A close look at an EVOLUTION 26 GT gasser

This is a very clean and compact engine. Because it's a factory conversion engine from a 1.60 glow, the engine will fit nicely into many airplanes. But it isn't "just" another conversion. The port timing has been optimized for gasoline and it has full complement needle bearings in the rod. The carburation is a small Walbro, and it has an electronic ignition. The head utilizes a 10mm sparkplug. For those of you that are engine savvy, you may notice a striking resemblance between the Evolution 26 GT and an MVVS 3094i.

                                                        Exhaust: 150 degrees
                                                        Transfer: 112 degrees (19 degrees blow-down)
                                                        Boost: 108 degrees
                                                        Induction: from 45degrees ABDC to 45 degrees after TDC (180 degrees total)

These engines are similar  but not identical. I've owned many MVVS engines over the years, and they are excellent! Horizon took a great engine and up'ed the standard even higher with good marketing and great service. Make no mistake. As 26cc engines go, the Evolution 26 GT is expensive. On average it's about $100.00 more than other 26cc engines. Is it worth the extra money? In a single word, YES. I will examine the features and benefits and prove why this engine is worth every penny. I will also show you how to extract maximum horsepower from this engine. You will be astonished to see just how potent this engine "really" is.

The chart below depicts a direct comparison of a Zenoah G26 and an Evolution 26 GT.

Displacement: Both engines are within 1/10th cc of one another.
Bore & Stroke: You'll see the Evolution is a substancially longer stroke engine, by 2.1mm.
Weight: The Evolution is considerably lighter.
Benchmarks:The engines are very close in performance, with the Evolution being slighty stronger.       
RPM Range: This is fairly subjective, based on engine durability at peak RPM.
Ignition: Electronic vs. Magnito. I perfer electronic, but magnito is more trouble-free.
Rated HP: This is very subjective! It depends on who's doing the testing. A side by side comparison would do much better.

Don't mis-understand me regarding the Zenoah G26. It's a superb engine, and an excellent side by side comparison. Zenoah engines are high-quality durable engines.

Some FEATURES & BENEFITS of the Evolution 26 GT

FEATURE: SIZE
The 26GT is compact using a front carb, side exhaust, and rail mounts.
BENEFIT: This engine will fit into any aircraft that will support a 1.60 glow engine, making it very nice for scale model cowlings.

FEATURE: WEIGHT
The 26GT is considerably lighter weight than most all other 26cc gassers.
BENEFIT: It weighs only slightly more than a typical 1.60 glow engine and it's a lot lighter than a Zenoah G26.

FEATURE: HORIZON HOBBY
Engines, Parts, and Accessories are readily available
BENEFIT: Great support, reasonable prices on accessories and parts. Options readily available and in stock.

DRAW-BACKS:
I bet you thought this wouldn't happen... but every engine has its draw-backs.
The single biggest draw-back is the Electronic Ignition used on the Evolution 26GT. It is heavy by comparison to other Electronic Ignitions, AND it requires a 6 cell battery pack! It's also a very expensive Ignition carrying a price tag of $239.00 for replacement. OUCH, That really sucks!  At least that explains the higher price tag for the engine... Another item to watch out for is your tuning. Because the engine IS compact in size, you need to be careful not to let it get too lean. It can over-heat fairly easily especially in tight cowlings. 

HIDDEN POTENTIAL:
This is my favorite part! An Evolution 26 GT is a genuine schnurle ported engine... and what does this mean? It has a high potential for power, lots of  POWER! All you have to do is take advantage of it. The easiest way to tap into this hidden potential is to use the "optional" tuned pipe. This will get you an instant extra 300 RPM's or more. Very nice! We're not done yet... you can also modify the Tuned Pipe. (SEE; bottom of page)    If you opt to tinker with the Ignition by replacing the factory module with an RCEXL Ignition, you will get rid of the 6 cell pack and the extra weight. You will also have the option to re-time the engine to your liking. This can get you another few 100 RPM's all by itself, regardless of the type of muffler you use. And there's even MORE! Because the engine does have schnurle ports, it breathes much better than a plain old piston port/transfer port engine such as Zenoah. This extra breathing capability allows you to put a BIGGER carb on the 26 GT. How much bigger? I am using a Walbro WT-540! It's over double in CFM as compared to the stock WT-613 carb.
SEE: bottom of page

My Evolution 26GT equiped with an RCEXL Ignition, a WT-540 carb, and a tuned pipe yields 10,500 RPM's on an APC 16x8 prop!  Replacing the Ignition: SEE: bottom of page

That my friend, is serious POWER for a 26cc engine. Doing the math, it yields 4.3 HP. You will never see this kind of power from a Zenoah G26. I know, as I've tried it many times!

My BIELA 16x8 is the toughest of all my props to spin up. It's a wide blade carbon fiber prop. The best I could do with it before the engine mods was 7700 RPM . And that was on a really good tune! As you can see, the engine has no problem with it now.

It's important to understand that when referring to horsepower, there's a lot of room error depending on the method and mathematics used. HP is a mathematical caluculation based on actual torque & RPM. I really much prefer to benchmark props and use a relative comparison.

10,500 RPM's is really too much for this engine. So I switched to a Mejzlik 16x10 carbon fiber prop to slow it down a bit. It still SCREAMS at a solid 9500 RPM. Because this engine will be running in the mid to upper 9's range, I have decided to make ONE final upgrade. The crankshaft bearings are not rated to run consistantly at such high RPM's. So I ordered a set of Hybrid Ceramic ball bearings. The term "hybrid" means the bearings have stainless steel races and ceramic balls. These bearings are much lighter weight, much stronger, much smoother, and will withstand RPM's in the upper 40's without any problem, even if the engine gets a little lean. 

My engine was test-run on 87 octane unleaded gas with 32:1 Lawnboy Ashless oil. When I set the timing at +28 degrees, the engine didn't like it with the 87 octane. I moved the timing back to +26 degrees and all is well. The new RCEXL ignition has an advance curve of 18 degrees, so at idle the engine is running at +8 degrees. At approximately 4000 RPM the ignition is at full advance.  The single biggest power gain came from the carburator.  However, the WT-540 Walbro is discontinued. You will discover the WT-610 is its replacement. I'd like to note here that if you go with a bigger carb, you need to keep the prop diameter down. The reason is, the 26 GT is border-line in size for such a big carb and it needs good RPM to keep the venturi velocity up. A tuned pipe was the next biggest power increase. However  I modified my pipe to cut the upper RPM back-pressure. SEE:  Evolution 26GT Tuned Pipe Mods

I have 2 Evolution 26 GT engines. One of them is in my Super Kraft  REARWIN SPEEDSTER 1/5th Scale. It has a LOT of flights on it, and it kicks butt at the airfield. Rookies, Sundowners, and whatever else happens to show up. This clunky old high-wing really shocks people when they see it keep up with (and sometimes out run) those HOT-BIRDS!

The bottom line is, the Evolution 26 GT is a magnificent engine. Right out of the box it will run like a top. It will provide dependable performance and it will last for years. However, with a little tweaking here & there this engine will blow you away. The throttle responce will be super fast, and the top-speed is nothing less than AWESOME! The only down-side is, by the time you have it screamming like a raped ape... you've spent a fair chunk of money... but it's worth every penny!

With the correct prop and a good tune, my speedster will hit 105 MPH.