Don

Don

Well Known Member
My 9A has an Aerosport O-320-D2A engine with about 600 hours on it. When I read various Lycoming charts in their Operators Manual, it seems like I should be seeing 12.2 to nearly 14 GPH on a full power take off. I seem to recall reading here (but now can't find it) that 12.5 to 13.5 GPH on take off is normal.

Can anyone confirm what the fuel flow should be (am I reading the charts correctly?).

And, if I am, my fuel flow appears to be low (somewhere around 11 GPH). Is there a simple adjustment, or is the carburetor fuel jet to small, or is it something else altogether? I'm not rushing to any conclusions here. I'm still pondering whether this is even an issue.
 
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What are your CHTs doing in take off/climb out??

What prop are you running?

What is your RPM in take off?
 
D2 means a fixed pitch prop, right? Are you looking at full power fuel flow on the charts? If you have fixed pitch and/or are a significant distance above sea level, fuel flow will be less because you can't make full power.
 
9A with IO-320 D2A, Catto 3-blade

I always see something in the range of 12.x to 14 gph during full power take-offs.
 
If you're fixed pitch and getting less than 2500 RPM on takeoff, then 11 GPH wouldn't surprise me. I'm at 14+ gph at 2680 RPM with the Hartsell (IO-320 D3G)
 
Mike S said:
What are your CHTs doing in take off/climb out??

What prop are you running?

What is your RPM in take off?
Click to expand...

Mike,

My CHTs are higher in climb that I think they should be. During warm weather I need to pay attention to keep them under 400 and I know they'll go to at least 430 and I'm sure they could go higher. I did the DanH mods to the baffling to get more air to the bottoms of cylinders 1 and 3.

My prop is a fixed pitch Sensenich 70CM-789-0 (79" pitch).

I'm not certain what my take-off RPMs are and I don't want to report a guess. I'm likely going to fly tomorrow and I'll check.

My airport elevation is 135' MSL.
 
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Don said:
?........
Can anyone confirm what the fuel flow should be (am I reading the charts correctly?).

And, if I am, my fuel flow appears to be low (somewhere around 11 GPH).
Click to expand...

I can't confirm your reading and ff estimate but I know (from my reading VAF) that fuel flow should be significantly higher. My O-360 shows closer to 17 gph on take off, full power full mixture and that's a tad low.

Your CHT's will be reduced a great deal at take off power with proper ff. I know some replace the carb main jet(or drill it out) to accomplish the correct ff.

Hope this helps..

I'm getting smarter all the time reading VAF. :D :D

Best bang for your buck.
 
Flow

Don,
My 9A was also burning 11gph max at take off when I first flew it. I was also bumping 400 when I pulled back the throttle on climb out. I asked here and several respected engine people who all told me that I should be able to lean and get 150 to 200 degree rise in EGT from full rich. I could barely get 100 degrees.
I opened the jet to a #38 drill size if memory serves. That and some help from DanH on the baffles got me cooling properly. I now get about 180 degree rise and burn around 14gph on full throttle climbs. Because of the fixed pitch prop the flow goes up with the rpm's as you climb.
 
PaulR said:
I asked here and several respected engine people who all told me that I should be able to lean and get 150 to 200 degree rise in EGT from full rich. I could barely get 100 degrees.
Click to expand...

Paul,

Can you explain how you measured your EGT rise? I'm guessing it was in cruise at some moderate altitude (say 2,500' but not likely very critical) and done slowly (not "the big pull") after the EGTs and CHTs came into equilibrium but I'd like to confirm that.

GLPalinkas,

I've learned a lot here, too. I wouldn't have known to even ask the question without reading this board. Of course, there's always a need to sort the wheat from the chaff.<g> My problem is my ignorance in some areas is pretty profound and knowing who is expressing an opinion vs who is expressing knowledge, is sometimes a challenge?but not necessarily an insurmountable one.
 
Don, as others have said the flow sounds too low.

In basic terms, on an ISA day, 1013.2HPA or 29.92" and 15dC at sea level you should see around 14.5-14.6GPH. As a result the EGT should be around 1250-1270 with the probes around 2" from the head.

If you have 10% less RPM the flow would be expected to be 10% less. If you are some what less than that, you are not running rich enough on takeoff.

This is a significant problem on TCM's and less so in Lycoming land, however I have seen Avstar FI units flowing too little of late and Carbs can too. Cabs are easy to adjust in the field however so you will be lucky in that respect.

Ensure you have no intake leaks at the head gasket and the intake tube joints.

Hope that helps.
 
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