Engine Running Rough

luv2flypilot · #1 08-16-2009, 10:10 PM

My RV-7A has just about hit the 10 hour mark and I have started having some engine issues in the last few hours. I first noticed it on Friday when I was staying in the pattern and working on full stop landings and heard some back firing and engine roughness when I pulled back the power to turn base to final. After I landed I performed a run up and it seemed to be running a little rough. I then cleaned the fuel injectors and well as checked the plugs. Nothing appeared to be wrong with what was found. Did another run up and everything seemed to be fine. I flew it for about an hour and did not appear to have any problems until I came in for landing and started hearing bad back-firing on final when I pulled back the power to around 15 MP. I did some research on here (VAF) Friday night and read that the "Shotgun Approach" was normal with an RV that has Vetterman exhaust (like I have) and was caused from unburned fuel, so I decided not too worry too much about it (however this was the first time I have heard this). Also, I should mention that from the start I have had intermittent issues with abnormal high EGT temps on #3, however the CHT temps seemed to be normal so I did not worry about it and thought that maybe I had a bad sensor and was planning on swapping it with another sensor to see if the problem followed. Yesterday when I went to go fly, I did my run up and everything seemed to be just fine. The only issue was the intermittent EGT temp going up around 1650 to around 1750 during the run up, but stabilized on normal idle . On take off and climb at about 150' and around 3/4 down the runway I heard a few backfires. I started looking for a good spot to put her down in the event I lost the engine since I knew I would not make it back to the runway at that point. I slowly pulled back on the power to around 70% and reduced my climb attitude and the backfiring stopped. I was able to keep a tight pattern and get back and land, but it did not seem to be running very smooth. I was worried about pulling back off the power until I new I could make the runway, so I slowly pulled back when I knew I would make it and kept a little power in until I was over the numbers. When I pulled power back right before flare, the engine never stopped but I thought it was going to by how rough it was running. While taxiing back to my hanger I leaned it a little, however it still sounded like a "Harley" popping and sputtering. An A&I on the airport that heard and saw what happened and said he thought it was running too fat and that I may have a timing issue, but was not familiar with the dual LASAR ignition I have. From what I have been reading the last day or so, it looks like I will have to get a hold of a syncro timing tool in order to check the timing or to see if it is possibly that the LASAR ignition is the problem. Today I went back and cleaned my fuel injectors again as well as checked the plugs again and did not see anything that appeared to be abnormal. I tried to do another high RPM run up and found the engine still seemed to be running rough at high RPMs and will not stay running at idle with quit a bit of sputtering and backfiring at low rpm below 900-950 RPM. It seems to run the best around 1300-1400 RPM, but not as smooth as it should. I plan on calling Eagle Engines tomorrow (where I purchased the brand new engine) to see if they have some recommendations. If anyone has any suggestions that could help me out, it would be greatly appreciated.

The following is my engine set up:
Engine: IO-360-B1BC3, 9 to 1, Roller Lifters, Flow Matched Cylinders, Dual Unison LASAR Ignition, Sky-Tec Starter, Silver Hawk Fuel Injection

Mike S · #2 08-16-2009, 11:59 PM

I have the Lasar timing tool, contact me by email or PM if you need to use it.

luv2flypilot · #3 08-17-2009, 12:04 AM

I am going to call Eagle Engines in the morning to see what they suggest at this point. I am thinking that I may need to check the LASAR with the timing tool and really appreciate your offer and may take you up on it depending what suggestions Eagle Engines give me to try first.

Bob Axsom · #4 08-17-2009, 01:09 AM

If you have a LASAR ignition system you must have a LASAR timing tool to make sure the timing is right both now and when you have to eventually replace a "MAG". My engine was delivered directly from Lycoming as a drop shipment ordered through Van's. It was accompanied by test cell data saying that everything was fine when the timing was off by approximately 65 degrees! I ran it and flew it that way until working with Unison and Lycoming via telephone I bought the tester from Van's and fixed the problem. The instructions for using the tool are easily misread and the first time I set the timing I came up with precisely the same setting as Lycoming which I knew was wrong! I went back and did it again without glossing over a single word and it worked perfectly. Things like TDC can be read as physical top dead center of the compression stroke of cylinder #1 when the instructions are actually referring to a light on the box labeled TDC. As soon as I started reading you problem description, even the number of hours if brought back memories of my early flights with the incorrect timing.

I recheck the timing every year as part of my annual condition inspection and I can assure you that once set it is very stable and reliable. I race my RV-6A in the Sport Air Racing League races (www.sportairrace.org) and I won the RV Blue class in 2007 and 2008. I had the non-sensor mag fail after around 400 hours but no other difficulty.

Bob Axsom

CNEJR · #5 08-17-2009, 07:51 AM

You really need the timing tool. Have Lasar on mine, never misses at beat, but you just can't time it without one.

luv2flypilot · #6 08-17-2009, 08:18 AM

It looks like I will have another investment and tool to put in my hanger. Hopefully I can still purchase the tool somewhere since Unison is no longer from what I understand. I have read about people having problems with their LASAR systems and getting rid of them, so I would first like to borrow or rent a tool to make sure that is the problem and it corrects it. I would hate to invest the money in the tool and find out that my mags or LASAR box is bad and have to go with another electronic ignition or straight slick mags if I cannot get the parts under warranty since the engine is new. Thanks for all the replies so far.

Bob Axsom · #7 08-17-2009, 10:24 AM

Quote:

Originally Posted by luv2flypilot

It looks like I will have another investment and tool to put in my hanger. Hopefully I can still purchase the tool somewhere since Unison is no longer from what I understand. I have read about people having problems with their LASAR systems and getting rid of them, so I would first like to borrow or rent a tool to make sure that is the problem and it corrects it. I would hate to invest the money in the tool and find out that my mags or LASAR box is bad and have to go with another electronic ignition or straight slick mags if I cannot get the parts under warranty since the engine is new. Thanks for all the replies so far.

I just called Unison at 1-904-739-4000 and got the normal Unison Industries automatic menu system. I followed the number selection sequence to get to technical support for GA. I ended up with voice mail for some guy who was "in the office but away from my desk" response followed by please leave a message and I will call you back. Anyway, they are still there and if you are going to keep your LASAR system you need your own timing box for the independent ability to maintain your system. I bought mine through Van's.

Bob Axsom

luv2flypilot · #8 08-17-2009, 11:45 AM

Thanks Bob, I also called and left a message in hopes to get a call back. Mike Starkey is kind enough to let me borrow his timing tool so I will first make sure this is something that I can correct and verify is an ignition problem before I start running down the wrong rabbit trail. If I end up being able to get the problem fixed without junking the LASAR system, I plan on gpurchasing a timing tool and learning more about what is needed to keep the maintenance on the system.

luv2flypilot · #9 08-17-2009, 06:25 PM

After a few phone calls speaking with James Dean at Eagle Engines and Joe Logie with Champion Aerospace and formerly with Unison I think I have things figured out. Eagle Engines recommended I adjust the fuel servo on the throttle body back to be a bit more lean and see what happens and after speaking with Joe Logie with tech support for the LASAR he seemed to think it was NOT a LASAR ignition symptom based on what is going on. Joe seems to be the man to talk to regarding LASAR as he told me that he use to be with Unison and was the man guy working on the LASAR system and after GE then Champion purchased the rights he was recruited.

After slowly adjusting the fuel servo adjustment on the throttle body and chocking up my airplane, I was able to do high power run ups to 2500 RPM without the engine missing a beat. It took me 4-5 adjustments before it seemed to get better and better and then what seems to be the best and smooth setting. I am thinking that even though I have put 6 hours on the engine without any trace of a any problems with exception to what I thought was a possible bad EGT probe, that this was a problem from the start and was just getting worse and worse as it was too rich and the engine was breaking in. Now with the fuel flow adjusted, I even have stable EGT temps on #3 as well as a more consistent CHT temps that is even with the other cylinders. Another thing I noticed today before I made the adjustment was that the EGT on #3 was running really hot and the CHT seemed to be 40-60 degrees cooler than the other cylinders. Does this seem to make sense to anyone that is more familiar with engines? I feel much better that the EGT temps have stabilized and I have things back to normal. Tomorrow I plan on cowling her up and doing a few more run ups and hopefully go flying again.

Thanks for everyones help. It is awesome that there are so many helpful people on here!

AlexPeterson · #10 08-17-2009, 08:31 PM

The after-firing (popping in the exhaust) is normal for throttle reductions with FI, as is the crummy ground idle when hot. Was it hot outside then?

Seems like the non-normal event was during your takeoff. The popping on throttle reductions and crummy ground idle can be ignored for now, but your takeoff power problem is very concerning, and may or may not be related to fuel. Do you have a fuel flow sensor, and if so, what is the fuel burn during WOT take off power? C/S or fixed pitch? I'm not familiar with the Silver Hawk system, but isn't the adjustment only for idle and just above idle mixtures? If so, it shouldn't be related to your take off power problem.

As for checking the Lasar system, once you have verified TDC timing of the left Lasar mag, and base point timing of both mags, you could try running the Lasar in backup mode. This is simply where you pull the breaker on the Lasar's power (after you have started the engine), and run on magnetos at base timing. This will eliminate any possible misbehaving Lasar electronics. It is helpful to know that the Lasar is in backup mode for some number of seconds after you do a mag check, I don't remember how many. If it is running poorly at high power settings, you could switch off a mag, which also forces it into backup mode, then switch back to both. If it runs ok for xx seconds, and then goes awry, it is likely the Lasar system. (BTW - if the TDC of the left mag is correct, but the point break is not at the baseline timing of 20 or 25 degrees, the points need to be adjusted.)

Keep us posted please.