VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Main > RV General Discussion/News
Register FAQ Members List Calendar Today's Posts

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 12-22-2015, 05:52 AM
Darren S Darren S is offline
 
Join Date: Apr 2009
Location: Canada
Posts: 439
Default Can running too far LOP be damaging ?

My friend made a comment the other day but forgot to ask his rationale.

He said that you don't want to run the engine more than 70 degrees LOP.

Why? I have a Superior IO-360, CS Hartzell. 180 hp.

My "go to" numbers for cruise are: 22.8 MAP, 2380 RPM, leaned to 7.5 GPH fuel burn, EGT's are usually low 1300's.

The engine runs smooth, no issues. With the Advanced LOP feature I did check it the other day. I am more in the 90-100 degree LOP range.

Since his comments I've been running 8.0 GPH. That's more in the 50-60 LOP range.

Comments, explanations please??

Thanks

Darren
Reply With Quote
  #2  
Old 12-22-2015, 06:23 AM
Jesse's Avatar
Jesse Jesse is offline
 
Join Date: May 2005
Location: X35 - Ocala, FL
Posts: 3,679
Default

From everything I have read, there is no problem running as lean as you want as long as the engine doesn't start to miss. Many engines won't get that lean and still run smooth. I have never heard any reason not to run further lean if you can except that economy can experience the law of diminishing returns (losing more power and speed without an equivalent drop in fuel flow).

I have heard that above 65% power you need to be more careful with leaning. Your power setting seems to me to be around 70%.
__________________
Jesse Saint
Reply With Quote
  #3  
Old 12-22-2015, 09:11 AM
Ironflight's Avatar
Ironflight Ironflight is offline
VAF Moderator / Line Boy
 
Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,256
Default

Quote:
Originally Posted by Darren S View Post
My friend made a comment the other day but forgot to ask his rationale.

He said that you don't want to run the engine more than 70 degrees LOP.

Why?
You've asked the most important question! And his answer will probably that somoene else told him that - not that he has any real reference.

From all of the research I have done, I agree with Jesse - if its smooth,i ts fine. Heck, according to Lycoming, if it is below 65%, then even if it is NOT smooth, its OK - just uncomfortable, and maybe not good for somethign else in the airframe - but the engine won't care.

LOP is good until you end up so slow that you wonder if it is worth it.

Paul
__________________
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
Reply With Quote
  #4  
Old 12-22-2015, 09:34 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
Posts: 4,652
Default

Going exrtemely LOP is just like turning the flame down on a gas stove. I've run the RV-8 out to near 150 LOP, and it is smooth as glass. The more I lean, the slower the airplane goes and the cooler the CHT gets, right up to the point where the engine quits.

The ICP and temps are very low, there's not enough fuel/lead to foul plugs... I'd be interested to hear anyone come up with a reason how this can cause harm to the engine.
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
Reply With Quote
  #5  
Old 12-22-2015, 11:03 AM
Steve Barnes Steve Barnes is offline
 
Join Date: Jul 2008
Location: Santa Rosa, CA
Posts: 580
Default Not rocket science (Sorry Paul)

Michael, Paul and Jesse are right on. Couldn't have put it better myself.

Steve
Reply With Quote
  #6  
Old 12-22-2015, 11:47 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 5,516
Default

Lean of peak will provide more oxygen in the chamber and exhaust post combustion, so that some would say that it would contribute to more rapid oxidation of the exhaust valve. But - the oxidation rate drops by 50% for every 10C in temperature, so going cooler (and leaner) is better.

Large natural gas fueled engines are extremely lean and allow high compression ratios, high levels of turbocharging and thermal efficiency as good as the best diesels.

So, the answer is a qualified NO. The only area of concern is the exhaust valve, and with as many people we have running LOP, there would be evidence of an issue there, indicating, probably not an issue in our specific engines.

What is your compression ratio, that helps keep power up with altitude and LOP operation.

Maybe David Brown will weigh in here with some data, but using the big pull method to keep from creeping past the EGT peak is better as the exhaust valve (as well as other associated hardware) does not reach that peak only to be exposed to higher oxygen exhaust.
__________________
Bill

RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
Reply With Quote
  #7  
Old 12-22-2015, 01:04 PM
StuBob StuBob is offline
 
Join Date: Oct 2015
Location: Indianapolis, IN
Posts: 254
Default

Quote:
Originally Posted by BillL View Post
Lean of peak will provide more oxygen in the chamber and exhaust post combustion, so that some would say that it would contribute to more rapid oxidation of the exhaust valve.
I don't buy that. No matter what you do, you can't get the oxygen concentration above 21%. I understand what you're saying, but I don't think it holds stoichiometric water.

Best economy mixture is roughly 20-50 LOP. Leaner than that, you'll burn less fuel per hour but you'll go so much slower that you'll wind up with fewer miles per gallon. There's no harm in running (smoothly) leaner than that, but there's no reason to.

Disclaimer: All of my study and experience with this is in 6-cylinder Continentals, but I don't think the physics is any different.

Recommendation: If you haven't taken the APS class, either in person or online, it makes EVERYTHING related to combustion much more understandable.
__________________
Stu F.
RV8
Reply With Quote
  #8  
Old 12-22-2015, 03:02 PM
RV10inOz's Avatar
RV10inOz RV10inOz is offline
 
Join Date: May 2008
Location: Brisbane Qld. Aust.
Posts: 2,271
Default

There is no problem for the health of your engine operating very LOP. None. Do not let anyone tell you otherwise.

Paul and others are correct, it just results in much slower airspeeds, which is fine if you are trying to extract a long range out of a fuel load, the issue is the engine efficiency is not at its best, but it is more than offset by the greater loss of drag due to less airspeed. The optimum amount LOP is never a fixed number, it simply depends on where you are in terms of power.

John Deakin published this little table years ago on AvWeb, and what it does is gives you the recipes to aim for.

________________________________________
Red Box = No Fly Zone
• At and below about 60% power, there is no red box. Put the mixture wherever you want it.
• At about 65% power or so, 100ºF ROP to Peak.
• At about 70%, 125ºF ROP to 25ºF LOP.
• At about 75%, 180ºF ROP to 40ºF LOP.
• At about 80%, 200ºF ROP to 60ºF LOP.
________________________________________


________________________________________
Outside the Box
• At 65% power, use richer than 100 ROP, or leaner than peak EGT.
• At 70%, use richer than 125ºF ROP, or leaner than 25ºF LOP.
• At 75%, use richer than 180ºF ROP, or leaner than 40ºF LOP.
• At 80%, use richer than 200ºF ROP, or leaner than 60ºF LOP.
________________________________________


Print that off and keep it in the plane. Remember not all EMS are equal when it comes to % power and if you start at say 75% power ROP by the time you are LOP you will be between 65-70% so you just take a rough stab at something like 10-20dF LOP on the richest cylinder and all is good with the world. Do not split % points. near enough is good enough.

Quote:
My "go to" numbers for cruise are: 22.8 MAP, 2380 RPM, leaned to 7.5 GPH fuel burn, EGT's are usually low 1300's.

The engine runs smooth, no issues. With the Advanced LOP feature I did check it the other day. I am more in the 90-100 degree LOP range.

Since his comments I've been running 8.0 GPH. That's more in the 50-60 LOP range.
With all respect to my friends at Dynon and AFS, they lean find features are really a great teaching tool and for establishing the order of peaks, but in flight every day, they are almost useless. Hysteresis in probes, the speed at which you adjust, many things can confuse the algorithms so get comfortable doing it yourself.

I am not a fan of cook book recipes, your "Go To" numbers are fine but you have an RV, you want to go fast or go far. Pick which ever you need for the flight and do it.

Go Fast..... WOT, get every inch you can, use an RPM that is smooth, that could be 2364, 2348, 2507....I dont care, just pick a sweet spot. Then select the appropriate LOP setting, and the best way to do this is do a BMP (big mixture pull) and you will land square in the zone for appropriate LOP. If that is down low at 28.5" you will BMP it and land about 70-90dF LOP, but if you are up high at 22" it will be about 10-20dF LOP. It is almost like magic, but really you are surfing the curves.



Watch the video and play with the tool here > http://www.advancedpilot.com/redbox.html

If you want to actually gain a really good understanding bookings are filling up for the Feb class in Brisbane, or March in Ada OK. It will be the best money spent in aviation.

Ohhh and the excess oxygen eating up your exhaust, you should be worried about that so please fly and store your plane in outer space, perhaps Paul D can suggest how to achieve that one, thats his backyard Seriously, that is an OWT and has zero scientific credibility.

Just be diplomatic in telling your friend the earth is round not flat and he may be enlightened by you.

Hope that helps, but I seriously think investing in a class would be good for everyone. it is the only place you get to see what really happens inside your engine on the GAMI/TAT dyno.
__________________
______________________________

David Brown

DYNON Authorised Dealer and Installer


The two best investments you can make, by any financial test, an EMS and APS!

Last edited by RV10inOz : 12-22-2015 at 03:10 PM.
Reply With Quote
  #9  
Old 12-22-2015, 05:09 PM
donoltman donoltman is offline
 
Join Date: Mar 2011
Location: Tulsa, Ok
Posts: 98
Default LOP

They are right. I fly a O-470U every day at 23 inches, 2200 rpm and 50 on the lean side for 7 hours a day. It now has 2500 hours on the engine, 70's across the board and has never had a jug off. I also have 1 CHT gauge and 1 egt guage. There is way too much time spent and way too much money spent on probes for every cylinder. The engine will tell you when something is wrong. We used to be pilots that actually listened to our engines. Now we just look at graphs that we download. Just fly the thing.
Don
Reply With Quote
  #10  
Old 12-22-2015, 05:10 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 4,218
Default

Quote:
Originally Posted by Ironflight View Post

LOP is good until you end up so slow that you wonder if it is worth it.

Paul
Isn't the intent of LOP to choose a power setting and adjust the mixture LOP while maintaining that setting? Yes, you will have to move at least one more knob, but if your intent is to fly at <say> 65% and 170 knots while minimizing fuel burn, you can do it. You don't have to allow the power to drop below your target setting (density altitude issues excepted)...
__________________
Kyle Boatright
Marietta, GA
2001 RV-6 N46KB
2019(?) RV-10
Reply With Quote
Reply



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 03:18 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.