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Sep 23, 2017, 05:33 PM
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AA5BY's Avatar
Quote:
Originally Posted by Newbie1980
Gas engines are just as cheap as a glow engine converted to gas. So why not just buy a gas engine?
In my case I had two glow engines not in use or intended to be on glow fuel.

I could see that if a used engine could be bought for a good price, it might be worthwhile.

Otherwise, I think there may be some advantage to converting a glow engine in that the carbs are simpler. The use of throttle servo slow down, really has opened the door to converting some of the Saito engines and successfully using the glow carbs. A glow carb has no regulator or fuel pump that can be a problem.
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Sep 24, 2017, 05:35 PM
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Gary Cee's Avatar
The glow carbs indeed are much simpler. In many ways, when properly adapted more reliable than the sophistry of a pumper type carb. In some cases the compression ratio may need to be lowered for the use of gasoline. All part of the enjoyment for the itinerant tinkers who at one time dominated the hobby of Radio Control Modeling , before it became RC Flying.

Worthy of mention is that spark ignition is readily adaptable to glow fuel as well. Plenty of positives when that route is taken. Cheaper fuel (where cost is an issue) Better fuel economy. Higher specific output (more power) which leads to quicker, crisper throttle response.
Sep 25, 2017, 12:36 AM
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Quote:
Originally Posted by Gary Cee
Worthy of mention is that spark ignition is readily adaptable to glow fuel as well. Plenty of positives when that route is taken. Cheaper fuel (where cost is an issue) Better fuel economy. Higher specific output (more power) which leads to quicker, crisper throttle response.
Definitely! 0% Nitro is no issue, whatever the engine (but you won't get the power of say, 30% Nitro and glow), engine gets lots less temperature sensitive, can handle higher temperatures, handles lean runs better but is definitely more finicky to adjust.

Just one important tip: If you use a high strung engine designed for FAI fuel (like the Rossi engines as just an example) check whether the engine runs "on the spark" (stops when cutting the ignition throughout the full throttle range), because if it it doesn't, you'll risk wrecking your engine.
Lower compression until it stops when you cut the ignition and you're good to go.
Sep 25, 2017, 04:59 AM
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Gary Cee's Avatar
Quote:
Originally Posted by Brutus1967
Definitely! 0% Nitro is no issue, whatever the engine (but you won't get the power of say, 30% Nitro and glow), engine gets lots less temperature sensitive, can handle higher temperatures, handles lean runs better but is definitely more finicky to adjust.

Just one important tip: If you use a high strung engine designed for FAI fuel (like the Rossi engines as just an example) check whether the engine runs "on the spark" (stops when cutting the ignition throughout the full throttle range), because if it it doesn't, you'll risk wrecking your engine.
Lower compression until it stops when you cut the ignition and you're good to go.
Lower nitro makes settings a little bit more critical with either ignition system. Often the difference is barely noticeable. iHowever easier than the same fuel on glow ignition. Glow fuel settings on spark (glow carb) are generally far easier than with gasoline fuel as well.

Getting the compression right makes for a much happier engine indeed.
Sep 25, 2017, 05:20 AM
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Quote:
Originally Posted by Gary Cee
Lower nitro makes settings a little bit more critical with either ignition system. Often the difference is barely noticeable. iHowever easier than the same fuel on glow ignition. Glow fuel settings on spark (glow carb) are generally far easier than with gasoline fuel as well.

Getting the compression right makes for a much happier engine indeed.
I sparked a few Rossi's that ran excellent on 0% Nitro on glow, but got pretty finicky on spark, and 2% Nitro really made a huge difference, especially in the low speed range. Full throttle I did indeed not see any difference.

It's just that on glow you Always run a slight excess fuel, and on spark you don't, so margins get smaller.

Those Rossi's also were the ones that once dialled in, above half throttle continued to run with the ignition switched off....
I lowered compression until that went away.
Sep 25, 2017, 07:14 AM
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Gary Cee's Avatar
That's why I mentioned the CR initially in other threads.
More likely than not, the compression ratio was involved. I have found when swapping fuels and/or ignition systems getting the CR correct will tame an otherwise fussy engine.

Also note, the self-ignition is usually caused by a glowing spark plug component. With higher CR any thin or sharp part of a spark plug can ignite the mixture. In fact, that phenomenon has been used intentionally at times with spark engines as a tuning dodge. People would intentionally thin or sharpen the plug side wire element to induce self-ignition without spark.
Last edited by Gary Cee; Sep 25, 2017 at 07:22 AM. Reason: Also note, the self-.. .. ..
Sep 26, 2017, 05:19 AM
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Gary Cee's Avatar
Pe Rivers years ago demonstrated the carb modification to the helical groove on glow carbs. I am pretty certain there is an illustration that Taurus Flyer "Cees" posted Should be able to find that pic in his attachments.
Last edited by Gary Cee; Sep 26, 2017 at 05:34 AM. Reason: Found the Pe Rivers carb mod . From Taurus Flyer
Sep 28, 2017, 01:07 AM
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Eccentric's Avatar
I remember seeing that illustration (or a similar one) in a discussion about curing the midrange transition issues with SuperTigre 20/23 and 2300 engines a while back.
Feb 19, 2018, 09:48 PM
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jsparky's Avatar
my conversions...

skip to about the 4 minute point

nitro to gas conversion (11 min 7 sec)


skip to about the 4 minute point .. just a lot of flying

nitro to gas conversion (7 min 20 sec)


this is interesting

enya 60 fuel and glow plug testinng (13 min 52 sec)
Feb 20, 2018, 06:27 AM
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Gary Cee's Avatar
Good videos! Very entertaining too. The Gaspoline glow with garden variety auto fuel seemed promising. (If you like the stuff).
Looks like glow fuel is getting to be tough to get over there. Any time you feel like a trip , come on over. I'll supply the fuel too.

Waterloo is a nice town. We drove through there quite a bit on our way to St. Catherines back in the winter of 1982. Sometimes we even stopped at a certain roadhouse and had a beer with the dancing ladies. Always a fine ballet.
Feb 20, 2018, 07:42 AM
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AA5BY's Avatar
Interesting that type F will work with gas with ethanol.
Feb 20, 2018, 11:57 AM
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Gary Cee's Avatar
Quote:
Originally Posted by AA5BY
Interesting that type F will work with gas with ethanol.
Looked like he was having a load of fun there

One issue that may not get enough mention is the value of aluminum mounts with gaspoline conversions. Aluminum mounts are specified by Saito with their conversions for the added heatsink capacity. Could be some of the conversions out there that are blessed with high temp issues could benefit from a mount change.
Feb 20, 2018, 12:58 PM
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Could be... but I have done quite some testing in that regard, and although all little bits help, the heat dissipation via the engine mount is not that much....
Not even when I fitted the aluminium engine mount with large cooling surfaces it did not make measurable differences.
The biggest difference I achieved was with a large heatsink wedged between the exhaust stack and the muffler body on a 2-stroke.
Feb 20, 2018, 01:10 PM
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Gary Cee's Avatar
Several factors at play. The case ears are not the hottest spot, by a long shot. The contact area is slight. Without a heatsink compound, heat transmission is further impaired. The mounts have limited radiating area and are usually not in the free air.

Yet Saito does suggest that their gasoline converted engine utilize aluminum mounts for their cooling advantages.
Feb 20, 2018, 01:18 PM
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I did all that and more (heat sink compound and the likes).

And yes, Saito says that,well, sometimes, manufacturers say things like that, just to have something to clear themselves from warranty claims, like OS claims their engines need 18% oil, which you from personal experience know not to be true.

Don't get me wrong, it is not a bad thing to use a metal engine mount, and it DOES drain away some heat, but it is at best a few % (2 or 3, that order of magnitude) of the total heat that needs dissipation.


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