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Help troubleshooting a new engine.

UnPossible

Well Known Member
I have fired up the IO-540 on the RV-10 I am building, I am seeing some weird data, and am trying to figure out if I have a problem, or if it is likely related to being a new engine that is still breaking in.

This is a brand new Io-540 that my son and I built with assistance at AeroSport Power. Ignitions are 2X Surefly... pretty much a standard IO-540.

I have two cylinders (#3 and #5) whose EGTs are quite a bit higher than the other four. When I shut off one of the ignitions, the EGTs on those same two cylinders seem to spike higher than the other four as well.

I've checked the timing on both ignitions, and they are right on TDC for #1. I've checked the plugs on cylinders #3 and #5 and they look clean. I've pulled and cleaned the injectors on both cylinders and didn't see any sort of clogging or debris.

The engine starts easily, but seems to run a little rougher than I would expect (not data to back that up). Any suggestion I should be looking at, or is this most likely something that will smooth out once the engine is broken in?

Thanks,
Jason
 

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EGT numbers are relative and not absolute.

However, this might be due to fuel issue. If this is an injected engine, you can check the restrictors in your nozzle and see if they are partially clogged. Take them out and look inside you should see a nice and round hole, or swap them with another cylinder and see if the higher EGT moves to that cylinder. If not, for further investigation, you can check the fuel flow of each cylinder to verify there isn't anything in the spider that reduces the fuel to these two cylinders.

There is an easy procedure for checking the fuel flow to each cylinder.
 
Before swapping out injectors I suggest you look for an air leak on those two cylinders.

If the engine runs well ROP then fly it. After 10 hours or so do a GAMI check. On my stock IO-540 from Lycoming my GAMI spread was 1.5GPH - and the engine did not like to go lean. I swapped out 4 of 6 injector nozzles to get the GAMI spread down to 0.1gph.

Injectors nozzles are relatively cheap from Don at AirFlow Performance. They are a direct replacement for the stock Precision/AVSTAR FI systems as well. Don will help you on what nozzles to replace and what size.

After three airplanes I have a collection of stock 0.028” nozzles on the shelf…..

Carl
 
I've checked the timing on both ignitions, and they are right on TDC for #1.

Thanks,
Jason


Are both ignitions timed to fire at TDC for #1 cylinder? Typical spark for a Lycoming IO-540-D4A5 is 25 degrees before TDC for #1 cylinder.

Bill
 
#3 appears lean. Even the CHT points to that. My 3 and 4 run a good bit cooler than the other four; Your #3 is a good bit hotter than 5/6. This assumes you had the cowl on during the run. #3 should not be hotter than 5 & 6. If this didn't have an hour on a test stand, then all bets are off, as during the first hour or two, the rings can seat at different times and once they seat, the temps come down. It's possible that #3 is just being stubborn with the ring seating.

Check the #3 restrictor for a very small piece of debris and look for an intake leak on #3 (spray carb cleaner at all leak points-if RPM rises when you spray, you have an intake leak near the location where you are spraying). If those are good, run it up to 1800. If #3 EGT starts to come back in line with others at the higher RPM, look for debris in the bottom of the #3 V slot in the spider. Machining debris from manufacture can lodge there. Have seen it twice now. Lean at idle and normal at higher RPMs is the symptom. Unfortunately that is also the symptom for an intake leak, so that must be checked first.

Larry
 
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EGT numbers are relative and not absolute.
I agree here. They could be influenced by many things, including sensor uneven installation distances on the exhaust tubes.


You don't mention if the fuel system has been adjusted for idle cut off yet, this could cause a bit of unevenness at low initial power settings.


Carl
"If the engine runs well ROP then fly it. After 10 hours or so do a GAMI check."
Don't spend too much time playing with graphical data outputs at this stage. If it runs as Carl suggests, get on with the critical process of breaking in the engine.
 
I agree here. They could be influenced by many things, including sensor uneven installation distances on the exhaust tubes.

True, but that doesn't account for the high CHT on #3, which is 30* hotter than it's twin on the other side (#4). Something is going on in #3 and likely candidates are slow ring seating and a leaner mixture. If this engine had 2 hours on the test stand, I would be looking for a mixture problem. If not, I wouldn't bother for a couple of hours to give the rings time to seat.
 
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Thanks for all the suggestions. Let me try and answer all the questions.

1) Timing - I have double checked both ignitions and they are both timed as instructed at #1 TDC.

2) Engine run time. This engine was run on the test stand for 2.5+ hours

3) Debris in injector. I pulled all three injectors on the right side (1,3,5) and did not note any debris. I soaked then in Hoppe's for a couple of hours, dried them out and reinstalled them.

4) EGT probe location - I was very careful and EGT probes are all the same distance from the flange (+/- 1/16")

5) This run was done without the cowl on. Next run I will install the cowl and see if the numbers change.

6) Adjusted for idle cut off - I assumed that this would be done when they ran it on the the test stand. If not, I would love to hear the best process to adjust it correctly.

Thanks,
Jason
 
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Hi Jason on a newly overhauled engine you want to be careful not to get your cht’s above 350 degrees during ground runs; anything higher and you are at a high risk of glazing the cylinder walls.

As far as idle cutoff goes you want to let the rpm’s stabilize around 750-850 and pull the mixture to full lean (idle cutoff) and note the rpm change; you want to see a 25-50 rpm rise. If you don’t see this happening you correct it by adjusting the idle air/ fuel mixture.

Bill
 
If all the cylinders' peaks fall closely together in time/mixture position/fuel flow, then they are all leaned to the same degree, right?

The absolute value of the EGT doesn't show you when a cylinder is lean, only the peak and the point relative to the peak matters, as I understand it.
 
If all the cylinders' peaks fall closely together in time/mixture position/fuel flow, then they are all leaned to the same degree, right?

The absolute value of the EGT doesn't show you when a cylinder is lean, only the peak and the point relative to the peak matters, as I understand it.

correct, BUT the CHTs are a different story. With CHTs, absolute matters. Also, if the probes are at the same distance from the flange, it is NOT common to see a 200* spread across EGT peaks, when all else is normal, especially when the other 5 are bunched into a 50* range. Yes, the #3 EGT probe could be misreading, but the out of character CHT on #3 points to that cyl running at best power while the others are 100-200* rich of best power. CHTs peak at best power or 80-100 ROP and lower on either side of it.

I have one EGT that consistently runs 100+ degrees cooler than all the others. I believe the probe is misreading, but it works fine on a relative basis so don't feel like spending the $$.

Larry
 
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Ground Lean

Try ground leaning the mixture at idle to obtain the maximum rpm increase. Then while the engine is in a ground lean condition do the same check. It sounds to me like you’ve got a richer mixture or retarded timing on those two cylinders that’s sending unburnt fuel out the exhaust, then igniting the fuel closer to the probes causing the EGT spikes you are experiencing.

If it runs fine with both ignitions on ROP, I would fly it 10 hrs and then do a GAMI check and adjust the restrictor sizes to balance all your cylinders.

If you had an intake leak that cylinders EGT would be higher when both mags are on.
 
I did not see what your RPM and MAP was for the OP photos. (?) I was concerned about the same thing on my new IO360 M1B, but the engine ran smoothly and as soon as the engine was off the idle circuit (18-1900 RPM) the EGTs and CHT's were much more even. My EGTs were wildly different.


You might do a quick power run up (2000 rpm or as much as brakes can hold) keeping CHT's under 300F (or so) and see how the EGT's are with some load.

Is the cowl off?
 
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Too much info

2) Engine run time. This engine was run on the test stand for 2.5+ hours
Seems to me there is no need to motor around with this engine other than making sure there is no leaks and that it produces full power.
More engines get glazed cylinders and a lifetime of high oil consumption by
well meaning experimenters, needlessly ground running the engine, especially without a cowling on.
You have 2.5 hours on the test stand, no issues found I presume??
Do as you wish but if it was me, I would keep ground runs to a bare minimum, perhaps a couple of minutes, checks for leaks, and keep the cowl on for those tests. Next, run it up to make sure it develops full power and go fly.
There will be time to fine tune those temperatures later on when everything is settled in a bit.
 
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