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Fuel flow takeoff power

8

8 ball

Well Known Member
I have an o-320 that has 9.37:1 cr. (measured). It turns a metal Senchenich 72x75 2280 shortly after takeoff. Fuel flow is 11.5 gph. How does this sound? Lean? On hot Texas days I have to keep it
above 140 mph up to about 4000 ft. to keep cht's. below 425 f. The baffeling is very tight (all holes and cracks filled). It has the air exit ramp between the dual exhaust.
RV 8. 1155 lbs
 
I see 19 gph on takeoff and climb at full throttle and 2700 rpm. O-360-A1A, Hartzell c/s, Marvel M5 carb., 120kias climb speed with no CHT exceedance.
Sounds lean to me.
 
Check the Lycoming operating manual for your O-320. Your numbers sound about right but I really don't know for sure.

The (I)O-360 can drink some fuel. When I was breaking in my O-360 I was planning on between 16 and 17 GPH at full throttle and full rich.
 
The lycoming chart showed about .58lbs/bph/hr that's about 15 gal/hr full rich,full power, standard sea level day.l

Bob burns n82rb rv-4
 
Takeoff fuel flow

Thanks folks, anyone have experience with jet size? Just open it up a few thousandths?
 
n82rb said:
The lycoming chart showed about .58lbs/bph/hr that's about 15 gal/hr full rich,full power, standard sea level day.l

Bob burns n82rb rv-4
Click to expand...

Time out; he's got a fixed pitch prop. .58-.60 is likely a good number range, but you need to find power at his actual takeoff rpm (2200) & full throttle, not full power (2700rpm).

I see around 13-14 gph with an O-320/160 hp. I'm suspicious that it runs a bit richer than Lyc spec at full throttle.

What does the chart say at sea level MAP & 2200rpm?

Charlie
 
8 Ball
I have 9:1 comp o-320, 72" fixed pitch sensenich prop combination and get very similar RPM's after take off. I see 11.1 gph at that RPM. Not saying that this is good just a data point.

From the Lycoming chart I calculate aprox 110hp at 2300 rpm or 69% of 160 rated power. Using .6 BFSC x 110hp = 66 lbs/hr or 11gph. If I am reading the chart correctly at 2300 rpm and between 24-28"mp the flow is 9.5-12gph.
 
I see at full power on ground this:

IO-320 / 160HP
Sensenich metall FP
2200 RPM
79% Power
12.2 GPH

Hope it helps!
 
Takeoff fuel flow

Bean counter sounds like a fairly close comparison.
I am definitely in the 9 to12 range. I have had the timimg all over between 20 to 30 degrees. 20 helps some but costs over 50 rpm at altitude.
Thanks for all the help fellows.
 
8 ball said:
I have an o-320 that has 9.37:1 cr. (measured). It turns a metal Senchenich 72x75 2280 shortly after takeoff. Fuel flow is 11.5 gph. How does this sound? Lean? On hot Texas days I have to keep it
above 140 mph up to about 4000 ft. to keep cht's. below 425 f. The baffeling is very tight (all holes and cracks filled). It has the air exit ramp between the dual exhaust.
RV 8. 1155 lbs
Click to expand...

Those are about the same numbers (rpm and flow) that I see with my RV-6 (O-320, Sensenich 70x80).
 
8 ball said:
I have an o-320 that has 9.37:1 cr. (measured). It turns a metal Senchenich 72x75 2280 shortly after takeoff. Fuel flow is 11.5 gph. How does this sound? Lean? On hot Texas days I have to keep it
above 140 mph up to about 4000 ft. to keep cht's. below 425 f. The baffeling is very tight (all holes and cracks filled). It has the air exit ramp between the dual exhaust.
RV 8. 1155 lbs
Click to expand...

Lean. Brake Specific Fuel Consumption is always a good yardstick. Simply remember 0.50, which is pounds of fuel per HP per hour.

Example: assume 160 hp. 11.5 GPH x 6 lbs per gallon = 69 lbs per hour. 69/160 = 0.43, which is lean.

Stock Lycomings typically make safe best power around 0.50~0.52 BSFC. I don't have any hard dyno data for the 320, but an angle valve makes max power around 0.47. Like any engine, that's just short of, or at detonation onset....which may be contributing to your high CHTs. At 2280 RPM at WOT, you're certainly oversquare enough.
 
Sam Buchanan said:
Those are about the same numbers (rpm and flow) that I see with my RV-6 (O-320, Sensenich 70x80).
Click to expand...

O-320 (160) with Catto FP here and I see similar numbers. My EGT's are in the low 1200's (~250 ROP) in this state. As I transition to a 100-120 MPH climb and the RPMs come up, it leans up a bit to low 1300's. This could be a bit richer, but it is pretty much where I want it. I have an 4 SPA carb and I drilled the jet out with a #39 drill. I have no real problems keeping the CHT's under 400 in climb. During my early flights it was under 420, but some baffling work and break in helped me get this down. However, I have not done any climbs in 90+ days since all of that work. The hottest day was 80.

Larry
 
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DanH said:
Example: assume 160 hp. 11.5 GPH x 6 lbs per gallon = 69 lbs per hour. 69/160 = 0.43, which is lean.
Click to expand...

Dan,

Always appreciate your input. However, I am not sure that I agree with your math here. At 2250 with an FP prop, the 320 is not producing anywhere near 160HP. I don't have my chart handy, but I would guess the engine is producing less than 130HP at this RPM.

Larry
 
lr172 said:
Dan,

Always appreciate your input. However, I am not sure that I agree with your math here. At 2250 with an FP prop, the 320 is not producing anywhere near 160HP. I don't have my chart handy, but I would guess the engine is producing less than 130HP at this RPM.

Larry
Click to expand...

Agree; that was the point of my earlier post, as well. Flow needs to be up in the .58-.60 range due to max manifold pressure & poorer cooling at low climb speeds, but HP will be down in the 60-70% range at that rpm.
Charlie
 
lr172 said:
Dan,
Always appreciate your input. However, I am not sure that I agree with your math here. At 2250 with an FP prop, the 320 is not producing anywhere near 160HP. I don't have my chart handy, but I would guess the engine is producing less than 130HP at this RPM.
Larry
Click to expand...

Whoops, good point Larry...you're right, I'm overstating HP. What HP would you estimate with 9.37 compression? 135~140 would put BSFC right where it should be.
 
My IO-320 with Catto 3 blade shows 2250 RPM on full rich takeoff power, but closer to 13gph. It stays plenty cool during climbs at that rate.
 
DanH said:
Whoops, good point Larry...you're right, I'm overstating HP. What HP would you estimate with 9.37 compression? 135~140 would put BSFC right where it should be.
Click to expand...

I guess I was off a bit. My chart shows 2250 / Max MP is 142 HP @ sea level (8.5:1) I suspect the added CR might take it to 145.
 
Just re-installed my AFP injection system from rebuild and as well as new hoses from Tom Swearengen at TS Flightlines. I have the FM100, flow divider and purge valve. I Replaced the Floscan with the Red Cube and relocated it from between the electric and mechanical fuel pumps to AFTER the fuel servo. AFP changed the Main jet from 55.5 to 56 and flow tested the unit. The plane started right up and I adjusted the idle to 900. There is a little unevenness at idle. I have not fooled with idle mixture settings yet.
I did a few run ups and rejected take off's to make sure I was getting full power then a quick run around the pattern. I got the following data and want to make sure no one sees anything significantly amiss:

Density Altitude 2000ft OAT 31.3C Fuel flow at take off 14gph RPM at 2680
93% Power on G3x Peak EGTs spread between 1335-1345 CHT 333-348

Anything seem out of sorts? I am always a bit nervous fooling with the fuel system.

Thanks,
David
 
kaweeka said:
Just re-installed my AFP injection system from rebuild and as well as new hoses from Tom Swearengen at TS Flightlines. I have the FM100, flow divider and purge valve. I Replaced the Floscan with the Red Cube and relocated it from between the electric and mechanical fuel pumps to AFTER the fuel servo. AFP changed the Main jet from 55.5 to 56 and flow tested the unit. The plane started right up and I adjusted the idle to 900. There is a little unevenness at idle. I have not fooled with idle mixture settings yet.
I did a few run ups and rejected take off's to make sure I was getting full power then a quick run around the pattern. I got the following data and want to make sure no one sees anything significantly amiss:

Density Altitude 2000ft OAT 31.3C Fuel flow at take off 14gph RPM at 2680
93% Power on G3x Peak EGTs spread between 1335-1345 CHT 333-348

Anything seem out of sorts? I am always a bit nervous fooling with the fuel system.

Thanks,
David
Click to expand...

Since you installed a different fuel flow sensor and moved it to a different location, you probably shouldn't put too much trust in the indicated fuel flow until you are able to fly the airplane enough to do some calibration checks and confirm it's accuracy.
 
kaweeka said:
Density Altitude 2000ft OAT 31.3C Fuel flow at take off 14gph RPM at 2680
93% Power on G3x Peak EGTs spread between 1335-1345 CHT 333-348

Anything seem out of sorts? I am always a bit nervous fooling with the fuel system.

Thanks,
David
Click to expand...

Do you really mean "peak" EGT. You can only know peak EGT if you lean your engine to the point of hitting peak and going past it. Just guessing that you didn't do this during the take off run. If you did, I would suggest not doing that again.

Absolute EGT readings can't realistically be compared across different installations as they can read very differently due to several factors.

Dan posted a good calculation earlier in this thread that will help you assess the fuel flow assuming, as Scott mentioned, that your FF is properly calibraed.
Larry
 
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lr172 said:
Do you really mean "peak" EGT. You can only know peak EGT if you lean your engine to the point of hitting peak and going past it. Just guessing that you didn't do this during the take off run. If you did, I would suggest not doing that again.

Absolute EGT readings can't realistically be compared across different installations as they can read very differently due to several factors.

Dan posted a good calculation earlier in this thread that will help you assess the fuel flow assuming, as Scott mentioned, that your FF is properly calibraed.
Larry
Click to expand...

Sorry for the vocabulary error. No I did not intend to suggest I leaned to peak during takeoff, just the highest EGT noted at full rich during takeoff as seen on the G3x data upon review. .
 
That's interesting. Thank you. I flew this morning and noted the totalizer showed 5.3 gallons used in flight, filled it and actually added 6.4 gallons. I reset the k factor and will see what it shows next flight.
 
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