EGT and LOP

[Browncbr1]

After watching mike Busch webinars , he said 1/10 HP is about the correct FF for takeoff. 200hp = 20gph. And he said egt should be somewhere between 1200 and 1300. Other than that comment, he said egt value doesn't matter much.

[KSMooniac]

20 GPH will be a bit rich for us.  The APS guys said it is closer to 1/11 IIRC.  Splitting hairs, certainly.  Regardless, you need to verify your K factor first by checking the fuel burn and fill-up results.

[Shadrach]

After watching mike Busch webinars , he said 1/10 HP is about the correct FF for takeoff. 200hp = 20gph. And he said egt should be somewhere between 1200 and 1300. Other than that comment, he said egt value doesn't matter much.

 On a standard day at SL.  I think you're operating under slightly different conditions in Knoxville this time of year!

[M20F]

Regardless, you need to verify your K factor first by checking the fuel burn and fill-up results.

This is one of the things I really like about my MVP-50 is that you can put in what you added and it will compare to what it expected and tell you the % +/- to adjust the K factor if need be. Mine has always been within 1-2% so never needed to futz with it, but really amazing the things these monitors will do for you.

[Browncbr1]

I did a few gami tests, but I think I should redo them with WOT at higher altitude and also do them a little slower so things could be a little more accurate.. 

Based on the few I did at 3000', 2500rpm, 21.5", 76 OAT.. it seems my average gami spread is around .8 gph......  cylinders 4 and 3 peak first nearly together...  1 and 2 peak later nearly together.. 

 

I think I had better do a few more tests with different power settings.. 

[aaronk25]

I was referring to his FF being a bit on the low side (now clarified) EGT values when leaning are meaningless. However, it's all we have when full rich, it's one marker of whether the engine is getting enough fuel. The Bendix RSA fuel system is not adjustable, so it's likely his instrument needs to be calibrated.

Prior to overhaul ff was 17.8-18.2gph on rollout now it's 16.8 and egts went from 1250 to 1330-1350ish. We returned the servo back to the shop in MI and I specifically asked him to turn the fuel flow up and he quoted your response. But what I don't get is why did it flow more before overhaul? Egt correlates with the fuel flow so I don't think it's instrumentation on my end.

[Browncbr1]

Prior to overhaul ff was 17.8-18.2gph on rollout now it's 16.8 and egts went from 1250 to 1330-1350ish. We returned the servo back to the shop in MI and I specifically asked him to turn the fuel flow up and he quoted your response. But what I don't get is why did it flow more before overhaul? Egt correlates with the fuel flow so I don't think it's instrumentation on my end.

 

Eventually, I will have enough time to set my K factor accurately and will report back FF then.. 

[N601RX]

You might consider removing all the injectors and cleaning them in Hoppe's #9 before spending a lot of time with Gami test.  Once you are sure they are completely clean then rerun the test and move the injectors around if needed.

[Shadrach]

Prior to overhaul ff was 17.8-18.2gph on rollout now it's 16.8 and egts went from 1250 to 1330-1350ish. We returned the servo back to the shop in MI and I specifically asked him to turn the fuel flow up and he quoted your response. But what I don't get is why did it flow more before overhaul? Egt correlates with the fuel flow so I don't think it's instrumentation on my end.

 

That is indeed odd.  With the DA variance you will get FF variance. EGTs at full rich should be pretty much be the same all of the time.  When you say "rollout" what phase of flight are you referring to? 

[Shadrach]

I did a few gami tests, but I think I should redo them with WOT at higher altitude and also do them a little slower so things could be a little more accurate.. 

Based on the few I did at 3000', 2500rpm, 21.5", 76 OAT.. it seems my average gami spread is around .8 gph......  cylinders 4 and 3 peak first nearly together...  1 and 2 peak later nearly together.. 

 

I think I had better do a few more tests with different power settings.. 

Take your time... Have you established which cylinder is the richest (last to peak)?  If so, set to that cyl and then pull the mixture to ruffness. Enrichen until just smooth and note EGT.  Continue to enrichen note peak EGT.  Let us know what it is. If it's in the neighborhood of 70-50 degrees from smooth to peak, there is no way your GAMI spread is .8.

[Browncbr1]

You might consider removing all the injectors and cleaning them in Hoppe's #9 before spending a lot of time with Gami test.  Once you are sure they are completely clean then rerun the test and move the injectors around if needed.

 

I had the entire fuel delivery system overhauled and injectors soaked about 25 hours ago...   Do you think they should soak again?

[Browncbr1]

Take your time... Have you established which cylinder is the richest (last to peak)?  If so, set to that cyl and then pull the mixture to ruffness. Enrichen until just smooth and note EGT.  Continue to enrichen note peak EGT.  Let us know what it is. If it's in the neighborhood of 70-50 degrees from smooth to peak, there is no way your GAMI spread is .8.

 

The caveat to my gami spread results is that I was not running WOT...  That's why I need to retest... 

[Shadrach]

The caveat to my gami spread results is that I was not running WOT...  That's why I need to retest... 

 

Why were you not WOT?

[Browncbr1]

Why were you not WOT?

Because I was at 3000' and didn't want to do the slow leaning procedure at over 65%

[aaronk25]

That is indeed odd. With the DA variance you will get FF variance. EGTs at full rich should be pretty much be the same all of the time. When you say "rollout" what phase of flight are you referring to?

Take off 1300msl same as previous take offs

[Shadrach]

Take off 1300msl same as previous take offs

 

 

True, but the density altitude likely varies quite a bit...  My field is at 703msl. But the DA differs quite a bit.  I pulled up some historical data for this year.  The density altitude at my field varies by nearly 7000ft from the cold days of winter to the muggy hot days in August. These are just numbers I picked from the looking at the monthly data for this year.  As you can imagine, WOT fuel flow would be quite different on Jan 8th vs Aug 3rd.  Take-off EGTs should be relatively close if not somewhat higher in the winter.

 

01/08/2015

Temp. (°F) 5

Dew Point (°F) -8

Humidity (%) 33

Sea Level Press. (in) 30.58

Density Altitude = -3666'

 

08/03/2014

Temp. (°F) 93

Dew Point (°F) 50

Humidity (%) 78

Sea Level Press. (in) 29.81

Density Altitude = 3292'