XJet

With nitromethane costing $100 a gallon around these parts, there's no way the average modeller can afford to feed an ST90 fuel with 15% nitro in it. Besides which, the prevailing wisdom is that the STs prefer *low* nitro fuel.

Maybe we should try unbalancing the prop? :-))))

telejojo

Is that 100.00 a gallon for pure nitro or at 15% thats 15.00 a gallon,thats about the going rate around here.

XJet

Yeah, but don't forget that's just the *nitro* component. You've got to add another 1/5th gallon of oil (that's about $12) and the methanol $3.70, which comes to a grand total of: $30.70 per gal.

Now my ST90s suck a lot of fuel so a gallon is probably only good for a day or two's flying -- that's quite expensive!

If we go the 5% nitro route we can save quite a bit -- because the cost of the nitro is lower and the fuel consumption of the engines drops quite a bit too.

Not24

My Feedback: (1)

Nobody ever said this was a poor man's hobby. A G90 doesn't burn that much fuel compared to a Saito 1.80. I know it's apples and oranges, but the people who have those have a reason to complain about fuel prices.

My Ford Ranger is supposed to run on 87 octane. I bought it new, and have never been able to run anything less than 93 in it, or it will ping. So much for what the engineers intended. I do what works. If my engines run fine on 5%, I'll use it. If they need 15% to run good, I'll use that. If the price of fuel ever becomes an issue, I'll fly smaller planes or go electric.

XJet

Yeah, but all my other engines are happy to run on 5% nitro -- and the ST manual says it's okay to use any fuel from 0%-15% so you would expect the engine to run satisfactorily on 5%, I mean, they wouldn' lie would they? :-)

In reality, you *can* get your ST to run just fine on 5% (or even 0%) if you chuck that awful carby away and fit a decent one.

So is it my fault for not using fuel that costs twice as much as that I feed to my other engines, or is it ST's fault for not updating their carby to something a little more sensible?

proptop

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Mark me down as a member...I've got probably a dozen or so...

proptop

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Hey...is there a ST timeline like the one for O.S. so one could tell when a particular engine was made? (photographs and etc. )

buzzingb

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I use to be one of the Super Tiger bashers but I listened to Not24 and now I love these little jewels. They are a little more tempremental so if you don't know how to set an engine properly go for another brand and pay twice as much and get an engine that will only last 1/4 as long.

buzzingb

My Feedback: (2)

Lets face it everyone wants an engine that will run for a cheap price. Well the Super Tiger Line deviates from the saying, You get what you pay for. With the iron liner and ring you have an engine that will last a lifetime if you run it properly and don't use as earth auger.

Flyer95

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xjet,
Have you tried the OS-F plug?

speedster 1919

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I read an article on the web today (should have marked it) from a self proclaimed Super Tigre expert. He said the fix to ST carb mid range problem was in glow plug selection. Not to throw an OS F or other hot plug or even an OS 8 in them. The fix was (silence) Idle bar plug After all these were invented with Super Tigre in mind. It was pointed out , that it was an issue of timing for low and high end which effected tuning. Just like throwing high nitro in a Super Tigre won't give good results. I have always used FOX IDLE BAR LONGS in tigres and all other engines I use with good (last for seasons) results. I will have to do an experiment and put a hot plug in and see if tuning and mid range chages and see if I gain 200 RPM which is claimed by some ,that an idle bar plug will cause..........The only engine I own that does not run a Fox RC long is a TIGER SHARK 61 that made funny sounds on cold start up and 1 member suggested a K&B 1L plug was the only plug that engine liked. He was right on . Hot or cold outside that engine never made another funny sound..........

XJet

This is what I mean about the ST engines... one person suggests and OS-F, others say "no, don't use an OS-F"

The truth is that there is a *major* problem with the ST carbies that requires people to try all manner of voodoo magic to try and overcome it. Sometimes it works, sometimes it doesn't.

Yet OS, Thunder Tiger, Magnum and a raft of other manufacturers can design and build carbs that don't require all this crazy playing around with nitro percentages, idle-bar plugs, 4-stroke plugs, magical prop-sizes etc.

Just about everyone except ST can build a carby that just works well, regardless of your prop, plug, fuel or whatever.

To all those who suggest that these other fixes are the solution -- you're busy trying to address the symptoms, not the *cause* of the problem -- which is the carby.

The proof is -- just replace the ST carby with a Magnum, Perry or OS carby and all the problems go away, as if by magic.

Point proven, problem solved.

But, for whateve reason, ST refuse to make the incredibly minor alterations that would be all it takes to turn an "okay" engine into a superb one.

Bax has repeatedly dodged this question in the ST support forms -- why?

Flyer95

My Feedback: (1)

The OS-F does not solve the midrange problem completely. What it does is that it keeps the fire going much better than a say OS 8 and makes the engine more reliable when flying at partial throttle and also gives super low idle.

I think a smaller bore carburetor or sleeve in the carb., a less restrictive muffler and a long reach fourstroke glow plug is one solution. Changing the carb is another solution.

XJet

I've tried a less-restrictive muffler (in the form of a mousse-can pipe) and, while it improves the throttling and power somewhat, the carby still provides very poor midrange mixture-control, resulting in poor transition and loading up at throttle settings from 1/3-2/3.

All ST has to do is use a decent carby and they'd have an engine that was even better than an OS.

The only reason I can think of to explain why they don't fix their carby designs is that they simply don't have any design-engineers on staff. I get the impression that ST is (now) just a company which has bought the rights for the current design, commissioned their manufacture in China, and don't have a clue themselves how to fix or improve things.

This would also explain why the long-awaited and long-rumored replacement for the G4500 (the G3750?) has never actually eventuated.

The STs are good engines but their carb design is two or three decades out of date and it's now really hurting them as the other Chinese manufacturers start to roll out some very nice engines which are lighter, stronger and much better suited to today's modern highly-powered models.

ST maybe able to squeeze a few more years out of the current line-up but, unless they update those carbs, they're going to find themselves with only a few totally brand-loyal customers left. As it is, they sell mainly on price but, with other Chinese engines now undercutting them, that can't last either.

I've designed my own carby for my G90s (with responsiveness even suited to 3D) and I'd gladly *give* the design to SuperTigre if they wanted to manufacture them -- but it seems they just don't care. So long as folks keep buying them, they won't change a thing -- which is a shame.

buzzingb

My Feedback: (2)

The carbs aren't perfect so let move on. I don't think the carbs on any of these engines are designed correctly but some do work better than others. If you think about it they work like a ball balve designed pro fluids not for metering fuel and air.

downunder

I'm not really up to date on the latest ST carbs so I have to ask when the design was changed to make them into a bad carb. I've only got 2 RC ST's, one is an ABC GS45 that I got second hand and it runs flawlessly. The other is an unrun 80's ringed G45 (with the earlier round head) and with an external needle for the idle mix. I nicked that carb to use on an OS61VF but took out the venturi restrictor to get the same area as the original carb. It was dead easy to set the high and low mixtures and it gave the fastest and cleanest transition I've ever seen. So, no complaints whatsoever with either of those carbs which leads me to think they must have been changed at some point.

buzzingb

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Question for some of the engine gurus. Why is it that glow engines need so much oil content in their fuel? If you look at gas engines today you can find some that run on 50:1 oir ratio. That is just is just over 2 oz. of oil in each gallon of oil. Well if you look at glow engines they use about 25 oz of oil in a gallon. I can't figure the ratio but I bet some of you can so lets hear it. If we could use less oil our engines would use less fuel and be more powerful. What exactly requires us to use this much oil? Cylinder/piston rod/crankshart bearings fuel ?????

speedster 1919

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Buzz First it is an RPM thing . A glow 2 cycle will do 16,000 RPM easy and a gas 2 cycle around 8,000 RPM. Second methanol has no lube qualities by itself , were as gasoline has a petrolium lube quality built in. Not much-but enough to help out........

speedster 1919

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XJET your in the wrong forum . You should be in club Thunder Tiger or club Magnum...........I say the carbs are a proven design and too many people get along with them just fine. ST use to be one of the more expensive and now the less expensive. Thanks to TOWER or Great Planes.

buzzingb

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Without a doubt the price is what led me to Super Tiger and I must say I wasn't expecting much. I got much more from the Super Tigers than I expected. The things will run like mad and hold up much longer than other engines. I am able to buy twice as many Super Tigers as other engines. I am stoked on the Super Tigers now and elated with the torque and power these engines produce.

XJet

Our tiny engines have a plain bushed conrod -- most gas engines have needle-roller bearings on the conrod's big-end.

Roller and ball-bearings need only a tiny amount of oil to function -- bushings need far more.

If you fitted needle-roller bearings to a regular glow motor, you'd also be able to run 25:1 or 40:1 oil ratios too -- but unfortunately there are a number of practical limitations that make it impractical to do so -- mainly the fact that needle-rollers have quite a high "overhead" in terms of diameter. This means that there's a significant difference between the diameter of the crankpin and the hole in the conrod. Fitting a roller-bearing to a small engine like our glow motors would involve *significantly* increasing the size of the crankcase to allow for this overhead -- and that would produce a noticeable performance penalty.

However, one area where we still lag behind is the quaity and performance of the oils we're using in our motors.

I suspect that the methanol-fueled 2-stroke market is absolutely tiny compared to the gas 2-stroke one, and as a result, not a lot of R&D goes into producing newer, better oils for us.

While there is a small army of oil-makers competing for the very large and profitable racing 2-stroke gas engine market, nobody much cares about toy airplanes :-(

This means the average model oil (Morgans Coolpower, Klotz Techniplate, etc) is not exactly stunning in its protection and lubricity when compared to oils for mixing with gas from the likes of BelRay, Amsoil, etc.

Apparently the Europeans have Motul and Aerosave which offer full protection in much lower ratios, and there is at least one US-sourced oil with similarly advanced technology -- but the fuel that 95% of modellers buys is pretty poor by comparison -- hence the need to run ratios in the order of 4:1-5:1 or so.

And, while lots of folks (including myself) extol the virtues of castor oil, those virtues are often only realised when it's a "lubricant of last resort" -- polymerizing at high temperature to protect the piston/liner interface. At the lower temperatures found in an engine's bearings and con-rod bushings, it's high viscosity and drag produce a performance hit. What's more, its protective effects are diminished quite significantly by over-dilution -- so has to also be used at relatively high percentages to provide adequate protection (or used as part of a synth/castor blend).

Now I'm not an oil expert, but I do listen to folks who are, and this is what I've picked up over the years. I know there are some real experts on RCU who might like to correct me if I've made any errors.

XJet

Hey, I've got several ST engines and I love the fact that I get so much engine for such little dollar -- but it frustrates the hell out of me that they could be a *fantastic* engine if only the carbs were updated!

Every time I slam the throttle open on a "stock-standard" ST90, they cough, burble and finally burst into full song and I'm reminded that all my other engines just spool right up without any hesitation.

Hell, even the air-bleed carbys on my TT61GP and TT42GP provide snappier response and better mid-range fuel-metering than my G90s when running with the standard carb.

But I can't use a stock ST90 for 3D, or any other kind of flying that demands rapid throttle response throughout the mid-range, or any kind of plane that needs to be run at 1/3-2/3 throttle for extended periods of time -- they just load up and run way-rough in this part of the throttle curve. That is of course, unless I fit another carby ($$ or hours in the workshop turning and milling), in which case they become real jewels worth far more than the street-price that's usually charged for them.

Maybe ST are missing an opportunity here. I (and I bet a bunch of other folks) would gladly pay an extra $30 if my ST engines came with a better carb. It would save me the hassle of making the change myself.

The only reason I can think why some folks are happy with their ST throttle performance is that they simply don't need or appreciate the importance of a clean mid-range to some kinds of flying and therefore find the ST's burbly mid-range acceptable.

proptop

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XJet...I would be interested in the results of that oil testing session you talked about in another thread...got any idea about when you might get the time to do it?[8D]

happypappy

My Feedback: (10)

Actually Klotz Techniplate is one of the finest lubricants for alcohol and gas fueled two strokes ...period. Alky Hydro guys use this lube all the time as well as the folks at Mercury Racing and the old OMC performance group when they dominated Formula one racing on the water with their awesome V8 outboards. The world record for a single engine outboard, 178mph, was set with an alcohol fueled Evinrude V8 running on Klotz Techniplate. That was one incredibly expensive outboard as well as the fact that OMC Engineering did not want to risk a life due to failure at those speeds! The fact is that there isn't a lube made that can protect these little engines from the abuse we put them through.

XJet

Klotz used to have a chart on their website where they compared the various attributes of the oils they sold.

Techniplate was rated (by Klotz themselves) rather low at 6 or 7 out of 10 if I recall correctly (compared to castor or castor-blend) in the "wear protection" area.

They rated castor as 10 out of 10 and "Super Techniplate" at around 8 or 9 from memory.

The reality is that synthetics are fine, so long as you're operating within their designed range of pressure and temperature. Unfortunately that range is smaller than for castor but castor has other drawbacks -- so life is a big compromise :-)

The oil tests will be completed and published in a week or so