Glow Engines Discuss RC glow engines

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Old 03-05-2012, 07:53 PM
  #21701
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Hey guys could someone explain the power comparison between the 62 and 72? How big of difference is it? I would really have to do some cowl hacking to fit the 72!

Thanks!
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Old 03-05-2012, 08:32 PM
  #21702
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hi, i have a saito FG 36, takes gas
20 to 1 mix ratio
use evolution oil with it

i have tested several different props
used a 3 blade 16 x 8
a zinger 18 x 8
and a nylon APC 18 x 8

the max rpm i have gotten is 7800

i cannot get to 8000 range.

i have had engine on (not all at once) for about 3 hours, breaking it in.

any suggestions?
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Old 03-05-2012, 08:50 PM
  #21703
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That sounds about right for a engine this size.

Make sure the exhaust valve is not binding on it's stem.
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Old 03-06-2012, 05:25 AM
  #21704
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Quote:
ORIGINAL: show871

Hey guys could someone explain the power comparison between the 62 and 72? How big of difference is it? I would really have to do some cowl hacking to fit the 72!

Thanks!
Anybody? I need to purchase one and a power comparison would be greatly appreciated!

Thankyou
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Old 03-06-2012, 09:52 AM
  #21705
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I have a 72 with a lot of time on it, and it's one of my favorites. While the 56 sounds good all the time, the 72 sounds better at full throttle. I don't have a 62 to compare, but it will turn a 13x6 up around 9500 rpm, which is pretty good. I think I got around 10,500 with my 72 and the same prop. You probably can't go wrong with either engine. If you really, really need that extra 1000 rpm out of the 62 you could just increase the nitro, but I doubt you would notice a whole lot of loss compared to a 72. The 62 is about an ounce lighter. You may get other opinions, of course.
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Old 03-06-2012, 06:26 PM
  #21706
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i took the valve covers off
then engine has run for almost 3 hours

the gap between valve stem and rocker was greater than 0.1 mm

i adjusted them to be about 0.05 mm

do you believe this may help get me the 8000 + rpm?

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Old 03-07-2012, 06:19 AM
  #21707
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Quote:
ORIGINAL: cshahrdar

i took the valve covers off
then engine has run for almost 3 hours

the gap between valve stem and rocker was greater than 0.1 mm

i adjusted them to be about 0.05 mm

do you believe this may help get me the 8000 + rpm?


Why are you so concerned W/max RPM when static?

I always prop for several hundred RPM less than max (static) to allow for the prop unloading in the air @ speed.

Sounds to me like you could use a bit more prop to bring the static RPM down a bit to avoid over reving the engine in the air..
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Old 03-07-2012, 07:02 AM
  #21708
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The only way the 2.20 or any engine will benefit from cheating on the clearances, (tightening) is to lighten the load so the engine can rev and take advantage of the slightly longer valve durations. My 2.20 glow engine would turn a Just Engines Jen-C 20x6, ( rebadged Biela) at 8,150 on WildCat Premium Extra 10%. I don't think you'll see that with gasoline.
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Old 03-07-2012, 08:04 AM
  #21709
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Quote:
ORIGINAL: blw

I have a 72 with a lot of time on it, and it's one of my favorites. While the 56 sounds good all the time, the 72 sounds better at full throttle. I don't have a 62 to compare, but it will turn a 13x6 up around 9500 rpm, which is pretty good. I think I got around 10,500 with my 72 and the same prop. You probably can't go wrong with either engine. If you really, really need that extra 1000 rpm out of the 62 you could just increase the nitro, but I doubt you would notice a whole lot of loss compared to a 72. The 62 is about an ounce lighter. You may get other opinions, of course.
Thanks so much BLW for taking the time, this sounds very promising!

If someone has ran both I would love to hear about it thanks guys
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Old 03-08-2012, 11:43 AM
  #21710
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hello

what does that mean?
sorry to ask this question.

i know the pushrod goes to rocker, which then presses down on stem valve
and there is a gap
should be at 0.03 mm to 0.1 mm
when piston is at TDC

i do not know what it means for the stem valve to bind

does that mean, it may be bent??

i take it this has happened to you??
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Old 03-08-2012, 11:45 AM
  #21711
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ok
i am good with that

so i should make gap clearance 0.1 mm?

and not 0.05?


thanks again

i appreciate your advice

i definitely do not want the engine to be damaged.

best regards,
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Old 03-08-2012, 01:25 PM
  #21712
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Quote:
ORIGINAL: cshahrdar

ok
i am good with that

so i should make gap clearance 0.1 mm?

and not 0.05?


thanks again

i appreciate your advice

i definitely do not want the engine to be damaged.

best regards,
Generalities follow....

Somewhere between 0.04 and 0.1mm is common to most 4 stroke model engines. Personally, I set to 0.06 as that puts it somewhere in the middle (and it suits my feeler gauges). You're looking for the "Goldilocks" setting....not too tight, not too loose, just right.

If the gap is too tight the valves may not close fully (particularly with engine temperature changes) which can lead to a worse case scenario of burnt valves and loss of power.

Be careful when adjusting the valves, you don't want to over tighten the adjustment and locking mechanism. Too many people overtighten bolts and adjusters are very easy to snap...

After adjusting a valve, turn the motor over a few times by hand and remeasure just to make sure.

On the issue of valve clearances affecting RPM. Assuming the valve clearances are within spec, it will have a negligible impact on valvetrain drag which will make an unmeasurable difference to peak RPM. Getting the clearances right ensures the valves get the maximum lift when open and, close positively. Setting a tighter gap (say 0.04mm) will ensure maximum valve lift occurs and will tend to open the valves fractionally earlier and close them fractionally later (say compared to 0.1mm). This gives the valve more time to pass the gasses (in and out) with a little more overlap. This may result in a small but noticeable power increase (note: many other factors also apply).

Valves will only bend if they are held open long enough for the the piston to hit it. Two basic engine designs apply here. "Interference" designs means the valve can hit the piston if the timing is wrong (piston and/or valve damage), "non-interference" designs means that valves can never hit the piston. Piston to valve impacts are more of an issue with certain high performance designs with minimal running clearances OR when the valve timing goes really bad (stuck valve, broken cam drive etc).
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Old 03-09-2012, 05:55 AM
  #21713
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Thats exactly how my lawyer would explain just about anything
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Old 03-09-2012, 02:08 PM
  #21714
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There's only one thing worse than lawyers, self-proclaimed internet experts....
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Old 03-09-2012, 02:17 PM
  #21715
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i bought a sig rascal 40 with an inverted saito 82 in it and i keep hearing rumors that a saito does not run good inverted without an onboard glo driver..any truth ? i've never had one inverted.
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Old 03-09-2012, 02:45 PM
  #21716
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They run fine inverted. But the oil tends to settle into the bottommost part of the engine over time. So it could clog up the glow plug. Plus oil tends to fill up the rocker arm boxes after some time too. I tend to prop my planes up against a wall, nose down, so I don't normally see the problem. But folks who set the planes in racks right side up at home and on the drive to the flying field would run into the problem first. Four stroke engines do not have the glow plug positioned dead center in the top of the combustion chamber, so they don't have the oil clogging problem that two stroke engines would have.

You might need to double check the fuel tank location and make sure it is still centered on the carb. With the engine inverted, the fuel flows into the carb and intake manifold and doesn't drip out onto the ground like it would with the right upright. Also be more careful priming the engine with it inverted too.

Now if you have a rare model engine with a oil sump and or a float carb on it, then it cannot be run inverted.


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Old 03-09-2012, 03:53 PM
  #21717
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Quote:
ORIGINAL: SigMan

i bought a sig rascal 40 with an inverted saito 82 in it and i keep hearing rumors that a saito does not run good inverted without an onboard glo driver..any truth ? i've never had one inverted.
When i store an inverted Saito engine (over the winter) i remove the good glow plug and install one that has been used for quite sometime. I also store the engine right side up and with the tail section higher than the nose. I use after run oil as well, making sure that both bearings are well lubricated. I have never had bearings rust up on me. I occasionally open up the back cover and check out the condition of the rear bearing and at the same time give it the max lubrication. All this of course is a winter maintenance. During the flying season I lubricate with after run oil (mystery marvel or air tool oil) each time after I'm done with the flyng.
My Saito 100 on my ucando is inverted, it ran ok for a couple of seasons but then it started to act up. A person on this thread told me to lean out the idle needle, which I'll do this coming season. I do have a Sullivan onboard glow driver which is controlled by the throttle stick and it also runs on its own battery a 4.8v ncd. Two clicks up on the throttle and the glow comes on. It's an insurance during landings.
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Old 03-09-2012, 04:52 PM
  #21718
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On your on board glow. Do you leave it on at two clicks up when starting and leave it connected to the on board battery during flight?
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Old 03-09-2012, 05:28 PM
  #21719
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thankx for the info guys !
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Old 03-09-2012, 05:45 PM
  #21720
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Cshahrdar,

Regarding your stem valve, yes, it could be bent but my guess is that it might only have some old dried up oil making it stick. I had a friends OS-91 that was like that. I had to totally disassemble the head to get at it but once I did, I was able to free it up OK.

Try hitting it with some heat, like from a heat gun, and then some penetrating oil to see if this loosens up your stuck valve. I'm going to bet that it's a simple fix,

Just my $.02

Bob
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Old 03-09-2012, 11:46 PM
  #21721
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With large gasoline engines the valve clearance gets tighter when they get up to operating temperature. Aren't our little Saito's just the opposite, and gain clearance as they heat up possibly due to the aluminum jug?

I think it's a good thing when I store my Saito's with the cylinder facing down and then the ARO slowly finds it's way into the rocker area. Sure saves having to lubricate them manually from time to time.

Ernie
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Old 03-10-2012, 12:32 AM
  #21722
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2-82's,a 91 and a 100.Love them all. [link=http://www.hobbyhot.com][/link]
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Old 03-10-2012, 01:04 AM
  #21723
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Quote:
ORIGINAL: Ernie Misner

With large gasoline engines the valve clearance gets tighter when they get up to operating temperature. Aren't our little Saito's just the opposite, and gain clearance as they heat up possibly due to the aluminum jug?

I think it's a good thing when I store my Saito's with the cylinder facing down and then the ARO slowly finds it's way into the rocker area. Sure saves having to lubricate them manually from time to time.

Ernie


I'm with you, Ernie. I let gravity lube the upper end for me.


Ed Cregger
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Old 03-10-2012, 04:57 AM
  #21724
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Quote:
ORIGINAL: mjraines1

On your on board glow. Do you leave it on at two clicks up when starting and leave it connected to the on board battery during flight?
I have the SULLIVAN on board glow driver........check it out. It needs to stay connected all the time to the glow plug and grounded to the engine. It also needs to be programmed. Mine is set up to stay on at two clicks, past that it turns off authomatically. On landng approach and at two throttle clicks and engine is idling it comes on again. In this case I'm using it on my great planes ucando size .60 and where I couldn't move the fuel tank centre line to line up with the centre of the carb., the ucando has a very narrow fuselage.
A SULLIVAN glow driver is for my insurance. Saito engines mounted sideways runs OK, inverted tends to load up if running a bit on the rich side.
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Old 03-10-2012, 05:08 AM
  #21725
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Quote:
ORIGINAL: mjraines1

On your on board glow. Do you leave it on at two clicks up when starting and leave it connected to the on board battery during flight?

It is left connected, "And programmed to stay on from idle to two clicks of throttle" Beyond two clicks of throttle there's no glow from this device.
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