David-aviator
Well Known Member
I did a bit experimenting with LOP returning from OSH yesterday.
First off, I spoke with Greg from GRT at their booth to clear up a few unknowns to me with their system and discovered the second EGT page with an L in the bottom right corner, most interesting page. What it does is show, in a minus number, the EGT falling off as peak is passed during the leaning process.
What I found at 8500' and 22" manifold pressure, after careful leaning, was
-36 -37 -44 -39 which would indicate reaching peak temperature across all 4 cylinders at nearly the same time.
However, reaching peak EGT is not consistent at different manifold pressures. At WOT, 22.7", the numbers were -52 -33 -48 -35.
I flew for some time at WOT at the above LOP setting and these are the performance numbers.
RPM 2580
MP 22.7"
FP 23 psi
CHT (highest) 363F
OT/OP 162F/71 psi
FF 8.3 gph
EGT (highest) 1471F
ALT 8750'
DA 10,020'
IAS 135 knots
OAT 50F
TAS 157 knots
The airplane is performing OK. I like it and am beginning to see the advantages of LOP. Based on the Barrett dyno run data, best power BSFC on this engine is .51. That would be running at 50F ROP and compute to 54% power with the above numbers. However, running LOP the BSFC is less and if it were .41, which I doubt, power would compute to be about 67%. The real power output is somewhere between 54 and 67%. To see 75% power at this altitude, fuel flow would have to enriched to 11.5 gph.
In any event, I am concluding there is little chance of damaging the engine doing what I did. If anyone has a different point of view, lets hear it. I am on a learning curve with this stuff.
And all this on a couple ancient magnetos.
First off, I spoke with Greg from GRT at their booth to clear up a few unknowns to me with their system and discovered the second EGT page with an L in the bottom right corner, most interesting page. What it does is show, in a minus number, the EGT falling off as peak is passed during the leaning process.
What I found at 8500' and 22" manifold pressure, after careful leaning, was
-36 -37 -44 -39 which would indicate reaching peak temperature across all 4 cylinders at nearly the same time.
However, reaching peak EGT is not consistent at different manifold pressures. At WOT, 22.7", the numbers were -52 -33 -48 -35.
I flew for some time at WOT at the above LOP setting and these are the performance numbers.
RPM 2580
MP 22.7"
FP 23 psi
CHT (highest) 363F
OT/OP 162F/71 psi
FF 8.3 gph
EGT (highest) 1471F
ALT 8750'
DA 10,020'
IAS 135 knots
OAT 50F
TAS 157 knots
The airplane is performing OK. I like it and am beginning to see the advantages of LOP. Based on the Barrett dyno run data, best power BSFC on this engine is .51. That would be running at 50F ROP and compute to 54% power with the above numbers. However, running LOP the BSFC is less and if it were .41, which I doubt, power would compute to be about 67%. The real power output is somewhere between 54 and 67%. To see 75% power at this altitude, fuel flow would have to enriched to 11.5 gph.
In any event, I am concluding there is little chance of damaging the engine doing what I did. If anyone has a different point of view, lets hear it. I am on a learning curve with this stuff.
And all this on a couple ancient magnetos.
