IO 360 M1B FF at T/O full power

[N743RV]

My RV-7A has a Mattituck IO 360 M1B with a blended foil C/S Hartzell and Precision FI with horizontal induction. I have a "red cube" connected to an AFS 3500. The indicated fuel burn and the fill-up values always match well within +/-0.5 gallons. I fly from KLVK with a field elevation of 400 feet MSL. Here are some typical fuel flow values at wide open throttle.

OAT ?C Fuel Flow RPM
2 15.1 2675
14 15.2 2675
14 15.6 2680
18 15.0 2670
25 15.1 2680

[Airhead]

I wanted to add my test test results to this post to help future researchers.

In my earlier posts, I mentioned that Precision Airmotive (supplier of the FI system) had told me that the definitive test was "at full power setting lean from full rich to peak EGT. The EGT should rise between 100 - 200 degrees". Not wanting to do that during takeoff, I leveled off at 2000' pushed all knobs forward and waited until EGT (hottest cyl) had stabilized at about 1330. Then slowly pulled mixture to peak EGT. Drum roll....EGT peaked at 1480, or about 150 degree rise.

My conclusion is that fuel flows of 15 to 16 GPH (even low end of that range) during full power application appear to be in line with overall experience by others as posted herein, and does not constitute an "abnormally low" flow rate. I will continue to fly as is.

This may only apply to Lyc IO 360 M1B CS Prop, Precision FI.

[RV10inOz]

Bob,

What was the OAT (or the DA) and at 2000' you had?

As a comparison at 2000' I would see and expect other similar CR engines to have EGT's at 1250-1300, and in my case 25.2GPH, which adjusted for your HP is 17 and a bit.

Now the original posts you made complained of decreasing fuel flow and a corresponding much higher CHT in the climb. None of this has magically corrected itself I gather.

So the facts are you have less fuel, higher than I would expect EGT, and higher than I would expect CHT.

Of course we could be looking at just one cylinder being the worst and the rest being all good, in which case an induction leak or two would do it.

Have you managed to upload a data file yet?

Something is still sounding fishy and I would hate for you to fall for a small dose of "Confirmation bias" which is not out of the question.

By the way, it may not be a huge difference but the DeltaT 100-200 would reduce also as the power (altitude) is reduced. Again I typically get 200dF Delta at low level.

[Airhead]

OAT during test was 59 F, DA -2500'. I was assigned 2000 by ATC shortly after TO. Low level turbulence (wife uncomfortable) kept me from repeating test that day.

EGT's are typically 1225 to 1325 (peak). I do not use full power except for a couple of minutes during TO. CHT's and EGT's are tightly bunched. I removed cowling just before test and checked for possible intake air leaks and even removed snorkel to examine FI for any visual abnormalities. Adjusted mixture cable to make sure that was not problem.

To reduce my CHT's during TO, I modified my procedure to slightly increase airspeeds. Examining my data (on savvyanalysis.com), I saw that the CHT's were very responsive to IAS. Modified TO procedure yields CHT's peaking at about 420 for a minute or so, then dropping back below 380. This is well within Lycoming's recommendations (and other clone specs that I have reviewed), so while lower might be better, I do not believe my engine is being harmed, however, I will continue to keep an eye on this as weather warms up again.

Keep in mind that virtually all the other posts claiming this exact setup have experienced similar FF. It may be that the Lycoming / PA design is intended to yield this FF (PA says they get their flow specs from Lyc.). It seems to me that as long as the parameters stay within specs, the slightly leaner mixture might result in a cleaner upper cylinder and spark plugs. I removed mine after 50+ hours, and they looked like new. I also lean aggressively during ground ops.

[RONSIM]

I have observed my -6A on the last few takeoffs:

O360A1A Parallel Valve, 180HP with added Bendix FI and Bendix mags and Hartzell CS

Only 80ft MSL, full rich, 2700rpm ----- 17.2 to 17.4gph

Ron

[RV10inOz]

Ron, That is exactly what I mean


Bob, my APS partner down here runs one of the top two or three engine shops in Australia, he is the reason George Braly I think even entertained my getting involved. His shop also does fuel servo calibrations, (they can be adjusted by shimming the internals) and he talks in Pounds per Hour, but when I converted the numbers he agrees that these lower flows are are just not right.

You say EGT tightly bunched? Yet 1225-1320?

You say you looked for leaks, but what exactly were you looking for? They can be very hard to spot in many cases and usually the best or only way is doing a GAMI lean test at 7500 & 2500 using the same MP&RPM. Then they show up.

Modified TP procedure So applying a band-aid approach is the right way to deal with a sub-optimal set up? That is like turning up the stereo in your car so you can't hear the diff about to fall apart. Sorry if that sounds harsh, but this is the message you have portrayed. TO should be WOT/2700 and lean to a target EGT.

IAS, what were you climbing at Vs now? Just out of interest if you know your best glide speed, add about 30-33% to that, I am guessing this will be about 110knots and that will be the optimum efficiency climb speed.

I do not accept the claim that virtually all the other posts claiming the same proves yours or theirs is optimal. The laws of physics apply equally to all men/women and machines. Be it a IO320/360/540. Lets look at a few;
Lars 17.2-17.7
Bob Redman, about the same as his data needed adjusting for DA.
Neal@F14's mate with a calculation adjustment about the same range
Smilin Jack adjusted for DA = 17.25 approx
CFI1513840 adjusted for DA and CR = 17.9+

When these are taken not as face value and corrected to the same ISA benchmark, you start to see a trend. The one anomaly is Richard Connell and I might just phone him up and quiz him. I bet there is an answer to his data too.

One last time, send me some data files or links to your Savvy data if you would like to have me look at them. I would hate to think you incorrectly apply confirmation bias. Of course in the next five years you will not crater an engine from it, but if you did 200-250 hours a year like I do and want a good engine to overhaul down the road, you might want to think about it some more.

[Airhead]

David,

Thank you for your interest and concern. I originated this post to get information, determine if I really had a problem, and ultimately make an informed and thoughtful resolution. Hopefully, it may also serve to benefit others with similar concerns. I have not decided never to take corrective measures (sorry about the double negative), but based on info herein (and other outside sources) I am not convinced of the immediacy, nor that ultimately, FF must be increased (yet). I will send you a PM with my savvy link.

Clarification/correction from previous post; Typical EGT range between the 4 cylinders is only about 20 to 30 degrees. I incorrectly used 1225 to 1325 (meaning from rich to lean (@ peak EGT) which should have been 1325 to 1425. That is, when I usually start leaning at 3,000' (or above) the EGT's are low 1300's going to peak at something just over 1400. When at low altitudes, mid power settings, EGT's in mid 1200's.

You mention leaks that I may not have discovered. Can you tell me where air intake leaks might be other than intake manifold connection to engine and FI base mounting. Also, please direct me to info on the "GAMI lean test" to which you refer.

When I refer to similar FF, I am only referring to others with my exact setup of which there should be many given that it is the "stock" setup ordered from Van's (shipped direct from Lyc.).

How about some thoughts regarding a graph in the Lycoming Handbook which comes the closest to the target subject. Figure 3-39. This graph shows a "minimum allowable fuel flow" vs power output for an IO 360 180 hp. According to this graph, the min. fuel flow at 100 percent power is 14.8 gph.

At this point one might ask ; What say Lycoming in response to this rather simple question. After all they did design and build my engine for a rather handsome sum. I posed the same question to them..................silence. Same answer as the previous questions I asked. My next engine will be built by someone that gives a ___about us small fish. They might ultimately notice....we do school.

[RV10inOz]

Bob, I have just been through several of the flights in your Savvy uploads, and it appears to me that all the takeoff EGT values from near sea level are in the range of 1330-1370. For an 8.5:1 CR engine that is too high. We know they should be in the 1250-1300 range.

The fuel flow (14.7) you have indicated at this time is supporting the above data.

The CHT's which result are ranging from 420-440

The IAS which I assume is Knots is 110 +/- a bit.

DA= approx 850-1000' at the point climb out commencing

All things being equal, does this sound like there is enough takeoff fuel flow to you?

The good news is the GAMI spread is VERY good indeed, so I doubt you will do any better with anything else. GAMI will not want to take your money on that data. They would say go away and be happy!

Just been talking to Andrew Denyer, and he said that Lycoming do not specify in their manuals a flow rate, however the RSA calibration data is something like 120PPH at a specific airflow rate. This rate is a bit above the CFM an engine will consume, however when he tests the engine later, a typical minimum flow will be 98PPH and maybe a bit more depending on the day.

The data in the savvy graphs shows about 87PPH, so again from just talking to the leading engine builder in Australia, I get another confirmation that the data is not lying.

Conclusion, your fuel flow is too low and the FCU needs a visit to a good FCU overhaul shop and given a calibration to something like 18% more flow.

All the best.

[Richard Connell]

Ill save a data file next time I'm at the hangar.

I suspect that when adjusted for the generally warm conditions in which I fly, the FF will be higher than I first estimated.
In 500 odd hrs I've never seen CHT > 400F or OT > 200F and thats with plenty of 40C+ OAT days so I'm pretty comfortable with the temps. (I have a SW 8406R Oil cooler)

I dug up the break in data from Aero-Sport.
48F / 25.63mmHg / 16.8 gph / 389 hottest CHT / 1220 hottest EGT / oil 179.

cheers

[Walt]

As a data point I just went down this road with a Glasair II, Superior IO360/CS and silverhawk FI. Customer complained of high CHT during climb with associated higher than normal EGT's (1300 + T/O), FF in 14 GPH range, airplane had this issue since new.

The shop that checked the servo said it looked like it was flowed for a 320, after calibration customer can now do unrestricted climb, CHT down by 50 deg, FF in the 17 GPH range, EGT's in the low 1200's.