Step 2 \u2013 Trim cylinder fuel flows so all cylinders peaked at same time<\/strong><\/p>\n\n\n\nThis was a very simple process. I performed this at WOT at 10,500\u2019. I selected this altitude as it seemed representative of where I would typically cruise.<\/p>\n\n\n\n
Initially I slowly leaned the engine allowing the EGTs to stabilize after each *slight* turn of the mixture knob. Once one cylinder peaked a waited 15-20 seconds to see if any more went peak. I then continued to lean, noting the fuel flows, as each cylinder went lean.<\/p>\n\n\n\n
Once I identified the too lean cylinders, I adjusted the cylinder trim values by +\/-1% as required.<\/p>\n\n\n\n
In my case I found that one cylinder went lean sooner than the rest. I added +1% fuel trim for this cylinder.<\/p>\n\n\n\n
I then went ROP and reperformed the leaning exercise. The leanest cylinder was still too lean so I adjusted the cylinder trim values by an additional 1%.<\/p>\n\n\n\n
When I repeated the leaning exercise again I found that two other cylinders were peaking a little late. In this case I reduced the fuel trim for these cylinders by -1%.<\/p>\n\n\n\n
After a couple more iterations of going rich and then leaning to peak EGT I was able to get all cylinders peaking with .2 GPH<\/p>\n\n\n\n
Step 3 \u2013 Validate Cylinder Trim Settings art various altitudes<\/strong><\/p>\n\n\n\nTo validate the fuel trim settings were acceptable, I next leaned the engine to peak EGT at 10, 12, 14, 16, 18 and 20 thousand feet. I noted the fuel flow spread between when the first cylinder to peak and the last. In each case the range was acceptable and LOP operation was smooth.<\/p>\n\n\n\n
Step 4 \u2013 Adjust spark advance when LOP<\/strong><\/p>\n\n\n\nThe default spark advance for my engine was set to 24 degrees before top dead center (BTDC). Other engines may have different default values \u2013 be sure to set in accordance with engine manufacturer recommendations. When running lean of peak, it is advantageous to advance the spark somewhat more as the leaner fuel charge burns slower in the cylinder. A greater advance allows more fuel to burn generating more power at the optimal crank angle.<\/p>\n\n\n\n
Best economy occurs 30-50 degrees LOP. However the fuel savings will result in a noticeable power loss \/ decrease in TAS.<\/p>\n\n\n\n
With the SDS EFI\/EI system, the LOP switch can be used to add an additional spark advance and\/or mixture reduction when turned on. Initially, I left the mixture adjustment set to zero and only used the switch to add additional spark advance.<\/p>\n\n\n\n
At 16,000 ft the engine was manually leaned to about 100 degrees LOP. Then various spark advance values were tested using the LOP. It was found that advancing the spark by an additional 6 degrees increased TAS by 2-3 kts. Parenthetically, EGT values dropped as expected as more of the fuel was burned before the exhaust valve opened. Increasing the spark advance beyond 6 degrees yielded no discernable benefit.<\/p>\n\n\n\n
Step 5 \u2013 Find how far LOP to go.<\/strong><\/p>\n\n\n\nLeaving the spark advance set to 6 degrees, the mixture was adjusted to see the TAS result \/ fuel savings at various LOP points. Once I found a \u201csweet spot\u201d that worked for me, I noted the mixture adjustment value (% shown on the SDS programmer display). <\/p>\n\n\n\n
Step 6 \u2013 Adjust ROP fuel settings<\/strong><\/p>\n\n\n\nThe final in-flight test was to see how Rich of Peak then engine was running when the mixture knob was in a neutral position. In flight I found that my engine was running considerably richer than I desired and so I had to manually lean the engine. I wanted to \u201ctune out\u201d the need for this manual adjustment.<\/p>\n\n\n\n
Inflight, I noted the mixture adjustment (% shown on the SDS programmer display) required to lean the engine to a setting between peak and best power. In my case this was a 10% reduction.<\/p>\n\n\n\n
Step 7 \u2013 Adjust maps in ECU<\/strong><\/p>\n\n\n\nThe data collected above was used to adjust the ECU maps while on the ground.<\/p>\n\n\n\n
When changing ECU maps \/ data, be sure that the data is entered into both <\/u>ECUs. The maps must<\/u><\/strong> be identical.<\/em><\/p>\n\n\n\nIn my case I reduced the fuel factor settings in the ECU map by 10% for all RPM settings at or below 2500 RPM. <\/p>\n\n\n\n
When I did my LOP testing I found that an 19% decrease in fuel would cause me to be 30 degrees LOP. This was the \u201csweet spot\u201d I wanted. As I had changed my base map in the ECU by -10% I set the LOP switch to further reduce my fuel flow by an additional 9%.<\/p>\n\n\n\n
Then end result was that when I flip the LOP switch, my spark advances by an additional 5 degrees and my fuel flow to the engine is reduced by 9%. This is about a 1 GPH savings in cruise.<\/p>\n\n\n\n
There is a very interesting interaction between the spark advance and the fuel flow. Normally when the engine goes LOP there is a sudden reduction in fuel and a corresponding reduction in power. This in turn causes a noticeable deceleration of the aircraft. However, I found that when I go LOP by only 30 degrees or so, the spark advance seems to compensate for what would otherwise be a power reduction from reduced fuel flow to the engine. Consequently, my TAS remains relatively constant and there is no discernable deceleration. Ultimately I see a 2-4 TKAS speed reduction with a nice drop in fuel burn. How great is that!<\/p>\n\n\n\n
All that being said, if I went 100 degrees LOP, I would see a much larger fuel savings and would see a drop in TAS. While that may be more cost effective, I want to go fast(er).<\/p>\n\n\n\n
Step 8 \u2013 Adjust maps for take-off power<\/strong><\/p>\n\n\n\nTypically in normally aspirated engines full rich is used when take-off power is applied. The extra fuel cools the engine. Without the extra fuel CHT temperatures would rapidly climb.<\/p>\n\n\n\n
During my break-in, I manually adjusted the mixture, usually adding an additional 25% of fuel when taking off or climbing. Once I reached cruise I would manually reduce the mixture to remove this extra fuel.<\/p>\n\n\n\n
Post break-in, I have eliminated the need to manually increase the mixture on take-off by changing the fuel factor in the ECU map by +25% for 2600 and 2700 RPM. As I only use these RPM settings for take-off & climbs, the engine receives the extra fuel required whenever these RPM settings are selected.<\/p>\n\n\n\n
So as not to run the engine too lean with a high power setting, I make a point of never using 2500 \u2013 2550 RPM and typically cruise at 2400 RPM or less.<\/p>\n\n\n\n
Additional Notes<\/strong><\/p>\n\n\n\nWhile the tuning I have done has minimized my need to manually tweak my mixture knob, I do make a point of keeping my CHT temps below 390 and prefer to keep them below 380. Therefore I will adjust the mixture, as required, if these limits come into play.<\/p>\n\n\n\n
It remains to be seen if the ECU maps will need additional tweaking when hopefully warmer summer weather arrives.<\/p>\n","protected":false},"excerpt":{"rendered":"
Over the past few months I have tuning my -10 engine\u2019s SDSEFI supplied electronic fuel injection \/ electronic ignition system to get the best possible performance for my needs. This document details I how approached tuning the engine, an approach that may be applicable to others. My -10 has an […]<\/p>\n","protected":false},"author":1,"featured_media":551,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"_links":{"self":[{"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/pages\/332"}],"collection":[{"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/comments?post=332"}],"version-history":[{"count":6,"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/pages\/332\/revisions"}],"predecessor-version":[{"id":1146,"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/pages\/332\/revisions\/1146"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/media\/551"}],"wp:attachment":[{"href":"http:\/\/localhost\/rv10ca\/wp-json\/wp\/v2\/media?parent=332"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}