Talk:Lycoming IO-390

Weirdness with compression ration and IO-390-X

I found this kitplanes article with a picture of an IO-390-X dataplate(!) with an 8.7 compression ratio. I am very confused.

https://www.kitplanes.com/magneto-timing-made-simple/ https://www.kitplanes.com/wp-content/uploads/2019/05/mag-dataplate.jpg — Preceding unsigned comment added by 173.164.250.125 (talk) 05:35, 12 May 2020 (UTC)

It seems that at least some of the "X" generic models are 8.7:1, while the certified engines are all 8.9:1. That was just one reason why I changed the specs to a certified version: clearer data from the FAA type certificate. - Ahunt (talk) 12:18, 12 May 2020 (UTC)

I still suggest the operating manual as a much better reference. The fuel flow numbers on the page are not in the FAA type certificate, among other specs. If you web search for "IO-390 specifications" the operating manual comes up. It is a much richer source. 173.164.250.125 (talk)173.164.250.125 —Preceding undated comment added 05:52, 27 May 2020 (UTC)

We could use it as a supplementary ref to the type certificate. Do you have a link for it that is not WP:COPYLINK? - Ahunt (talk) 11:54, 27 May 2020 (UTC)

Design and development

Hi all. The article states that the IO-390 uses cylinders from the IO-580 to increase the O-360's cylinder bore. However, that is not what's in the reference cited. Can anyone help to clarify? Thanks. --Now wiki (talk) 03:06, 9 October 2020 (UTC)

The cited ref is oblique about explaining it, but says:

Two decades later, Lycoming was working to develop and certify a 580 Series engine. The 580 Series was built off the proven Lycoming 540 Series rotating system. The extra horsepower and displacement was achieved mainly through expanded cylinder bore and a small increase in compression. To certify the powerplant, Lycoming had to go through several generations of 580 Series cylinder development.

During this same timeframe, Lycoming engineers were working on a four-cylinder version of the big bore engine. Again, several variations were assembled and tested. Test results appeared positive, but, again, with no OEM customer, the project was put back on the shelf.

Lycoming officially launched the IO-390-X Engine at the 2002 EAA AirVenture.

If you follow the thread of that, it does indicate that the IO-390 used the "Lycoming 540 Series rotating system", which would include the crankshaft, connecting rods, cylinders and pistons, but not the block, etc. - Ahunt (talk) 12:35, 9 October 2020 (UTC)

From your reply, shouldn't the article read the IO-390 uses cylinders from the IO-540?? --Now wiki (talk) 00:26, 16 October 2020 (UTC)

I think what it is saying is that the 580 is based on the 540 and then the 390 is based on the 580. - Ahunt (talk) 12:48, 16 October 2020 (UTC)