LOP operations in a high compression IO360

[sailvi767]

I am curious if anyone can pass on any advise and actual fuel flow and performance numbers for a IO360 with high compression (10 to 1) pistions. I am interested if LOP operations are feasible and safe as well as some sample fuel burn numbers. The engine would have dual electronic ignition and full monitoring.

Thanks!
George

[RVbySDI]

Originally Posted by sailvi767

I am curious if anyone can pass on any advise and actual fuel flow and performance numbers for a IO360 with high compression (10 to 1) pistions. I am interested if LOP operations are feasible and safe as well as some sample fuel burn numbers. The engine would have dual electronic ignition and full monitoring.

Thanks!
George

Although there are some differences in my engine and an IO-360, I do not believe they would be enough that my experiences would not be useful for you to consider.

I have an IO-340 that has 9.0-1 pistons. One Slick mag and one Lightspeed Plasma III EI. It is rated at 185 HP. I do believe the performance would be close. I run this engine LOP whenever I fly and mostly see fuel flows in a range of 6.5-7.4. This is running usually around 60-65%. At this setting I see around 150 MPH. I know my plane can fly much faster than that but it costs in fuel by doing so.

As far as feasibility and safety, the engine can most definitely fly LOP and do so safely. I see temperatures that are well within the safe operating parameters of the engine. When LOP I see CHT's in the 290 - 330 deg F range and EGT's in the 1385-1415 deg F range when running at these settings.

Hope this helps.

[Ron Lee]

Do a google search for "Deakin." Lots of articles by him on this subject. You may even be able to search this forum for "Deakin" and find the appropriate links.

The GAMI website may also have info on this.

[David-aviator]

There is a ton of stuff written on this subject, some IMHO a marketing effort by FI advocates, and the bottom line is rather simple.

Fuel flow is 7% less and speed 3% less. That's why pilots fly LOP. The benefits beyond this simple bottom line MAY be longer engine life.

I fly LOP locally at 8 gph and MP at less than 23 inches. It definitely keeps the plugs clean.

Is there a risk with high compression engines? I don't know. There certainly is with a Subaru H6 engine running at 10.7:1. With it anything less than A/F ratio of 14:1 is like a coffin corner. (A/F ratio is just another way of looking at it)

One way to find out if it is OK with your engine is to go out and try it. Someone has to do it to get an answer.

[cdmiller]

I have an RV-8 with an IO-360 M1B engine with 9.2 to 1 pistons and one LS ignition and one Slick mag. I balanced fuel injection nozzles so that all cylinders reach peak EGT at nearly the same fuel flow. I normally run LOP at cruise altitudes (7500--10,000 feet). I usually cruise at about 62% power (2350 rpm and 22" MP) and about 40 degrees LOP. My fuel flows range from about 7 to 7.5 GPH and TAS ranges from 170 to 175 knots. I have a WW 200RV prop, which accounts for some of the amazing efficiency.

Dan Miller
RV-8 N3TU 887 hours since July 2006 and loving it.

[sailvi767]

Thanks for all the replies. I love some of the numbers posted. If I can get 170 at 7.5 GPH I will be a very happy man. It sounds like running LOP is not a problem for the long term health of the engine.

George

[RV10inOz]

It sounds like running LOP is not a problem for the long term health of the engine.

In fact it is the best thing for your engine. Read all the John deakin articles, do an APS seminar. You will learn so much about how an engine really works and how to fault find its worth it all and more.

Print of Deakins Pelican's Perch articles on where to run my engine, there are 4 of them, once printed bind together and read nightly......yes nightly, as many times as you can, until you are confident in the "whole concept".

Ohhh and one thing I learned, plug gaps really matter LOP so keep them between 16-18 thou, check them every 50 hours. ROP masks many deficient things like plugs mags etc.

All the best!

DB

[Caveman]

Originally Posted by sailvi767

Thanks for all the replies. I love some of the numbers posted. If I can get 170 at 7.5 GPH I will be a very happy man. It sounds like running LOP is not a problem for the long term health of the engine.

George

Another data point: A few weeks ago the wife and I flew 441 nm to West Houston to visit her sister... non stop in 3 hours and five minutes. I have an IO-360 M1B with 9.0 : 1 pistons and one LSE ignition, in my 7. At 9500' we indicated 173 to 175 smph TAS and we were burning an indicated 7.3 gph. I was running about 40 deg. lop. This seems to be right in line with what the other guys are reporting. Total gallons used was 23.0 according to the fuel truck's meter. I had a 4 knot headwind most of the way, with an initial 12 knot wind for the first 15 - 20 minutes or so. When I landed with nearly half my fuel left in the tanks after flying 500 + statute miles I was very pleased. All my cylinders peak within .2 gallons of fuel flow above 8000' and I have not needed to balance the injectors. The more I fly my airplane the more I like it.

[RV8iator]

Originally Posted by sailvi767

Thanks for all the replies. I love some of the numbers posted. If I can get 170 at 7.5 GPH I will be a very happy man. It sounds like running LOP is not a problem for the long term health of the engine.

George

If you can get 170KTS at 7.5 gph, you'll not only be a happy man, you'll be lucky, almost defying physics.

I may believe MPH, but KNOT KNOTS

[sailvi767]

Originally Posted by RV8iator

If you can get 170KTS at 7.5 gph, you'll not only be a happy man, you'll be lucky, almost defying physics.

I may believe MPH, but KNOT KNOTS

I agree with you however the one poster said he was seeing 170 to 175 knots true. I suspect he may have meant MPH. I have been reading the Deakin articles and its very interesting info. I thought LOP was a bit hard on the motors but it looks the opposite. It looks like proper LOP operations will increase the engine life.

George