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 Post subject: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 00:03 
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Cessna 182 0 470 guys...need some help.

I just installed an Insight G4 engine monitor on my Cessna 182K and my CHTs are near 400 dF on take off. Max take off power fuel flow is 25.4 gph at 1200 ft msl. The old factory gauge is in the mid green arc (360 dF max)...nowhere near the red.

I have an FAT supercharger on an 0 470 engine. For the purpose of this question, I have the supercharger on boost cutoff (28 in MP) so it should be nearly the same performance as a stock 0 470.

What take off max fuel flow do you see on your 0 470? If you have a engine monitor, what max CHTs do you see?

Thanks in advance for the help,

KJ


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 09:58 
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Aircraft: Cessna 182M
O-470R, so should be same engine.

Normal t/o, near sea level at BTR reasonable OAT (50-75F) I see ~22gph at full throttle, CHT might get to 395 or 400.

I do not take off at max climb and if my CHT gets near 400 I shallow the climb a bit to get speed and cooling air.

Are your cooling flaps full open? Have you checked the timing? Baffles? Is the CHT high on all cylinders (maybe timing?) or only certain ones? Correct heat range plugs?

That FF seems rather high to me for a O-470R, even with the FAT. Frankly, if I could flow 25gph on t/o I would expect CHT <350. Have you checked the FF against useage to make sure the K factor is set correctly?

RAS

PS David Welch has a 182 w/ the FAT and hangs here, perhaps he will chime in.


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 10:38 
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Thank you Richard.

My engine is hot on all cylinders but especially hot on 2, 5 and 6. Cowl flaps appear fully open, but will double check.

We have increased the fuel flow and replaced or repaired all of the baffles.

Good idea on timing and plugs. I will head there next.

Would love to talk to someone else with the FAT supercharger. It works very well. I mostly keep it on boost cut off unless I need it at altitude or for short field.

Thank you,

KJ


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 10:43 
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What year 182


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 13:27 
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He said it’s a K, that makes it a ‘67.


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 13:33 
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Keith,

What is the egt at takeoff power? Do you happen to have induction air temp on the monitor? Have you checked your MP gauge against an uncorrected altimeter or other source? Have you checked the FF transducer against actual fuel used?


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 13:49 
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Username Protected wrote:
He said it’s a K, that makes it a ‘67.


Paul is correct, 1967.

KJ


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 14:00 
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Keith,

What is the egt at takeoff power? Do you happen to have induction air temp on the monitor? Have you checked your MP gauge against an uncorrected altimeter or other source? Have you checked the FF transducer against actual fuel used?


Chris:

EGTs at max (non boosted) take off power are 1380-1440. The non injected engine is really fuel flow imbalanced.

I do have a carb temp monitor. The inlet temp is higher than a normal 182 due to the supercharger. Even at boost cutoff the supercharger increases the inlet temp. I think it is about 20 dF hotter than stock.

Fuel flow transducer is new and fuel flow monitor is new. I have not checked it since installed. I will check the MP gauge against ambient pressure next flight.

Thank you for the help,

KJ


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 14:37 
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Username Protected wrote:
I do have a carb temp monitor. The inlet temp is higher than a normal 182 due to the supercharger. Even at boost cutoff the supercharger increases the inlet temp. I think it is about 20 dF hotter than stock.

Fuel flow transducer is new and fuel flow monitor is new. I have not checked it since installed. I will check the MP gauge against ambient pressure next flight.

Thank you for the help,

KJ


Keith,

I find it very odd that your are running 20F hotter intake air, flow 25gph at t/o and still have CHT issues. With hotter inatke air the engine is necessarily running richer, even w/o the extra 3 or 4 gph over a normal O-470. Necessarily so because hotter air is thinner, has less O2 and thus a richer mixture for the same FF.

I think you really, badly, need to check your K factor/FF. Fill tanks, use a plain wood dowel and a marker to precisely measure the level of fuel, fly for an hour, fill back to same tank level using the marked dowel and then compare actual fuel used to what gauge says and do the /hr computation yourself using a timer on the flight. I strongly suspect your K factor is set wrong & you are using much less than 25 gph at t/o. Either that or your timing is off a good bit.

RAS


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 14:43 
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Thanks Richard. Will check this out. I have suspected low fuel flow since the monitor was first installed.

KJ


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 14:46 
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Keith,
I don't have a fuel flow gauge on my 182M but I can tell you the hottest CHT I see on climb out is 352 degrees on Cylinder #2 which runs the hottest. That's with cowl flaps fully open, full rich, and 100 mph indicated air speed. All the other cylinders run cooler than that.

Dave


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 17 Jan 2020, 14:52 
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Thanks Dave. That is what I recall from my early flying with 182s. 380 max CHT, usually lower.

The hot CHTs really surprised me in this plane. I suspect something is wrong with my setup.

Thanks for the help in getting a baseline.

KJ


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 21 Jan 2020, 13:14 
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Keith,
Confirm what type of CHT probes you have.

The sparkplug type will reflect a higher temperature by the order of 40-50 degrees.

I have a STOCK O-470R on my C182M (1969) model and had the same issue you did with 400 degrees + (also with the G4) until I switched probes and now I rarely see 375 even in the summer.

All the other points are valid also, baffles, timing, cowl flap settings.

Paul


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 21 Jan 2020, 13:47 
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Username Protected wrote:

EGTs at max (non boosted) take off power are 1380-1440.

KJ


Seems like those should be 1300 or less... your fuel flow is too low... bet that K factor is goofy...

Paul


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 Post subject: Re: Cessna 182 0 470 Fuel Flow and CHT Question
PostPosted: 21 Jan 2020, 22:31 
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Username Protected wrote:
Keith,
Confirm what type of CHT probes you have.

The sparkplug type will reflect a higher temperature by the order of 40-50 degrees.

I have a STOCK O-470R on my C182M (1969) model and had the same issue you did with 400 degrees + (also with the G4) until I switched probes and now I rarely see 375 even in the summer.

All the other points are valid also, baffles, timing, cowl flap settings.

Paul


Paul:

The probes are all new they came with a new Insight G4. I am not certain of the model. I will check.

Which probes are right? Are the lower temp probes correct?

KJ


Last edited on 21 Jan 2020, 22:34, edited 1 time in total.

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