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titan io370 pmag timing

mmcelrea

Member
Hi. I know there has been a lot of discussion about dual pmag's and fm150's on io370/375's but I'm hoping to get a definitive answer, if thats even possible with these engines!
I have an io370 with dual pmags and fm150 afp fi system.
After starting from cold the engine runs fine but threatens to cut out after a few seconds. If I manage to keep it running it runs with steady rpm with fuel flow showing about 5-6 gph, 1200rpm. After it warms the ff drops to maybe 1gph and starts to run rough. After a flight, during taxi in I have seen it even lower, less than 1/2 gph and it runs rough. Over about 1400rpm it smooths out again tho. On approach there is also some misfiring but at higher rpm. Max ff I have seen is 15gph on takeoff and fulll power climb which I believe is too low. Cht's in cruise are around 380 but rise to 450 during climb. The engine only has about 6-7hrs. I haven't been able to check the mixture as described by afp as it doesn't run evenly enough to allow this. Reducing mixture on the ground whilst idling doesn't appear to do anything as the engine runs too rough to tell. I have checked for intake leaks but there isn't anything obvious. All cylinders temps are fairly even, none stand out.
I slightly retarded the pmags which are now timed at about 22.5 btdc.
Baffles all seem good, no gaps and nice pattern on the top cowl, the same as all the other rv's on the airfield which all struggle to get the temps up.
I had to change the oil cooler for a 13 row which has helped oil temps.
I think that its running too lean but I don't know what could cause the ff to drop as it warms up and also how to reduce the chts during takeoff/climb.
Any ideas?
Thanks
 
Well I hope so because I have the same configuration brand new in the crate sitting in my hangar.

Are you sure you have the timing set correctly?
 
Fuel Flow

I have a Titan IO-360 rated at 191HP. According to Bobby Looper (Continental), the fuel flow at takeoff power should be 17.5. If it was 180 HP, he recommended 16.5 at 2700 RPM and 28.5 " MP at sea level.

He recommended 1/8 turn adjustment CW on the fuel pressure at a time to achieve appropriate fuel flow.

Don
 
Other than my having the FM200A instead of the FM150, your setup is the same as mine. Have you tried richening up the idle mixture adjustment? If all of your problems are on the ground, I'd be willing to be the idle mixture is the issue.
 
I slightly retarded the pmags which are now timed at about 22.5 BTDC you said??

Pmags are to be timed at 0 degrees or up to 5 degrees ATDC.

Best to read to PMAG install Manual before you ruin your engine??
 
I set the timing with the engine at 2.5 degrees after tdc which, according to the mag manual should set it at the equivalent of 22.5 btdc if it was a normal mag. I had it timed at tdc (equiv of 25btdc) but retarded slightly to drop the chts.
What I find strange is that the fuel flow is fine when cold but drops right off when it warms up.
Also the max fuel flow during climb is 15gph. It should be over 17. According to the manual from afp the idle mixture has no effect at that point.
 
What compression ratio do you have? I have some notes from JB at Titan on the timing or at least how they set it at the factory, but it is different for the different CRs.
 
According to the manual from afp the idle mixture has no effect at that point.

That's right, but when you're running on the ground, it sure does and it sounds like that's where you have one problem. It sounds like you have at least two problems. If you haven't enrichened up your idle mixture, I'd do that and see if ground running improves. You don't have to do that while the engine is running. On the FM200, this involves lengthening the idle mixture arm. Just add a flat or two, start the engine and assess the performance. You know you have it right when as you're going to ICO, the RPM goes up about 50 RPM before the engine quits. Once you have your ground running set correctly, you should address the takeoff fuel flow performance. Your high CHT on climb is because the engine is too lean. Don and his crew do a good job of presetting things before he ships so I'd look at the entire fuel system first. Make sure your fuel filter isn't clogged. Disconnect your injector fuel input and do a flow test. Take it step by step through the system. good luck.

There's nothing wrong with your retarding the timing 2.5 degrees as long as you have accurately determined TDC. I would double check that as well
 
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What would cause the fuel flow to drop during low rpm? When cold its about 5-6gph bu it drops when warm to about 1.
 
I too have a IO-375 with dual Pmags and the FM-150. Idle was unstable and hard to adjust. I found three issues and things are much better now - still not perfect however:

- the diaphragm in the flow divider had a leak from the very beginning
- the spring in the flow divider was installed incorrectly so that I always had
max flow through it.
- I installed smaller injector nozzles, went from .028 to .022.

Might be worth to have a look into this.
 
Hey Miller, what did you end up finding out about this issue?

I sometimes see rough running right after start with high fuel flow, and I just turn on the electric fuel pump for a couple of seconds and it all gets back to normal. This on a cold engine, on a hot or cold day.
 
Hi
We ended up swapping out the crank, pistons and pmags due to a crack in the leading edge of prop after 16 hrs. The engine is now an io360 with slicks. Oil temps are now fine but chts still approach 420 on climb out, fuel flow and pressure start to fluctuate after about an hour, engine will stilll not idle when warm. I’ve done the mixture test several times so the main jet is supposedly the correct size. Can’t set the idle mixture because it won’t idle smoothly at all when warm. Love the plane but I don’t trust the engine. Customer experience from Titan and afp have been very very poor. Maybe because I am in the Uk they just don’t bother.
Rv10 on order and everything will be coming from vans.
 
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