New Engine - Nozzle Tuning

Bill Dicus said:

My -8 is at 32 hours. Cruise CHT's within 9 or 10 degrees (320-330) on Lycon IO360M1B with 10:1 compression. EGT's vary more, with 1 and 4 being higher (1229,1180,1149,1241). Seems time to perform GAMI lean test and consider swapping/changing injectors. Would you do anything else first?

My injection is mechanical. The figures were for the rich side of peak, probably about 100-150°....I've also been not sure how to lean with the 10:1 compression and what detonation dangers exist.

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Start with two in-flight checks. The first will confirm that full rich is rich enough. The second will gather data for nozzle tuning. In my opinion, both are checklist items for completion late in Phase 1, others say wait until 50 hours. If you have settled temperatures and oil consumption, you're probably ready.

A few more questions please. What brand of injection system? Do you have a good, stable fuel flow indication? And can you record EGT data with your EMS for posting here? Most systems record many columns of data, but you'll delete most of them for our purposes, keeping only the EGTs, fuel flow, manifold pressure, RPM, and the time hack.

Savvy.com website has a tool to help you determine your GAMI spread. Depending on what type of efis or engine management system you have, you may be able to use it. The service is free, you just set up and account and upload your flight data. Here is a link https://www.savvyanalysis.com/upload_files

EGT

The individual EGT's actual value is meaningless until compared against fuel flow. There is no normal or redline, nor are any two planes or ex pipes around with the probes in the same position. We work only from the peak number reported.
The fuel flow at the point where the individual EGT peaks is what is important and what we are trying to match cylinder to cylinder, not the temperature. I think that is why Dan asked if you had a good stable fuel flow report.
Tim

Bill.Peyton said:

Savvy.com website has a tool to help you determine your GAMI spread. Depending on what type of efis or engine management system you have, you may be able to use it. The service is free, you just set up and account and upload your flight data. Here is a link https://www.savvyanalysis.com/upload_files

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While I agree that Savvy Analysis is a great tool, it can generate inaccurate information in regards to GAMI measurements. I found that both the sample rate on your EFIS and the speed you move the mixture control can cause the GAMI measurements to be skewed and generate false peaks.

I discovered this comparing data on the manual process defined by Don Rivera and looking at the data on savvyanalysis.com afterwards. The results didn't match.

I switched from a 5sec sample to a 1sec sample which improved accuracy.

The faster you pull the mixture, it appears to have a negative effect using Savvy's GAMI tool. i.e. moving before the EGT temps settle, since there is always a lag of temperature following mixture movement.

I would recommend stopping at every 0.2gph for a few seconds to let EGT temp changes to catch up if you are looking for GAMI results.

same here

If you do a BMP (big mixture pull) going from climb mixture setting to
LOP cruise in about a second, you'll see 0 GPH GAMI spread, at least on my
EGT analysis software.

Don Rivera recommends .2 GPH increments for leaning, reducing fuel flow at 30 second intervals and finding peak egt
and make a note of fuel flow for each cylinder when it peaks.

The results are very different when using these 2 procedures.

I agree absolutely. To determine your spread you need to be well under 75% power. I purposely did all my calibrations at 8000 feet and full throttle. I followed Don's advice and very slowly leaned the mixture. The probes are slow to respond and the sample rate on most of the engine analyzers is not that fast.
Now that I have my nozzles tuned for .3 spread, I usually do the big mixture pull and get everything on the lean side of peak, then come at peak from the LOP side. The first to peak is the new reference for LOP operations.

I am not sure what advice to give you regarding the 10/1 compression other than don't do the GAMI test at more than a 75% power setting. Dan H. has posted some good data regarding detonation, along with some very good charts showing the "red zone" , or where not to operate.

There is a very informative thread on LOP operation in the Traditional Engines section here on VAF . It is a "sticky" at the top of the section.

One more factor

RPM.

I suspect the GAMI spread is usable only in the tested RPM range. EI might skew those results tho...

I fly behind a TCM IO550N - this is the engine with the top induction. Supposed to be very good at fuel and air mixing, as it is designed to run LOP thru its life. It is, but only at the factory recommended RPM: 2500 or 2550. That is a pretty narrow range!

My normal cruise is 2200 (2500 uses the blue wing solvent too fast). So, I have to settle with not so good spreads there, but at 17500 where I can run 2500, it's great. A change to turbo style injectors helped limit this problem. TCM is not interested in this test..."can't be duplicated in a test cell". Well: DUH!!

When I had Lycs on the nose, I used 2300 for the GAMI test - it worked great, as far as I could tell. I do not recall testing at other RPM ranges after getting it right at 2300 to see if it held through an RPM range.

Question: have any of you tested a 'corrected' engine at varying RPM and throttle butterfly settings to see if it all still holds true? Or, is the GAMI setup good for a narrow band?

Carry on!
Mark

New engine - ? GAMI check.

Thanks everybody for your responses to my (misplaced) post about when to do the GAMI spread test. All are appreciated and will be considered carefully.
Dan I apologize for taking so long to respond ? because the hoped for end of phase one got complicated. Take off and climb went well starting at Hobbs 36.25 hours. Temps, never a problem so far were fine; max cht 356 in climb, EGT?s 1100-1200, oil temp max 180. All with OAT 80 F on the ground, IAS 80 mph initial, increasing above 1000? to 120 mph. Had been worried about detonation or pre-ignition with my IO-360 M1B?s 10:1 pistons, so was running rich. Returning from a 130 mile x-c leg I got brave and leaned to peak EGT on 1 and 4, the two leanest cylinders. Everything looked good but I was still leery of LOP so stopped there. Downloads from the AFS 3400 gave peaks of 1421, 1376, 1340 and 1432. One and four peaked at the same fuel flow of 8.2 gph (MP 23.1, RPM 2360, alt 4500). Pulled RPM back to 2200 (MP at 22) to try low cruise (avoid continuous ops 2200-2350 for my engine-prop combo). Engine had always been very smooth but felt rough just as rpm reached 2200, suddenly. Stayed that way despite varying MP, RPM and mixture. On landing roll-out the engine quit . Never happened before. Rolled off and tried to restart, failed x2 and pushed plane to the hanger. Cowl off, everything looks good. Next day got engine started, ran OK on both and Rt (LSE III) positions and stopped firing on Lt (mag). Repeating the check improved the Lt mag firing but it was still spotty. Took out lower plugs (fired by Lt mag) which looked wet and dirty. Cleaned. Run up now good at 1800 rpm, so went flying. At 4500 ft, 22 square tried Lt mag again and engine quit firing. Back to take cowl off again (engine did not quit on rollout). Decided to pull mag, which failed resistence test on primary coil. New coil installed, lower plugs cleaned and regapped, mag installed and timed to 20 BTDC. We chose 20 BTDC based on threads here and the LSE manual. The engine data plate from Lycon says it?s an IO-360 (no mention of the M1-B in the logbook data) and specifies timing as 25 BTDC. We called Lycon and spoke to Lauren who initially said 25 BTDC was correct even with the 10:1 compression. But when he asked about electronic ignition and I told him the Lightspeed III was on the right, he said whatever it was set to should determine the timing. The LSE seems to be set for 20 BTDC and that?s why we chose the 20 degrees. Did a run up at 1800 rpm and found slight roughness, 160 rpm drop, and 200 degree rise in EGT on the left mag. Our A&P suggested going to 25 BTDC and this was done. Weather et all stopped us there and no run has been done with the new timing. Oh ? when the engine quit on rollout, it had stopped by 38 mph IAS with FF @4 gph. I?ll try to post the data dumps from the AFS later ? they?ve been printed out but I can?t get them up to include here. We checked the mag/starter switch - OK. Wiring harness to lower plugs looks good. We?re now at Hobbs time of 37.88 on the overhauled engine from Lycon ? but it?s old, delivered to me just about 10 years ago. Wonder about replacing the harness to plugs because of age? To your earlier ?'s Dan; It says Bendix on the servo body. Fuel flows from the red cube are very stable, but lag behind movement of the mixture control.
I respect your opinions Dan and would like to hear your thoughts about all this, if you?re willing. Thanks in advance to you, and again to all other posters.

Bill, do you have old Champion plugs connected to that mag?

New engine nozzle etc

Yes Dan. They are champion massive electrode plugs. The gaps were too wide initially and were adjusted properly. The plugs tested satisfactory. Ran it up yesterday and mag (Lt., lower plugs) checked out on ground, so went flying. The engine performed well. I did an airborne mag check at 22 square and the left mag did well. The EGT's only went up about 100? and the engine ran smoothly on just the left mag. Subsequently, flew 1.7 hrs and even was able to get LOP on 1 & 4 with 2 & 3 close to peak. Going below peak with the last two caused about 8 mph loss of IAS but still smooth. Since it went so well, I had decided not to replace the spark plugs. What do you think? Would you go ahead with nozzle (insert) tuning at this time? Yesterday that flight took 69D over 40 hours so can go to phase two! Everyone - thanks for any new thoughts you have. I still have concerns. For example, I have no explanation for why the engine quit on the roll out with a supposedly good electronic ignition firing the top plugs.??? Any ideas are most welcome. I did read all the material by Deakin and Bush on leaning. Still confused. I've been involved with two Lycoming IO-540's which together exceeded TBO for three cycles. I flew over three thousand of those 6000+ hours, routinely taking the leanest cylinder 100 degrees ROP for cruise-climb and to peak for cruise. The engines did well as far as wear and tear. The Lance engine did have a case crack and case was replaced with a previously welded case. Two years later we had another crack and got a new case. Expensive! Think these cracks could be related to my leaning practices or were they due to manufacturing defects?

Bill,
Champion has had some issues with their plugs and most recently redesigned the way the resistive element is manufactured and installed. Your situation sounds like it could have been caused by the plugs resistive element issue. There is a thread in the engine section about this that is a good read. If you have the old plugs, which can be identified by looking into the top of the plug and determining if there is a removable screw in the center, I would return them to Champion for new ones, or replace them with Tempest.
On the subject of matching fuel flow to cylinders, I would certainly at least understand where you are with your cylinder balance. It's easy to obtain the data and you can decide after you collect the data if it's worth the effort.
Congrats on completing Phase 1

Bil Peyton summed it up very well. If you have the old style Champions (screw plug core), replace 'em, then we'll walk you through injector balance.

New engine, nozzles

Bill and Dan: Thanks for your responses. I flew today and was able to reach peak EGT on all four within about a 0.2 to 0.4 gallons per hour spread in fuel flow. Have read all the posts about Champion plugs and should have measured my plugs' resistance but didn't do so. Hard to spend the money to replace plugs that are running well....! Do you think they should be changed? Today running just LOP the CHT's were higher than usual, 350-360 (2350 rpm, 23.5", 9000 DA, just LOP on all four). The engine was very smooth. Had to remind myself I had been flying very rich mixtures previously with attendant lower EGT's. Will try to post data dumps from the AFS 3400 - still having trouble with that. Just a few things to do before entering phase II and taking Jane for her first ride! Thanks again for following and posting back.

New engine, nozzles

P.S. Will check a plug tomorrow see if it's got the screw. Think the plugs are pretty old (i.e. over 10 years).