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jakent(at)unison.ie
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 Posted: Sun Aug 05, 2012 5:52 am Post subject: Engines-List Digest: 3 Msgs - 08/04/12 |
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Just a thought, have you checked your fuel tank venting?
J.K. EI-DIY RV4.
| Quote: |
On Aug 3, 2012, at 6:55 PM, Speedy11(at)aol.com wrote:
>
> Engine gurus,
> I have a problem with my engine that has me stumped. Maybe someone has seen
this situation before or has an idea for resolution.
> I have a Barrett IO-390 (essentially same as IO-360) that began missing and losing
power in June. I tracked down several "problems" which the solution to
I thought would solve the power loss. I found one spark plug that seemed to be
a problem. Replaced all plugs and tested them before installation. Problem
still there. Checked resistance in harness. All good. Replaced harness anyway.
Problem still there. Sent P Mags back to factory for overhaul. Essentially
have new P Mags now. Problem still there. Cleaned injectors and flow
tested. Flows all equal. Cleaned fuel filter - nothing there. There is no air
filter when I run ram air, so nothing to inhibit air flow. I checked the sniffle
valve but no leak there.
> On takeoff roll there seems to be slightly less power, but the power loss is
more noticeable (approx 20% loss) once airborne. At pattern altitude with reduced
power the engine runs ok. But as I add throttle (high RPM on prop) the engine
loses power as if it is loading up. The EGTs and CHTs are normal. The
RPM and MP are normal.
> So, there you go. Any ideas?
> Stan Sutterfield
> RV-8A.
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speedy11(at)aol.com
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| Posted: Mon Aug 06, 2012 8:33 am Post subject: Engines-List Digest: 3 Msgs - 08/04/12 |
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Wow! Lots of great responses from several guys. Thanks!
After reading the responses I realized I had not made a complete post. I left out too much info.
The engine is an IO-390 with filtered and ram air induction running two P Mags with automotive iridium fine wire long reach spark plugs. It has 135 tach hours total. The AFS-3400 engine monitor allows me to download and analyze engine readings - which I do regularly. This all began just after I added Camguard to the oil although I cannot imagine that the two are related. I believe it was coincidental that the problems coincided with the use of Camguard. I have taken a Blackstones Lab oil analysis and it showed increased iron, but not to a significant degree to warrant concern. I will follow up with another oil sample soon so as to have something to compare.
E Mag Air overhauled the P Mags and added new circuit boards. I've been running the P Mags at 39 degrees advance, but reinstalled the jumper wire to bring them back to 35 degrees. I've added cooling tubes for the P Mags because they had indications of running too hot. I considered replacing the P Mags temporarily with regular mags, but the changeover would be a huge task and I'd rather save it to last.
I check the fuel vents and they are clear.
I cleaned the injectors in Hoppes #9 in a hydrasonic cleaner and flow checked the injectors. They were evenly matched. I have a purge valve on the engine and I use it for shutdown per recommendation from Airflow Performance. I have not yet taken apart the fuel spider so the fuel divider could be a problem. I checked the fuel injector lines and found no damage. I have a plenum on the engine that does a good job of controlling air flow. Oil temps and CHTs are in the heart of the envelope but for the #3 CHT which runs on the high side, but still well within limits.
I tested all of the spark plugs before installation using a maintenance shop tester. I replaced the lower wiring harness and tested the upper one.
When running the engine, I set high RPM for takeoff and did not change it on any of the flights, so RPM changes were eliminated.
We borescoped the engine and all cylinders look good except for a bit of corrosion on the cylinder walls. We also compression checked and readings were in the high 70s. I'm not familiar with SB-388 but I will check on it.
The engine runs the same regardless of filtered air or ram air. The ram air intake is metal, so it is not collapsing to restrict flow. I also switched off each mag airborne and each is running good now. Before the mag overhaul, I would lose significant power (one cylinder quit firing) when switching a mag off. After overhaul, the mags are running correctly and the power loss is related to high throttle settings.
I've checked the sniffle valve and it appears to be working properly, but I may remove it anyway.
Next I'm going to look at the intake tubes. If one of the gaskets is leaking that could cause a problem. I'm also going to inspect the manifold pressure hoses and then remove them for testing. The P Mags also have MP sensing so I'll recheck those lines.
If that does not work, then my next step will be to start taking apart the fuel system. That is another task I dread, but it may have to be done.
I will be sure to post on the forum if I find a solution.
Keep those ideas coming. Maybe someone will think of something that works.
Thanks,
Stan Sutterfield
From: Steve Thomas <lists(at)stevet.net (lists(at)stevet.net)>
Have you checked the integrity of your engine electrical ground? Steve Thomas
From: FLYaDIVE <flyadive(at)gmail.com (flyadive(at)gmail.com)>
Stan: Some ideas I had: - How did you clean the injectors? A standard way is to soak them in Hoppies #9 Gun Solvent. The flow could be all equal - But they could be all slightly restricted. - Does the fuel lines from the spider contact any part of the engine? HEAT could be causing a vapor bubble. - Since you have a CS prop, do you think or feel the loading ONLY when increasing the RPM? This could be a SLOW reacting Governor and that would cause loading. - Can you monitor your ALL your EGT 's at the same time and see if a cylinder drops in temperature at the same time loss of power occurs? - The spark plug that was a problem: Was it indicating Oil or Carbon? Keep an eye on that plug and see if the problem begins again. It could indicate a sticky Exhaust Valve. So, replacing the plug will not fix the valve. - Have you done the Valve Wobble test (SB-388)? - OK, with this one I am reaching a bit: I have read about someone that "Improved" the intake air flow to the engine. And in doing so, the forced air was so great that it disturbed the airflow through the Carb. - I know you do not have a Carb, but how does it fly without the Ram Air? - Have you inspected the ducting - I'm guessing SCAT Tube. Could that have an obstruction or could it be collapsing? That's all for now... Barry
From: "DEAN PSIROPOULOS" <dean.psiropoulos(at)verizon.net (dean.psiropoulos(at)verizon.net)> Subject: RE: Engine power loss I had a problem with a bad idle on my AFP injected parallel valve 0-360 Stan. After 5 months of trouble shooting I discovered that the flow divider (on top of the engine) was sticking. How I figured that out was to tee in a mechanical pressure gauge between the servo and the flow divider (not at fuel pump outlet, you won't get accurate readings there). You'll need one calibrated with a 0-10 PSI range. I ran a hose up to the canopy from the tee and connected it to the gauge there so I could see the reading from the cockpit. Then I started the engine and watched the gauge while I was advancing the throttle. The engine stumbled and the pressure reading went a couple PSI above where it should have been before dropping back and acting normally (ie. going up and down with throttle movement). After consulting with Don Rivera at AFP the conclusion was a sticky flow divider so I returned it to him for repair. The engine ran like a top after it was fixed
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MONTY(at)bpaengines.com
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| Posted: Mon Aug 06, 2012 1:08 pm Post subject: Engines-List Digest: 3 Msgs - 08/04/12 |
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Do not remove the sniffle valve. The reason is that after shutdown fuel will " dribble " out of the nozzles if the fuel percolates, it then runs down in the inlet portion of the plenum, condenses back to liquid and becomes a fire hazard at the next start if you do not have the sniffle valve installed.
Monty Barrett
Barrett Precision Engines, Inc.
[quote]
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