B

Bavafa

Well Known Member
In my recent flight, I was running her at LOP with the numbers below. I wonder if I should invest in getting my injectors tuned/replace or how close to each other should the EGTs be? All advise are welcomed.

MAP 21.5 and 2310 RPM and the EIFS was showing to be at 60% power, Density altitude around 9000+ if memory serves me right (I was flying at 8k). Fuel burn was 6.8 and TAS 142 (I know I should increase my MAP for that setting)

Cylinder CHT EGT
1 343 -31 LOP
2 347 -32 LOP
3 329 -35 LOP
4 331 -50 LOP

thanks in advance
 
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Analysis

If you are LOP and running 6.8 gph you are generating 102 BHP, assuming a SFC of 0.40. If your SFC is .41, your BHP is 99.5. Either way, that's not 60% for your engine.

If your EFIS is anything like mine, it tends to read high for % power when LOP because it assumes you are using "best power" mixture.

You did not indicate density altitude, but for my 7A, those numbers would not be unusual if I were down below 6k. If I were at 8k or above, that would be a tad slow for that fuel burn. Still, not out of a normal range. Some guys, especially with electronic ignitions, do better.

Your CHT range seems excellent to me. Your EGT LOP range is reasonable, too, but that is not the way you check for injector balance. Search the forum for better information on how to do it. Try "airflow" as a search term. You have to do it 1 cylinder at a time, based on fuel flow and with time in between each one to stabilize.
 
fuel flow

You need to record the fuel flow as each cylinder peaks, then take the difference between the first to peak and the last. That delta in fuel flow needs to be less than .5 gal, some say .3 gal. That is the missing info that you did not provide. If the fuel flow delta is greater than .5 gal, then you need to change an injector insert to narrow the delta. I changed the one that peaked first.
 
Injector Nozzle Tuning

Here's how to do it. Send me the data when your done and we'll see what needs to be changed if anything.


Nozzle Tuning Data

The basis of nozzle tuning is to get each of the cylinder EGT?s to peak at the same fuel flow. Your aircraft must be equipped with EGT information on each cylinder and fuel flow information. A digital flow meter is preferred.

To gather correct data for nozzle tuning, set a cruise power setting. Typically 24? MAP and 2400 RPM. Set the mixture to be 0.5 GPH richer than peak on any cylinder. At this setting record all the EGT?s for each cylinder. Lean the mixture 0.2 GPH and record all the EGT?s again. Lean the mixture an additional 0.2 GPH; record all the EGT?s again. Continue leaning the mixture 0.2 GPH and record the EGT?s until all the cylinders have peaked.

An alternative method although not as accurate is to lean each cylinder to peak and record the fuel flow at that point. You will get the same data, but since the EGT reacts slower than the leaning process you may go past the peak and not know it. This is especially true if an engine monitoring lean find function is used. We get more accurate data taking the EGT data manually. If you use an automatic data acquisition function, allow 30 seconds or so at each fuel flow setting so the EGT value can stable out.

After the data is taken, we determine which nozzles to change to get all the cylinders to peak at the same time. You will notice that the EGT number at peak may not be the same for each cylinder, THIS IS NOT IMPORTANT. The cylinders that peak first (higher fuel flow) are the lean ones; the cylinders that peak last (lower fuel flow) are the rich ones.

Getting all cylinders to peak within 0.2 GPH is ideal.


Don
 
Don,
I will run another test in the next couple of days and will share the info. Thanks for the procedure.
 
I ran a second test last night and these are the numbers.

MAP = 22" (WOT)
RPM -= 3340
DALT = 10334
OAT = 58

First column (8.2 FF) is .5G before peak. Also the first one to peak was #1 cylinder and the last to peak was #2.

FF 8.2 8 7.7 7.5 7.2
EGT1 1485 1458 -10 -18 -20
EGT2 1407 1411 1410 -12 -29
EGT3 1447 1447 -11 -23 -23
EGT4 1428 1419 -12 -30 -50
CHT1 354 354 349 327 328
CHT2 354 354 350 340 332
CHT3 347 347 339 326 317
CHT4 337 336 327 315 309
 
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