|344 forum posts|
Completely new to petrol engines so do not want to spend a fortune on a petrol engine then find I that prefer a glow engine ,So the price of the NGH petrol engine looks good but what are they like ????
|Kim Taylor||02/09/2018 23:29:04|
|307 forum posts|
I've got a GT17 which is in a Wot4 XL.
Early days for me as I haven't used it much, but it seems to have plenty of power and isn't too difficult to set up, although the screws for the mixture are very sensitive, so very little movement required to affect a change.
You MUST run in on 20:1 mix of good 2T oil and then use 25:1 once it's loosened up - there are stories of people trying to run on 32 or even 40:1 and it never ends well, as the con rod has plain bush bearings, not races, so needs plenty of lubrication
It's a bit noisy on the standard 'silencer', as seems to be common to all petrol motors, although Just Engines (who I bought mine from) do a wrap around type muffler, which is supposed to be quieter. I got mine down to 82dB by stuffing the silencer body with coarse stainless steel scourer material and using resilient mounts between the mount and airframe (again, available from J-E).
Currently it's turning a 15 x 8 Graupner Sonic prop at around 8700 rpm, although I want to try an APC of the same size to see if there's a difference in revs / noise output.
Overall, particularly for the money, I'm happy enough to consider getting a GT9pro to go in my next planned build.
|Manish Chandrayan||03/09/2018 03:08:35|
630 forum posts
|Rocker, what size NGH are you contemplating?|
My suggestion would be to stay far off from the 9cc.
The mid size 17 and 25 I have not used do can not comment.
The 35 is fine, but I didn't have success with rear exhaust version and the supplied muffler gave me serious grief. I replaced that with an aftermarket job. Also installed a Venturi on the carb to minimize raw fuel spitting out of carb. That single prop bolt is convenient, the engine has option of beam or backplate mount.
The 38 Four-stroke I have had few bench runs. Not a power House but fine enough. Another flyer at the field had the same engine that threatened to shake apart.
Now take your pick
|Ron Gray||03/09/2018 07:27:12|
|1894 forum posts|
I have a 38 4 stroke. Summing it up, for me, looks nice but noisy, underpowered, messy and vibrates (have to lock wire the exhaust on having lost 2 in mid air). I spoke to Propguy at one of the shows and he reckons that the timing is not correct on a lot of them which results in the excess vibrations. I’ve taken it out of the model it was in, not too sure if I will try it again or move it on.
113 forum posts
I have a GT9 that is 3 years old now and is used every time I fly. The first year was a pain, as has been widely publicised, because the carb was useless. All changed after I fitted a Just Engines carb from their .56 glow engine and did a mod to the fuel scheduling by regrinding the slot as others have done. It does not need a pump, if you place the tank centre in line with the spraybar as for glow engines, although one was supplied with the engine. I also replaced the silencer with one from my old ASP .40 and it is quiet. The basic engine is fine and a real workhorse. Starting is easier than any other engine I have had. Most problems I have had since have been caused by fuel plumbing, it is sensitive to air bubbles in the fuel line and the plug cap must have perfect contact. Any problems here will cause havoc with the radio from personal experience, definitely brown trousers. Not hugely powerful, about the same as the old OS 46 AX it replaced. The new GT9 Pro has a completely new design carb with temperature insulation and a built in pump like the bigger engines with Walbro carbs. First impressions from users on other web forums are good. Just Engines are selling it so you can't go wrong. I would not go back to glow as I was using at least 4 gallons of fuel a season and getting glow fuel is such a pain if you don't go to the shows.
Edited By Philflyer on 03/09/2018 09:12:12
|344 forum posts|
Was thinking on getting the 25 or 35 NGH depending on which one "Just Engine " recommends for the model I have ready for the engine .It looks like the 35 NGH would be the better buy .Hope it will be a good introduction to petrol engine as buying a large glow engine is getting harder and harder to do with most of the big manufactures now turning to producing petrol engines in favour of glow engines bigger then the 90 four stokes
113 forum posts
I can't comment on the 25 or 35. I had a NGH GT 17 as my first petrol engine and it was great in a .60 size aerobat but again I don't know how long it would have lasted because a broken wire on my Spektrum rx resulted in the destruction of the model and engine after only a few hours flight time. My first petrol experience with that engine however caused me to sell all my glow engines and go totally gas. As I said, the biggest problem I had was with plumbing and the use of Tygon tubing. It is a lot stiffer than silicone tubing we are used to with glow fuel, so getting good sealing on to nipples and tubes needs new skills and good selection of diameters. Getting a tank clunk with a Tygon tube and felt pickup to fit a small tank and fall properly was a trial. I now wrap the end of the clunk tube with lead. Good luck. You will have a few problems to start with I'm sure but I have found the experience was worthwhile and the forums are a great place to learn. All the experience I have gathered has given me the confidence to not bother with the expense of buying a specially manufactured petrol engine but to look for a suitable (ringed) glow engine and convert it to gas, even using the glow carb. I have an ASP 120 heli engine (£40 bargain from HK, no silencer) on the go at the moment to fit to an AcroWot type plan build and it's looking good! A Just Engines inverted silencer is £66.50 and should be quiet too.
140 forum posts
Just wondering if you had the rear exhaust piston fitted? Both the side exhaust and rear exhaust pistons were supplied in the box when I bought mine......
|Manish Chandrayan||04/09/2018 13:50:47|
630 forum posts
Oh! yes, they would not run if I tried with the side exhaust piston.
The engine did run fine in the rear exhaust configuration, it was the muffler that cracked up. It was the OEM muffler with those six odd bolts to keep the halves together.
I finally went back to side exhaust and changed the OEM muffler to an aftermarket one and all my problems went away. And I did install a venturi to minimize the raw fuel spitting out from the front mounted wlabro carb
|Engine Doctor||04/09/2018 15:55:36|
2466 forum posts
From experience petrol engines under 20 cc are way behind the same size glow for power and a lot noisier.As already said the supplied mufflers are useless, noisy and can even crack and fall apart .A well designed aftermarket silencer like a krumscheid silencer not only silence well but don't adversely affect the performance much but they are not cheap. Petrol really comes into its own on engines of 30cc and above . The difference in power output with four-strokes petrol and glow is even more pronounced.
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