Glow Engines Discuss RC glow engines

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Old 09-21-2012, 10:09 AM
  #23201
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I will go back and adjust the valves to see if that will help. The fuel I use is 15% Omega, and my other saito four strokes run great off of that fuel.
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Old 09-21-2012, 12:33 PM
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ORIGINAL: airborne14830

I will go back and adjust the valves to see if that will help. The fuel I use is 15% Omega, and my other saito four strokes run great off of that fuel.

Is this a new engine? It kinda make me wonder if your cam timing is 1 tooth advanced.

If you pull the glow plug to observe the piston & the rocker covers to observe the rocker arms, you can see if you have equal (overlap) valve lift @ TDC on the EX/IN TDC.
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Old 09-21-2012, 04:50 PM
  #23203
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Another possible problem could be if one of the pushrods has slipped out of its cup in the rocker arm. That happened to a friend of mine after he had a bit of a rough landing and caught the prop in the ground.

Bob
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Old 09-22-2012, 03:59 AM
  #23204
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I'm sure he means me too, but we're all just guessing, if I had the engine in my hands for a few minutes I could most likely solve it. I agree with the 9,000 rpm if the APC is not a wide blade.
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Old 09-22-2012, 04:34 AM
  #23205
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I'll bet you could.Maybe we could ask airborne to post some pics/be a bit more detailed as to what prop and fuel etc..even the handbrakes confused and i always get into trouble when she gets a bit cranky with someone
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Old 09-22-2012, 05:27 AM
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Quote:
ORIGINAL: Hobbsy

I agree with the 9,000 rpm if the APC is not a wide blade.

Standard prop @ 9000 RPM = 1.522 HP

APC @ 9000 RPM = 1.613

APC W @ 9000 RPM = 1.659

According to this [link=http://personal.osi.hu/fuzesisz/strc_eng/index.htm]STATIC THRUST CALCULATOR[/link]

My FA91S turned a Graupner 13 3/4 X 8 @ 9300 RPM. That calculated to 1.56 HP so it's pretty close, @ least for comparison purposes..

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Old 09-22-2012, 05:29 AM
  #23207
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Quote:
ORIGINAL: Old Fart

I'll bet you could.Maybe we could ask airborne to post some pics/be a bit more detailed as to what prop and fuel etc..even the handbrakes confused and i always get into trouble when she gets a bit cranky with someone

14 X 8 W/15% Omega.
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Old 09-22-2012, 12:41 PM
  #23208
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Tiger 2 with Saito 125.

extra 1/4 ply firewall and fuse doublers of 1/8 ply- lots of epoxy.

hope it holds together.
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Old 09-22-2012, 03:12 PM
  #23209
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Now THAT looks like a lot of fun.Do you really need the wheels or are you just going to hand launch?
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Old 09-22-2012, 03:30 PM
  #23210
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Thanks OF. Wheels, we don nee no stinkin' wheels

the landing gear is rather thin for it size, It has a wicked lope at idle and the whole thing rocks and flexes.

hopefully a vid tomorrow.
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Old 09-22-2012, 06:24 PM
  #23211
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Grabbed my second 100 today. It came dragging a Super Skybolt along behind it and has the same 13/8 MA 3-blade I run on my smaller 91 powered 'Bolt. Should be a real honker.

I'll have some pics up once it's assembled.
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Old 09-23-2012, 05:14 PM
  #23212
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Speaking of HS RPM ....I have two FA-80's and both top out at 8100 to 8400 RPMswinging a ProZinger 14x6 on PowerMaster 20/20 and Cool Power 30/23 Heli fuel.
According to an old review Iread, this engine with this prop should turn 9400 RPM. If that's correct, I'm making the same mistake on both engines but, can't figure out what it is. Ihave a steady idle on both engines around 2100rpm and they are both running a bit rich as the idle speed "pinch test" shows a rise in rpm.

Anyone have an idea of what the max rpm should be for this set-up? Is the article correct?

I remember getting around 9200 on my first FA-80 with Turboheader (the other one is a GK version w/stock muff). I noticed the rpm drop last Sat. when Istarted it up. The weather was overcast and humid, temp was in the low 80's. Can't figure out why rpm would drop 800 after a week of sitting in the garage. My carb adjustments resulted in the same settings and, needless to say, performance was off.

HELP

Thanks,
RJ
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Old 09-24-2012, 02:15 AM
  #23213
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Quote:
ORIGINAL: rowdyjoe

Speaking of HS RPM ....I have two FA-80's and both top out at 8100 to 8400 RPM swinging a ProZinger 14x6 on PowerMaster 20/20 and Cool Power 30/23 Heli fuel.
According to an old review I read, this engine with this prop should turn 9400 RPM. If that's correct, I'm making the same mistake on both engines but, can't figure out what it is. I have a steady idle on both engines around 2100rpm and they are both running a bit rich as the idle speed ''pinch test'' shows a rise in rpm.

Anyone have an idea of what the max rpm should be for this set-up? Is the article correct?

I remember getting around 9200 on my first FA-80 with Turboheader (the other one is a GK version w/stock muff). I noticed the rpm drop last Sat. when I started it up. The weather was overcast and humid, temp was in the low 80's. Can't figure out why rpm would drop 800 after a week of sitting in the garage. My carb adjustments resulted in the same settings and, needless to say, performance was off.

HELP

Thanks,
RJ

DA (density altitude) can significantly reduce power. High temperature, high humidity & low barametric pressuer can result in a high density altitude yeilding a less dense air charge. Less air = less HP.
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Old 09-24-2012, 04:00 AM
  #23214
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RJ, I have always run a 13x6 Scimitar or a Bolly 13.5x6, the Scimitar would turn 9,700 on my old high compression .80. I used 14x6s on the Saito .91 when I had one briefly and 14x7 Graupner or a 15x6 Pro Zinger on the 1.00. I like to prop Saitos for mid nines except for the little .30 and .40. The .80 just can't manage mid nines with a 14x6 but I also only run 10 and 15% fuel. More later.
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Old 09-24-2012, 06:01 AM
  #23215
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Hi rowdy i always run 10% in the glo saitos and think your prop speeds arn't far off what you should get out of an 80.My 82's on a 14x6 run mid eights to nine depending on how hot it gets over summer.39C is about 100F and hottest iv'e flown an 82 was a 44C day,at a guess i lost about 25% in performance terms.If i notice the engine just don't go the way it used to after a long period of no fiddling i pull the tank,do the valves and also change all the engine o rings,good as gold then
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Old 09-24-2012, 06:28 AM
  #23216
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Quote:
ORIGINAL: Hobbsy

RJ, I have always run a 13x6 Scimitar or a Bolly 13.5x6, the Scimitar would turn 9,700 on my old high compression .80. I used 14x6s on the Saito .91 when I had one briefly and 14x7 Graupner or a 15x6 Pro Zinger on the 1.00. I like to prop Saitos for mid nines except for the little .30 and .40. The .80 just can't manage mid nines with a 14x6 but I also only run 10 and 15% fuel. More later.

Unless I misread his post, his quandry was the loss of RPM from 1 session to the next.


Quote:
ORIGINAL: rowdyjoe


I remember getting around 9200 on my first FA-80 with Turboheader (the other one is a GK version w/stock muff). I noticed the rpm drop last Sat. when I started it up. The weather was overcast and humid, temp was in the low 80's. Can't figure out why rpm would drop 800 after a week of sitting in the garage. My carb adjustments resulted in the same settings and, needless to say, performance was off.

HELP

Thanks,
RJ

Agreed he is overpropped, but the 800 RPM loss W/the same prop could be due to a low DA (dense intake charge) when he ran the higher RPM & a high DA (less dense intake charge) when he ran less RPM.

At the drag strip is is not uncommon for ET to vary as much as whole second when comparing times from an East coast, sea level track in november to a midwestern track in the summer.

That's about a 100HP drop or 20% to 25% HP.

Yes, the less dense air will allow the prop to spin easier as it takes a less dense "bite" of air, but that still doesn't equate to = RPM output as the power output can drop drastically.

In aircraft, a high DA is a double edge sword. Not only does it reduce power output form the engine, it also reduces lift.

I've seen a 200 RPM drop in RPM on my FA300TTDP W/a 15* rise in temperature W/higher humidity.

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Old 09-24-2012, 07:02 AM
  #23217
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You should see what temp and DA does to turbine helicopters!!!!
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Old 09-24-2012, 09:47 AM
  #23218
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Quote:
ORIGINAL: blw

You should see what temp and DA does to turbine helicopters!!!!

Well helicopters don't really "fly" anyway.

They vibrate so badly that the ground rejects them.
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Old 09-24-2012, 09:54 AM
  #23219
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Quote:
ORIGINAL: rowdyjoe


I remember getting around 9200 on my first FA-80 with Turboheader (the other one is a GK version w/stock muff). I noticed the rpm drop last Sat. when I started it up. The weather was overcast and humid, temp was in the low 80's. Can't figure out why rpm would drop 800 after a week of sitting in the garage. My carb adjustments resulted in the same settings and, needless to say, performance was off.

HELP

Thanks,
RJ

Something else to consider: Since the prop is BIG for this engine & it is not operating @ maximum power under the best of conditions, the DA factor could reduce TQ substantially resulting in a bigger RPM drop than what might be expected if the engine were running @ peak HP under the best conditions.
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Old 09-24-2012, 11:11 AM
  #23220
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Thanks guys. I figured those wx conditions would have an adverse affect on performance, just didn't expect it to be that much. Since the humidty was up and temp was down I thought it might all equal out. When Iwas getting 9200 with the 80s it was hot (near 100F) but, much lower humidity.
Then again, it might be my cheap tach not readying accurately. Even if it's not accurate it's still helpful in showing an increase or decrease in rpm. I've decided to buy a better tach. On the other hand, there was a noticable decrease in performance in flight.
Speaking of props. I've been wanting to try a 13x6 to test the difference in performance against the 14x6. Wouldn't you know that Ijust ordered more 14x6 props (duh). I'll have to make a trip to the LHSand pick up a couple of 13x6 props.

I'll be tuning on the 80GK again today because Iknow it's not right. It seems that as Iapproach best LS idle the transition sucks and it will die. Can't seem to peak the top end properly due that problem. It seems to run fine with the low end tuned rich but, it's not at optimum idle. Ithink I'll change plugs to see if it helps.

RJ
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Old 09-24-2012, 02:07 PM
  #23221
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Was just tuning the 80GK with a 13x6 prop and it makes a BIGdifference in rpm. It peaked 10,100 on the last run but, the idle is only 2200 to 2300 rpm. It's also surging at peak rpm and haven't figured that one out yet but, on the last run it seemed to be steady. I've been filling the tank about 1/2 full and it's down to about 1/8 tank now. Seems strange to me how it peaks higher when the tank is almost empty. I'm stil not happy. Maybe a carb overhaul will help. Don't know how much time is on the engine but, it appears to be low. Paint is still in excellent condition, it's very clean, and compression is high. Of course, Idon't know how long it's gone unused either.
I'm going to change the plug as soon as it cools down and see if that will help. It can't hurt. I pulled and tested the plug that came with it and it glowed good and hot right away so Ifigured it was good to go. However, it has died a couple of times when I pull the igniter off.

The HSneedle is approx. 5 turns out and the LSis just about even with the end of the throttle barrel. The transition bogs down a about mid throttle but, picks up again if Iopen up at moderate to slow speed. If Iopen it fast it dies or tries to die just above idle.

Haven't had a chance to start the 80s with the TH. That's the one that had the large rpm drop. If I can get the GK tuned I'll tackle the other one tomorrow.
I need to go to another LHS that's better equipped and buy 2 good 13x6 Xoar props. I don't like blunt ended props.

Garry
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Old 09-24-2012, 02:41 PM
  #23222
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Quote:
ORIGINAL: rowdyjoe

Was just tuning the 80GK with a 13x6 prop and it makes a BIG difference in rpm. It peaked 10,100 on the last run but, the idle is only 2200 to 2300 rpm. It's also surging at peak rpm and haven't figured that one out yet but, on the last run it seemed to be steady. I've been filling the tank about 1/2 full and it's down to about 1/8 tank now. Seems strange to me how it peaks higher when the tank is almost empty. I'm stil not happy. Maybe a carb overhaul will help. Don't know how much time is on the engine but, it appears to be low. Paint is still in excellent condition, it's very clean, and compression is high. Of course, I don't know how long it's gone unused either.
I'm going to change the plug as soon as it cools down and see if that will help. It can't hurt. I pulled and tested the plug that came with it and it glowed good and hot right away so I figured it was good to go. However, it has died a couple of times when I pull the igniter off.

The HS needle is approx. 5 turns out and the LS is just about even with the end of the throttle barrel. The transition bogs down a about mid throttle but, picks up again if I open up at moderate to slow speed. If I open it fast it dies or tries to die just above idle.

Haven't had a chance to start the 80s with the TH. That's the one that had the large rpm drop. If I can get the GK tuned I'll tackle the other one tomorrow.
I need to go to another LHS that's better equipped and buy 2 good 13x6 Xoar props. I don't like blunt ended props.

Garry

You mentioned high humidity in your earlier post.

Is it possible that your fuel absorbed moisture?

As far as the engine peaking higher when the tank is low, that is an idication that there is a fuel delivery factor @ play. The engine will tend to run leaner when the tank is low if there is insuffecient presure in the tank to push the fuel "uphill".
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Old 09-24-2012, 02:59 PM
  #23223
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Rowdy should be about two turns out on the hsn? then tune the lsn(you'll notice that's the only abreviations i've used in this post)
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Old 09-24-2012, 03:55 PM
  #23224
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Rowdyjoe,

I agree with OF. Your are way too rich. As the tank gets lower the engine will lean. The TurboHeader provides a bit more tank pressure which limits this effect. Try retuning and things should stabilize.

Jim
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Old 09-24-2012, 04:19 PM
  #23225
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Thanks for the suggestions guys. I set the initial carb settings according to Bill Robinson's method ....LSN adjusted even with the throttle barrel and HSN5 turns out. Did Imis-read that part? 2 turns out on the HSN seems extremely lean to me compared to the method I've been using. I'll give it a try and see what happens.

The results from the latest tuning attempt were not good. As you recall, Ihad the engine peaking arount 10k but, the idle was a bit high and rough. Irefueled with heli fuel (30% nitro 23% lube) and retweaked the low end until it tried to die and then fattened it up about 1/8 turn. However, when Iwent back to check the high end, it bogged down and died (transition was shot). So, Ifattened up the low end enough to allow it to peak and the best Iwas able to get was around 8600 rpm with about 4 clicks on the HSNtoward lean. Going richer with the HSN brought the rpm down to 6400 before it died. It was running very hot so Ishut it down.
I'm really frustrated with this thing but, I'll give it another try with the HSN2 turns our instead of 5 turns out. If this doesn't do it, I'll start looking for parts to rebuild the carb.

RJ

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