13 PM
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Originally Posted by the Wasp
you bought 1 of the most cheapest, lowest tolerance engines on the market! my friend bought one straight from Towers. it was a monster to tune until it had 2 gallons run threw it. he pulled the back plate off and you could see that it's lower Rod bearing was way too lose.
I hope you didn't pay much for it, causse you could have bought a nice OS 46AX on RCG for $75.
I say, you bought it. it's an overpriced $80 engine. don't compline about it, just fly it for what you get out of it. if you get 5 gallons out of it feel lucky.

Jim

And I didn't think it was the best made engine in the world but nobody's complaining. I didn't know asking a question that applies to all engines was complaining? At least I know I'm not getting an engine with 100 hours on it that's pretty much shot for $80. How is that a horrible price anyways when that was around the price from 2009? The question was is that a normal RPM drop with the prop sizes I mentioned. I'm not complaining about that, I just never knew that RPM drop should be that significant as I never tried a 9x6 ever before. I only ran the 9x6 a small amount before switching. I don't think you would have much to say right now with how much RPMs it's making now with a 10x6 apc. And I'm convinced there's still more in it at only 2 liters in.

I had a small amount of fuel run through it and still not that much when I posted the numbers. That on 25% oil also. The numbers are already way better as I switched to my normal 10% nitro 20% oil with more run time. But I believe it's the run time here and not so much the oil content I think.

That same 10x6 APC I saw a peak of 14,150+ and it was about 62 outside Fahrenheit near sea level. It re peaked to that number consistently. From the looks of it that's seems pretty good already. I'm assuming it would run 17,000+ now with the 9x6. But it's still not run in enough for me to want to fly with it because of the way it's tuning now because the engine is still tight.

The engine was super tight so I don't know what that means that it's low tolerance? It was squeaking the first couple starts. I had it apart to wipe down any machining material, of which there was some to clean off before I even started it. Everything looked good to me and the rod had zero play. Taking quite a while to break in seems to be a better thing for longevity from what I understand. A tight engine is usually a good thing to have so I've read many times. At least I don't see much negatives with that besides longer run in time. I accept that it's going to take some fuel on the ground before it's not filthy rich with the normal low speed gap between the spray bar and low speed needle. (2-3mm) at the stock setting its sucking the fuel and is too rich to fly unless at WOT the whole flight. It seems most people's problems on a new engine is going to be not enough run time because they seem to be usually super rich with a normal low speed needle setting when new. And then all of a sudden at some point it just changes. My OS .55ax did the similar thing but not quite as much as the tower engine I think. I posted something not that long ago thinking there might be something wrong but it just needed more run time before it started tuning normally. I'm really shocked that there's pretty much no details on this on any manual I've read. They're not even flyable(to me) unless you're at wide open throttle the whole time until they break in more. You'd have to crank in the low speed needle so lean that it's going to start restricting your fuel flow at wide open throttle because of not having a gap between the spray bar and low speed needle. Then your high speed needle is turned out some ridiculous amount like 5 turns out and it doesn't tune properly when it's restricted like that. In my digging I actually found one post with this same engine that said the exact same thing. Surprised it's not brought up way more. They had their low speed needle cranked in with no gap and HS needle cranked way out. But later that person posted that their gap is normal now and it's tuning normal. So it just needed more run time and wasn't junk. I fault the manuals for there being "problems" on a new ABC/ABN engine. But maybe it would wear in quicker if I ran four-stroking rich for a while on the first start? Well I'm not willing to do that and have not done that.

But I wouldn't call the engine junk because of the way it's tuning right now because I know at some point it's going to drop it's balls and change and be normal.

Its clearly not fully broken in yet. If I wanted to actually fly it I'd have to turn the low speed in so much that there's zero gap at full throttle between the spray bar and low speed needle, and even that was still a bit too rich. At that point the high-speed needle is needing to be backed out a huge amount and the fuel restriction is too much at full throttle. So I richened up the low speed some and I'm just continuing to run it at full throttle until it "drops its balls" and isn't so filthy rich at half throttle and under.

I don't know why it's assumed that there was some kind of complaint for asking if the RPM drop was a normal thing from a 9x6 to a 10x6. But I'm pretty happy seeing 14,150 peaked out now with 10x6 APC and its still not fully run in yet, but I'm guessing the majority of the power is there now. I have about 2 liters through it.

​​​​​​If someone has a different theory on why it so filthy rich when the engine is new for a normal low speed needle setting by all means share it. The only change I see is that the engine loosens up over time. And when it's extra tight it somehow has better fuel draw through the carb and is sucking fuel much harder at the same needle position. I can't fault an ABC engine for being tight when new.
But something should be said about this in the manual for all ABC engines. I'd love to see someone try to fly this engine right now while it's still new to see how they would manage that without a deadstick. The only way I see it is that you're at wide open throttle the whole entire flight and then when you make a landing it better be right the first time because it's going to dead stick from being super rich. So I will stay away from flying it until I know it's tuning normally. Seems like a major detail to miss that you need to be at wide open throttle the whole time or else it will dead stick from anywhere at half throttle or under from being too rich. I already mentioned the above for how much the low speed has to be cranked in on this engine for it not to be too rich. It's not flyable when you have zero gap between the spray bar and low speed needle at wide open throttle. Actually in the negative with the needle in the hole some for it not to be too rich at part throttle. I tried this and it doesn't tune normally because the restriction is too much and you can't even get it rich enough at WOT like that. It is clearly drawing way more fuel while it's new. If someone doesn't know this they're going to wreck a plane or call the engine trash. This one shocks me because I'm pretty sure every ABC engine does this more or less. My OS certainly did and it was my fault for forgetting this detail and thinking something was wrong with the carburetor when it wasn't. My OS tunes perfectly now with no problems. I believe the same will happen with this tower engine.

That's not me complaining but just saying it how it is right now. How is this not mentioned in any manual? That I am complaining about because someone that's completely new that doesn't know this it wouldn't end so good for them.

It's not flyable in my opinion unless someone is an expert and knows exactly what they're doing and can fly at wide open throttle the whole time until It breaks in more. Right now I'm not willing to do that, that's too risky for me. I'm not a pro.

Someone else also mentioned here that it needs plenty of run time. I'm okay with that and not in any rush.

Why would this engine be lucky to get 4 gallons through it when it takes 1 or 2 gallons to really get it run in?

Has that been your actual experience that you wore out this engine in less than 5 gallons? Is the piston made out of butter and something different than another brand? Or maybe the opposite is true that this thing will last longer than the average ABN engine when you do everything right? So virtually everyone says that true ABC is the better material over nickel. I've read a lot on the forums and there would be plenty of people that say the exact opposite of what you said for this specific engine and other engines that aren't too expensive.
I believe any negative reviews on this engine is for the reasons stated above that isn't understood or known. I'm thinking even the people that say the engine leans out...... might even be due to not running it in enough on the ground. Because that's exactly what needs to happen is for this thing to lean out so that it can have a normal low speed needle gap setting. Or someone is not willing to spend the time. That doesn't make an engine junk to me. Maybe to you it does.

​​​​​​​A lot of car guys brag about still further breaking in after a gallon on their rc car engine. It seems that's the better thing if anything compared to a looser engine. But sure I guess there is a con also, but that doesn't make it junk to me. I thought getting a 2009 price on the engine wasn't too bad considering the way things are now. The way I understand it any fault to the way it runs while it's new has nothing to do with being a bad engine or a bad carburetor like I was mistaken with my OS.55ax after not flying for a few years and just not being aware that the engine was still pretty new and tight. I still have yet to see how this tower engine handles after its run in properly, at that time I will start to judge it. But I like that it has dual o-rings for the carburetor and dual o-rings for the high-speed needle and an o-ring for the back plate. I used loctite on all the fuel nipples and the exhaust nut and exhaust bolts and sinch nut. So far so good on the ground and I like the way it looks and the machining looks pretty decent for its price. It's starting up consistently and it's side mounted. Which I believe makes it slightly harder to get a perfect prime than upright mount. I'll say that it's actually starting easier than my thunder tiger thats side mounted. Although that engine has way more time on it and I spent about 75 to 80 bucks back in 2009-2010 for it. If I were to get a new thunder tiger for that price today that would be a good deal to me. When they do pop up they are usually sold for more than that from what I've seen. Let people buy their junk if they want to.
Old 12-05-2023, 08:19 PM
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1967brutus
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14150 RPM on an APC 10 x 6 corresponds to about 1,1 hp, and given that you first saw 13500 with that prop (0,95 hp) that indeed is a fairly respectable and to be expected gain.
Whether there's more in it, remains to be seen, things can be a bit unpredictable at times, but I'd say you might see something like 1425~14300 with one or two additional quarts of fuel through it.
It is most likely indeed going to break the 17K on a 9 x 6, and if I were the betting type I'd say, 17300 right now, maybe 17500 when fully broken in.
Realistically, I'd say that's about it unless you intend to use tuned pipes and high Nitro, then all bets are off.

It still is not overly powerful, but it is absolutely useful power, and I have seen worse, much worse so indeed, your engine really "ain't all that crappy"

For what it's worth: raw horsepower ain't all that it is hyped up to be, those small props more or less only work well with small, sleek and fast airframes.
For general sports flying, usually 11 x 6 is better suited. Expect about 11500~12000 with one of those. That is less than 1 hp, but usually performs better on say, a 62~64" wingspan low wingailleron trainer like a Calmato or similar. The small props make a lot of noise and if the airframe allows, a lot of speed, but they do not provide all that much pull, horizontal speed will be (a fraction) lower but vertical performance much better with a larger, slower turning prop, even if the sheer hp-number is lower.
Old 12-06-2023, 08:49 PM
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the Wasp
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Originally Posted by 1967brutus
14150 RPM on an APC 10 x 6 corresponds to about 1,1 hp, and given that you first saw 13500 with that prop (0,95 hp) that indeed is a fairly respectable and to be expected gain.
Whether there's more in it, remains to be seen, things can be a bit unpredictable at times, but I'd say you might see something like 1425~14300 with one or two additional quarts of fuel through it.
It is most likely indeed going to break the 17K on a 9 x 6, and if I were the betting type I'd say, 17300 right now, maybe 17500 when fully broken in.
Realistically, I'd say that's about it unless you intend to use tuned pipes and high Nitro, then all bets are off.

It still is not overly powerful, but it is absolutely useful power, and I have seen worse, much worse so indeed, your engine really "ain't all that crappy"

For what it's worth: raw horsepower ain't all that it is hyped up to be, those small props more or less only work well with small, sleek and fast airframes.
For general sports flying, usually 11 x 6 is better suited. Expect about 11500~12000 with one of those. That is less than 1 hp, but usually performs better on say, a 62~64" wingspan low wingailleron trainer like a Calmato or similar. The small props make a lot of noise and if the airframe allows, a lot of speed, but they do not provide all that much pull, horizontal speed will be (a fraction) lower but vertical performance much better with a larger, slower turning prop, even if the sheer hp-number is lower.
thank you!
Old 12-06-2023, 10:06 PM
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Originally Posted by the Wasp
thank you!
You're welcome although I'm not sure why... I mean, I did not post that to prove anything to anyone, it was just common generally useful information.

If there's some feud going on that I know nothing about, please leave me out of it

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