Problems getting full power from IO-360 on my Velocity
I'm nearing the final steps building my Velocity (http://thegerhardts.com/velocity). A few weeks ago, I started the engine for the first time. After taking care of a few minor issues, I was able to taxi around for awhile. When I tried to do a static RPM test, there were a few anomalies that I'm having a tough time working out. While I'm a reasonably experienced mechanic (cars, motorcycles), I'm not all that familiar with aircraft engines, so I'm hoping the experts out there can give me some advice.
It is a Lycoming LIO-360 engine. Its a 500hr SMOH engine that I purchased from another Velocity owner who was parting out his project. The seller is an A&P who had originally purchased the engine off a wreck (it had been on a twin that some sort of crash that did not damage this engine). He removed the cylinders to inspect the crank, pistons, cylinders, rods et cetera. He indicated that he found everything ok, changed the rings and reassembled it. He also indicated that it was running fine prior to selling it to me. He seems like an honest enough guy, so I trust him on this. He also installed a LightSpeed EI on it, which came with the engine. Since acquiring the engine, I rebuilt the vacuum pump and replaced the mechanical fuel pump (although there were no indications it was faulty, it seemed like an easy thing to do while I had the engine out on a stand and they are not expensive). I also took off the intake tubes, media blasted them and repainted them as they had been painted at some point and were rather grungy looking. Other than that, I didn't do much to the engine.
I have a Catto fixed-pitch prop on it that should generate ~2150 RPM static.
So, after warming up the engine, I tried to go full throttle to see that static I could get. The first thing I noticed was that as I eased up to full throttle with the mixture full rich, the engine would sputter, and I needed to lean it out quite a lot (I'm in MA, at KORH - 1000') to achieve full power. The max static RPM I could get was ~1900RPM after leaning it out. As I said, at full rich, the engine would just sputter and it was far to rich to run well.
I've been through the engine fuel system, intake and ignition systems but can't find any issues. At full power, EGT's are only ~1100deg, #2 CHT is higher than 1,3,4 but I've heard you can't interpret much from CHT's on the ground. The actual mixture range (i.e. the throw of my mixture lever) that the engine will run well at full throttle in is actually quite narrow and is at the lean end of the mixture lever throw range. I haven't any experience with IO-360's only carberated Lycomings which run fine at full rich. Is it normal that the engine will not run properly at full rich? Any ideas what might be going on here and what I should check? Both the Lightspeed EI and mag seem to be operating properly.
Velocity 173RG, N173VS
You should be able to run at full rich. I don't think it's a fuel delivery issue. Could be clogged injectors....my first thoughts are though is something with the ignition. I know nothing about Lightspeed, but it almost seems like something isn't firing? Bad plugs, bad timing, multiple plugs not firing.
But because you can't get to static rpm with any mixture setting (ps, did you check your fuel flow #'s?) It sounds like a timing thing to me. That would be the first place I would look.
What fuel control is on your engine? Is it a stock RSA? How long did it sit with the internal diaphrams dry? I understand that they do not like that. Airflow Performance is currently reputed to be the best shop for fuel control repair and overhaul.
Clogged injectors is not likely. I can tell you from experience that one clogged injector will make your engine run really really badly at all RPMs. With more than one clogged, you would hardly run at all. That said, taking them out and putting them in Hoppes #9 for a few minutes to clean them is easy. Doing the same thing with the injector bodies is also easy. I do it every annual inspection.
What do your spark plugs look like? Champion hands out a chart that has pictures of all of the plug conditions including running too rich, too lean, too cold, too hot, etc. That is a big clue.
If you are in Worcester, MA, you might drag the engine up to Fitchburg to Unlimited Aero Engines. One of the Red Bull mechanics has opened a shop there. He has a dyno that can run your engine and probably get a handle on your problem. Will cost a couple of $$ but probably let you walk away with confidence in your powerplant after the work is done. That's the only shop local to you that I know of with a dyno.
Best of luck,
The previous owner of the engine indicated that it ran fine and was properly timed. I have not touched the mag or EI sensor, so it should still have the correct timing (although this is something I should check). I've checked fuel flow at the injectors, all are approximately equal. The engine has the standard RSA fuel controller. The engine sat pickled for ~1yr, so the fuel controller would have been dry for about that time - I wasn't aware that was a problem.
While it could be an ignition problem, I have a Light Speed EI and Slick mag (new). Switching the mag off gives no RPM drop (EI is more efficient), switching the Light Speed off does give an RPM drop.
The most troubling issue seems to be that it can't run at full throttle with full rich mixture. I was thinking it might be a leaky sniffle valve or induction leak, but those would cause it to run too lean, not too rich. Clogged injectors or low fuel flow would cause an overly lean condition, as well, not the overly rich situation I have.
One question - my mixture level allows actuation through the full range of the RSA fuel controller mixture arm. In most installations does the pilot mixture lever only allow actuation over a narrower range (i.e. in the leaner range)?
I may need to call in a professional to help diagnose the problem.
Thanks for your advice - I'll be out at the hangar again today and will pull the plugs to inspect.
One of our members on BiplaneForum.com had the same issue. Turned out that oil had gotten into the air passage in the venturi of the RSA. Evidently this is not an uncommon occurrence and can happen with horizontal or vertical induction units. Cleaning it out cured the issue in his case.
I would take the statement "should" and throw it out the window. You can't make any assumptions with this sort of troubleshooting.
I would double check all your plugs, leads (is the firing order proper on all cylinders, top and bottom) are the right leads going to the right cylinders. There's 100 things you can do to troubleshoot this, you just have to take the most logical and start knocking things off the list. Def check the timing.
Can you not run it up on just the mag or just the EI? Maybe try to narrow it down to one system.
Now that it has been brought up, I would also look at oil in the venturi and back into the diaphram area. Someone in my locale had that problem too.
To answer the mixture control throw question, the pilot mixture control lever or knob should indeed move the linkage on the fuel control through its full range of motion.
I will note that saying that there are 1000 things to check is not helpful at all when it comes to solving real world problems. From the information provided by the original poster, I would rule out ignition and the upper deck fuel injection components. That leaves us with the fuel control. The bad news is that you probably need to send it out.
Best of luck,
Out at the hangar today and did some more troubleshooting. Looks like I have/had a couple problems. I found a leak in one of the intake tubes - the rubber o-ring gasket that seals it where it fits in to the intake plenum wasn't sitting right. Once I took care of that, the mixture issue was better and I could generate a static of 2050RPM. I then turned my attention to the ignition as it was still running a bit rough and stumbling. I found that when I turned off the mag, the engine ran better. When I turned off the EI and ran on mag alone, it ran better - I actually got an RPM drop when I turned the EI on.
So, I check the timing of the EI. From the documentation I have for it, it was way off. The documentation I have indicates that you put cyl #1 at TDC and rotate the hall effect sensor (mounted on the empty mag spot) until the light on the back illuminates. I found that it was set for ~40deg advanced. I set it for TDC and ran it again, but it actually ran worse. But, I seem to have found an issue. I removed the EI unit and brought it home. I'll be contacting the guys at Light Speed Engineering tomorrow to discuss it with them.
Thanks for your help.
On your data plate for the engine, what does it state for the timing? 40 degrees does seem way off, but it shouldn't be TDC either. Probably around 20* (if it wasn't late, i'd look up your tcds)
Sounds like the EI and mag were fighting each other possibly. Again, I know nothing about EI, so what's causing your problems more specifically will have to be someone else. If you have a buzz box, check the mag, for all we know they are BOTH off and mismatched....just one was closer making it seem to run better.
WLIU: My 1k remark was obviously joking, but these sort of trouble shooting issues are hard, especially over the internet. They can be narrowed down but only by educated guesses. I'd like to hear why you ruled out ignition?
Last edited by uavmx; 02-27-2012 at 11:57 PM.
One of the challenges of communicating on the internet is that humor often does not come through text and you can only process the information presented by the individual describing the problem. So you take anything that you read with a large grain of salt. Advice based on incomplete information has to be processed carefully. You will not that I described the logic chain, rather than just advocating a single solution.
The timing on the data plate is for a simple magneto ignition with fixed timing. The newer electronic systems have variable timing so you go with the ignition manufacturer's spec, not the engine manufacturers spec. The electronic ignition should start with no spark advance for starting, and then quickly advance the spark to match the RPM.
Many builders who use an electronic ignition use one magneto and one electronic unit. Normally, the electronic unit and the magneto work OK together. When starting, a lot of setups turn off one side of the ignition and with a mixed setup, the off on start side should be the magneto. The rest of the time, the electronic unit creates a spark that is so much hotter, the magneto plays a supporting role, whatever the timing that the electronic unit has shift to.
Best of luck,