Degrees ROP (With Poll)

[201er]

Ok, out of interest sake, I'd like to copy the LOP Poll but with the question on the ROP side. If you regularly fly LOP but occasionally cruise ROP, vote where'd you'd be ROP. Also adding another poll for climb ROP.

 

What's your basis for the amount ROP that you fly at? Dr Dentist, do you have the data that proves ROP is best and exactly how much?

[fantom]

What's your basis for the amount ROP that you fly at? Dr Dentist, do you have the data that proves ROP is best and exactly how much?

Excellent point

 

I believe Dr. Fang is a recent LOP convert, having done extensive investigation (i.e., soliciting instruction, off-line, from some MooneySpace members).

 

[scottfromiowa]

Do they (dentists) just give it to Chiropractor's?

[John Pleisse]

How about the other way around. Regularly fly ROP and LOP in cruise only. As a non convert, this makes sense. Not trying to eake a half gallon out of a long climb or leaving the mixture knob unscrewed all the way through your decent (only to forget to enrich when you suddenly need power, then dotonate).

 

80-100 ROP and 1300 EGTS get my vote.

[Seth]

It was different for my 1967 M20F - I'm answering as for now, which is the Missile, and currently breaking in the six new cylinders.  So, I'm a little more Rich than usual (I do understand you can break in LOP as well.  However, I'm breaking in ROP).

 

-Seth

[jetdriven]

How about the other way around. Regularly fly ROP and LOP in cruise only. As a non convert, this makes sense. Not trying to eake a half gallon out of a long climb or leaving the mixture knob unscrewed all the way through your decent (only to forget to enrich when you suddenly need power, then dotonate).

 

80-100 ROP and 1300 EGTS get my vote.

 

 

If you forget to enrich the mixture when you suddenly need power, you wont run into detonation. It is leaner than the LOP cruise power setting you were using, and if you firewall it, you won't make full power for the MP and RPM. 

 

I always set the mixture ROP (usually 1/2" from full rich) at the same time as lowering the gear for landing. If you forget, all three knobs forward for a go-around anyways.

[John Pleisse]

Perhaps detonation is the wrong word......forget to enrich and add power....and the engine will make a loud pop. Simplified?

[carusoam]

I think they meant sound of silence... Not pop. Going from LOP to extreme LOP after descent... -a-

[201er]

Hey you guys who are voting, can you provide some explanation as to why you do what you do? For example, why is 80-100F ROP the most widely used ROP cruise mixture? Why are the majority of you climbing to cruise at full rich mixture? Unless you like to cruise low.

[jetdriven]

Perhaps detonation is the wrong word......forget to enrich and add power....and the engine will make a loud pop. Simplified?

In 250 hours of M20J LOP I havent experineced that. But I havent descended from 12K to sea level without enriching the mixture a slight bit either.

[201er]

In 250 hours of M20J LOP I havent experineced that. But I havent descended from 12K to sea level without enriching the mixture a slight bit either.

How is the engine capable of running soooo lean? You're already lean of peak at a high altitude and thin air. How is there enough gas in the mixture to let it work when you get low? Or is it because you are continuing to maintain that high altitude manifold pressure during the descent using the throttle? If the throttle is used to maintain the same MP as WOP at high altitude, mixture never changes right?

[DaV8or]

I can't operate LOP at this time, so I've gone ROP. I go 125 over 65% and if under 65% I go with either 80, or peak depending on whether I want speed, or economy. A little arbitrary numbers based on reading I know, but at some point you have to just get on with flying your plane and enjoying it.

[jetdriven]

How is the engine capable of running soooo lean? You're already lean of peak at a high altitude and thin air. How is there enough gas in the mixture to let it work when you get low? Or is it because you are continuing to maintain that high altitude manifold pressure during the descent using the throttle? If the throttle is used to maintain the same MP as WOP at high altitude, mixture never changes right?

 

Moving the throttle will change the mixture on an RSA-5 fuel injection system. Bringing the throttle off the forward stop will lean it out, as there is a circuit for full throttle enrichment that you are turning off.  I think in the middle range it wont change the micture very much of it was already set in that range.

 

FWIW in two years, the throttle has never left the forward stop until 2 miles out from landing, and once on a very long and max range X/C.   Thats 200 hours worth.  If someone asked me what it does  at "24 square", I can't answer them.

[sleepingsquirrel]

 

Of course not , as I have explaned in the past ,I just fiddle with the knobs until it flys right. I do cruise at lower altitudes unless going somewhere.

[takair]

80-100........it goes fastest that way.

[aaronk25]

Wow....I can't believe with the cost of gas that people arnt running as lean as possible, regardless of lop or rop.

Once in cruise just leave throttle forward and lean until the in set of roughness he enriches just enough to smooth the motor out if you don't have a engine monitor.

I can't believe people don't get this!!! But waste gas, carbon up your motor and dilute your oil with blow by if you want I won't and will be happy with a engine that goes 1.5-2 past overhaul.

[takair]

I get it and yet I still prefer to go fast, that is why I bought a Mooney. Some people buy them purely for efficiency. Non aviators would argue you should drive to save fuel. Others buy twins and burn 3x more. Do whatever you please. This is why I hate commenting on the LOP vs ROP discussions. Plenty of engines running ROP go well beyond TBO. I have yet to see data on the number of LOP 360s going beyond TBO, have you?

[aaronk25]

Lets specify a bit how many run at high power setting rop and have all the cylinder make it to tbo time? In a m20j rop at 75% is 400 cht or higher temps.

75% at lop 10ish gph is 380 or less. No statistics but if the problems that have plagued cylinders especially the heads with crack resulting from heat and valves that fail from unburnt exhaust Byproducts I the stems wearing out valve guides its easy to see rop is hard in cylinders.

[jetdriven]

Its the heat primarily, and the deposits secondarily, I think. I will occasionally run 20 ROP at high altitude CHT permitting if I need the speed.

[201er]

Wow....I can't believe with the cost of gas that people arnt running as lean as possible, regardless of lop or rop.

Once in cruise just leave throttle forward and lean until the in set of roughness he enriches just enough to smooth the motor out if you don't have a engine monitor.

 

But the problem is that this is about the hottest place you can be running things. I don't think anyone denies they want to go fast. Not everyone wants to save gas but many of us do. If 0-30ROP was a safe/cool place to run, I think most of us would. But in reality it gets way too hot, esp at the higher power settings that we want to cruise at. So realistically it only leaves the choice of 100ROP or 20LOP to fly over 65% power.

[aaronk25]

I too will run slightly rop at 15k if I have a nice tail wind and I agree heat is primary concern to get every bit of available power because as you know fuel flow is low at altitude and if I remember right it takes 7.4 gallons or less to stay peak or leaner at fl15.

[takair]

400+ CHT ROP on a 201, perhaps it's not apples to apples between the 201s and vintage models.  I guess the big guppy mouth inlet had some benefit on the earlier models.  My CHTs at 75 % and ROP are right around 300, sometimes not even.  In a hot Savannah climb I might break 330 on the hottest cylinder.  I do agree, heat is the enemy and you have to manage that, however you can.

[aaronk25]

201er,

Leaning to the onset of roughness should actually be lean of peak or peak and cht should also be lower than running 50-100 rich. I don't run 20rop down low as its always between peak - 50lop but way up high around 15k it needs the extra gas so I run slightly rop.

If I recall from my archer days that wot or just off of wot and lean to roughness is lop.

[Hank]

Those of us without Fuel Injection have a hard time running LOP. My engine stumbles and runs rough at or just lean of peak. According to my OM, max economy is 25ROP, and max power/speed is 100ROP, so I generally compromise and run 50ROP [just like the nice folks I bought her from used to do].

 

I've experimented a little bit trying to run LOP, but the engine just doesn't like it. I generally pull the throttle back just enough to move the MP needle, lean to peak/rough and enrichen 50º; regardless of altitude, I verify that I'm below 75%, and like to cruise around 70% when able. Pulling back the throttle creates turbulent flow in the carb, and should improve fuel atomization and mixing for a more uniform distribution to the cylinders--GAMI doesn't make a "balanced carburetor."

 

Running LOP with a carb is sometimes possible. It generally involves reducing throttle to get out of the auto-enrichment circuit, leaning, adding some degree of carb heat [found by experimenting, there are no markings on the carb heat lever but I do have the optional carb temp gage, interestingly enough marked in ºC], and then leaning again.

 

For instance, in my C, at 10,000 msl, full throttle is 20.2", so I'll generally pull her back to 20" which is significant travel of the throttle lever. At 2500, this gives 70.1% [vs. 71.0% WOT]; at 2600, this is 72.0% [vs. 72.9% WOT] and the throttle reduction costs 1 mph at both RPM [though 2500 RPM saves 0.3 gph vs. 2600 at the cost of 2 mph].

[Greg_D]

400+ CHT ROP on a 201, perhaps it's not apples to apples between the 201s and vintage models.  I guess the big guppy mouth inlet had some benefit on the earlier models.  My CHTs at 75 % and ROP are right around 300, sometimes not even.  In a hot Savannah climb I might break 330 on the hottest cylinder.  I do agree, heat is the enemy and you have to manage that, however you can.

 

The large opening on the older models actually provides less cooling, not more.  You're quoting 300 deg CHTs while running ROP at 75%.  Is that with a multi-probe CHT gauge or with the single factory gauge?  If it's the latter, I suspect you have an instrument error.