Finally got around to converting my asp180 to ignition.Undecided whether to run gasoline or nitro. I am using an rcexl ignition and magnet at 30 btdc. Hope it runs OK!!

The folks at Just Engines did a conversion like yours. They report that 2 gaskets needed to be added to drop the compression ratio when using gas.
I'm doing a similar conversion with a ASP FS91 I've ordered from them for that purpose.
If using regular methanol fuel, you can stick with 80% methanol and 20% castor (ASPs love and need castor), and you'll find that the HSN will only need to be open around 1 turn or less! That's what happened with my ASP FS52 conversion, the throttle barrel was barely open, not even a hair would fit there!

Hi Francisco, thanks for the info.I'll have a look at the Just Engines website.I don't reckon I can lay my hands on 2 head gaskets at short notice and fabricating one can be a chore. Wonder if running with ignition backed a bit and high octane (98) will help.

OK, tried running it today.It was a bear to start.Finally,retarded the ignition a bit and got it going.RPMs were down a little. The idling and transition was fine except you could tell when the retard point came in- quite pronounced.
Engine lost rpm and quit on 2 runs- I reckon it overheated.
I'm done with gas- don't think its feasible what with the overheating issue.I reckon one would have more success with 2 strokes as there's less friction and more cooling fuel running thru. I'm going to run methanol instead.

Depending on the costs of methanol, it could be as cheap to run on spark as gas, due to the leaner mixture and more efficient combustion permited by the spark ignition. Don't give up on spark!

EDIT:

Here's a video of my ASP FS52 running on spark and glow fuel, with fixed timing. My main problem was the sparkplugs that leaked

http://www.youtube.com/watch?v=TSrZ3-LS_j0

Was this engine broken in before you converted it? If JE is recommending two additional head gaskets overheating could be due to preignition or detonation.

I reread the JE site, and they just added one head gasket. Sorry for misleading you guys[&o]

The engine has had a few tankfuls and flights before the conversion.Easy backflip starting and great idle.

I tried running on gas initially- Engine was difficult to start, so I retarded the ignition a bit and resorted to using a starter. Engine started, ran alright but down on rpm.I had 3 runs, First run neoprene melted while using muffler pressure. Subsequent 2 runs had the engine overheating. I can only guess that engines run hotter on gas and as tank level goes down the engine will run a bit lean as theres no pressure feed. RPM was about 6500rpm.How do you detect detonation- throwing props or pinging sound like frying eggs?

Changed the plumbing and switched to 7% nitro glow fuel. This time the engine was easier to start but even with timing advanced, I could only get 6800rpm tops.

Finally, took out the ignition and ran glow. Rpm this time was 8450, what a difference! and idling was good.

I can only surmise that you need pressure of some sort to run reliably. The 2 needle carb is not ideal for gas use as the fuel/air ratio is not consistent for the whole range and could be a fire hazard as there was substantial spitting at low idle. Just my views,could be wrong.A walbro is the way to go.


That said, it was a good experience, yes fuel flow seems to be lower using ignition and the sound was like a staccato bark, very pleasant and unique.

The basic power changes we have seen in converting hundreds of engines is....
1. Most power is from glow fuel and spark ignition
2. Next in power is glow fuel and glow plug.
3. Least powerful is gas and ignition.
As always there exceptions. The big STs will develop more power on gas and ignition than on glow/glow. But the most power is still glow/ignition.

I'm only getting 6800rpm with glow fuel and spark ignition and 8450 with glow fuel and glow. Starting was more difficult with the spark. Am I doing something wrong here? Timing? compression? I'd like to try again as if I can get more power, nice sound and low idle as a package it'll make my day!
BTW, the magnet I'm using is a 5mm type and timing set at about 30deg BTDC.Thanks

My FS-52 starts very easily. Have a look at the video. It's does have to be wet. I think your timing is out. Are you setting timing by measuring the position of the magnet or crank angle at which the spark is actually made?

Greg, I placed the magnet about 30deg before the crank hit tdc. I subsequently set the timing based on the position of the magnet. Is my timing too low to get such a result?

You need to reset the sensor position. With the magnet 30º BTDC as you have, the sensor needs to be right in front of the camshaft, on top of the front bearing housing.
Considering the first photos you posted, your ignition is retarded around 40º! No wonder the engine lacks power.
Reset the sensor position and run that baby once again

I set mine so that the spark occurs at approximately 28° BTDC when I turn it over. This is different than centering the magnet at that angle because the ignition doesn't fire until the magnet passes the sensor. I have not attempted to optimize the timing yet, as it ran pretty well. I think there are a few hundred RPM more to be found though.

Went to the rccdi web and you are right Greg, I set it wrongly based on magnet angle rather than point of spark. I was probably off by 10degrees i.e 20 degrees advance only.Will give it another run and see.It'll be only glow fuel for me.

Francisco, the picture doesn't show the correct orientation.

Ran the engine again. First run managed 7600rpm which is a step in the right direction.Advanced the timing again and rpm went up to 7900rpm. I think I'm over 30deg advance. Engine was easier to handle and I got the idle to 1750! Amazing. Prop used apc17x8.
Is fuel economy improved with spark ignition?

Great news!
Yes, fuel economy increases since you can dial the carb for the correct mixture and not the overly rich one needed on glow to set the correct timing.
If I'm not mistaken, timing on glow fuel needs to be a wee bit more than 28~30º, the burning rate of methanol is diferent than that of gas.

Excellent. Fuel economy even with glow fuel is improved. Like Francisco said you don't have to be tuned rich to get it to run well. I think that glow is virtually always tuned rich of optimum due to the nature of the system.