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So who's doing this reviewing then?
Well I've been building and flying or driving radio controlled models for over 40 years and during that time I like to think I've built up a reasonable amount of knowledge.
I'm also a qualified electronics engineer who has worked in radio frequency, analog, digital systems and software for more than three decades. In fact I designed and built my first RC set back in 1969.
For the past nine years I've also been involved in the design and manufacture of some rather sophisticated engine technology and UAV flight control systems.
So, chances are I've been there, done that and have a huge pile of tee shirts to prove it.
Right now I'm heavily into 3D flying and enjoy all aspects of the RC hobby. I may be old but I don't feel it.
In the Pipeline
Here's just a little bit of what's to come on this site...
RC explained: Demystifying terms such as PCM, PPM dual conversion, single conversion, full-range etc., this feature will explain it all.
Cheap Chinese Engines: Just how good are those cheap Chinese glow and gas engines that sell for half the price of their "brand-name" equivalent? I put several to the test.
Build your own radio gear?: Back in the old days, building your own RC gear was not uncommon and now the arrival of 2.4GHz has made it practical again.
Review: SK90 Model Airplane Engine
Here is the SK90 in action, on its first tank of fuel
A torquer, not a rever
As mentioned earlier, the SK90 has been designed for large props and low RPMs.
Although it was tested with smaller props such as 12x6, 12x7, the engine was very difficult to tune and was obviously suffering from severe choking in the transfer port area at RPMs over about 11,000 RPMs.
As a result, I really wouldn't recommend using anything smaller than a 14x6 or 13.5x8 as the power really starts to drop off as the RPMs go up.
So far, the best props for this engine appear to be the 14x8 MAS K-series or a good 15x6.
Yes, a 14-15-inch prop may sound like a lot for a .90-sized 2-stroke but the SK90 performs very well, delivering close to 9,500 RPMs (as good as the OS91FX) on the ground with the MAS 14x8 prop and fuel with 5% nitromethane.
A nice reliable idle of around 2,200 RPMs was obtained on all props and the transition, although not as super-crisp as some other "big-dollar" engines, is actually better than the SuperTigre 90 that costs more than twice as much.
The SK90 I purchased is a fine sport-type 90 engine and would likely be well suited to slower-flying models (especially scale) where the ability to swing a big prop is an advantage.
On a "value for money" basis, it's pretty hard to think of an engine that offers more bang for the buck right now.
However, if you're after a real screamer that will deliver high power levels and spin a small prop until it screams -- then the SK90 is not the motor for you.
Think of it more as a tractor than a Ferrari.
The issue of quality control
At this stage I have to issue a caveat in respect to my experiences with SK engines.
This particular example from the SK factory is indeed a great little engine but I had far less joy with an SK50 I purchased at the same time. This SK50 will be the subject of another review to be published shortly. However, it's fair to say that it is obvious that a factory which can produce engines at both ends of the quality spectrum has real issues with quality control.
I therefore issue my standard warning when it comes to the purchase of products that sport the "Made in China" label...
Don't be tempted to buy an SK engine from a dealer or distributor that doesn't perform pre-sales inspections and checks of the product. While you might save a few dollars buy purchasing directly from China, there's always the chance that you'll have wasted money rather than saved it. If your engine is a dud, the only option you have is to ship it back to China for a replacement -- which will almost certainly be uneconomical.
Do yourself a favor and buy from a local dealer with a good reputation for after-sales support. It'll likely be cheaper in the long run.
As usual, the manufacturer's power claims are exagerated and the weight is understated.
Displacement: .90cu/in / 14.9cc
Bore/Stroke: 28.12mm / 24mm
Power: 2.6HP @ 16,000 RPMs
Weight: 25.96oz (measured: engine: 21.1oz, muffler: 7oz)
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Updated: 20 Sep 2012
Here's a blog that will keep you informed just what's going on behind the scenes at RC Model Reviews and also tells you a little more about myself.
23 Mar 2010
How come there's no compatibility between different brands of transmitters and receivers? Why can't you use a cheap Chinese receiver with your Futaba FASST radio?
4 Mar 2010
Since this has become a very frequently asked question, I've posted this simple guide to getting your product, or a product you're thinking of buying reviewed here at RCModelReviews
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