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Old 08-20-2019, 08:17 PM
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Sorry about the double post, trying to figure out editing................ It sounds like the mix ratio is more about the brand itself rather than the engine requirements? A 100:1 mix in one brand may be safe to use as 30:1 in another?
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Old 08-20-2019, 08:36 PM
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dino oils do not provide the same lubricating or cooling as synthetics, so when you read the lower numbers like 30:1, it's for natural oils. the chemistry of synthetics allow for higher ratios, and are brand specific. Amsoil at 100:1, Stihl at 50:1, and Redline at 40:1. I have friends that run each and have never seen a problem. DA recommends RL at 40:1 based on their testing and that's what many have adopted. I use Stihl Ultra because it's easy to get, and drop it down to 40:1 for a little more peace of mind.
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Old 08-20-2019, 08:46 PM
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That makes sense now. The recommended oil is lawnboy ashless (dino). That would explain the 30:1 recommendation. Thank you, I will use the synthetic and join the 21st century. Maybe someday, I will get rid of my FM electronics as well.
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Old 08-20-2019, 08:47 PM
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At one time (quite a few years back at this point), Amsoil Sabre was recommended at 100:1 by Desert Aircraft. It was popular for large engines at that time to run this oil and ratio. Over time, DA discovered that the 100:1 Amsoil Sabre contributed to hard carbon deposits in the engines. Other pilots who ran Redline or Stihl HP Ultra (or Belray, etc) with higher oil content and sent their engines in for service did not have this issue. DA later revised their oil recommendations to Redline Racing Oil 40:1, Stihl HP Ultra or Motul 800 50:1.


Petroleum-based oils are sometimes run at 32:1 for break-in for a gallon or 2 or 3 in the belief that it expedites the seating of the piston ring. This subject tends to start debates. Increasingly it seems that folks are just running a good synthetic like Redline or Stihl HP Ultra from the beginning and skipping the use of petroleum based oils.
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Old 08-20-2019, 08:58 PM
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That's great info. At the risk of starting that debate, what is the general consensus on skipping the 32:1 natural oil breaking in and going directly to the synthetic mix I will run from then on. If its safe, it should prevent the need for a re-tune.
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Old 08-20-2019, 09:05 PM
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One last question, when testing and tuning, what max temp should I be looking for on my heat gun?
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Old 08-20-2019, 09:25 PM
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Tuning by heat gun isn't really a thing as far as I know. Your temp on the ground will be tremendously different than in the air, so not sure it's all that helpful. Personally, I use telemetry to monitor engine temp during flight.



Attached is a gas engine tuning guide, courtesy of Terry's Customs
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Old 08-20-2019, 09:40 PM
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I appreciate that link. Based on the many years of tuning glow engines, I found that monitoring engine temp while tuning on the ground is a good indicator of over lean set-ups. I was hoping someone had some advise on the temp range to watch out for on DLE55 as to not over lean and over heat my engine. Maybe I should ask in a new discussion? I'm obviously new to FG. Thanks for your help.
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Old 08-20-2019, 09:58 PM
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Nothing over 400. Ideally you should stay in the 300-320 range. My DA-120 runs about 270 during easy flying and about 320 in extended low and slow 3D.

My DA-70 runs hotter but this is largely due to the round cowl on my mamba. It runs about 300 in easy flying and 390 in extended 3D.

These numbers are also influenced by the 100 degree Houston weather that I fly in.

As your engine breaks in, expect to lean both needles several times. Just remember you want to make very tiny adjustments. 5 degrees in the needles is a good place to start.
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Old 08-20-2019, 10:10 PM
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I would humbly suggest that where and how the temp is being measured is important when comparing person A's temp numbers to person B's temp numbers. My thermistors for in-flight telemetry are mounted to a brass ring secured under the heads of the spark plugs. That might be a hotter value than the side of a cylinder fin.


YMMV
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Old 08-21-2019, 05:00 AM
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Originally Posted by Threepete View Post
Thanks for that. I was trying to be careful not to make this about a brand but about the actual mix ratio. I would like to use the HP Ultra but my concern was the 2.6 oz bottle in a gallon of gas, yielded a 50:1 mix vs the recommended 30:1. Being new to gassers after a long run with glow, I'm confused about the importance of the actual mix ratio.
I was very happy with the ultra. I just made the ratio a little richer than the bottle ratio. The biggest reason I switched was redline was easy to get on Amazon and i wanted to try it out. The HP was available locally but I didn't always have the time to get over there to get it. Redline I buy by the gallon.
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Old 08-21-2019, 05:02 AM
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Originally Posted by Threepete View Post
Sorry about the double post, trying to figure out editing................ It sounds like the mix ratio is more about the brand itself rather than the engine requirements? A 100:1 mix in one brand may be safe to use as 30:1 in another?
Kind of. Oils like Redline have many different ratios they can be mixed at. Even amsoil.
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Old 08-21-2019, 05:05 AM
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Originally Posted by Threepete View Post
That's great info. At the risk of starting that debate, what is the general consensus on skipping the 32:1 natural oil breaking in and going directly to the synthetic mix I will run from then on. If its safe, it should prevent the need for a re-tune.
As I mentioned before, i run full sun right from the start. I think most here do the same now. Rings seat fairly quick and you will need to adjust the needles a little as the rings seat in. Mainly the low side.
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Old 08-21-2019, 05:07 AM
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Originally Posted by RCAddiction View Post
I would humbly suggest that where and how the temp is being measured is important when comparing person A's temp numbers to person B's temp numbers. My thermistors for in-flight telemetry are mounted to a brass ring secured under the heads of the spark plugs. That might be a hotter value than the side of a cylinder fin.


YMMV
From my understanding that is the most ideal place to monitor engine temps.
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Old 08-21-2019, 05:09 AM
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Originally Posted by dshriver View Post
Nothing over 400. Ideally you should stay in the 300-320 range. My DA-120 runs about 270 during easy flying and about 320 in extended low and slow 3D.

My DA-70 runs hotter but this is largely due to the round cowl on my mamba. It runs about 300 in easy flying and 390 in extended 3D.

These numbers are also influenced by the 100 degree Houston weather that I fly in.

As your engine breaks in, expect to lean both needles several times. Just remember you want to make very tiny adjustments. 5 degrees in the needles is a good place to start.
When i talked to DA along time ago about this they said engines like the 120 and 170 had thinner cooling fins. (70 might be similar). This was to reduce weight and it did affect cooling. My temps for my old 120 was similar and it ran very good. I measured at the upper most fun at the back of the cylinder.
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