Petrol or Glow?

I have a 30cc size aerobat to equip with a motor.

The choicevis between 4 stroke glow, possibly large 2 stroke, or 2 stroke petrol. Such as ASP 180FS glow. or MVVS 30cc petrol. I have experience of glow but petrol seems increasingly popular. Proz and cons? I'm interested in relative aspects such as noise levels, ease of use, reliability, power to weight and fuel economy. Please contribute your experiences. Thanks

A petrol engine will need a good exhaust (canister) to be reasonably quiet, Probably cost c100.00 for header and can. Fuel cheap and easy to obtain, fuel consumption low.

Four stroke glow, great sound reasonably quiet but glow fuel is expensive - normally run on 10% nitro so c22.00 gallon - on the plus side they are frugal on fuel. 500cc will last a 120 4 stroke glow about 15mins

MVVS 30cc petrol two stroke- noisy if not on a pipe / canister. MVVS pipe and header will be over 100.00

Everything that Brian says . The range of Krumschied silencers distributed by Stuart McKay are brilliant and yes are expensive . but you get what you pay for . Two stroke glows tend to scoff the fuel and are still noisy but on the plus side are considerably more powerful than a similar sized petrol . Have you looked at the NGH 38cc or the 30cc four-stroke petrol from just engines ? Good sound frugal on fuel and not overly expensive . Very mixed reviews around . A club member has two and had no problems and swears by them and the supplied silencer is adequate for most sites if propped correctly .Any of the two-stroke s available that come with a so called silencer will need a decent silencer added to the cost as the supplied units are flying site losers

Silencers, especially for two strokes, have always been an issue with engines whether they are glow or petrol . . The ones supplied by manufacturers are rarely adequate for keeping the noise down, and the "silencers" supplied with petrol engines are pathetic.... they are constructed from the thinnest materials possible and behave more like amplifiers.

So, yes, additional costs for a decent silencer have to be considered when using a petrol engine if noise is an issue at any given flying site.

Four strokes can be just as loud but, with only half as many exhaust beats, they tend to be more pleasant to listen to, so we can get away with the standard silencers.

As a general rule, glow is good up to an engine size of about 20 cc. For anything larger, a petrol engine comes into its own. . The running costs for petrol engines is miniscule compared to glow engines.

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+1.

You have to budget for and make sure that the model will accept a decent silencer if you go the two stroke petrol route.

Silencer manufacturers -

• JMB (Czech, imported by IAD Model Designs)
• Zimmermann (German).
• Krumscheid (German).

Less expensive glow fuel is available, Weston 5% Prosynth is currently £14.29/gallon, works for me.

Yup, another vote for Pro-Synth here. . I changed to this fuel over 20 years ago, and haven't looked back.

Engines run faster, cooler and sweeter on this fuel, and they also remain clean inside and out. . It is by far the BEST glow fuel available, regardless of what some detractors might say.

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Not mentioned so far is smell. Not so much running bit but carting petrol and petrol engines in the car. The smell can invade the car some. If you and others using the car don't mind then ok. I do not have model petrol engines but sometimes carry strimmer/ brush cutters and am not keen on the smell.

Forget Petrol ,get a Laser 180 four stroke .I was in the same mind has you I was persuaded with my Wots Wot XL to go for the Laser 180 and that is what I put in my Wots Wot XL .Sounds great ,more then enough power and oh so reliable .Go with the Laser 180 you will not regret it

Personal experience; much more frugal, much cleaner. Nasty smell. Walbro carbs seem to come in two disparate versions; those which take and hold tune, and the others. Zenoahs fairly docile and not too loud but heavy. Slight extra complexity with ignition, kill switches and tank plumbing in an aerobat, to maintain air flow into the tank without emptying it. Tygon a bit dearer.

Observationally; I've watched clubmates spend far longer sorting petrols than glows, and whatever the noise meter says, even if you find a way of getting below 82dB it will still sound loud because they all seem to have a particular frequency which is intrusive.

I gave up with a DLE and put a Saito in.

BTC

Either choice is fine, each have there own pluses and minuses, reliable ? There's thousands of flyers using both with little or no trouble, then there's the fiddlers who're never sorted.

By detractors i guess you mean me as i wouldnt recommend this fuel to my worst enemy and will not warranty any of my engines on it. I know its see as a marmite issue, but if it wasnt a problem then i wouldnt be avoiding it would i?

As a curiosity, beyond anecdotes i am curious regarding your qualifications to grant the award of best fuel

On the OP, as has been stated both have advantages and disadvantages but the one everyone loves to talk about is cost. 'oh the fuel is so cheap' they all cry.

True, petrol is cheaper than methanol, but does it really matter? I drive 70 miles round trip to my flying field. While i am there i order a pizza for lunch, and then consider flying a bit. On the BH weekend i flew 5 flights with my 50cc glow powered P39, 2 with my laser 80 powered hurricane and 2 with my saito 45 powered Niuport 17. That little lot cost me about 2/3 of a gallon of glow fuel so call it 12 quid for the fuel? Certainly the cost of the glow fuel was less than the cost of travel and lunch.

Petrol engines have their place for sure, but forget the cost argument as like for like a petrol engine will be more expensive to buy and (depending on how often you fly) could take a decade to break even vs a glow.

Ignore the reliability claims too. John Stone's point is absolutely correct.

Love the simplicity of glow. No ignition battery. Laser 180 in my Pilot 78” Extra and flies for at least 15 mins on a 16oz tank. Plenty of power for vertical manoeuvres and sounds brilliant.

Out of interest Jon, why would you not recommend that fuel, and which fuel _would_ you recommend? I'm using prsynth 10% at the moment and it's fine for my ratty old second hand super tigre 45, but that's 2 weekends flying, without looking inside the engine!!!

Hi Jon.

I've only recently heard of Pro-Synth fuel from a couple of very satisfied users at our field. I was considering buying some the next time I need fuel. Your comments have got me questioning it's suitability though. I run exclusively Saito 4 stroke glow engines - an 82 and a 150. Other engines are all petrol.

Could you please clarify what exactly is the problem with Pro-Synth fuel that makes it so bad that it invalidates Laser Engine warranties? Is it a problem with something specific to Laser engines or is it bad for all engines?

One factor that hasn't been mentioned yet is the ease of cleaning the model after use. Glow fuel leaves an oily sticky residue which can be quite difficult to completely remove. Petrol fuel leaves only soot, which can be easily removed using petrol on a rag - i.e. no need to carry special cleaning fluids.

Lots of people use Weston fuels and are very happy with them. The only person that I am aware off who says bad things about them is Jon. I have always assumed that it because somebody from Weston kicked his dog or something like that.

Gave up on glow years ago, i cannot stand getting my models covered in the oily slime then having to clean it all off............

Petrol or electric for me

I dont want to get drawn into another prosynth debate as we will be here for a week and then the mods will send the heavy gang in to break it up. Its also not the point of the thread.

I also have a problem as i am walking the tightrope of saying what i want as a modeller, and representing a company as Laser.

So, all i can really say is this.

it is not suitable for use in Laser engines as it does not comply with our warranty spec and use may result in mechanical failure.

Consider for a moment what would cause us to make such a bold statement. Especially when we are working with other fuel manufacturers on reduced oil options that we know are perfectly safe.

This is not a bias thing and i dont own a dog. Sure model technics make our laser fuel but we get no kick back from that and i hate plenty of their fuels as well. If the product isnt good enough i wont warranty the engine. For example...

Duraglo - Please, i beg you all to stop using this.

I am also not a fan of Contest 10. Its expensive, messy, awful. Engines run ok on it, but techpower 10 would be so much better.

Gary, your point about cleaning is mostly valid but it depends on the engine. I have had a number of customers come back to me after finding their petrol engines were spewing gallons of black stuff everywhere. I think you need to get to about 40:1 before they go clean. The 20:1 2 strokes etc i believe are still pretty messy.

Edited By Jon - Laser Engines on 17/09/2020 16:23:57

The main plus for me with glow is simplicity inside the model so I don’t need to worry about ignition systems, leads and batteries (although I obviously stIll need a glow igniter and lead, but that’s all outside the model) . Methanol is also a great fuel for models with cowling due to its latent heat properties, so much less prone to overheating. My personal preference is for four stroke glows as I love their easy handling good throttle response and relatively soft sound. Some petrol two stroke engines I have seen don’t seem to throttle the well...(possibly due to carburettor design/set up). The main drawback for me in using glow fuel is fuel proofing and the need for specialist paint finishes.