Optimizing 201 engine performance

[carusoam]

Gami is in the business to sell services and balanced fuel injectors.

They hand You the tools to make your own judgement.

Use your current set-up, measure your own gami spread.  Then decide on your next steps...

A really good gami spread has them all peak in in about 0.1 - 0.2 gph of each other.

If it gets outside of 0.5 gph, improvements can be made...

Some engines come naturally well balanced...

Some have a dirty FI and can use some cleaning...

The gami spread test is a great way to see something not quite right with one of your FI...

A smooth running engine is going to have nicely balanced FIs to go with nicely balanced air flow into the cylinders...

PP thoughts only,

-a-

[Bug Smasher]

Guys, thanks for all the great info! I'll find out my GAMI spread on my way to Sedona on Thursday and report back.

[laytonl]

Chris,

The guys have already given you some good suggestions, especially to read John Deakins articles on the redbox/Redfin issue.

Personally, I do not ever let my CHTs exceed 380F. I only fly ROP and consistently see 160 kts at 8,000' flying WOT, 2500 RPM with FFs between 11-12 GPH.  My CHT are generally in the 360F range and EGTs at 1,400F.

Lee

[mccdeuce]

1 hour ago, laytonl said:

Chris,

The guys have already given you some good suggestions, especially to read John Deakins articles on the redbox/Redfin issue.

Personally, I do not ever let my CHTs exceed 380F. I only fly ROP and consistently see 160 kts at 8,000' flying WOT, 2500 RPM with FFs between 11-12 GPH.  My CHT are generally in the 360F range and EGTs at 1,400F.

Lee

I also have been flying ROP at 8000' wot/2500 ff:11gph but I only see 150ktas. I wonder if I'm slow or if that really is the difference between a 1978 and a 1992?!

[bradp]

Many variables play into KTAS: engine calculated HP / FF performance is just one of them 

- OAT

- engine alignment 

- engine ignition performance

- airspeed indicator 

- rigging is a big one 

- drag (TKS, antennas, fairings or lack thereof, gear doors hangining in the breeze, etc)

 

I'm sure there are dozens more...

[jaylw314]

One point to add so far is that ROP, your power is predominantly determined by the engine's airflow (air intake per sec).  MAP/MAP(max) x RPM/RPM(max) is a direct measure of this, which is why you can make a power chart out of just those to numbers.  Mixture (and fuel flow) only affects your power by a few percentage points, because it is the amount of air that limits the power produced.  At 10k ft, WOT should give you a MAP of about 20.5", and at 2500 RPM, my 1986 M20J POH lists that as 60% power.  If you do the math, (20.5/29.92) x (2500/2700) = 63%.  Actual power is always a little lower since there is some friction to airflow in the intake system.  The POH lists fuel flow as 10.2 as best power, 8.7 at best economy (25 degF ROP).

LOP, the opposite occurs--your power is only determined by fuel flow.  The MAP and RPM do not appreciably alter your power produced LOP, because there is already excess air; it is the fuel that limits the power produced, or Power = fuel flow x constant.  The constant is essentially a measure of the engine's practical efficiency, which in turn is largely related to he compression ratio (which is constant for all IO-360's).  I've not been able to dig up any numbers for the IO-360, which has a compression ratio of 8.7:1, but engines with 8.5:1 put out 13.9 hp per GPH LOP.  That suggests the IO-360 might be about 14.2 hp per GPH, so your fuel flow at 120 hp (60%) LOP should be about 8.5 GPH, which is consistent with others have posted here.  Getting above 9 GPH LOP is a real challenge at any altitude higher than 7-8k ft.

OK, one other point--Lycoming officially says below 75% power you can lean to anything without risking damage.  So officially, Lycoming says above 5000 ft at 2500 RPM, you can lean to anything.  I'm not saying those settings are smart, but at 10k ft and 2500 RPM, you should be fine leaning to your heart's content without worrying

[Bob_Belville]

'66E, IO360A1A. The GAMI folks told me several years ago that my engine probably would not benefit from their balanced injectors. They gave me the gami spread procedure and they were right - with stock injectors spread is usually about 0.2, never over 0.5 GPH.

Another good check to run is the LOP mag check which Savvy recommends along with their LOP spread procedure. Visit the Savvy (Mike Busch) site, you might want to sign up for their paid service, $150(?) per year. I just renewed. Paul Kortopates (on MS as well) is a very knowledgeable resource.   

[laytonl]

On 5/30/2017 at 10:28 PM, mccdeuce said:

I also have been flying ROP at 8000' wot/2500 ff:11gph but I only see 150ktas. I wonder if I'm slow or if that really is the difference between a 1978 and a 1992?!

I previously had a '78 J and it was a little slower, around 156 kts.  This speed and the '92 J speeds were determined from several triangular course runs so I think they are valid numbers.  Rigging,timing, etc make a big difference. Lee

 

 

 

 

[Bob - S50]

Chris,

I have a '78 J.  I always run just a little LOP (10 - 40F).  I can plan on:

9500' - 10,500', WOT, 2500 RPM, 8.7 GPH, 150 KTAS

6500' - 7500', WOT, 2500 RPM, 9.2 GPH, 156 KTAS

In the summer, above 10,000' my #3 CHT approaches 400F.  If it does, I lean a little further to keep it below 400F.

Bob

[ArtVandelay]

Chris,

I have a '78 J.  I always run just a little LOP (10 - 40F).  I can plan on:

9500' - 10,500', WOT, 2500 RPM, 8.7 GPH, 150 KTAS

6500' - 7500', WOT, 2500 RPM, 9.2 GPH, 156 KTAS

In the summer, above 10,000' my #3 CHT approaches 400F.  If it does, I lean a little further to keep it below 400F.

Bob

By comparison my 78J CHTs highest is CHT4 because my CHT3 is a ring sensor, about 30-40 LOP my highest is 375°,

10000'-11000' WOT, 2300 RPM, 7.5 GPH, 145KTAS

I sacrifice the speed for better MPG, if you run a little hot you might try a lower RPM.

[Bob - S50]

13 hours ago, teejayevans said:

By comparison my 78J CHTs highest is CHT4 because my CHT3 is a ring sensor, about 30-40 LOP my highest is 375°,

10000'-11000' WOT, 2300 RPM, 7.5 GPH, 145KTAS

I sacrifice the speed for better MPG, if you run a little hot you might try a lower RPM.

Actually, I have a couple choices.  Anything that reduces power will help.  That might be the same mixture and a lower RPM or MP.  Or it could be the same RPM and MP with a leaner mixture.  Either of those cases will result in a lower speed.

If I really want to keep my speed up and still cool the the CHT, I'm guessing I could increase the RPM.  That would result in higher power and higher CHT.  However, if I then leaned to the original FF (further LOP), I would be back to (approximately) the same power and speed.  However, the higher RPM will move peak pressure further from TDC and should (at least a little) reduce peak pressure and CHT.  Also, the leaner (LOP) mixture to get back to original FF will result in a slower burn which will also push peak pressure further past TDC and also (at least a little) reduce peak pressure and CHT.

Standing by for corrections from the GAMI school attendees.

[Bartman]

Today I flew home from work at 7,500 ft at 2,350 RPM and 23 inches MP.   Instead of leaning slowly and worrying about every tweak of the mixture knob I just did the big mixture pull and set her at 8.6gph and felt the expected slight loss of power as she went LOP. That calculates to be 64% power.  I figure I was probably about 15 LOP and although it was bumpy and this decreases speed I was seeing 145 KTAS.  Before leaning I calculated 150 KTAS in less than smooth air.  

Best I ever saw was just me, smooth air, 8,500 ft, no baggage, and about 15 gal fuel which resulted 155 KTAS while ROP, and then 150 KTAS while LOP.

[Riddle78]

Ok everyone,

After reading through all of your responses and John Deakin's article I flew roughly an hour today to test the waters again. The conditions weren't super ideal (somewhat bumpy and OAT of 70F at 8,500 ft) but I did get a good initial data point. The plane was pretty empty aside from my pink body and full tanks.

WOT with 2550 RPM and, after doing the somewhat unsettling "big mixture pull", got me on average 135 KTAS and 9.4 GPH. I was able to keep the hottest CHT around 365 and an EGT of 1440ish which so far seems to produce the best result. Not the 145-150 KTAS I'm used to but I think I'll keep tweaking in better conditions over the foreseeable future. Regardless, it's pretty cool to see what LOP can deliver.

As alway I welcome your feedback, perspective and critiques.

Chris

[carusoam]

How deep LOP did you go?  (°F)

Peak, 10°, 20°, 30°...

Deeper LOP is cleaner and cooler along with slower...

At high enough altitude to avoid the red box, peak seems the way to go...

A few °F to make sure all the fuel gets converted.

Ordinary PP thoughts, with some quirky engineer efficiency idea mixed in...

Best regards,

-a-

[jaylw314]

That still seems pretty high FF for 135 KTAS.  If you're LOP, you prettty much have to be getting 145-150 KTAS wtih 9.4 GPH no matter what combination of altitude, throttle and RPM you are at

3 hours ago, Riddle78 said:

Ok everyone,

After reading through all of your responses and John Deakin's article I flew roughly an hour today to test the waters again. The conditions weren't super ideal (somewhat bumpy and OAT of 70F at 8,500 ft) but I did get a good initial data point. The plane was pretty empty aside from my pink body and full tanks.

WOT with 2550 RPM and, after doing the somewhat unsettling "big mixture pull", got me on average 135 KTAS and 9.4 GPH. I was able to keep the hottest CHT around 365 and an EGT of 1440ish which so far seems to produce the best result. Not the 145-150 KTAS I'm used to but I think I'll keep tweaking in better conditions over the foreseeable future. Regardless, it's pretty cool to see what LOP can deliver.

As alway I welcome your feedback, perspective and critiques.

Chris

Wait, I'm looking at your panel and not sure what airspeed is KTAS.  You've got

[wpbarnar]

What position are you flaps in?   The flap toggle switch in your photo looks like it is in the take off position.        

Bill

[Riddle78]

Bill,

That's how the switch in mine appears in the neutral position from the camera angle. I remember checking them during climb out...that'd be pretty embarrassing if they were down.  

TAS is displayed in the lower left corner of the ADI just above GS.

I'll do some more flying today and refine my data, particularly where I was xx degrees LOP and MP. I'll get there eventually! More to follow....

Chris

Edited June 4, 2017 by Riddle78

[Bob - S50]

I agree.  135 KTAS is way too slow for 9.4 GPH.  I would expect 135 on maybe 7.4 GPH.  Are you sure your fuel flow indicator is accurate?  Have you had your pitot system checked?  Are you sure all the gear doors are closing?  Are you running with cowl flaps open?  Either you have some type of indication error (fuel flow or airspeed) or you have some extra drag someplace (gear, flaps, cowl flaps, misrigged).

And at 8500', 2550 RPM, I would think that 9.4 GPH would still be ROP.  When I'm at 6500', 2500 RPM, WOT, and barely LOP, I'm at about 9.2 GPH and getting 157 KTAS.  When I'm at 9500', 2500 RPM, and barely LOP I'm at 8.7 GPH.

What does your Fuel Flow say at peak EGT?  At 8500', your engine is not going to blow up as you lean slowly through peak.  At that altitude you can't even make 75% power because of the lack of oxygen.  Watch your EGT and start leaning.  It will go up and eventually start back down.  When it JUST starts down, what is your fuel flow?

Something is wrong.  Either that or you have the worlds slowest J and I hope that's not the case.

[Riddle78]

Bob,

I think it's just my crap technique. It just recently went through an annual. The gear doors were flush with the aircraft skin and no problems were noted with the pitot static system. Motor had good compressions. Cowl flaps were closed during cruise on the last flight. I need to get over the thought of blowing up the motor and just calmly/deliberately take it through peak and record all numbers along the way. 

Chris

Edited June 4, 2017 by Riddle78

[bonal]

Just a comment on speed flying my C in a very relaxed 2450 at 20mp 6500 ft gives me 135 knots true so something is definitely not right in your situation for a J. There has to be something amiss with your instrumentation 

[jetdriven]

2 hours ago, Riddle78 said:

Bob,

I think it's just my crap technique. It just recently went through an annual. The gear doors were flush with the aircraft skin and no problems were noted with the pitot static system. Motor had good compressions. Cowl flaps were closed during cruise on the last flight. I need to get over the thought of blowing up the motor and just calmly/deliberately take it through peak and record all numbers along the way. 

Chris

At 7000 feet there is no mixture setting that can harm the engine, except if it runs so hot to exceed redline CHT. Even 4000' is too high of an altitude for the red box. 

Edited June 4, 2017 by jetdriven

[jaylw314]

1 hour ago, Riddle78 said:

Bob,

I think it's just my crap technique. It just recently went through an annual. The gear doors were flush with the aircraft skin and no problems were noted with the pitot static system. Motor had good compressions. Cowl flaps were closed during cruise on the last flight. I need to get over the thought of blowing up the motor and just calmly/deliberately take it through peak and record all numbers along the way. 

Chris

I just can't imagine it is a technique problem, since ROP at that MAP and RPM,  that FF should be near best power, and those settings should get you even faster.  What does your POH say at those settings?  

Ifyou are slow because you are actually LOP, then you may have a FF instrument problem, although it's hard to imagine that being off by more than 10%--check your FF calibration setting and note your takeoff FF should be between 17-19.  

Couldyour pitot static be wonky?  Check your IAS against your GPS speed.  

Is your RPM gauge accurate?  Again, this would not be an issue LOP, but if you are ROP, your power settings might be lower than expected.

I have a hard time imagining that a rigging problem could account for 10-15 knots alone, it would have to be pretty bad.  Anyone lose that much speed from rigging before?

Edited June 4, 2017 by jaylw314

[cnoe]

On 5/31/2017 at 0:44 AM, jaylw314 said:

 I've not been able to dig up any numbers for the IO-360, which has a compression ratio of 8.7:1, but engines with 8.5:1 put out 13.9 hp per GPH LOP.

I believe the constant most commonly referenced for computing HP in a normally-aspirated engine (with a CR of 8.5:1) is "14.9".*

For the IO360s with a CR of 8.7:1 the constant "14.95" seems to be more prevalent.

* Ref. John Deakin - https://www.avweb.com/news/pelican/pelicans_perch_84_mixture_cht_194816-1.html

On 5/30/2017 at 9:28 PM, mccdeuce said:

I also have been flying ROP at 8000' wot/2500 ff:11gph but I only see 150ktas. I wonder if I'm slow or if that really is the difference between a 1978 and a 1992?!

Older Js are indeed slower than newer ones, but not by that much. Mine is a stock 1978 model that I consider to be middle-of-the-pack in terms of speed. When moderately loaded running LOP I routinely see right at 150 KTAS w/ fuel flow of ~9 gph. 

My last speed check running 80F. ROP (GPS 3-direction confirmed) showed 163 KTAS at 75% power and 11.1 gph FF.

Jetdriven's '77 J is a few knots faster than mine, and @Mike_Elliott routinely flies a J (N984VW) that puts us all to shame.

14 hours ago, Riddle78 said:

WOT with 2550 RPM and, after doing the somewhat unsettling "big mixture pull", got me on average 135 KTAS and 9.4 GPH

As others have said, something's not right with those numbers. 

50 minutes ago, jaylw314 said:

I have a hard time imagining that a rigging problem could account for 10-15 knots alone, it would have to be pretty bad.  Anyone lose that much speed from rigging before?

Good question. I'd start by looking out the window to see how the ailerons, flaps, and elevators are positioned in level flight. 

[Bartman]

Something is not right. My EDM 700 came set up from the factory with the K factor set correctly.  If you did the BMP and felt her go LOP with that slight but noticeable loss of power and your fuel flow is 9.4 then you have a fuel flow indication problem.  If you were truly at 9.4 gph then you were not LOP. You cannot produce enough power at that altitude to hurt the engine. If the OAT was 70 degrees then the density altitude was no doubt over 10,000 feet and the red box does not exist for your normally aspirated engine at that altitude. 

Since you are new to LOP ops I will say this......  Make sure you have the EDM 700 set up for LOP, not ROP.  

[Riddle78]

Welp, today was kind of a wash. It got very bumpy and it was hard to keep the plane stable and get good readings. Regardless, I deliberately pulled mixture back and saw the EGT rise to 1504 before it started to fall off again. I continued pulling until the engine started feeling rough, then bumped it forward a hair. This had me at 22" MP, 2550 RPM, WOT, 1460 EGT and 365 CHT. Result: 145 KTAS so a slight improvement. What's interesting is that FF told me I was at roughly 10 GPH, so it definitely sounds like a few of you maybe on to something with that measurement being off. 

CHT is supposed to trend the same as EGT, correct? When I tried going ROP the CHT kept climbing above 380 and I was already above 12 GPH, but at that point I was getting bounced around quite a bit and decided to call it a day. I really appreciate everyone offering their insights. My next task is to check the EDM 700 and wait for a calm weather day to start doing some longer legs.