Test Data on Head Mount vs. Tube Mount Injectors
Dave finally had some decent weather:
"I was able to test today to compare the 60 lb injectors on the induction tubes verses the 46 lb injectors on the heads.
OAT varied today from 59 degrees F @ 600? decreasing to 17 degrees @ 17500? Palt. Tests with the 60 lb injectors were done with OATs from 97 at 600' to 23 at 17500?.
Time to climb from 600' to 17500? Palt 10 minutes 28 secs @110-120 mph IAS, full fuel and with everything in the plane that is always there included the O2 system. So the climb is about the same.
It generally seems the max mpg and max speed is about the same, maybe slightly less on the mpg. I don?t know why that would be perhaps the difference in the injector spray pattern.
Injector temps in degrees F: OATs on the days tested were different as indicated below.
4000' OAT 52 59
#1 63 #2 71
#3 67 #4 84
It appears the injectors operate at around 11-25 degrees above ambient. During the test today, the #1 & #3 continued cooling during the climb to 17500? until #3 indicated 38 degrees F and #1 wouldn?t register a temp (below 32) at an OAT of 17 degrees at 17500?. It still demonstrated 11 degrees above ambient in those conditions. It may be that the injector temp is actually lower than the recorded temps due to the cold fuel flowing through the injector.
The gain above ambient with the tube mounted 60 lb injectors was about 160 degrees so it left little room for the 284 degree F max injector temp. However, with OATs during the 60 lb injector tests being 90 -100 F the maximum temp I observed was 274 F under the most adverse conditions with the injectors in my original location.
I will get comparable temps when the OAT comes up in the summer and the heat rise after shut down.
Vmax:
injectors
17500? Palt 60 lb 16.4? MAP, 12.4 AFR, 2820 RPM, OAT 23 F, AFR 12.4 232 MPH TAS
46 lb 16.3? MAP, 12.8 AFR, 2820 RPM, OAT 17 F, AFR 12.8 231 MPH TAS
6900? Palt 46 lb 24.6? MAP 12.8 AFR, 2800 RPM, OAT 55 F, AFR 12.6 241 MPH TAS
5500? Palt 60 lb 26.0? MAP 12.4 AFR, 2800 RPM, OAT ? , AFR 12.4 243 MPH TAS
1500? Palt 46 lb 30.1? MAP 12.6 AFR, 2820 RPM, OAT 60 F, AFR 11.0 243.5 MPH TAS
EGTs & CHTs:
Injectors 60 lb 46 lb 46 lb
Cruise: EGT CHT EGT CHT Vmax EGT CHT
1. 1292 296 1166 296 1241 287
2. 1304 295 1173 291 1337 291
3. 1273 277 1160 282 1302 292
4. 1253 295 1158 307 1299 300
spread 51 19 15 25 96 13
I may have had #1 cylinder trimmed a little rich Vmax test because I believe that cylinder CHT should have been hotter than #2.
It appears the cylinder trim is more variable with the 46 lb head mounted injectors requiring different percentages of trim for each cylinder at different power setting and is perhaps more sensitive.
I intend to get better numbers and check it again before reporting.
It runs smooth at 17500' all the way to 19.7 AFR and down to 3.6 gph if the cylinders are trimmed.
For the ease in installation in the heads verses the induction tubes, the performance difference, if any, is not worth the effort."
Dave finally had some decent weather:
"I was able to test today to compare the 60 lb injectors on the induction tubes verses the 46 lb injectors on the heads.
OAT varied today from 59 degrees F @ 600? decreasing to 17 degrees @ 17500? Palt. Tests with the 60 lb injectors were done with OATs from 97 at 600' to 23 at 17500?.
Time to climb from 600' to 17500? Palt 10 minutes 28 secs @110-120 mph IAS, full fuel and with everything in the plane that is always there included the O2 system. So the climb is about the same.
It generally seems the max mpg and max speed is about the same, maybe slightly less on the mpg. I don?t know why that would be perhaps the difference in the injector spray pattern.
Injector temps in degrees F: OATs on the days tested were different as indicated below.
4000' OAT 52 59
#1 63 #2 71
#3 67 #4 84
It appears the injectors operate at around 11-25 degrees above ambient. During the test today, the #1 & #3 continued cooling during the climb to 17500? until #3 indicated 38 degrees F and #1 wouldn?t register a temp (below 32) at an OAT of 17 degrees at 17500?. It still demonstrated 11 degrees above ambient in those conditions. It may be that the injector temp is actually lower than the recorded temps due to the cold fuel flowing through the injector.
The gain above ambient with the tube mounted 60 lb injectors was about 160 degrees so it left little room for the 284 degree F max injector temp. However, with OATs during the 60 lb injector tests being 90 -100 F the maximum temp I observed was 274 F under the most adverse conditions with the injectors in my original location.
I will get comparable temps when the OAT comes up in the summer and the heat rise after shut down.
Vmax:
injectors
17500? Palt 60 lb 16.4? MAP, 12.4 AFR, 2820 RPM, OAT 23 F, AFR 12.4 232 MPH TAS
46 lb 16.3? MAP, 12.8 AFR, 2820 RPM, OAT 17 F, AFR 12.8 231 MPH TAS
6900? Palt 46 lb 24.6? MAP 12.8 AFR, 2800 RPM, OAT 55 F, AFR 12.6 241 MPH TAS
5500? Palt 60 lb 26.0? MAP 12.4 AFR, 2800 RPM, OAT ? , AFR 12.4 243 MPH TAS
1500? Palt 46 lb 30.1? MAP 12.6 AFR, 2820 RPM, OAT 60 F, AFR 11.0 243.5 MPH TAS
EGTs & CHTs:
Injectors 60 lb 46 lb 46 lb
Cruise: EGT CHT EGT CHT Vmax EGT CHT
1. 1292 296 1166 296 1241 287
2. 1304 295 1173 291 1337 291
3. 1273 277 1160 282 1302 292
4. 1253 295 1158 307 1299 300
spread 51 19 15 25 96 13
I may have had #1 cylinder trimmed a little rich Vmax test because I believe that cylinder CHT should have been hotter than #2.
It appears the cylinder trim is more variable with the 46 lb head mounted injectors requiring different percentages of trim for each cylinder at different power setting and is perhaps more sensitive.
I intend to get better numbers and check it again before reporting.
It runs smooth at 17500' all the way to 19.7 AFR and down to 3.6 gph if the cylinders are trimmed.
For the ease in installation in the heads verses the induction tubes, the performance difference, if any, is not worth the effort."