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Fuel Flow Rate

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planecrazzzy
Guest

Posted: Sun Jul 01, 2007 7:12 am Post subject: Fuel Flow Rate

Hey Guys,

               My fuel flow rate seems to be worst since I changed from



3 blade ( IVO ) to 2 blade....



 My CHT is 250 ....EGT 1080.....



 I don't think changing the Needles would be good , because my



Tempertures seem to be almost perfect.....



 Before , at 5900 , I'd burn around  4.0 - 4.5 at cruise



 Now it's more like 4.5 - 5.1..... I'm hauling azz at the same 5900



 but I'm paying for it in fuel flow....

 Just thought I'd throw this out there and see what you guy think...



                          Gotta Fly...

                                          Mike & "Jaz" in MN

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jindoguy(at)gmail.com
Guest

Posted: Sun Jul 01, 2007 9:20 am Post subject: Fuel Flow Rate

Mike, I'm assuming the CHT and EGT readings you gave are both in Fahrenheit. According to the Rotax Operators Manual, page 10-1, the CHT your getting is outside the normal operating range on the low side. You should be seeing 350 to 430. Seems like you could safely drop the needle one groove and see if that helps. 

Just for grins, I looked up the fuel consumption charts for the 447 and 503 (pages 10-3, 10-4). Interesting that both engines have the same specific fuel consumption of about .85 lb per horsepower hour. At 6000 RPM the 447 makes about 37 HP and the 503 about 47. So, according to the good engineers in Austria the 447 should use about  31.5 lb. of fuel per hour (5.2 gph) and the 503 should use about 40 lb. (6.6 gph)



Rick



On 7/1/07, planecrazzzy < planecrazzzy(at)yahoo.com (planecrazzzy(at)yahoo.com)> wrote:[quote]--> Kolb-List message posted by: "planecrazzzy" < planecrazzzy(at)yahoo.com (planecrazzzy(at)yahoo.com)>



Hey Guys,

               My fuel flow rate seems to be worst since I changed from



3 blade ( IVO ) to 2 blade....



 My CHT is 250 ....EGT 1080..... 



 I don't think changing the Needles would be good , because my



Tempertures seem to be almost perfect.....



 Before , at 5900 , I'd burn around  4.0 - 4.5 at cruise



 Now it's more like  4.5 - 5.1..... I'm hauling azz at the same 5900



 but I'm paying for it in fuel flow....

 Just thought I'd throw this out there and see what you guy think...



                          Gotta Fly... 

                                          Mike & "Jaz" in MN



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planecrazzzy
Guest

Posted: Sun Jul 01, 2007 9:43 am Post subject: Re: Fuel Flow Rate

I Don't have my "sender" under the Spark Plug....I put it under a



Head bolt....I think it runs "alittle" cooler there....



 I'm mostly looking at the EGT....



   I guess it wouldn't hurt to lower the needle and see what it reads...



                        Gotta Fly...

                                         Mike & "Jaz" in MN

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[quote="jindoguy(at)gmail.com"]Mike, I'm assuming the CHT and EGT readings you gave are both in Fahrenheit. According to the Rotax Operators Manual, page 10-1, the CHT your getting is outside the normal operating range on the low side. You should be seeing 350 to 430. Seems like you could safely drop the needle one groove and see if that helps. 

 	  Quote:

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Sun Jul 01, 2007 12:38 pm Post subject: Re: Fuel Flow Rate

 	  planecrazzzy wrote: 	
		  Hey Guys,

               My fuel flow rate seems to be worst since I changed from



3 blade ( IVO ) to 2 blade....



 My CHT is 250 ....EGT 1080.....



 I don't think changing the Needles would be good , because my



Tempertures seem to be almost perfect.....



 Before , at 5900 , I'd burn around  4.0 - 4.5 at cruise



 Now it's more like 4.5 - 5.1..... I'm hauling azz at the same 5900



 but I'm paying for it in fuel flow....

 Just thought I'd throw this out there and see what you guy think...



                          Gotta Fly...

                                          Mike & "Jaz" in MN 	




Ok, going to p*** some guys off because I'm going against the books, but safety first....



On the CHT for the 447 and 503: the temp range for the CHTs given in the Rotax manual is wrong. Do NOT attempt to run CHT's hotter than about 350F. The engine WILL sieze at about 410F and consistent operation at 375F up will bring that TBO down a BUNCH. 



On a broken-in 503, the CHT's should sit at around 300F. If you're working the motor hard, 310 to 320F will be seen and is ok. On the 447, you'll see 320 to 330F at typical cruise and it'll run up to 350F in a climb. that's ok too.



BUT, if you seen CHT's hotter than 350F on a consistent basis on either engine, you've got a problem that needs to be addressed.



Ok, now that that's out of the way....



1080 on the EGT at cruise is fine, it's even ok at full throttle, though I like to see between 1000 and 1050 at WOT.



What is probable is that you have more load on the motor at cruise now. This was a similar result I got with my IVO when I flew it on my trike. I took off a blade and the EGT's went down about 50F at cruise due to the additional load at the same RPM's (I cruised about 5300rpm on that plane).



5900 rpm on a regular basis is working the engine a little hard (what's your cruise speed at that rpm) on a FS II (is that your plane?), so fuel burn that high doesn't surprise me.



I run about 5300 to 5400 rpm on my FSII (about 60mph) and burn about 3gph....



LS

_________________
LS
Titan II SS

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Sun Jul 01, 2007 12:41 pm Post subject: Fuel Flow Rate

What is the rpm at full throttle in level flight?

Richard Pike

MKIII N420P (420ldPoops)



---

_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

planecrazzzy
Guest

Posted: Sun Jul 01, 2007 1:14 pm Post subject: Re: Fuel Flow Rate

I haven't kept it full throttle very long in a cruise....Since I've changed



the prop , I've only had windy / gusty flying....



 At one point yesterday I reached Vne (Slight decent/downdraft) 



  I've got it set MORE for cruise....



 I think it's about 64 MAX rpm ( maybe a pinch lower )



  I've been more busy "Flying" the plane , than studying things...



 



 	  Richard Pike wrote: 	
		  What is the rpm at full throttle in level flight?

Richard Pike

MKIII N420P (420ldPoops)



---

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Sun Jul 01, 2007 2:01 pm Post subject: Fuel Flow Rate

5900 at cruise seems awful high. My 582 will poke at 6500 at full throttle 

in level flight, but I cruise around 65 mph with the tach in the lower 5,000 

range, and at that rpm, my fuel burn is less than yours.

Richard Pike

MKIII N420P (420ldpoops)

do not archive



---

_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

George Alexander

Joined: 10 Jan 2006
Posts: 245
Location: SW Florida

Posted: Sun Jul 01, 2007 3:47 pm Post subject: Re: Fuel Flow Rate

Kolbers & Kolbettes:



For what it is worth........



Lucien's numbers are a close representation of what I experience....



FS II, 75 hours, R503, dual carb, DCDI, C box, Powerfin, 3 blade 68".   Hardly worth mentioning, but for normal operations..... 1 TO, cruise for a while, 1 Landing..... burn rate is just under 2.75gph.  Got these results this morning in SW FL where the OAT was 84 at 0715. (Didn't check the OAT while cruising, but it wasn't much different at 1500MSL than it was on the ground 27 MSL.) 



George Alexander

N709FS

http://gtalexander.home.att.net



 	  lucien wrote: 	
		   	  planecrazzzy wrote: 	
		  Hey Guys,

               My fuel flow rate seems to be worst since I changed from



3 blade ( IVO ) to 2 blade....



 My CHT is 250 ....EGT 1080.....



 I don't think changing the Needles would be good , because my



Tempertures seem to be almost perfect.....



 Before , at 5900 , I'd burn around  4.0 - 4.5 at cruise



 Now it's more like 4.5 - 5.1..... I'm hauling azz at the same 5900



 but I'm paying for it in fuel flow....

 Just thought I'd throw this out there and see what you guy think...



                          Gotta Fly...

                                          Mike & "Jaz" in MN 	




<<<<SNIP>>>>



On a broken-in 503, the CHT's should sit at around 300F. If you're working the motor hard, 310 to 320F will be seen and is ok. On the 447, you'll see 320 to 330F at typical cruise and it'll run up to 350F in a climb. that's ok too.



BUT, if you seen CHT's hotter than 350F on a consistent basis on either engine, you've got a problem that needs to be addressed.



Ok, now that that's out of the way....



1080 on the EGT at cruise is fine, it's even ok at full throttle, though I like to see between 1000 and 1050 at WOT.



<<<<SNIP>>>>

I run about 5300 to 5400 rpm on my FSII (about 60mph) and burn about 3gph....



LS

_________________
George Alexander
FS II R503
E-LSA N709FS
http://www.oh2fly.net

planecrazzzy
Guest

Posted: Sun Jul 01, 2007 5:08 pm Post subject: Re: Fuel Flow Rate

Basicly , I'm going off what John said for Best Performance



 5,800 RPM / 75% power  for the 503...



 Maybe , I'll take a little pitch out of it.....and put the R's back to 6500

                Gotta Fly...

                                Mike in MN,  FSII / N381PM

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Sun Jul 01, 2007 6:50 pm Post subject: Re: Fuel Flow Rate

 	  planecrazzzy wrote: 	
		  Basicly , I'm going off what John said for Best Performance



 5,800 RPM / 75% power  for the 503...



 Maybe , I'll take a little pitch out of it.....and put the R's back to 6500

                Gotta Fly...

                                Mike in MN,  FSII / N381PM 	




Agreed that 5800 continuous is running the motor a bit hard. It won't really hurt it in the short term, though it may eventually take a few hours off the TBO down the line, as well as burn more gas than you really have to. 

The "sweet spot" on the 503 is about 5400 rpm for cruise (i.e. according to Mark Smith who's been running/servicing the Rotaxen for several decades). 6500 is a good maximum for climb, though on my FS II, I have to run the pitch too fine in cruise if I prop for 6500 on climbout. A good compromise on mine has been 6300-6350 for climbout, then I can run around 5300 to 5400 at an about 60mph cruise.



LS

_________________
LS
Titan II SS

ceengland(at)bellsouth.ne
Guest

Posted: Sun Jul 01, 2007 7:00 pm Post subject: Fuel Flow Rate

planecrazzzy wrote:

 	  Quote: 	
		   

 

 Hey Guys,

                My fuel flow rate seems to be worst since I changed from

 

 3 blade ( IVO ) to 2 blade....

 

  My CHT is 250 ....EGT 1080.....

 

  I don't think changing the Needles would be good , because my

 

 Tempertures seem to be almost perfect.....

 

  Before , at 5900 , I'd burn around  4.0 - 4.5 at cruise

 

  Now it's more like 4.5 - 5.1..... I'm hauling azz at the same 5900

 

  but I'm paying for it in fuel flow....

 

 

  Just thought I'd throw this out there and see what you guy think...

 

                           Gotta Fly...

                                           Mike & "Jaz" in MN



Assuming that your original prop was anything close to correct for the 
	


airframe:



If the only thing you changed was the prop, and now you are going 

faster, then your fuel burn will be higher; it's simple physics. Power 

required goes up at something like the cube of the airspeed change. If 

you had a manifold pressure gauge, it would almost certainly read higher 

than before as you are going faster at the same RPM.



Think about a manual shift car in 1st gear or 5th gear. 2000 rpm in 1st 

gear burns less gas than 2000 rpm in 5th gear, because you aren't going 

as fast & the engine isn't working as hard.



More speed (power) costs more fuel. How much do you want to spend? 



Charlie

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