MTK

I used a piece of sponge foam I purchased from Home Depot. You know the type, for car washing. Wrapped the chunk around the carb inlet with tie wraps. Not too tight, just snug enough to stay put without compressing the foam.

But to be honest, in my installation, I got practically no improvement in noise reduction. My installation doesn't use the standard muffler or mount and is very quiet by any standard..... The one important thing the foam did was eliminate the gas spitting into my fuse, making it a good reason to use some type of foam in the intake.

MTK

I saw the new FUEL INJECTED EVO60 on the back of this month's Model Aviation. Anyone flying it, please report on adjustability, fuel use, power and field manners.

josephcraig

Haven't been on the chat line in a while..i have had my evolution 10cc for about a year..Its a great engine,but i put it on too heavy of a plane to begin with.Putting it on a 40 trainer now.I would say th power equal to 50 to 55 size glow...What do you guys think,have you tried the engine?

Fidelity101

My Feedback: (13)

I noticed my 33gx had less power than a DLE-30. I was suppose to be spinning an 18x8 - 18x10 at around 8.5k minimum. I was actually getting closer to 6-7k if I remember correctly. In a three blade prop, a 33 size engine is rated for a 17x10x3, but I had to step down to a 16x10x3 to get the rpms up a bit.

Engine runs great for me, until I decided to use some fuel additive to remove the ethanol...that was a bad mistake that almost caused a crash. From now on, I'm going to use 87 octane with 0% ethanol and HP-2 motor oil or similar quality synthetic oil. ( I actually purchased the Horizon oil just to be on the safe side...not sure if it's any better)

josephcraig

from my experience with evolution engines,they like rpm's.me personally i like to use smaller prop recommended for the engine.Just my personal liking.I rather underprop a little than overprop.2 strokes so much happier little higher rpms.Its hard to compare different brands of engines far as power difference cause of each engine likes different props.Find the one each likes.

cymaz

Finally getting my Evo33gx on Monday, not bad considering I put the order in 13th January

cymaz

Right, update.......run the engine in as per manual. It fits into a 1/4 scale Stampe very nicely


The baffles have yet to be shown to work as I have only run it on the ground to check things over. I have put some 16mm silicone tube over the exhaust stubs and this has deepened the exhaust note. I expect the cowl has made a difference to.


I had to move the firewall back only 1". I used the Evo radial mount supplied

A piece of aluminium was placed around the rear of the exhaust to stop the heat getting onto the tank bay.

cymaz

We have a strict noise policy at our club. So all new engines/planes need a noise test, a maximum of 84dB at 7m downwind. Two props were used.
A 20x8 and 18x8 wood. The 18x 8 was 89dB. The 20x8 was 86dB. The exhaust stub nearest the port was blocked off and retested.
The 18x8 came in at 85.5dB. The 20x8 was 83.5dB...result

Fish99

Nice interesting read through this thread. Picked up an Evo 20 cc for my newest addition, a H9 Spitfire MKII 60 size ARF. Have the first in air flight on the motor and I am very pleased with it and how it is breaking in. Just a bit curious, what kind of RPM's are others getting out of the 20 cc with the 15x6 break in prop? I didn't even open it up to full throttle and was just over 11,000 on my max in flight RPM. On the ground static, prior to the flight while doing the ground tuning I was getting around 9500 rpms or a bit more. (running a bit rich of max as suggested)

Seems very high, so was worried about that, but does not seem to have hurt the motor at all as I ran about 1/3 of a tank through it in the shop today and it purrs fine ...

Just curious what others are getting. (Still on the 20:1 ratio mix as well of course.)

cymaz

Got some preliminary noise levels today...it was in my back garden so the wooden fence might have something to do with the figures,

17x8 Xoar ; 89/90dB at 7m

20x8 Just Engines wood ; 86dB at 7m

Update

Ended up using the 20x8 wood JE prop. We blocked off the nearest stub to the exhaust opening. I had put silicon tubing over the stubs earlier.

Re-ran the noise test and this time it came in at 83.5 dB at 7 meters. Result!! Pass YES

So later on I will make up something to tidy it up and block it up altogether. Aluminium plug perhaps.

Max revs were 6450rpm with the 20x8 above. Hope this helps.

Also getting used to starting it. It needs the choke fully closed throttle fully open and turned over 8-10 times, then shut throttle and turn over again. Open choke fully and shut throttle and put it on fast idle setting. Turn ignition on , flick it hard over by hand and it should fire up after 4/5 flicks.

Still on 20:1 run in fuel and ever-so slightly rich

DocYates

My Feedback: (102)

I am retrofitting a older Pica 1/5 scale Spitfire which was originally flown with a Moki 1.80 two stroke. i want to go to gas and maintain the beam mount which is present in the Spit. The Moki measures about 50 mm or 2 inches across to the mounting lugs. Is the GT33 close to this and will I get similar power out of the Evolution 33 as out of a Moki 1.80?
Thanks for the help.

AA5BY

The mounting of the 33 is likely a bit narrower with the hole spacing for the mounting screws at 50mm and the between the beam mounts at about 42mm. I'm not familiar with the power of the Moki so can only compare to what I know. I replaced a Saito 125 with a 33GX and it is considerably stronger. The Saito 125 did not yield unlimited vertical on that airframe and the 33GX does with ease.

miker49

My Feedback: (4)

i'm sorry to say i'm not to happy with my 33.seems it has to be adjusted at every trip to the field.i get the top end good,200 rpm less than max rpm so not to be too lean,try to get the constant burble just about anywhere in the mid range out,no luck with that.i'm using c-9 VP fuel.92 octane,no lead,no methanol,pennzoil at 32:1.never a dependable idle.either too fast to land or dead stick.horizon did provide a new carb which did not change a thing.but thanks to horizon anyhow.i've tried what i know and have had help from the gas guru at the field.we are at wits end.then there are some who say unless you use 100 OCTANE AV GAS you are wrong.of course they are the guys who unless you use what they use,everything else is junk. i am using a 17x8 zoar prop.i am not ready to thro in the towel yet but if anyone has any ideas,please let me know..thanks

erieqc

Try running to your mid range and adjust that to run the best and see if that works. I did on one of my other off brand engines and it worked. Worth a try anyway.

AA5BY

One possible issue could be the effects of a cowled engine with wrong inflow / outflow air flow area ratio. It is often the cause of mid range burble. Here is why. The carb uses atmospheric pressure as the constant to set the mixture needles. If the inflow /outflow ratio is not proper in that there is equal or more intake area, pressures within the cowl will change dependent upon ram air from the prop. At full rpm, the ram air will cause the carb to flood and thus the high speed mixture has to be set lean to correct. When coming off the throttle, the lower rpms will ram far less pressure in the cowl and the high speed needle setting is then too lean, and normally gets countered by then adjusting the LS needle rich so as to obtain a reliable idle. With the LS needle set rich, the mid range then burbles.

The fix is to ensure that there is more exit area than intake area. Most cowled gas planes require baffling or blocking some of the inflow so that the inflow area is limited to just that directed at the jug and providing somewhere near twice as much outflow area. Some will suggest running an atmospheric line from the carb into the airplane somewhere to obtain non ram air pressure but in my opinion, it is not the best course as it could still leave cooling issues caused by stagnant areas inside the cowl becoming super heated. That doesn't happen when baffling the airflow properly.

When the atmospheric port is allowed to function normally, the HS needle will not need to be set on the lean side and the LS needle on the rich side causing the midrange burble.

Hope this helps.... btw, if the engine is not cowled... this post is of no help.

Warren

My Feedback: (72)

Hey all I have a quick question about fuel/oil mix.

The manual for my 33GX states 20:1 for the first gallon and says to add 6.75 ounces of oil to the gallon - A 20:1 ratio is 6.4 ounces to a gallon or am I missing something here? I mean it's very close but?

Thanks!

josephcraig

Yea,
I noticed that too on the oil.I think they just want to make sure on break in period there is plenty of oil.I seen that in the 10cc and 15cc manual.I will probabaly use 6.4 oz in both engines from now on.They say you can go down on the oil in the 15cc,but i don't want two different jugs for both engines.

AA5BY

I'm in the same boat... now dealing with two fuel mixes 20:1 and 40:1 and not wanting any more have stayed with the 20:1 on all my Evos and will do so unless doing so causes a problem.

ahicks

My Feedback: (2)

Mike, if it's quitting, it's almost always because it's hot or lean. If it's doing that at low stick up to about mid, it's the low speed screw.

That mid range burble isn't going to hurt anything but your ears, but you can sometimes help that issue quite a bit by opening the plug gap up to .025-.026. For whatever reason, the plugs burn that rich mixture easier when opened up a little - and there is no downside to running the wider gap.

And about any pump gas should run fine. If your buddy wants to run av-gas, non ethanol, or whatever else, let them. I'm sure they run fine on that too. Fact is, they'll run fine on about anything.... Pretty sure both versions of 20:1 (6.4 vs.6.75) will work good too.



Good friend AA5BY, re: storing both 20:1 and 40:1 containers? I was dreading doing that too, so as soon as I started running the 10cc baby gasser, I started running running 20:1 in the bigger gassers. Half way through the season, happy to report the bigger stuff didn't even notice they were running on a mixture containing twice as much oil! Might have been able to see the difference with a tach, but from a practical (seat of the pants) standpoint? No difference. No more 40:1 in my hangar... Even the lawn equipment is running 20:1 now. -Al

josephcraig

I think all us that are not familiar with these gas engines find ourself chasing the settings.We are not used to engines taking a period of time to breakin.But once they have seated in really good,you can't ask for no better engine.From my experience with the 10cc and 15cc,don't get too happy with wanting to lean low side too much until broken in good.I actually found myself opening low side up for first gallon to get good throttle responce.Then later dialing down after engine is settled in.Don't know if this helps anyone,but it worked for me on both engines.

ahicks

My Feedback: (2)

Matches what I'm finding as well.

cymaz

Does anyone have the diamensions of a 20gx with the muffler attached? I'm looking for total length, width, height difference between the muffler and engine bearers etc. I want to mount it inverted but not sure if the rear can will foul up the firewall. Thanks.

The manual only gives engine size.

Reading what has been said about poor running, it could be vapour lock, blocked screen in the carb, leak on the feed tube in the tank. I opted for genuine Tygon in the feed and clunk. Only going to the supplied pipe out of the tank. The supplied tubing was too stiff. Blow through some fuel through the feed pipe and thoroughly clean out the tank again.

AA5BY

I'd have to pull a cowl to provide the measurements... but speaking from memory the muffler requires either a fairly long set of engine standoffs or what I call a half fire wall where the muffler sets beneath the fire wall. On my install in a Seagull Spacewalker, I had to cut away the lower section of firewall and shoulder it to provide muffler clearance.

bayfield16

My Feedback: (2)

I have a very perplexing problem with a new Evo 15cc gas engine. The engine is installed in a 70 inch revolver and initially ran great (with cowl). Then all of a sudden it started stalling when the nose is pointed down and increasing rpm when the nose is pointed up. It still runs fine when level. The engine was returned to Horizon and assessed. They replaced the carb, ignition, fuel line, cylinder and ring, ran a tank of gas through it and tuned it. I replaced all fuel lines, replumbed the tank, and put in new batteries. When the engine was returned by Horizon, I put it back on the plane and it still does the same thing. I am at a loss as to where to go with this. any suggestions. Horizon was great by the way.

ahicks

My Feedback: (2)

First thought is it might be a little rich. Second thought is that the regulator built into the carb should be keeping fuel pressure constant - and it might be struggling due to tank placement?

No experience to base that on. Just a guess.