View Single Post
Old 12-30-2006, 01:51 AM
  #70  
XJet
Banned
 
Join Date: Mar 2003
Location: Tokoroa, , NEW ZEALAND
Posts: 3,848
Likes: 0
Received 0 Likes on 0 Posts
Default RE: *** CLUB SUPER TIGRE ***

ORIGINAL: rc34074
xjet- Since you have found the 2 strokes you list to run well, why don't you just buy then and run them?
I do!

Alongside my SuperTigre engines are a number of other brands.

I believe in "horses for courses". I use Saito and TT engines on my 3D planes -- because they have superb throttle response and an excellent power-to-weight ratio.

I use the STs on those planes that don't need a good reliable throttle response or good mid-range characteristics and where price is more important than performance. For example, if you've got a warbird that usually gets flow either WFO or cut back to idle for landing then there's nothing wrong with the ST -- chances are that the extra weight will also help the model balance properly.

But that makes the ST a very inflexible engine when compared to its peers from other manufacturers.

why do you take time to post the messages you do complaining about the st carbs? If I had the complaints that you and some others have I wouldn't buy the tigers, I would buy engines I liked.
Because I find it intensely frustrating (and perplexing) that ST are effectively hog-tying what is a potentially a *great* engine by not updating the carby. If they fitted a decent carb so that I could use my ST's for 3D, aerobatics and other kinds of flying where good mid-range and transition are essential, I would probably by *only* ST -- and I suspect a lot of other folks would do the same.

Or I would either 1. buy the Jett carb and maybe his muffler and be done with it, or 2. come up with a recommended change kit to fix the carb problems you list. Maybe you could make some money selling them?
The problem is that one of ST's greatest benefits is the low-cost of their engines. For example, at $80, the ST51 is a well-priced engine that has the potential for being a great 3D power-house. Unfortunately, by the time you go buy a third-party carby, it's simply $20 cheaper to buy a TT46Pro (at $90) -- so why would I bother?

As for going into the business of making carby fix-kits, the same problem applies. Why would anyone buy an ST plus a carby fix-kit, have to mess around installing it, and then end up with an engine that's *more* expensive than one which performs perfectly well straight out of the box with no mods?

The only people who can fix the ST carby problem in an economic fashion is ST themselves. Simply stop making the existing carb and either retool to make a decent one -- or outsource the carbs to someone who can make them properly -- such as ASP.

Since you believe there is a problem it would be better for the hobby to come up with recommended solutions instead of spending the time complaining. However, I have no reason to change as I see no problem with the st carbs.
Maybe you don't -- but *all* the people around here who have bought them *do* see problems and you don't have to trawl very deep through these forums to see that they're not alone. Nor is it simply a problem of ignorance as to engine-tuning.

The reason some folks (such as yourself perhaps) "see no problem with the st carbs" is probably because your expectations are different to those who do.

You may be happy to use an engine that runs a little rough in the mid-range, is very sensitive to plug and prop selection, and can't be relied on to give a reliable or rapid transition. Others, who are used to more modern engines that are very tollerant of plugs, props, fuels etc, and which offer very smooth mid-range with excellent responsiveness find the ST carbies and their effects on an otherwise perfect engine to be unacceptable.

The other possibility is that you (and others) may be happy to live with ST's recommendation that you don't tune the engine with an idle below about 2750 rpms. The fact is that if you do set your idle this high, the ST carb *can* be made to transition beautifully and they become a wonderful motor.

The other truth however, is that many models (notably 3D and aerobatic models) are grossly overpowered, by the old-fashion standards which were in place when ST first designed this carb. A 2,750rpm idle may have been fine for those old underpowered models (and is probably still okay for your average warbird or trainer), it's simply impractical for many of today's high-performance models. Most of my 3D planes would be almost impossible to land with an idle that high!

As I've said before -- the only real problem with ST's carby is that it's only designed to accurately meter fuel down to a high idle and when you try to set what is today a *reasonable* idle of around 2,200-2,300 -- it excessively restricts the fuel flow. The only way to obtain an idle this low is to richen up the low-speed needle which then produces the ultra-fat mid-range and transition problems.

The crazy thing about this is that, if I choose to richen the low-end enough, my STs will idle down to about 1,850-1,900 RPMs almost all day. These engines have the potential for a *wonderful* idle -- but not if you want any kind of transition.

So, stick your ST in a draggy, heavy or underpowered model, adjust your idle to anything over 2,800RPMs and you'll think the ST is a brilliant engine with no carb problems.

Put it in a *modern* sleek, lightweight, highly-powered model and you'll either find that the recommended idle is way too high to land with, or you'll have to richen the low end so much your transition will be shot to hell.

Finally, this becomes even more ridiculous when you consider that one of the main markets for the ST90 (for instance) is to over-power aircraft that would previously have been fitted with a 60 -- thus seriously agrivating the need for a slower idle.

The bottom line -- the ST engines show *excellent* engineering, machining and quality control. The ST engines with the current carb design work absolutely perfectly when used in models with power-to-weight and power-to-drag ratios that were commonplace 20 years ago.

Until the update the carby, ST engines are not a good fit with today's relatively overpowered and underweight models for the reasons previously stated.

If ST spent a few measly bucks fixing that carb, they'd open up some of the fastest growing markets in the hobby: 3D, aerobatics, etc.

So why don't they spend a day in the design room, another day testing and a week re-tooling?

Baffles me! Unless they have absolutely no engineering skills in-house and are simply producing as many engines as they can before the tooling they bought from Italy eventually wears out and they shut up shop.