Evo .40NX
 

Not positive but thought this forum most appropriate for this class engine. Not even sure if they're worthwhile but felt $85 was a reasonable gamble for a new engine from HH. Decided to keep quiet until I got them so not to be disappointed by yet another disappearing act.

Told my wife I wanted a couple for Christmas because the once common .28 to .35 sizes seem scarce - at least NIB and OS's .35AX seems way over-priced now.

Sort of a small block .40 aka a .25 size case with a compact beefy cylinder and a large bore carb; looks like the kind of engine that would turn small dia, high pitch props at decent numbers.

Anybody have any experience with them?

I don't have any experience but it's fun to speculate.

First of all, the Benchmark Engine in this class is any of the hot .32s like OS or Webra. With a tuned pipe they will put out 18,000 rpm with a 8 x 8 APC. That's pretty serious performance for $130 or so.

This should give you a point of reference to compare the $85 Evo .40 to.
In a typical model engine case it's pretty hard to increase stroke, so I'm guessing the Evo has an oversized piston. The engine may or may not have increased breathing capacity through the carb and the crankshaft compared with it's .32 sized counterparts. If not, it would be like taking a 300 HP 350ci car engine, installing a 400ci rebuild kit into it without increasing it's air handling capability and expecting to get much more than 300 HP.
What you end up getting with just the extra cubes is about the same HP but at a lower rpm.
If Evo made this transformation from .25 to .40 worthwhile they hopefully went the extra mile to get this engine to rev a 8 x 8 APC beyond 18,000 on 15% nitro.

Great info. Thanks on that CP. I went so far as to ask to include the Jett mufflers taking for granted a review on the engine at HH's site but discovered hole spacing too narrow - bummer - should have chk'd specs first.

Instructions only acknowledge tuned exhaust systems.

Would Mac's be a good source for header and pipe? Equivalent recommendations for their H-9 #3 or #9 performance plugs?

Yes, MACs products and service is outstanding.
For plugs, I like to use the cheapest ones like FOX or K&B. If the compression is set too high or the mixture too lean, you can obliterate an expensive plug just as easily as a cheap one.
The absolute best value are Nelson plugs but they use a special 11/32" thread with a tapered seat like AN fittings have. Might as well not bring them up unless you are a machinist or want to have a machinist modify a Evo head.

Cool; thanks.

It just occurred to me that you should tell Macs that this engine appears to be an overbored .32
Check the bore and stroke specs on it if you can find them.
This will help Macs decide which pipe is best just in case you have a "borderline" application here.

Can you slot out the Jett muffler holes, a bit, so it is useable? I found the Fox plugs pretty fragile on a stronger motor, and higher nitro.

I didn't know that MACs offered more than a few subjects beyond a pre-tuned system for .40-.46's and another for .61's based on TH's listings. Nice to think that I might be able to acquire something that's optimized for this engine size... Instruction sheet specs show bore and stroke of 21.7 and 18.2mm respectively w/ disp of .41c.i.

Hope not too personal: good source for K&B plugs?

I looked at using one of the two holes in the Jett mufflers and looks like drilling/tapping second hole in mounting flange would be right up against other hole, i.e. no edge distance and a "figure 8'ed" hole. Also concerned about volume not optimized in this instance but am ignorant in this regard. Have option to use these mufflers on other subjects as well though.

Bisson makes some custom mufflers too. Not too sure about pipes. I would not wreck the Jett pipe if you have something else for it. Mecoa may have the plugs. He took over the K&B stuff. Not sure if the EVO has the middle reach plugs or the longs. I think it may be the middle reach, like most of the newer oriental stuff which would be OS or Enya. You would have to take the head off and look for the bottom of the plug being flush.

If I remember correctly, MECOA sells K&B plugs.
Nowadays, look for ebay sellers for odds and ends like this, it's worth a look.
Just make sure the seller has a 98% plus rating and a lot of prior transactions are a plus.
MACs has quite a lineup of pipes and headers for everything imaginable and they can piece together a header per your specs if it's a one of a kind situation.

About matching header flanges to 2 cycle exhaust ports....I've seen some pretty crude looking "matches" that worked very well. There might even be some science involved with the crude looking jobs I've seen.
The lesson is, never say die until you've tried everything that looks like it might work..!

Either forgot or more likely never realized there are mid-reach plugs; only thought longs and shorts w/w/out idle bar, various heat ranges...

Can you shim plug and achieve decent results?

Thanks all.

Plug choice has never been a huge issue with me [running wide open 99% of the time] unless I'm working with a super cold plug that my engine can't bring up to temp.

You want to monitor the condition of the combustion chamber and top of the piston. You don't want to see a clean, sandblasted surface. You want to see soot and a caramel finish in there.
If not, add head shims. Better to add too many than too few, you can always subtract as needed after you get the feel for what is going on in there.
A tuned pipe raises the dynamic compression ratio, so if you obliterate a glow plug you need to "detune" the things that you have control of like fuel mixture, pipe length, nitro content, head clearance and propellor load.
Too short of a pipe system or not enough volume causes excess heat.
A loose glow plug element rattling around inside your engine can get expensive.
When you hold your finger into the exhaust spray, you should see dark brown ooze and not black. Black means that the engine is over-compressed. Same exact symptom if you are tuning a diesel.

CP is right about the head shims. Extra plug washers are ok, but there is still a bigger gap between the threads that loses performance. I guess it is still better than sticking into the combustion chamber. I will admit that I have done it

Aah, the good old days of reading a plug with castor oil.
We fly all synthetic here in Q40, and I run it in everything else too. Downside is there's no plug reading. Engine doesn't quit either when it's too hot. It just drops a couple of thousand rpm but keeps on going. I've seen plug bodies of Nelson HD's burnt blue, but the engine was still running.

FWIW, I have one of these and ordered a JettStream JS-30 from Dub. I haven't run the 8x8 but mine turns 18,400 on an APC 9x6 running Powermaster 15% Air. The engine is used for sport flying.

Energyman

Out of curiosity, what's it installed in?

It was installed in a World Models LA Racer with the JettStream. I also had it in an Ultra Sport 40 with the stock muffler. Right now its in the box. It never caught on down here in Club 40 racing. I bought it more out of curiosity than anything. The Horizon data shows it as a 0.41, which would eliminate it from Club 40 racing as I understand. My measurements indicate it is slightly under 0.40. If anyone is interested I have other test data with the JettStream and with the stock muffler.

Energyman

Forgot, it is currently installed in a Goldberg Falcon 56 MkII modified for the extra power with a bolt on wing and dual aileron servos. APC 10x5 with the stock muffler and Powermaster 15%.

I'd be interested in hearing how this little engine pulled the Ultra Sport 40 since I figure this airframe as using more the upper end of the .40 spectrum i.e. .46 - .50 size engines. Did you prop it like the Falcon 56? If not too much hassle, also interested in any comparison figures between JS-30 and stock mufflers. Any mods to stock muffler you're operating with now?

The plane actually was an Ultra Stick 40. Sorry for the mistake. The plane was used as a test bed for engines in the 40-50 size range. As I recall the Evo actually flew the plane fine, but consideration had to be given to the CG due to the light weight of the engine, as would any plane of this size when using this engine. I found the engine works good on the APC 10x5 for general sport flying. The stock muffler was not modified, but I did JB Weld the rear cap on the muffler due to rotation issues. Following are some rpm numbers with the stock muffler and JettStream:

Prop Stock Muffler JS-30
APC 9x6 16,500 18,400
APC 10.5x4.5 15,500 17,100
APC 10x4 15,600 Not Tested
APC 10x5 Not Tested 16,300
APC 10x6 13,900 14,800 Peaky and inconsistent

Thanks for posting. I was going to ask if the baffle was removed on the stock muffler but decided to check before doing so. To my astonishment, there is none - at least not in the one I checked! I thought manufacturers were somehow forced to comply with some sort of environmental concerns these days when marketing to the masses and expected to find a baffle plate or cone of sorts inside the muffler.

I notice a cap on the left side of the carb; can the remote H.S. needle assy be moved to the carb and is there any benefit in performance?

I purchased 2 40nx engines and had them on a twinstar, when new they ran pretty good except the mufflers kept turning. after about 15 flights l was having problems keeping both running. next put one in a sonic low wing blew the rear bearing. other one put in a club 40 plane too slow to compete with the TT40s.

The needle valve can be moved to the carb. The engine performance is the same. To keep the muffler from turning, I secured the end cap with JB Weld.

I moved the needle to the carb and removed the stops. The bearings were changed and the engine was put in a sweet stick and really hauls it a round.