Performance charts IO-360-M1B

I'm in the final stages of completing my RV-7A with only the final inspection and paperwork between me and the first flight. I have fitted the subject engine on the aircraft with a fixed pitch propeller. As you are aware, the Lycoming recommended procedure is to cruise 65-75 percent power for 50 hours or until the oil consumption has stabilized. However, the Lycoming charts are predicated upon using manifold pressure (MAP). Now, I did not fit an MP gauge as I wouldn't need it.

Has anyone else run into this problem and if so, how did you establish your power settings based on only altitude, temperature, and RPM?

Thanks

John

If you identify your prop and if you have gearleg fairings installed, perhaps someone with the same configuration could give an RPM for 65% power. Use as minimum RPM in cruise.

Break in will be achieved in the first 5 or so hours, you will see this by the reduction in oil consumption and a drop in CHT's.

The 50 hour idea is somewhat OWT. Some boutique shops break in the engine before you get it and you can be sure they do not do 50 hours on it.

Two ways for you to do it, run around at 3000' max and 2500 RPM and FULL RICH or the cleaner and better way. That is provided the engine will run nicely LOP. 2000' max 2500 RPM and about 80dF LOP.

The second method gives you high mean average pressures over a greater sweep of the bore with lower peak pressures, it gives lower CHT's at the same time and much cleaner combustion chamber and exhaust ports, guides etc. It also saves a bucket of money, while achieving a better break in.

"Does everything it should, and nothing it shouldn't" despite what all the old wives tales sprouted by so called airport experts.

If you can't do the LOP method run method one and full rich. For that matter ensure you are getting the correct fuel flow. We have been seeing a high number of FCU's appear at bare minimum or less fuel flow out of the factory. I suspect the wise old guys have retired or something (Seen this with both Precision and Avstar)

PERFORMANCE CHARTS

Thanks for the replies. I'll be flying the aircraft without wheel pants or gear leg fairings. The prop is a Sensenich 72FM8S16-1(85).

Regarding the break-in period; it would be nice if things came together in five to ten hours. However, I did the break-in on an older 172 with an overhauled engine. Took over twenty hours to get the oil consumption to stabilize.

If anyone has charts for various altitudes, I'd appreciate receiving copies for the break-in and future flights.

Thanks

John

The charts will be useless to you without a measure of MAP anyway. Unless you fly around at WOT.

If you want to achieve the result you are looking for, my post above delivers that.

Simply put when ROP the power is expressed as a percentage of MAP/30 x RPM/2700. But without a map instrument you can't tell.

David: thanks for the info. I was hoping not to have to install a MAP gauge. However, I may have to do some more work. I'm not going to ruin an engine for the sake of a few dollars...

Merci

John

I think David's advice is good. As we discussed via pm, I have the carbureted 360 and the same prop, and base my power settings on rpm and fuel flow. If your target is 65-75%, you should be fine following his direction and running 2500 rpm at the altitudes suggested, a bit lower rpm if at lower altitudes, a bit more if higher, up to wot at about 8000 ft. The 10% range is a fairly broad target. Follow David's advice and I don't think you'll have any problems. It may be stating the obvious, and I apologize if so, but many, many engines have been successfully broken in with fp props and no manifold pressure gauges (think every 172, every Cherokee, every Grumman, every......). Good luck with your break-in!