Avcon w/ low RPM’s

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JGlad
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Joined: Wed Jan 24, 2024 3:30 am

Avcon w/ low RPM’s

Post by JGlad »

Hey there! I’ve got a 170B O360-A1A Avcon conversion w/ 72” Hartzell only getting up to 2400rpm. I’ve searched this forum & I can’t find anything about rpm’s in the STC except the max being 2700 & of coarse the avoidance range. Any reason for reduced power like this? Thank y’all in advance for your knowledge.
Jeff
N1896C '53 170B
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redacted
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Re: Avcon w/ low RPM’s

Post by redacted »

Is this new behavior? You getting full travel on the throttle linkage at the carb? What’s fuel flow at full throttle? Manifold pressure?
Nathaniel Perlman
1952 170B
N2282D S/N 20434
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JGlad
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Re: Avcon w/ low RPM’s

Post by JGlad »

It's a new aircraft to me, so not sure about new behavior. I attributed it to the hight altitude when I picked it up, but I can feel & hear the governor kick in so it seems to be set that way. No fuel computer to measure flow, I'll have to check the throttle linkage & MP is 28".
Jeff
N1896C '53 170B
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GAHorn
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Re: Avcon w/ low RPM’s

Post by GAHorn »

Prop gov’s are adjustable. (check that the correct gov is installed…and it is adjusted per mfr’s specs… and that the control-cable is correctly adjusted.)

Are you seeing this 2400 on the ground (static)? …or in flight.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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JGlad
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Re: Avcon w/ low RPM’s

Post by JGlad »

I’ll check the gov. It’s both ground & air.
Jeff
N1896C '53 170B
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DaveF
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Re: Avcon w/ low RPM’s

Post by DaveF »

300 rpm is way out of spec.

First thing to do is make sure your tachometer is correct.

Assuming your engine is making rated power and the governor is set up correctly, max RPM should be set by the low pitch stop in the propeller. That's the screw in the center of the prop dome. It should not be set by the governor.

The prop high and low pitch settings are listed in the Avcon STC paperwork, but even after being set by a prop shop, sometimes you have to tweak the low pitch stop to get 2700 rpm. But "tweak" only means 50-75 rpm.
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JGlad
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Re: Avcon w/ low RPM’s

Post by JGlad »

I think I'm going to have take it to the prop shop to be sure. Thank you everyone for your input!
Jeff
N1896C '53 170B
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ghostflyer
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Re: Avcon w/ low RPM’s

Post by ghostflyer »

A friend recently imported a Cessna 170 from New Zealand and this guy was taken to the cleaners. No inspection of aircraft or log book verification carried out. My friend had purchased it from another doctor . Both these guys had gone to uni together over 24 years ago . So the aircraft must be good?????. 🤪 Really ?? How much weed have you been smoking ? Brent gave me a funny look.
it was going to be put on the Australia register. I was invited down to the hangar to see his new acquisition. The engine wouldn’t make 2400RPM.
My doctor friend pointed out all the “Modern Mods that been done. The wings had been “metalized” [it was a really professional job done “]
The engine was a Lycoming O-360 and a fixed pitch prop. 😱 No mention in the logs at all about the engine . The prop had been repitched and I couldn’t read the stamping on it has to whether it was 60in or a 68 in pitch . What about the STC for the engine mod I asked. i could be wrong but I do not think there is a STC for a 170 for the engine swap. Sorry but you have just blown 110,000 dollars. I cant reproduce what Brent said,but he wasn’t happy. The aircraft was still under its transportation and storage insurance policy at that time [insured for 120,000 total loss] . Later that day the rains came and for the next week we had over 14 ins of rain. The runway had over 6 ft of water over it . Brent’s plane went under and was soaked in salt water for over 15 days . The insurance paid up total amount . The insurance company broker contacted me as the broker knew I had a 170a and asked did I want to buy the wreck . ERR NO . That decision took about . 0002 of a second to make that decision.
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