Campgems

One of our guy was out to the field Sat with his 1/4 scale Yak. He had been working on it and the cowl was off. There sat an O.S. 300 twin, with spark ignition. I was looking at it and it had the stock carb. I was asking how it was running with that carb, think he was using Gas. Nope Iginition on Glow fuel. He said it ran great, better than on Glow. Now, he has me wondering if this is somehing I should try. Any of you guys have any experience with spark iginition on glow fuel?

Don

w8ye

My Feedback: (16)

I've seen two different OS 91 Surpass I engines running with C-H spark ignition and Glow fuel. It works great when you want to do a lot of slow running with reliability.

Campgems

I wondered if it would be a good cure for inverted engines loading up at idle and stalling. Hummmm I've got an ignigion setup. I've got a Mag 91 that I've got to replace bearings in after it's last veritcal landing. May be fun.

Hey, I just ordered a Phonix Funstar to get me back in the air after wiping out my 4*60 Saturday. I believe it is setup for an inverted engine. I may try it on my Mag 52. Now to do some studying.

Don

w8ye

My Feedback: (16)

Ignition on an inverted engine should be the cat's meow.

Patxipt

I have used a fixed timing ignition on my ASP FS52. When set with retard, it idled with the carb barrel virtually closed at 1700rpm. With advanced timing, it ran beautifully as on glow. The engine also ran smoother and exhaust note was softer.
I'm having a CH ignition coming up on the mail for a permanent setup on this baby.

w8ye

My Feedback: (16)

In case any of you are thinking too much . . . . The four strokes only fire every other time the piston reaches top dead center so how do you pick up the proper timing pulse?

No problem, just use the crankshaft and the ignition fires every time the piston comes up but the is no combustion on the odd stroke because both valves are open and there is no compression or proper fuel air mixture.

Hobbsy

My Feedback: (102)

Jim, here is how I did it on the Saito 2.20, it has a wasted spark on the exhaust stroke, nearly all older (paralell) twin MC engines sparked both cylinders at the same time. That way it just required one coil with two output leads.

Campgems

How do you advance the spark?

THe guy at our field that started this all has a mechanical advance off the thottle linkage. The Pickup is mounted in a ring that rotates around the nose bearing housing. I sure wish I had taken photos and I even had my camera there. I've got everything I need in hand other that a pickup mount for the engine. I'll have to look over the instructions with it again.

Does this sound like a reasonable approach for tuning? Use a glow plug and tune the engine as normaly done. The replae the glow with spark and setup the timing of the spark. I'm guessing that the carb is going to require some additional adjusting at this point.

Don

Jezmo

With the CH units the advance/retard is built into the box. You set the initial timing at say 28 deg. and it automatically (electronically) retards the timing at idle to about 4 deg. give or take a few.

w8ye

My Feedback: (16)

The C-H ignition systems whether they are the fixed (mechanical timing) version or the synchro spark (electronically variable version) are trouble free. They run on 4.8V and you can use a battery-switch-charging setup with them much like you do for your airplane radio.

Once you get the timing within reason, tuning, either timing or mixture, is just straight forward.

Jezmo

Well said Jim. I agree, mine have been very reliable and user friendly plus you can't beat the service Bill and Company give.

rlmcnii

My Feedback: (3)

Those with Experience,

Would a Saito 3.00 twin run more smoothly on spark ignition than it will run with on-board glow power? Assume glow fuel in both situations.

The engine will be run in a 1/3 scale Spacewalker.

Thanks.

Dsegal

The December. 1997 issue of RCM has an article on running spark ignition on 4-stroke glow engines. Biggest gain was using fuel without nitro.

w8ye

My Feedback: (16)

Well, I have seen one of the ignition OS 91's quit on the guy for some reason or another. He was running it mighty slow and it didn't sound as though the mixture was as good as it could be. I didn't meddle into his business. I had my own plane to worry about.

The ignition would most likely help a 300 a little. I think TKG at C-H has a model with a double ended coil?

Ray Wasson

I have been running a ST 2300 with an OS 7D carb. & 15% Coolpower several years on 140 size IMAC planes. I use a Cline regulator and a home maid fuel pump cut from a Walbro carb. It had a Bison Pits style muffler. It turned an APC 18-6W 8700 rpm % idled as low as 1600 rpm. I normally set to 1800 and would idle a tank full out without loading & instant throttle response. The minus was if cruised in the 4 to 5K rpm for over 30 seconds or so the glow plug would go out with out warning as the engine ran smooth until flame out. An on-board glow driver solved this but I still had the extra battery weight and some systems I tried were unreliable. I had always wanted to try an ignition system because I had a theory which I think is proved. I installed a C&H without advance set at 28 deg. I removed the head gasket to raise the compression. It now turns 9K+ set rich for flying, not peak. The engine starts with no kick back & idles reliable but only down to 2K. The problem with the idle reliability now is the throttle is nearly shut at idle and much less open at cruise. this makes linkage and servo operation very critical. I am going to install a mini digital on my throttle next. The plus with the fixed timing is much decreased fuel consumption. Otherwise the engine runs the same as glow with no worry of dead sticks. By the way, my engine is inverted. It is in a CMP 140 Giles now.

Ray

Charley

My Feedback: (2)

Ray,

I wonder if it would idle lower with a auto-advance ignition module. My Saito 1.5 did. Might be worth giving CH a call.

CR

Patxipt

It would idle lower with auto-advance.

On my fixed timing tests on the ASP FS52, I ran the engine at around 1700rpm with very little advance over TDC. This particular engine is smooth as a sewing machine below 2200rpm, almost inaudible. Higher rpms suffered of course, max would be around the 7000rpm mark.
With advanced timing, it would have good peak rpm, but idle would only go as low as 2400rpm, almost the same (2300rpm) as with a glow plug with no driver attached (with glow driver, the engine would run down to 1800rpm too, but it would shake a lot!)

EDIT: Fuel used during testing was 80/20 methanol/castor.

Hobbsy

My Feedback: (102)

The unit I have on the 2.20 is the CH/ SynchroSpark which retards to 6 degrees at idle and is all up 28 degrees by 2,400. The SynchroSpark generates a curve as it reads the accelerate rate.

Sport_Pilot

The best spark advance uses both engine speed and load to determine the proper advance. Older automobiles used vacuum for load and centrifugal weights for speed. Throttle position is a less accurate way of determining engine load, newer ones use a computer and thus could use engine speed, throttle position, vacuum, fuel consumption, and even detonation to determine the spark advance. The electronic ignition can easily determine engine speed, but load would require a throttle link or manifold pressure sensor.

Ray Wasson

Yes it would idle lower but the fuel consumption would increase. For me 2000 RPM is slow enough. Our local hobby shop was selling 15% for $16.00 a gallon. After modifying my engine I was very happy with the fuel mileage increase. I thought to myself it is now affordible to run a glow engine. When I returned to buy more fuel the price was raised to $22.00 per gallon!. When you think you have the rat race won they just come out with faster rat's.

Ray

Campgems

$22 a gallon isn't bad. Considering a gallon of milk is about $4.50. Water, in the plastic bottles is around $12.00 a gallon.

I bought a 1/3 standoff scale Extra 230 kit last week and the guy had a Model Avaitaton magazing from 1987 that had an article on the plans and building it. I was scanning the magazine and there was an ad for a Gas engine. "Why buy Glow fuel when Gas is $0.79 a gallon". Then back to today.

I filled up my family sedan last week and the tank of gas cost more than the first car I owned. $75.00, and the pump cut off berfore the tank was full. And gas has gone up another $0.12 a gallon since then.

Lets see, say I'm flying my 52 four stroke with an 8oz tank. I'll get just at 15 minutes air time on that. So for $22.00, I get 4 hours air time. Add in a 3 to one ratio of BS time in the pits to fly time, and you are up to 16 hours of enjoyment for a mear $22.00. You can't go see a movie for that rate any more.

Food for though and great justification on why this hobby is "cost effective"[)][8D] Just in case the wife ask.

Don

PS, I need to go by another case of fuel before the price goes up.

NM2K

My Feedback: (14)

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IIRC, the C&H units use auto retard, not auto advance. The 28 degree initial timing is the advanced position, as Hobbsy has stated inso many words, and much more eloquently.


Ed Cregger

Charley

My Feedback: (2)

How did you arrive at that conclusion? Another thing I'm curious about is why all the nitro? I thought the big STs were designed to run on 0 - 5% nitro.

Anyway, if fuel costs are a consideration, why not run it on gas?

CR

Sport_Pilot

Where did I say anything about C&H and how they worked? And what differance does it make if the failsafe is the advanced or retarded position? The only differance is that if it fails it will behard to start, while with auto advance it will be easy to start but would run with poor power. Eather way it has to advance the timing as the engine speeds up.

NM2K

My Feedback: (14)

What is it with you folks the last couple of days? Everyone thinks I'm making digs at them, when I'm not.

I'm just contributing to the group conversation. Lighten up folks.


Ed Cregger