Running hot

[lost in the north]

my IO-550 in the 185 is running hot. It's the two front cylinders. The engine has been doing this since overhaul and is broke in. The baffling/seals have all been checked. Fuel flow is good. They are running between 380-400 degrees.The cylinders are 10 thou. Over size. Any idea's

[photofly]

Do the GAMI lean test; maybe the injector nozzles are running those two cylinders over-lean.

Alternatively, instrumentation error?

[cgzro]

Intake port leaks?
How are the EGTs?
What are the CHTs of the others?
Agree re checking injectors/balance.
Timing.

[lost in the north]

Checked, and double checked timing, intake leaks and fuel flow to the injectors. I have a 6 place get coming.The other temps are about 40 degrees lower. Engine shop is stumped as well.

[GA MX Trainer Dude]

Check the piston ring end gaps.

I had a cylinder turn blue on the initial run-in due to this problem and it was only the 1 cylinder that was affected. I don't remember if it was the top one but on choked cylinders it is often the culprit.

Mx

[photofly]

Checked ... fuel flow to the injectors.

What exactly did you check? How?

[lost in the north]

Engine shop told me they checked metered fuel, and pressures. Not sure how they did this.

[photofly]

Do you have EGT and fuel flow monitoring? Do a lean check. Take it up to 8,000, full throttle, and lean the mixture. Record the fuel flow at which each EGT peaks. See if the front two cylinders are running significantly leaner than the others.

If you've tried everything else, you've nothing much to lose.

[lost in the north]

I have one on order, wish I would of put it in when I add the cyl. Temp

[cgzro]

Plugs? Exhaust restricted?

Are you sure the cowl seals and inter cylinder baffles are not moving in flight?

Id do the flow checks again myself rather than trust the engine shop. They may have bench tested before installation but any tiny bit of crap in the injectors is trouble and thats easy to have happen during installation or if a hose was not clean when it was reinstalled.

[DonutHole]

how did you check fuel flow? with the gauge or a baby bottle test?

Bottom line is, fuel flow gauge is a TERRIBLE indicator of what is actually going on at the injectors as, in most of its failure modes it gives erroneous readings.

Example, This one is for the owners:

If you have a plugged injector what will happen to the reading on your fuel flow gauge?

[DonutHole]

I wouldn't do the peaking thing. I would take another look at the injectors.

[DonutHole]

Engine shop told me they checked metered fuel, and pressures. Not sure how they did this.

Well, you have to do it running. Low and High metered fuel pressures only get you to the flow diverter. It's the basic FCU setup. It's been awhile since Ive done it, SID 97-3 I think outlines the procedures. http://bonanza.org/documents/SID97-3E.pdf < there it is, I doubt if it is the most current issue, but it should have the relevant info for you. (I think I have seen version F of this document, could be mistaken)

Also, it is *NOT* the same as doing a flow test of the injectors.

There are a few gotchas when troubleshooting this stuff, it's been awhile since Ive had to do fuel but...

Your injector has a few parts to it. It has a hole into the cylinder for injecting the fuel, it has a hole in the back to accept the fuel and it has an orifice to aid in atomization of the fuel.

It's pretty confusing and counter intuitive but...

Say your injector is plugged. What do you expect on your flow gauge? Well intuitively we might be looking for a decrease in fuel flow, but being as most of the fuel flow guages in these small bug smashers are not transducers, we end up with a reading based on the pressure in the diverter, which is now reading HIGHER because of the plugged injector. This means that your gauge is reading a HIGHER fuel flow even though your cylinders are in fact running lean.

Say your orifice is plugged (some peoples orifices are plugged with their own head) Well, that casues the injector to puke fuel into the cylinder, but the pressure in the diverter is dropping so your gauge is reading a LOW fuel flow even though you are in fact running pig rich.

There is a pretty easy way to test the flow, but I would leave it to the AME.

[DonutHole]

I have one on order, wish I would of put it in when I add the cyl. Temp

Which one?

[photofly]

.

[Heliian]

Are your cht leads mixed up? Are you actually reading the rear cylindres which would naturally run hotter?

[lost in the north]

Baffles are all good, not moving in flight. will try the other ideas.