microdon2

My Feedback: (47)

Guess I'll admit to having to look up the meaning of "abstemious".


Funny, I try not to do that very often.

NM2K

My Feedback: (14)

What you are saying is true, but many do not know that even without nitromethane in the fuel, just methanol and oil can produce more power than gasoline/oil. It has to do with the fact that methanol needs less oxygen to burn well than gasoline, so more methanol (unit wise) is burned than gasoline, which has more power per unit. Confusing, isn't it?


Ed Cregger

Paul_BB

Because the conversion from glow to gas gives almost the same power (the Saito 4s gasser FG 14 is equal in power to the Saito 4s glow .72),

this means that at least two times more methanol (in volume) is burned than gasoline because the methanol BTU per unit of volume is twice the gasoline one,

and it also means that methanol requires half of the oxygen than gasoline, per unit of volume. Right ?

TimBle

its not really confusing. Methanol burns faster therefore you can incease the mass flow per second to compensate for it lower heating value.

The acid test is what prop can comparable methanol and gasoline engines turn at what rpm.

compare a OS 120Ax to a DLe20cc and theres not a lot of difference in weight nor prop rpm...
So is the OS a poorly designed methanol engine or is the DLE an exceptional gasoline engine?
considering the development that has gone into glow engines for RC purposes...


it is true that for small high revving engines methanol was the best choice. That is no longer true. Karting, RC...

pe reivers

Ask Ralph. I am sure he does not agree with that statement as far as racing is concerned. Or go to a racing track and ask about the difference between alky and gas. Same engine, same tune, well jetted, alky yields at least 15% more power at about 80- 90% increase in fuel flow. If taking advantage of the higher allowable compression ratio, power increase is about 20%.

Antique

My Feedback: (4)

Wnen we were still using carbs and methaol/nitro in our race planes I made the inlet needle hole .086 diameter and doubled the AREA of the other fuel passages...We figured twice as much methanol as gas...A stock G26 will turn 9000 with a Mejzlik 18-6 running gas and 9600 running glow fuel with mag ignition or electronic RC EXL....
We set the piston to combustion chamber distance at about ,020....

pe reivers

That is a gain of 21.4% in power, pretty close to the rule of thumb I used.

bgw45

My Feedback: (1)

PR, doesn't the ignition source of a glow plug powered RC engine limit what can be successfully used. I'm wondering what power limitations are placed on power output when a modeler uses a glow plug on an RC engine. Would not the timing have to be changed in order to really produce gobs of power?

Antique

My Feedback: (4)

We run glow plugs in our GT80 methanol race engines...11,500+ rpm....19-18 prop..Don't know about GOBS, but fairly strong
Pe's chart shows 20 hp, speed 196 mph...pretty much agrees with radar speed at the races...

pe reivers

The glow plug has no power limit. Power is defined by engine displacement, BMEP and rpm. Glow plugs work from 1000 to 45,000 rpm and even higher I suppose, whilst at the same time they are pretty much self regulating. In that respect they are better than spark ignition if high rpm operation is needed.

Antique

My Feedback: (4)

Haven't tried it, but the heat range of the glow plug apparently changes the timing somewhat....

bgw45

My Feedback: (1)

I was thinking about those large ignitions on dragsters.

Paul_BB

I don't hear a lot of feedback about the Saito FG 14. Did it encounter some problems ?And the Magnum .56 ?Is there a technological limit to small gassers ?

vertical grimmace

My Feedback: (1)

The only thing I see now is the ignition size and maybe the carburators. I am confident if someone is motivated enough, we will see better versions of both suitable for the needs of smaller engines. I can tell you after retrofitting a DLE 20 into my old Pica FW 190, a .60 sized plane, space is an issue. Careful planning and a shoe horn is in order! Funny, weight is not really a problem just space. This thing has it all though, flaps, retracts etc. so it was just that much more complicated.

Sport_Pilot

From a prior post the gasser FG 14 has more displacement.  So if manufacturing specs are accurate (they rarely are) it proves methanol has more power.  I don't think anyone is disputing that you have to burn more methanol, in fact that is part of the reason it provides more power.

Sport_Pilot

This is an apples to orange comparison. But generally gas engines are designed to turn larger props at lower RPM. Convert it to mehanol it will turn a larger prop at about the same or slightly more RPM if converted to methanol. Convert the higher reving glow engine to gas and it will turn a smaller prop at about the same high RPM.

Sport_Pilot

Those large 44 Amp ignition systems are needed to burn very very rich mixtures of nitomethane. So rich that the power of an elecric arc welding machine is needed. In fact if running dry, that is no fuel going into the cylinder, the spark plug electrodes will melt.

Kweasel

My Feedback: (29)

I remember Don Lowe installing glow plugs in his 1980s Sachs' because they made over the top of big loops better and were more reliable than ignitions of the day.

bgw45

My Feedback: (1)

Sport Pilot,

That's kinda what I was thinking. I thought that to get the increase in power from the glow engines you would have to increase the fuel mixture along with having a better way of timing the ignition. But, I'm no engine man for sure.

Sport_Pilot

While you cannot get the timing as perfect as with ignition engines, you can get it close by changine to a hotter or colder plug. Changing the mixture slightly will also change the timing, so slightly rich of peak with the right glow plug will not be far off from the ideal setting.

Truckracer

My Feedback: (19)

So much fuel in the cylinders they are just short of liquid lock at TDC. Incredible they run at all but they run well and the results are spectacular! Then there is the incredible amount of ignition advance they use .... quite a lot different than any sort of normal engine.

cloudancer03

My Feedback: (22)

I consider myself your average sundayflyer although being retired 5 years an everyday flyer since everyday is fri.sat.and sunday lol.

I dumped all my nitro engines except my satio and os four strokes and and a 0s bgx 1.08....yes I fly alot of electrics and love it.
but I also own and fly a DLE30..the smaller gassers forme fit my budget and the size planes I enjoy to fly..yes I believe the futureis electric as battery technology gets better those sitting on a fence will opt out for cleaner energy .and convenience.but and its a real but...I love gas motors.the dle30 opened up an untapped market and it doersnt take rocket science to see its increasing popularity..

the same goes for the dle20..I am selling my last os 2 stroke 1.08 and purchase a DLE 20.why not.burns gas cheaper than glow fuel.no slim afterwards and gobbs of torque..read model airplane article just out in the latest issue..the title says goodbye to nitro.....sure there will always be nitro diehards and thats fine .why not I did it more than 30 years and enjoyed every minute.

but technology and challenges facing our hobby make electrics platable and small gassers make flying affordable and convenient as well.

dirtybird

My Feedback: (5)

I just wonder if anyone has looked into using piezoelectric transformers to develop the high voltage necessary to fire a spark plug. I understand they are smaller than a magnetic transformer.

Antique

My Feedback: (4)

Tried and discarded many years ago by Briggs and Stratton for some lawnmower engines...

dirtybird

My Feedback: (5)

Perhaps the large progress made in materials in the intervening years might change things a bit. Also Briggs and Stratton was not known for innovation. ( my spell checker wants to change Stratton to castration)

edit:
Take a look at this:
http://homelandsecurity.psu.edu/disc...h_voltage.html

Research is going on. Piezoelectric transformers might make real small gas engines practical.