ROP vs LOP same speed comparison

[pinerunner]

While the ROP vs LOP debate seems mostly over, one complaint that always bugged me goes like this; "of course you use less fuel going LOP but you lose speed too so its a wash". This would be at a given manifold pressure and RPM. I fiddled around and got the following numbers at the same IAS of 135 KT at 4500 ASL level flight. That gives me exactly same power as close as I could get it. Voila. 

 

50 ROP 135 KT 4500 ASL 2500 RPM 23 in  Fuel flow 11.6 GPH

      CHTs 292 340 338 339

 

30 LOP 135 KT 4500 ASL 2500 RPM 25 in   Fuel flow 10.2 GPH

      CHTs 280 314 296 305

 

Using tables in the POH which assumed you leaned "properly" 2500 RPM 23 in should be about 75% power or 150 HP on my M20E. On the lean side fuel flow determines power and using the 14.9 HP per GPH gives 152 HP; that's all the validation I need. I could fine tune it with temperature corrections yada yada yada but I don't want to work that hard.

 

CHT's 30 degrees cooler with LOP at the same power setting which is NOT the same MP  LOP fuel saving better than 10%

 

#1 is my richest cylinder and #3 my leanest; saving for GAMI's

 

Dave

 

 

[Super Dave]

Nice write up, thanks for sharing. This is one of those things I keep meaning to do, but never get around to.

[Bob_Belville]

Are you comfortable running LOP @ 75%?

CHTs are very low for an E @ 75%, what was approx. OAT? Do you have a modified cowl?

[pinerunner]

Are you comfortable running LOP @ 75%?

CHTs are very low for an E @ 75%, what was approx. OAT? Do you have a modified cowl?

Given the CHT's I'm pretty comfortable there and would rather get 75% on the lean side than the rich side but I'd like to get GAMI injectors to be a little smoother. I only used 50 ROP to match up with the table in the POH, otherwise I do believe its not the best  place to be. The problem is finding peak at a higher setting. At the higher power I wanted to spend as little time as possible at peak and just took my leanest cylinder there briefly so I could report ROP and likewise with my richest for the LOP. In one of Busch's seminars he points out its not a good idea to spend much time at peak (right in the middle of the hot box or red box) setting up things up and recommends "the big pull" to get to the lean side. He also mentions using the fuel flow and it struck me, duh, once I know the setting I want that's the way to set it up quicker and avoid the red box entirely and that's what I usually do. I'm flabbergasted when folks talk of being cautious about LOP and so stop AT peak. The biggest reason I go lean is I want to minimize lead fouling of spark plugs and more importantly valve guides.

 

Dave

 

I have the original guppy mouth and an thinking about getting the lower cowl closure. I think the OAT was about 65 but didn't measure it.

[201er]

Going slower AND lop saves the most fuel. Lose 15 minutes on a 4 hour trip and you save $80. In other words it costs about $20/hour more to fly ROP for the last 5-15knots of speed.

[jetdriven]

Thats what I see, ~10% savings from ROP, and another 5% from flying a little slower.

[Rich]

I have a 2004 Ovation 2. When I fly LOP (which is almost always) I slow down ~10Kt. My fuel mileage improves by 19%.

[ncdmtb]

Does fylng LOP require GAMI? I have a 64 M20E and fly about 100F ROP. I watched the Mike Busch Webinar on leaning. After that I am almost tempted to fly LOP even w/o GAMI.

Is that a good or bad idea?

[201er]

That depends on how your engine does. Byron just spent woopdie money on gamis and his spread is just as bad as before them!

[ncdmtb]

So what would you recommend?

[pinerunner]

Does fylng LOP require GAMI? I have a 64 M20E and fly about 100F ROP. I watched the Mike Busch Webinar on leaning. After that I am almost tempted to fly LOP even w/o GAMI.

Is that a good or bad idea?

I don't have them yet but want them, basicly same plane as you. If you have the engine monitor with data dump capabilty and fuel flow then you can determine your GAMI spread. How to is in one of the Busch webinars found at the Savy Aviator website. Basicly you go slowly back and forth through peak at a fixed engine setting (I used 23 in 2500), then analyze the data on the ground. Watch the CHT's and make sure they don't start going high of course but mine didn't and certainly got nowhere near the higher 300's I see on take-off where I'm full rich. GAMI's not required but silky smooth engine engine ROP and LOP has got to be a good thing. I'd like to see comments on the difference GAMI's made for them and their experience in getting them.

[ncdmtb]

Thanks. I will check out the instructions and give that a try.

[pinerunner]

That depends on how your engine does. Byron just spent woopdie money on gamis and his spread is just as bad as before them!

How bad (or good) was it in the first place? Is he giving them a chance? They say they'll keep trying with you until its right.

[201er]

He said it was 0.8 before and about the same after. Gami only promises to get it down to 0.7 anyway. Mine has been running at around 0.3 since reman.

[pinerunner]

He said it was 0.8 before and about the same after. Gami only promises to get it down to 0.7 anyway. Mine has been running at around 0.3 since reman.

Yours must be like silk then, right? His sounds just a little better than mine is now. I wonder where the point of diminishing returns is.

[jetdriven]

How bad (or good) was it in the first place? Is he giving them a chance? They say they'll keep trying with you until its right.

At this point I suspect something in the flow divider. The #2 has always run quite richer than the other three, and GAMI's havent solved anything.

 

The situation sucks, a 0.8 GPH GAMI spread sucks, at 15 LOP on #4, the #2 cylinder is 90 LOP and it slows down. So you have a choice, cool CHTs, or losing ten knots. 

[mike_elliott]

Byron, have you swapped out the richest cyl. injector with the leanest yet, and if you have, did it change anything? if not, I suspect you are dead on about the flow divider.

[jetdriven]

Mike, I have spent too much time chasing this.  We swapped around injectors a few times, then swapped out a whole another set of injectors. Then swapped holes on those,  Then started swapping inserts. Then put in a set of GAMI's and changed that injector configuration three times. Next time I am investigating the flow divider.

 

John-Paul Townsend at GAMI thinks something is uneven about the delivery to the injectors, and the unusual behavior of my engine. He suggested putting small jars under the fuel lines going to the injectors and measuring the delivered fuel to them.

[Super Dave]

Does fylng LOP require GAMI? I have a 64 M20E and fly about 100F ROP. I watched the Mike Busch Webinar on leaning. After that I am almost tempted to fly LOP even w/o GAMI.

Is that a good or bad idea?

My IO360 runs fine LOP on stock injectors.

[Bob_Belville]

I can run LOP with my engine's stock injectors, IO360A1A. But my spread was only 0.2 as reported by JPI EDM 930. (I understand that's not necessarily what a proper GAMI test would show.)

[DaV8or]

My engine is stock and will run LOP up to about 15-20 degrees LOP. After that, it runs super crappy. So if you want to run deep into LOP like some of these guys at 50-60 degrees LOP, I think you probably need GAMIs. I'd like them, but I can not successfully run the GAMI lean test because my fuel flow reading is so erratic. They seem to require .1 accuracy on the fuel flow to do it and my fuel flow goes up and down all over the place at times by as much as .5. I have asked about this and even sent my data file to EI and they tell me they see nothing but normal. Nearly all mechanics will tell you not to even run LOP.

 

Bottom line is, setting up your engine to run smooth LOP can be a pain in the ass. You won't get much actual help, just advise.

[marks]

Before GAMIs my spread was .8 and after .2 or .3.  I usually fly 25 degrees LOP at 65% power and my J runs smooth as silk.