Originally Posted by chorner

can anyone in this thread comment on whether you can reliably run a thesöe gas engines (FG60 in specific) on glow fuel? I know for example Adrian at CH ignitions regularly tests between gas and glow on the same engine. Any drawbacks? I'd love to run an FG60 radial on glow and not have to bring petrol stained stuff into my basement methanol is much better in that regard.

Originally Posted by chorner

Thanks again for the reply Blair. Probably just caught him in his busy season/a bad time then, and you're right in that the options are limited. The only ones I know of are him and Morris' Mini Motors which both use the same ignitions and parts... all RCEXL based though I think the sensor pickup rings are custom to each. Anyhow... I'll give it some more time. I'm sure the product will make up for the bit of a lack of communication

I have no problem pulling down an engine at all, I just don't have the proper tools to cut down the cylinders accurately! Haha, yeah no doubt they are thirsty for sure but that's just crazy. My first foray into radials... but the 7-77 will get decent run times (~10+ depending on throttle usage of course) off a ~750cc tank, and on CDI it should be a little better in general so that's long enough to keep her up in the air for some fun!

Originally Posted by hpergm

Set-up:
1. SP-2 plug on top cylinder (smaller gap) and Rcexl plugs on the bottom cylinders (larger gaps to avoid fouling). Made sure plug caps were 100% securely seated on all plugs to rule-out misfiring from that source.
2. Changed Klotz Techniplate to Castrol Power 1 oil to avoid carbon build-up in No.1 and the huge oily mess from the exhaust evident in previous runs.
3. Changed oil ratio from 15:1 to 20:1 to improve combustion and avoid plug fouling.
4. High needles started @ 4 turns out and low needle @ 8 turns out (previous set-up from rich WOT running)
5.Prop is still an APC 22x10.

Observations:
1. Leaning the test stand ~20-35 degrees to either side at low to mid throttle does has an effect on cylinder temps when the engine is still rich; cylinder closer to the bottom will load-up and its temp will fall (misfires due to plug fouling most probably).
2. Low needle is dominant and the engine should be tuned by that - not the high. The high is relatively insensitive in most of the throttle travel and only affects maybe the top 5% of the throttle curve. The effect of the needle on the engine takes several seconds to take hold (i.e. requires a slow tuning reaction/decision).
3. Cylinder temps will balance only when the fuel mixture is close to optimum (i.e. leaned-out). Chance misfires/fouling will occur if engine is anywhere near rich.
4. After running the engine @ WOT for at least 2 minutes, with optimum mixture, cylinder temps will be balanced within less than 10% deviation at all subsequent throttle settings, including idle.
5. The only safe way to lean-out the engine (i.e. tune the low) is by observing temperatures near the peak rpm at 50-75% throttle; there is a "peak" regime where the rpm does not change much but temps will! Why this? Because a good state of tune basically matches cylinder behavior in terms of "misfires" (= non-explosions); for example, on one case, one of the cylinders may have many more misfires (= colder) than another (= hotter) while on another case, both cylinders will have an equal amount of misfire events and thus run at the same temps. However, in both cases, the average power output of the engine (rpm) will be the same...! A further indication of optimum tune is the absence of observation #1 above - little change in cylinder behavior while leaning the stand left or right with respect to horizontal.
6. After tuning the engine just so, there will be no misfires (plug fouling) at any throttle setting, no hesitation in transition. About 6,700rpm is achievable with a 22x10.
Based on my experience up to now, I would conclude that:
- The wider-gapped Rcexl plugs are perfect for this engine - avoid the small-gapped SP-2s, at least on the bottom cylinders

- Rotating the engine during initial rich running-in helps out tremendously. After lean-out, it is not really needed.

- The Castrol Oil gives out much less residue and seems to inhibit plug fouling. Also, the 20:1 ratio gives a better burn and less chance of fouling.

- The engine requires a good warm-up before achieving a perfect tune. The intake parts where the fuel is atomised and distributed need the temperature to atomise the fuel - the result will be even cylinder temps. Any rich running will cool the intake and will allow loading-up/richening and/or plug fouling of the bottom cylinders at different engine orientations. This is risky for flight. So, its good practice to run the engine @ WOT on the ground for 1-2 minutes. From idle to WOT, I found that it takes at least 30sec for cylinder temperatures to peak. The WOT running will heat-up the crankcase/inlet chamber to help good fuel gasification thereafter. Possibly also blow-out any residues from the plugs.

- The real trick is to tune the low by temperatures and not rpm. The high just needs to be open enough to provide enough fuel to the low. It is for this reason (mistake) that the top cylinder was a temperature runaway in the first runs (tuned the high first).

Originally Posted by Blair K.

What country are you in??

My radial should not be a reflection on the normal Saito FA325R5, its been given a little encouragement, she pulls an 11.4 kg P-47 thunderbolt at 188.3 kph and its not fully ran in yet either.

it pulls a Biela 19 x 12 @7200 revs if you get me and thats on 15% too!

If you measure your cylinder head at TDC by putting nice thick metered oil from a syringe through the spark plug hole we can work out it compression ratio and exactly what has to come off the bases, 12.2 to 1 compression ratio will get it cracking.

My FG33R3 only had about 85 psi compression which is really lazy for glow fuel.

Cheers Bk

Originally Posted by marksp

Thanks again for your sharing your experiences!

What did you determine to be optimal temp? The video shows ranges from 130 to 174C

Cheers

Originally Posted by hpergm

Mark, optimal temperature level is anything that will not seize or stall the engine and optimal temperature distribution is <10% differential between cylinders at any throttle setting.

Originally Posted by marksp

Thanks!

When I looked at the temp readings on your video, it appeared that your cylinders balanced around 130C, then at the end of the video the temps were in the 170's. My temps are in the 140C range [on 15:1 synthetic] and have yet to balance. Just wanted to check before going too far.

Cheers

Originally Posted by hpergm

Level depends on throttle setting. Honestly, I don't know what will happen if I leave the engine on WOT for more than 5 mins - maybe temps will go up to 200C..

But, it is safe to assume that this would never happen in reality - unless one decides to put the R3 in.... a pylon racer!

We are always talking about normal use. WOT @ 60mph (22x10 @ 6,4000rpm) for 30sec would represent a travel length of half a mile! More than we will ever fly pedal to the metal.

BR,
Hector.

Originally Posted by Blair K.

Hector my P47 flies at 171kph at 50-60% throttle and i never fly at less than 50%.

My other warbirds are at WOT for 5-6 minutes at a time, i fly formation most weeks with 2 or 3 other warbirds at 160kph+, we dont pull back unless someone gets out of circuit.

My radial has done at least 2 circuits back to back at WOT being more than 180kph.

If your temps continue to climb at WOT you need to baffle your cowl, my FG33R3 ran at 164 C at WOT with a baffled cowl.

Cheers Bk