pikeman401

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Looking for a strong 25 size engine that will give me a the need for speed. Medium price or a little more. Sorry Jett is out of my budget. Have looked at MVVS. How about the Norvel? Open to all suggestions. Best prop for the engine would be helpfull also. Thanks.

bob27s

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TT36, good power in a "25" size case.

Put a jett-stream muffler on it.

Hard to beat on a budget.

pikeman401

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Actually I am putting this 25 in a 15 size plane. It is an older one, you may remember it. Years ago they came out with a Birdie 40 and Birdie 15. I built them both. Very strong construction. Flew the Birdie 15 with an OS 15 in it and it flew ok but was under powered. I'm thinking a strong 25 will really make it scream. The tt36 might be too much for the 15 size plane. I'll talk about the 40 another day.

HighPlains

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That's why the RC engine is so neat. It has that little lump of metal or plastic with a hole thru it, usually mounted to the front.

Power to weight. In these small block engines, often the larger engine is lighter.

daven

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I agree, if your going to go with a .25, you might as well go with a .32 or .36. Same case, just bored out more. In most cases these overbored brothers are lighter than the smaller displacements.

Theres always the throttle, or you could pitch it down.

MJD

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Norvel .25 I can't say, but I looked at a review of the Norvel .40, and about the only thing I could see good about it was the light weight. As to power, I was not at all impressed by the numbers in comparison to other sport .40-.46's. 12 and change on an APC 10-6? Zzzzzzz.

RC-Captain

There is a guy on ebay who is selling NIB OS .25FX constantly. First let me warn you , they are NIB but the engine I received was ran before it made it to my house. Any way long story short I paid $61.00 minus $15.00 because he chipped in for the new cylinder and piston. So my final cost was $76.00. The engine goes for $84.00 on Tower Hobbies. The .32sx goes for $124.00. $40.00 dollars for such a little bit more power.

GL

RCF esq.

pikeman401

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Thanks for all your info. I am compiling some info and will post it ASAP.

SST

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The Norvel .40 may be unimpressive, but the .25 is supposed to be the one of, if not the most powerful .25 on the market. I have one with a mousse can muffler, and though I haven't used it yet, I've seen some very impressive Shrike video. Like you, I'm going to drop it into a .15-size plane (Ripmax Alienator). Hope it doesn't rip the wings off...

pikeman401

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Well this is what I have found Take it for what it is worth. I know that BHP isn't a solid value that gives great merit but it's there so I printed them.


Norvel .25 cu in Jet .25 cu in mvvs .28 cu in gfs/r abc tt pro 36
wt 8.03 oz rpm 17,600 wt 9.7 oz max rpm 17,000
HP .85 @ 15,500 rpm wt 14.6 oz HP 1.0 wt 11.0 oz
$ 65.00 $250.00 max rpm 17,000 HP 1.0
max rpm 15,500 $ 80.00 $ 84.00


Magnum 25 pro
max rpm 12,500
HP .80
wt 10.5 oz
$ not listed prob
$70 to $80

I threw the magnum in there only because I had one and seemed like a strong puller. Sold it . Wish I had it back. So that is what I found. What I have gleened from the people who know more than I do is if you want speed go smaller prop and more rpm's. Is that right? So--- more rpm more speed?? Or more hp more speed?? Have been in the hobby from many years and have tried alot of things, but I think I have finally found my nich. The need for speed. Am open to all opinios.

pikeman401

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As i thought may happen it didn't print the way I wanted it to. Will try again..

pikeman401

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will reprint it later


The info for each engin is below it if you can sort it out. they ran it all together.

pikeman401

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for what it's worth
I'll try this again


Norvel .25 cu in
wt 8.03 oz
hp .85
max rpm 15,500
$65


mvvs 28gfs/r abc
wt 9.7 oz
hp 1.0
max rpm 17,000
$80


Jett .25 cu in
max rpm 17,600
wt 14.6 oz
$250

tt36
max rpm 17,000
wt 11.0oz
hp 1.0
$84

Magnum 25
max rpm 12,500
wt 10.5 oz
hp .80
$ about 70 to 80

daven

My Feedback: (1)

Pikeman,

If you have the "need for speed" try and make one of our last remaining races in the Twin Cities.

email me at [email protected] if you have questions.

SST

My Feedback: (2)

Horsepower figures mean nothing...It's torque that spins the prop.

SSAN

pikeman401,

The Jett .25 weight approximate 10 oz without muffler, and 14.6 oz with muffler, prop nut and glow plug. The other engines mentioned are without glow pugs and mufflers etc. Also, the RPM listed for the Jett .25 is the actual ground RPM you will get when you run the recommended listed prop. Performance will even get better once fully broken-in. You can not say the same about those engines mentioned. Their listed performance numbers is no where close and nothing compare to the real world performance, and trying to compare those other engines to a BSE Jett .25 is like comparing a Formula 1 racing against the grass root racing. NO COMPARISON what so ever!

Like the old saying goes... "You get what you paid for!"
Speed cost and so is quality. I think we are learned those lesson.

bob27s

My Feedback: (19)

Thanks Sam. About 17.0k on a 9x6 or around 17.5K on a 9x5 is about right for the .25

The folks that buy the Jett .25 are the combat folks (rules). Most use a 9x5 or 10x4.
By enlarge most folks purchase the .30 or .35 engine Then we are talking 18K on a 9x6.

Engine weights :
OS25FX ABN 248g (8.8 oz)
OS 32SX ABN 270g (9.5oz)
Jett BSE.30 AAC 273g (9.6 oz)

Back to the original post request ......

I do know that set up properly, with the jett muffler installed and the right prop, both the TT36 and MVVS .28 can approach a realistic 17K rpm. There is some good performance to be had there, for a relatively budget price, when set up properly.

Its amazing how the engines sizes have blurred over the years. A lot of this was due to helicopter, marine and car development.

WAY back when, the standard "20 size" small engine was the Veco .19. The K&B .21 (3.5 cc) rear exhaust followed that. John Gorham used both of these engines in the early version of the (then, tiny) Cricket helicopter. The K&B.21 was a popular r/c car, marine and ducted fan engine too. Rossi, OPS, others made 3.5cc engines too for assorted applications. What you see today all derives from those engines. With no 'rules' event to keep them stuck there at a certain displacement, the sport helicopter community developed oversize engines. The OS28H came out to replace the K&B and original OS.25FSR in the small choppers. Everyone followed... Webra 28, Enya, all manner of OS 28 clones. The .25 thru .36 engines you see now (even up to the .39 and Jett 40L) retain that OS .28 footprint. A great deal is attributed to materials and CNC machining - it is not easy stuffing lots of displacement in a small case, and asking it to stay together in extreme conditions [&:] Who would have imagined an engine the size of a K&B .21 with displacement pushing a .40.

MJD

My Feedback: (1)

I think that might be oversimplifying the issue. A cordless drill can have more torque than a .50, but it can only produce that torque at low rpm because it produces less horsepower. Torque is not a rate at which work can be done, it is only a measure of force. Torque times rpm equals horsepower, and that is the rate at which the work gets done and that ultimately translates into how fast the motor can drive the aircraft.

A really effective way to get more horsepower out of a motor is to let it spin faster, increasing the number of intake and combustion cycles per second and thus the rate at which fuel is consumed and thus the rate at which work is done. Of course the motor has to be designed/setup to do so. Asking a .50 for example to be ported/timed to produce peak horsepower at 10,000 rpm might give you a nice torquey motor for turning larger load propellors, but it is not going to produce as much peak horsepower as the same motor setup to peak at 18,000 rpm and burning proportionally more fuel per second, and it won't ultimately drive the same aircraft as fast no matter what propellor you install.

Listing horsepower or torque figures at a specific rpm still gives you the same information in the end. Listing either without the rpm at which it is produced tells you little to nothing. The big problem with published horsepower figures (and I think this is where you're coming from anyway and I **wholeheartedly** agree if so) is the fact that they appear in marketing literature, and as such are subject to both creative interpretation and exaggeration. In other words many of those figures are BS!

Mike D.

bob27s

My Feedback: (19)

Yeah, that pretty much sums it up And its exatly the reason that Jett does not publish HP numbers. Only rpm numbers with a specific, known and consistant load. Thus, compair apples to apples.

Its very simple. Fuel is energy. Fuel burned over a given period of time produces a certain amount of power. More fuel/minute burnt, the more power produced. As you said, more power strokes per min, that is... rpm ..... (fuel burned/min) ... the more energy that is available to do work.

Torque I will not go into. Lets just say there is a balance that can be achieved, and then there is a trade in performance for more torque (big prop, low rpm) or more speed (small prop, high rpm) from that balance.

robert92679

I don't want to highjack the thread, but why is the OS 32SX basically being overlooked? Someone above mentioned that it doesn't do much better than a .25FX, but I thought it ran up to much higher RPMs than the FX. Is that not true? How about the .32SX with a pipe?

combatpigg

My Feedback: (3)

In many ways, when it comes to figuring out what is the best buy for a performance application engine, you have to remember that STEAK is really a much better buy than HAMBURGER. You can pay the money up front for what ever level of performance that you KNOW you will be happy with, or try to save money and buy a cheap engine, slap a performance exhaust system on it and take a chance on this set up being "enough" for you. Forget about all the other pitfalls with going the ECONO route, the main thing to know FIRST is what will it take to satisfy you? For the dollar, the TT .36 is pretty good and would put a smile on my face if I saw one in my XMAS stocking. The OS and WEBRA .32s are able to turn an 8x8 at about 18,000 with a pipe. With a pipe, the cost would be about $180 or so. I suppose the JETT .25 carries it's price for a good reason, I don't know off hand what its' performance numbers are though. I will add that the NORVEL .25 pulls a dirty combat plane pretty good, and I'll bet it does OK in a speed application, especially for the price.

bob27s

My Feedback: (19)

Robert,

Absolutely no doubt the OS .32SX is an excellent engine. With a tuned exhaust on it, it can really sing. And it is pretty much the standard by which all other "30" size engines are compaired by.

Perhaps it was not mentioned up front, because the initial post was focused on a "25" engine (to go in a .15 size plane).

combatpigg - good post Lots of good engines out there.

pikeman401

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WOW A lot of activity since I checked last. First I would like to say thanks for all the replys. I have noted all of them and each has it's point. All good. I would like to add this is my first "SPEED" plane. I have flying for agout 12 years but am not that great a pilot. On a scale of 1 to 10 I'm about a 7. So I am thinking that maybe I should get my feet wet with some that doesn't cost a lot and then move up from there. I agree you need to comape apples to apples and have no dought that the Jett 25 is the strongest and best engine of the group. But I would really hate to auger it in early on. I also take note of the meaningles nature of the hp reading. Again I agree it is a marketing ploy. If I continue in the need for speed I will Probably own a Jett someday but for now I may have to start with something a little more on the economy side. I'm sure I can sell it if I want to move up.

combatpigg

My Feedback: (3)

PIKEMAN, sounds like you have a realistic view. If you want to get a good product review about the NORVEL .25, lots of guys at the COMBAT forum can chime in about that engine in detail.

pikeman401

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Will do Thanks.