70* CHT differential, #2cyl, Superior's XP360 (IO)

[916Romeo]

15 flight hours in the40hr 'fly-off'...
all's smooth, engine seems to have rings seated...

#2 cylinder head Temp is 70*cooler than all others in all phases of flight.

-I've change out sensors, same reading
-EGT is similar on all 4 cylinders +/-25*
-added 3inch fence in front of #2, increased temp by no more than 10*
-checked plugs for fouling, no carbon or oil build-up

has anyone seen this much of a difference, is it OK to continue flying...
thoughts, solutions, anything is appreciated

 

[tommylewis]

what about leaned?

So when you lean, does #2 reach peak last? If so, what is fuel flow difference between when first cylinder peaks and last cylinder?

Mine had a similar issue with #4 running richer on my engine.

 

[erich weaver]

me too!

Everything about your description fits my experience on my engine (an IO-360B1B built built by AeroSport Power using ECI parts) exactly. I talked to Bart at ASP a couple of weeks ago - he was not concerned at all about this temperature differential, so I stopped worrying about it. As to WHY it occurs, not sure, but I have a suspicion that airflow into and out of the cowl is a lot different than most of us would guess. I have no real evidence, but wonder if the spinning prop and/or oil cooler position doesnt somehow result in a lot more airflow into the cowl on one side than the other.

regards

erich

 

[frankh]

Definately

Need to ee when each cylinder peaks...I agree with the first reply, i.e the nozzles could do with being tuned...Or at least you ought see at what fuelflow each of the ctlinders peak..

So fly to 8000 ft and set the RPM to 2400..Pull the mixture till the engine runs rough...richen the mixture till it JUST runs smooth. Note the fuel flow and set the utopilot if you have one.

Then increase the mixture s the fuel flow increases by 0.2GPH..Note down all the EGT's.

Repeat this and you will see the egt will increase on each cyl with incresing fuel flow...Keep doing it and you'll see the egt's will start going down again.

I would say you want the peaks all to be within about 0.5GPH to start with.

If they are all in that range then you need to look at baffling etc...Also check that there is no flashing obstructing the fins between the inlet and exh valves.

Get a flashlight and look carefully into the fins...its can be hard to spot but will make a significant difference if there is any.

If your peaks are well outside the above 0.5GPH that may explain the difference in CHTs

Frank

 

[tommylewis]

solution?

Rich, if you find the 70 deg CHT differential is because one cylinder is running rich, contact Don at Airflow Performance and he will provide a procedure to use for testing, and then will sell you a different restricter for the rich cylinder. Or if you live close enough to Airflow Performance, for a price they will do the testing and fix it. I did not live close, so I followed his procedure for testing, and then replaced the rich restricter when I first cleaned the injectors.

In my opinion, it is not really a serious issue to run with a CHT differential, BUT you are wasting fuel. Ideally, all four cylinders should peak at the same time. When fuel was $1 a gallon, most of us did not care, but now with $5 plus fuel, it makes a small difference in our operating cost.

 

[916Romeo]

Here's my numbers...

for what it's worth, if you see something, especially that I'm doing wrong, please let me know...

Fence, baffeling did nothing to change the temp diff., I even shielded 1/2 of the #2 cylinder head with an alum heat shield to no temp affect.

I swapped the fuel inject nozzels between #1 & #2

at 2500 ft, 23in/2300rpm (econ cruise)
Leaned to peak
#1 cyl 1575 EGT, 350 CHT
#2 1475 300
#3 1525 350
#4 1500 350

these EGT numbers seem hot, hope I didn't cook anything!

This morning I flew & around 8,500ft, 22" & 2500rpm
all EGT were 1375 +/-10
#2 CHT was 275, other 3 were 325*

I think I'm pretty happy with todays performance, and getting the diff to a max of 50* seem acceptable... thoughts?

(also, thank for the previous reply, I looked at airflow performance web site. $300 for tuning nozzels doesn't seem bad if I could make it to FLA.
I think I will call those guys & see if I'm smart enough to make some improv's)

 

[frankh]

Not quite

First of all the numbers are not high and you didn't cook anything...But the actual peak EGT number is not important as far as fuel flow balance is concerned.

Its not "what" the peak EGT # is thats important but "when" it occurs...i.e at what total fuel flow...More to the point you want the peak egts to occur ideally at the same fuel flow...Within 0.5 GPH o\is OK but within 0.2 is really good...Once you have that set (or know its approximately correct) then you can ajust the baffling.

Thats why you have to follow the procedure in my previous post.

I prefer to find peak from the lean side but Don Rivera's instructions have you doing it from the rich side..either way its the same result.

Frank

 

[916Romeo]

no flow meter

thanks for the support...
my problem is I do not have a fuel flow meter
I only have the basic instruments, 1 EGT 1 CHT with a 4 channel selector.
these are the Van's Steam gauge type
all my numbers quoted are +/-5* at best, I'm sure
my fuel gauge is the IE w/Capitance senders

This probably (or seems to) leave me a little in the dark!

 

[gvgoff99]

thanks for the support...
my problem is I do not have a fuel flow meter
I only have the basic instruments, 1 EGT 1 CHT with a 4 channel selector.
these are the Van's Steam gauge type
all my numbers quoted are +/-5* at best, I'm sure
my fuel gauge is the IE w/Capitance senders

This probably (or seems to) leave me a little in the dark!

Do you think that the 4 channel selector for the CHT has a little more resistance at the #2 position which would make for a consistent error? If it is possible to move the CHT wires at the 4 channel selector (i.e. make #2 read on the #4 and connect the #4 to the #2 position) it would be diagnostic for a switch problem.

On my O-320 the #2 CHT is cooler at full rich and hotter when leaned. This is consistent with more fuel getting to it when full rich and then it probably goes to 50 degrees rich of peak when leaned. 50 degrees rich of peak will give the hottest CHT and is the worst place to run but pretty unavoidable with a carb for one cylinder or another.