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Phase 1 engine issues...need advice

Zuldarin

Zuldarin

Well Known Member
Greetings all, I need some advice regarding some issues I am having with my IO-360. This week I flew my 9A for the first time and while I do have that RV grin the grin is not as big as I was hoping for.

The biggest issue that is concerning me is the engine does not develop full power. On takeoff I get smoother performance if I pull the throttle back about an inch with no noticeable decrease in engine output. Today I was running full power at about 2500' full rich and the engine just didn't seem to be putting full power out and my RPM was about 2300, . As a test I leaned the mixture about an inch and all of the sudden I was getting 2500 rpm and the engine was running much better. Manifold pressure remained pretty constant and of course fuel flow went from 16 to just over 14 gph. That probably makes sense to somebody on this forum but it doesn't me....yet.

Does anybody have an idea and a suggestion for remedy? I did email Don from airflow performance since its one of his fuel servo's (EX-5) and I'm sure he will have some advice as well.

Thanks for any help!

Darin
 
I assume you have a fixed pitch prop?

Sounds like it may be running too rich. Are you able to shut it down with the mixture control as per normal?

Have you verified that the mixture control arm has full travel to the stops?

Bevan
Not an engine tech, just my ideas since no one else has responded yet.
 
Bevan said:
I assume you have a fixed pitch prop?

Sounds like it may be running too rich. Are you able to shut it down with the mixture control as per normal?

Have you verified that the mixture control arm has full travel to the stops?

Bevan
Not an engine tech, just my ideas since no one else has responded yet.
Click to expand...

To add, make sure both the throttle arm and the mixture control arm have full travel. The mixture should be adjusted to give a 50 rpm rise beginning at rich idle, then sloooowly leaning the engine to peak rpm. More rise than that, and the engine is too rich, less rise and the engine is too lean.
 
Darin,

I do not experience any roughness, but as I roll onto the runway and move the mixture to full rich I can hear the engine kind of bog down and drop some RPMs. Since I am still in break in period I have not tried to do anything about that yet. I am at 4500' at my airport and I get the feeling full rich is a bit too rich for the altitude.

I see 16 GPH plus at full rich on my Aerosport IO-375. Like you I intend to talk to some injection system experts to determine if an adjustment is waranted. I probably just need to develop a leaning method that works for the altitude of my home airport, but that can wait till after break in.

Although the break in instructions for my engine say to run it full rich, if I do so my coolest cylinder will not get much above 300F CHT. I was cautioned by a tech rep at Aerosport that the CHTs need to be well above that temp to insure the rings will seat properly.

Since getting that information I have been leaning some but staying well rich of peak to keep CHTs between 350F and 400F.

Depending on your altitude, you may need to do some leaning also to get temps where you want and to make proper power.

OH, and congratulations on your first flight!

Randall in Sedona
 
Kyle Boatright said:
To add, make sure both the throttle arm and the mixture control arm have full travel. The mixture should be adjusted to give a 50 rpm rise beginning at rich idle, then sloooowly leaning the engine to peak rpm. More rise than that, and the engine is too rich, less rise and the engine is too lean.
Click to expand...

Is the 50 rpm rise thing for "at sea level"?. If so, how does one set the mixture when significantly above sea level?

Bevan
 
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Yes, I do have a fixed pitch prop. I was under the impression and probably misunderstanding that the mixture adjustment was only for idle and that the mixture at power was controlled by the mixture knob. Is that true? I am running at sea level for the most part and my temps are barely getting to 400 on my hottest cylinder.

Oh, and yes it does shut down nicely with the mixture control as normal.


Thanks for the quick responses!

Darin
 
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It does sound too rich. I don't know how you adjust the cruise mixture, but Don should be able to help with that. With a correct mixture setting at a full power takeoff, I usually see all EGT's in the 1,200 range. Much lower Han that and you are way too rich. Much higher than that and you are too lean. Those CHT's indicate too rich a mixture as well, so I assume your EGT's should indicate a rich mixture as well.

I usually lean the EGT's to the low 1,300's in the climb, while keeping the CHT's below 400.
 
Darin is this a fresh rebuild or overhauled engine?
Click to expand...

This engine has 4 new cylinders but the bottom end has a little over 350 hours since its last rebuild.

I usually lean the EGT's to the low 1,300's in the climb, while keeping the CHT's below 400.
Click to expand...

My EGT's are much hotter than yours. I see 1500's when leaning but I've been told that the number is not something you can compare between engines because of the variation in probe location.
 
Zuldarin said:
:cool:My EGT's are much hotter than yours. I see 1500's when leaning but I've been told that the number is not something you can compare between engines because of the variation in probe location.
Click to expand...

I didn't say that they only hit he low 1300's. I only lean them to that point. They would easily reach at least the mid to high 1400's if I kept leaning. What are your numbers at full power and full rich at takeoff?

Also, the general rule of thumb is about 0.9gph/10HP. So, at sea level and full power, if you have a 180HP IO-350, you should be seeing in the range of 16.2gph or so. Much more than that and you are too rich. Much lower and you are too lean. Of course, when you level off and pull back, that will drop considerably.
 
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What are your numbers at full power and full rich at takeoff?
Click to expand...

Ah, thanks for the clarification. I don't use full throttle to take off because of this issue but here are my numbers even at a less than full throttle takeoff.

MP-29.8
Fuel FLow-16.9
High CHT- Low 300's
High EGT- Low 1300's
RPM-2000-2300
 
If your redline is 2700, then basically, 30"MAP and 2700RPM would be 100% power, at which time you would expect to see roughly 16.2GPH. I would be worried about 16.9 at that point, but with only 2000-2300RPM you would be well below 100% power, so your fuel flow should be down into probably the low 15's or even 14's. I am sure someone on here can do actual calculations for RPM and MAP to get % power, but it sounds like you are running in the mid 80's on percent power. I think you are running too rich.

The EGT's don't jive with that necessarily, unless you are getting a little bit of igniting fuel in your exhaust, because it is so rich.

Try leaning a little at a time for takeoff and see how those numbers change. If you have a vernier, then try full rich on the mixture, then 2 full turns to the left. Takeoff and record numbers. Then next time 4 full turns to the left. Takeoff and record numbers. See if it is getting closer to where you want to be. Of course, the pitch of your prop will make a difference on your max RPM, so it's not a perfect system, but it will help. If you find that 4 turns lean gets you 29.8", 2550RPM and 15.9GPH, then you are probably getting in the range you want to be in. Give this information to Don at AFP and see what he recommends.

Just some ideas. Basically, this is how I would troubleshoot what you are seeing.
 
Thank you Jesse, Don just responded and he suggested I work on the mixture adjustment, and also look at the air inlet and ignition timing. I will give all of this a try today and hopefully report back good news. :)

Darin
 
Lean for best power.

Zuldarin said:
Ah, thanks for the clarification. I don't use full throttle to take off because of this issue but here are my numbers even at a less than full throttle takeoff.

MP-29.8
Fuel FLow-16.9
High CHT- Low 300's
High EGT- Low 1300's
RPM-2000-2300
Click to expand...

Hey Darin, These MAP #s suggest your airport must be close to sea level. Maybe you should do a runup on the pad and just lean it until you get max RPM and see what the EGT #s look like, and then go lean by 50f or so. This is similar to "lean for best power" on takeoff at say 5000' el.

Like others, everything says "too rich" to me. BTW if the excess fuel is not going out the exhaust you don't want to have it down the cyl walls and into the sump. Better check your oil level. It can happen.

HTH,
 
Thanks for the suggestion Jerry. What you suggest is pretty close to what I am doing now.

Today I was able to get the idle mixture properly adjusted so I went for a test flight. Still have to pull mixture almost an inch to get good RPM out of my engine at full throttle. Its certainly flyable and I seem to get full RPM when I lean it out like this even in normal cruise flight so maybe it isn't such a big deal but its not right and that bothers me.

Oil is not increasing, in fact its still going down very slowly as I would expect with new cylinders. On Don's advice I may visit the timing issue next.

Again, thanks for all the suggestions and if anything else comes to mind please let me know.

Darin
 
Here is a graph of my last takeoff after I adjusted the idle mixture. The Green arrow indicates when I reached full throttle and the bluearrow is where I pulled the mixture back almost an inch. You can clearly see the engine stumble and then RPM increase after I pulled the mixture back.

Last%2Bengine%2Blog.PNG
 
Something to keep in mind is that most times the throttle and mixture movement are not linear.

Moving a throttle back 1 inch or so may only be 1/4"-1/2" on the carb. Same for mixture. It's not uncommon to run full rich on take-off then after leveling off to reduce the mixture arm by 2/3 of it's travel before it makes a noticeable effect.

Running your engine as rich as it sounds can do damage. You can essentially wash the oil off the cylinder walls as someone above mentioned.

Checking your mixture before flying again would be the smart thing to do.
 
Sid,

Other than the red knob, is the fuel mixture field adjustable? I understand the idle mixture is but I thought the servo delivered fuel based on how much air it samples through the metering rods. I have a Precision but I'd imagine Airflow Performance is similar?

Would he have to send it in for this adjustment?

I'm just asking because I'm not sure myself.
 
Don's email response

For anybody that may be following this or having the same issue in the future, here is Don's latest response that I received via email. Don has been a huge help and very prompt. I'm glad my servo went through his shop (Airflow Performance), he knows his stuff!

The fuel control is calibrated based on a Lycoming spec. Looking at the data from your unit it?s set for a 180-260 HP engine. The parts list you have operates IO-360 to IO-540 engines, 180 to 260 HP. So fuel air ratio wise it shouldn?t be any different than the thousands of Lycoming engines that are using this same fuel servo. Of course you have a homebuilt so all bets are off. The engine operates on a correct fuel mixture (fuel air ratio) so let?s assume that when you lean the engine and you get the fuel air ratio correct because it?s running correctly the fuel flow is 14 GPH. That means the engine is not making 180 HP, probably around 150 to 155 realistically. Again the fuel control sets a fuel air ratio so two things can make the unit appear rich. Bad or incorrect ignition timing (weak spark will make you have to lean the mixture because the ignition cannot fire the correct mixture) or a poor induction air inlet is causing turbulence to the inlet of the fuel control and the fuel control cannot read the air flow correctly (which again will cause the fuel control to go rich). Intake leaks do not effect WOT running. Incorrect cam timing or poor valve lift (worn cam) will make poor power and high MAP at idle. The idle mixture setting will not affect WOT mixture.



Yes, on the surface the fuel curve (jet) can be leaned to cover the problem but if the problem gets resolved then the unit will be set to lean and the engine will get damaged for sure. It?s an experimental unit and we can do whatever the customer wants. Unfortunately since you have a Bendix fuel control, changing the main jet is not a field repair
Click to expand...
 
Possible cam timing problem

Darin several years ago I had a similar problem. This was on a fresh overhauled engine. The engine shop was no help and emphatically decreed the engine was as it should be and that I had a fuel delivery problem. After sending in the fuel injection for another overhaul (it had been overhauled not very long before the engine was sent in and was working perfectly before) and no change I finally called the Lycoming factory. They were very friendly and helpful and advised me to check the cam timing. Following their procedure the timing was off on my freshly overhauled engine!! I removed the accessory case cover and checked the marks on the gears. They were set correct. Strange!! I then reset the gears by one tooth and then checked the timing. it was now spot on using the procedure as detailed by the Lycoming tech. Ran the engine and all was well.

Apparently the gear was mis-marked from the factory. The engine shop assembled the engine according to the marks on the gears. The symptoms of being too rich and leaning for power were exactly as you described. I'm not alleging this is your problem, just what I experienced with a fresh engine. So if your engine has been apart or timing gears replaced or removed, it might be a solution to the problem. It's been 15 years since I performed the check, but I do recall that it was a simple and straight forward procedure and was done by removing the #1 cylinder valve cover and turning the engine thru while looking at the rocker arm movement vs. the flywheel timing marks.

Just sayin it can happen and drive you nuts trying to figure it out.
 
Wow, thats one I would not have guessed. Don did mention Cam timing as an issue but I didn't expect mismarked gears. I have an email into the original engine owner to see if the case had been split since its last overhaul. Thank you for the idea!

Darin

Jrskygod said:
Darin several years ago I had a similar problem. This was on a fresh overhauled engine. The engine shop was no help and emphatically decreed the engine was as it should be and that I had a fuel delivery problem. After sending in the fuel injection for another overhaul (it had been overhauled not very long before the engine was sent in and was working perfectly before) and no change I finally called the Lycoming factory. They were very friendly and helpful and advised me to check the cam timing. Following their procedure the timing was off on my freshly overhauled engine!! I removed the accessory case cover and checked the marks on the gears. They were set correct. Strange!! I then reset the gears by one tooth and then checked the timing. it was now spot on using the procedure as detailed by the Lycoming tech. Ran the engine and all was well.

Apparently the gear was mis-marked from the factory. The engine shop assembled the engine according to the marks on the gears. The symptoms of being too rich and leaning for power were exactly as you described. I'm not alleging this is your problem, just what I experienced with a fresh engine. So if your engine has been apart or timing gears replaced or removed, it might be a solution to the problem. It's been 15 years since I performed the check, but I do recall that it was a simple and straight forward procedure and was done by removing the #1 cylinder valve cover and turning the engine thru while looking at the rocker arm movement vs. the flywheel timing marks.

Just sayin it can happen and drive you nuts trying to figure it out.
Click to expand...
 
Maybe your prop is pitched to steep. If it was, it could cause this bog down you are seeing. If engine is putting out proper horsepower, with properly pitched prop, you should see 2700 rpm full throttle, straight and level at 2500 ASL. If you are not, prop is too steep or engine is weak. When you lean out you are only seeing 2500 rpm which means engine is weak or prop is too steep.
Weak engine could be the engine itself, cam timing, ignition timing etc. but could also be air inlet, air box, air filter issues and also possible exhaust restriction.
If prop is new or no history with this engine and aircraft, I would get the pitch checked and or adjusted if necessary.
Good Luck,
Mahlon
 
mahlon_r said:
Maybe your prop is pitched to steep. If it was, it could cause this bog down you are seeing. If engine is putting out proper horsepower, with properly pitched prop, you should see 2700 rpm full throttle, straight and level at 2500 ASL. If you are not, prop is too steep or engine is weak. When you lean out you are only seeing 2500 rpm which means engine is weak or prop is too steep.
Weak engine could be the engine itself, cam timing, ignition timing etc. but could also be air inlet, air box, air filter issues and also possible exhaust restriction.
If prop is new or no history with this engine and aircraft, I would get the pitch checked and or adjusted if necessary.
Good Luck,
Mahlon
Click to expand...

My prop is a fixed pitch Catto three blade so I'm pretty confident it is correct. As Don mentioned fuel flow is low for 180 HP so I'm pretty sure its engine related. I've got lots to look into when I get out to the hangar again.

Again, I appreciate the advice.

Darin
 
Darin---great thing about VAF is we have access to the guys that know their stuff. Don and Mahlon are experts in their fields! I'm sure you guys will get it figured out.
Tom
 
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