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Fuel mixing advice

Old 06-26-2011, 09:53 AM
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Default RE: Fuel mixing advice



Good Info. The wife picked up some more castor oil from Walgreens so I can mix up some more of the brew if I could just find my prop

Old 06-26-2011, 07:27 PM
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Default RE: Fuel mixing advice

With acetone, 3% is the recommended amount for 2 strokes and 5% for 4 strokes. One of our club members uses it in his 4 strokes and says it eliminates back firing and spitting props off. As far as starting and idling goes, it's got about the same affect as using 5% nitro in the fuel but has no noticeable affect on power. IOW, if you're using nitro then you don't need acetone.

As far as petrol in glow fuel goes, that was an ingredient used to make an engine more economical in CL team racing way back when because they needed both speed and range from a fixed (very small) fuel tank size.
Old 06-26-2011, 08:15 PM
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Default RE: Fuel mixing advice

Thanks Downunder. Acetone definately helps to improve the idle. How you noticed an increased amount of smoke when running FAI fuel? Today I tried some 10% nitro with asynthetic/castor blend again and there was a lot less smoke (plus it smelledmuch better). Is it the oil/amount oilcausing the smoke or is it the lack of nitro?

TCraft, did you ever find your prop?
Old 06-26-2011, 09:03 PM
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Expletive No!
Old 06-27-2011, 04:30 AM
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Default RE: Fuel mixing advice

ORIGINAL: downunder

With acetone, 3% is the recommended amount for 2 strokes and 5% for 4 strokes. One of our club members uses it in his 4 strokes and says it eliminates back firing and spitting props off. As far as starting and idling goes, it's got about the same affect as using 5% nitro in the fuel but has no noticeable affect on power. IOW, if you're using nitro then you don't need acetone.

As far as petrol in glow fuel goes, that was an ingredient used to make an engine more economical in CL team racing way back when because they needed both speed and range from a fixed (very small) fuel tank size.
Downunder is right on with the acetone use. If you read the MSDS for acetone and nitromethane you'll see they both have similar properties. We brew our own too which is very similar to Red #ax fuels. I prefer 50/50 castor synthetic at 20% in the 10% nitrobrew. We'll do 30% nitro and 20% all synth too because that's what some of the guys want. We are able to buy enough materialat one time to make it very worthwhile too and we mix up 5 or 10 gallons at a time. The nitro cost is the stickler for home brewers. Interesting reading on the Klean Strip brew, hats off to you guys for being innovative.
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Old 06-27-2011, 06:47 AM
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ORIGINAL: KeroPower
Have you noticed an increased amount of smoke when running FAI fuel?
Not really, but that's probably because all I ever use is either true FAI (80/20 all castor) or an oily FAI (75/25 all castor) . Actually I learned something new the other day when I was reading through some FAI rules. I've always used only Castrol M castor but the rules specifically mention Castrol M as not allowed because it has some additives in it. Only pure, first pressing castor is legal so in fact I don't use FAI fuel! No problem of course because there's no way I'm getting into CL speed, RC pylon or FF power .
Old 06-27-2011, 07:01 AM
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Default RE: Fuel mixing advice

Speaking of oily, some guys at our club use some kind of wax on the plane when it is new and clean to protect the finish from damage. I will try to find out what it is, but some of my older planes are looking pretty shabby from the heatshrink covering peeling around the edges and fading due to oily exhaust(not all though, some covering brands are better than others).
Old 06-28-2011, 05:37 PM
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Default RE: Fuel mixing advice

I have some test results. I have tried a few different mixes and I think I found what my SuperTigre S90K likes.
Mix 1. All homebrew 5%nitro 20% castor +1oz/gal. acetone
APC 13x6 - 12,000rpm APC 13x8 10,500rpm
Engine quits randomly. No needle setting would keep it running, period.

Mix 2. Byrons 15%/18% 80/20 oil blend thinned to 5% nitro and added castor to 21% total oil.
APC 13x8 10,300rpm
Same quitting problem. Random throttle settings, though mostly opening the throttle quickly. Way rich or way lean didn't matter.
Mix 3. Homebrew 0% nitro 80%methanol 20%SIG Castor +1 drop armorall.
APC 13x8 10,320rpm max, lowest stable idle 1900rpm, with a short toot at 1680. Idles nicely at 2000-2200rpm and transition is remarkably nice. A 7second idle to WOT is very clean. At peak mixture, I can go 3-4 clicks leaner without a sag in rpm. The best part is it didnt quit unless I closed the throttle. Single backflip starts.

Engine has about 1/2 gallon on it. I think I'll stick with FAI in this beast.
Old 06-28-2011, 05:46 PM
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Default RE: Fuel mixing advice

Wow, Good work. Those Tigres are keen on no nitro fuel.
Old 06-28-2011, 06:49 PM
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ORIGINAL: TCraft Lover

Wow, Good work. Those Tigres are keen on no nitro fuel.
Some people use 10 & 15% nitro in these and have no problems but this one doesn't want any. I'm quite surprised. I have a fresh bottle of 5% made up I'll try one more time on the same plug and prop. I am using a McCoy MC59. It'd be nice if the TT .46 will run well on FAI.

I did notice the exhaust note was different on FAI; somewhat snappy. Hard to describe. If I get time tomorrow, I'll do more testing. I definitely need bubble free tanks. I still got more bubbles in the line than I like to see.
Old 06-29-2011, 02:42 AM
  #111  
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Yeah I know that exhaust note you're referring to. I like it.
Old 06-29-2011, 06:28 AM
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They have run automobiles on acetone, but it leaves a streakblistered paint and bare metal below the gas cap!

Saw a use for nitromethane that I did not know about last night. They use it to shoot an oil well! That is when they blast it at the bottom to fracture the ground to unstop an older well where the oil has congealed and pluged up the rock fractures. They pour about 5 to 10 gallons of nitromethane (for the small well shown), then pour water to the top of the well. Since nitro is denser than oil or water it goes to the bottom below the oil and water, the water pressure keeps it confined improving the blast. Then they put a blasting cap to the bottom of the wll and detonate it. You could just hear the explosion, but about 10 seconds later water and oil spouts out the top of the well. It was pretty cool!
Old 06-29-2011, 06:36 AM
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ORIGINAL: Sport_Pilot

They have run automobiles on acetone, but it leaves a streak blistered paint and bare metal below the gas cap!

Saw a use for nitromethane that I did not know about last night. They use it to shoot an oil well! That is when they blast it at the bottom to fracture the ground to unstop an older well where the oil has congealed and pluged up the rock fractures. They pour about 5 to 10 gallons of nitromethane (for the small well shown), then pour water to the top of the well. Since nitro is denser than oil or water it goes to the bottom below the oil and water, the water pressure keeps it confined improving the blast. Then they put a blasting cap to the bottom of the wll and detonate it. You could just hear the explosion, but about 10 seconds later water and oil spouts out the top of the well. It was pretty cool!
Another reason nitro is expensive and hard to come by?
Old 06-29-2011, 06:40 AM
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ORIGINAL: hsukaria


ORIGINAL: Sport_Pilot

They have run automobiles on acetone, but it leaves a streakblistered paint and bare metal below the gas cap!

Saw a use for nitromethane that I did not know about last night. They use it to shoot an oil well! That is when they blast it at the bottom to fracture the ground to unstop an older well where the oil has congealed and pluged up the rock fractures. They pour about 5 to 10 gallons of nitromethane (for the small well shown), then pour water to the top of the well. Since nitro is denser than oil or water it goes to the bottom below the oil and water, the water pressure keeps it confined improving the blast. Then they put a blasting cap to the bottom of the wll and detonate it. You could just hear the explosion, but about 10 seconds later water and oil spouts out the top of the well. It was pretty cool!
Another reason nitro is expensive and hard to come by?

No, I don't think this is enough demand to cause the price to be high. I think mostly its that it is expensive to manufacure. You can't just use catalytic converters on natural gas as you can with methanol. You have to use nitric acid on heavier gases.
Old 06-29-2011, 07:00 AM
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ORIGINAL: hsukaria


ORIGINAL: Sport_Pilot

They have run automobiles on acetone, but it leaves a streak blistered paint and bare metal below the gas cap!

Saw a use for nitromethane that I did not know about last night. They use it to shoot an oil well! That is when they blast it at the bottom to fracture the ground to unstop an older well where the oil has congealed and pluged up the rock fractures. They pour about 5 to 10 gallons of nitromethane (for the small well shown), then pour water to the top of the well. Since nitro is denser than oil or water it goes to the bottom below the oil and water, the water pressure keeps it confined improving the blast. Then they put a blasting cap to the bottom of the wll and detonate it. You could just hear the explosion, but about 10 seconds later water and oil spouts out the top of the well. It was pretty cool!
Another reason nitro is expensive and hard to come by?

No, I don't think this is enough demand to cause the price to be high. I think mostly its that it is expensive to manufacure. You can't just use catalytic converters on natural gas as you can with methanol. You have to use nitric acid on heavier gases.
Ok, for us non-chemists....what you are saying is that to manufacture nitromethane, they have to use expensive nitric acid instead of the cheaper catalytic converters?
Old 06-29-2011, 07:17 AM
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Default RE: Fuel mixing advice

ORIGINAL: downunder

ORIGINAL: KeroPower
Have you noticed an increased amount of smoke when running FAI fuel?
Not really, but that's probably because all I ever use is either true FAI (80/20 all castor) or an oily FAI (75/25 all castor) . Actually I learned something new the other day when I was reading through some FAI rules. I've always used only Castrol M castor but the rules specifically mention Castrol M as not allowed because it has some additives in it. Only pure, first pressing castor is legal so in fact I don't use FAI fuel! No problem of course because there's no way I'm getting into CL speed, RC pylon or FF power .
This is correct. In theory ....
I was Team manager in a control line WCH held in western Europe some time ago ( not too long ago..): when I went in the organizers office to collect the official speed (F2A) fuel they where just mixing it with..you guess, Castrol M ! Being aware of the rules I asked why they where using it: "to use the better product !" was the answer.
'nuff said ! nobody complained !
Old 07-03-2011, 10:38 AM
  #117  
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I did some more testing on my homebrew FAI 80/20, 1 drop armorall in my SuperTigre S90K. (all rpm figures are peaked or 1 click rich - no difference in rpm across 4 clicks at peak)

APC 13x6 = 11,400rpm
Master Airscrew K-series 12x8 = 11,280rpm
APC 13x7 = 10,890rpm
APC 13x8 = 10,290rpm

The last time I ran 5% nitro on that same APC 13x6, it turned it at 12,000rpm flat.

I think I'll add maybe 2% acetone and see if that improves the idle and stransition a little. It wasnt backflip starting as well on my FAI as it did on 5% nitro.

As per the ST instructions, I opened both needles way rich and set the high speed mixture to peak, then set the idle mixture for as clean a transition as I could muster. The spraybar is set about 1/2 way between straight in and the engine mount lug. I could probably adjust that a little bit more to clean up the slightly rich midrange. I think for now I'm gonna run it on the 13x6 and get more fuel through it.

Old 07-03-2011, 01:12 PM
  #118  
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These tigres take quite a breakin period. I might suggest that for now you just set your LS needle for best idle (lowest steady idle RPMwith least fuel or just rich of that) and work on your spraybar position for transition.
Old 07-03-2011, 01:24 PM
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These tigres take quite a breakin period. I might suggest that for now you just set your LS needle for best idle (lowest steady idle RPM with least fuel or just rich of that) and work on your spraybar position for transition.
Well, the only real problem that I've had is the engine would randomly quit. Not due to bubbles, but I think due to intolerance of nitro. It has always idled really good until just recently. Trying the different fuels was one way to narrow down the quitting, because it isnt overheating. It actually runs quite well with no nitro, and it doesnt quit. I had just gone outside and tested 1/2 tank of a fresh bottle of 5% nitro and its back to its old tricks, using the same plug and 13x6 prop as the above tests it just quits. Idle, WOT, in between doesnt matter. I went way rich on both needles, leaned the main needle to peak RPM and went to the idle needle but no dice. I conclude it doesnt want any nitro, so I'm going to flog it one more time on FAI and if it runs like a top like it did earlier, I'll know for sure thats the issue or at least the main issue.

Top rpm on 5% nitro today is 11,500rpm which is 500 less than the highest reading I got awhile back, so I think FAI is the way to go. After my next test, I'm getting the TT .46 airboat out to dial in the fuel pump and give that a flogging. (Reliability has been low on both of these engines when on the watercraft, so I wanted to do some thorough testing in the yard before going back to the pond.)

I rebalanced all of my props, so I can rule out prop balance/bubbles from the equation. I do get a few little air bubbles here and there but not enough to change the pitch of the exhaust note (I dont believe the mixture is changing enough to matter, perhaps the bubbles are due to nucleation..)

Above all of this, I bought (youch!) a sintered clunk made by OS. So far, its not doing any better than the standard clunk I was using. (fuel line inside the tank was replaced when the new clunk was installed.)

More testing will yield more results, I'll post back later with what I find.
Old 07-03-2011, 02:10 PM
  #120  
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As far as your ST 90 goes what glow plug are using? I found last week that the OS 6 ran far better especiallyat idle that the OS "F" plug did when using home brew no nitro.
Old 07-03-2011, 02:32 PM
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ORIGINAL: TCraft Lover

As far as your ST 90 goes what glow plug are using? I found last week that the OS 6 ran far better especially at idle that the OS ''F'' plug did when using home brew no nitro.
The OS #6 is a hot plug, and the Four Stroke plug is supposed to be a hot plug too, but maybe not. I am using McCoy MC59 plugs, which are hot plugs.

Just came back in from test #2 on FAI. Similar quitting problem as with nitro, though not as bad. It will idle for a long time, transition to WOT rich, run WOT fine and if brought back to idle for a few seconds and jab the throttle open, it quits. It acts as if its loading up a little bit. I'm seeing more bubbles this time, so I'm going to add 1 more drop of armorall and a smidge of acetone and see if that clears things up.

Definitely the best reliability on FAI, but I dont get this quitting problem. I've tried the spraybar in several positions, the farther from straight in the more it acts up so I put it back to where it was earlier today; no dice. The fuel tank has almost an inch thick layer of foam between it and the boat hull, and is centered to the spraybar. Ran great earlier today, now its acting like a solid gold turd. <grumble>


Old 07-03-2011, 02:35 PM
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Sometimes those golden turds polish up real nice. Does the Low to high transition quit abruptly or does it cough and smoke before it quits?
Old 07-03-2011, 03:00 PM
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Sometimes those golden turds polish up real nice. Does the Low to high transition quit abruptly or does it cough and smoke before it quits?
Here's two short videos on the FAI with acetone and 1 more drop of armorall. First video, just pooped out right away. Second video I got to wind it up (the idle is set just rich enough to not cut out when advancing the throttle. Spraybar is about turned clockwise about 1/3 distance between straight in and the engine mount lug. If you dont touch the throttle, it idles forever. Midrange is rich, so it is burbly on transition. WOT sounds a little choppy, but its just cleaning out. Once it cleans out its fine, but then back to idle it poops out again. I had it idling high or low, didnt matter. In these videos, idle is about 3600rpm. It will idle lower, but the transition is worse and it quits.
http://s153.photobucket.com/albums/s...MVI_0014-1.mp4
http://s153.photobucket.com/albums/s...t=MVI_0015.mp4

I have tried almost everything but a new carburetor. Kind-of tired of it. Maybe my boat hull is just crap and I need to build a new one... I dunno. Far less bubbles than before, maybe not enough AA. Throttle response is better with Acetone in the mix, but it just wont get with the program. Ran almost 1 quart through it today, engine is about 1 quart shy of a gallon.. maybe a little less than a quart. Carb is original Italian carb which has been disassembled, cleaned and inspected, and adjusted initially the "Italian way" blowing through the lines. What I do with the carb on the engine is set the needles 5 clicks richer than what its settings were the last time it ran. WOT, set high speed mix to peak, then 2 clicks rich. RPM doesnt change a lick. After high speed set, engine quits and I restart. Lean idle mix until it transitions nice, let idle for 7 seconds and WOT jab. Revs up about 1/2 way, quits. Richen idle mix 1 click, runs up to WOT and cleans out find. Back to idle for 7 seconds, WOT jab and idle mix is now lean and cuts out slightly. And so the cycle goes.

I'd like to think of myself as an experienced engine tuner, have had glow engines for many years. Engines run flawless on test stand, run like crap on my airboat hulls. My car engines all run perfect, and tune like a dream on homebrew 20%/12% fuel.
Old 07-03-2011, 03:37 PM
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Sounds to me like its lean on both vids. Based on the way it dies immediately on idle down and when you tried to increase throttle. I'm no Tigre pro but I own a couple and really likem'. The carbs are good just different.

Old 07-03-2011, 04:30 PM
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Sounds to me like its lean on both vids. Based on the way it dies immediately on idle down and when you tried to increase throttle. I'm no Tigre pro but I own a couple and really likem'. The carbs are good just different.

I tuned the high end with a tach, not by ear. Tuned to max rpm and richened 2 clicks. Idle if set any richer makes the transition so rich and smokey it barely cleans out even with the main needle set at peak rpm.

Believe me, I've tried it pig rich, and dead lean. It will not transition remotely cleanly no matter what I do. The midrange is horrible.

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