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another "#1 cht high" post

D

danny

Well Known Member
I searched with no love for cutting the fwd baffle down. My CHT is high (430+) on climb out. Much higher than the other cylinders. It drops as soon as I lower the nose so I believe it's an airflow issue. I cut the baffle down maybe 3/8ths inch but since it's inspection time I haven't flown it yet.

So I'm just hoping to hear someone else's experience on cutting it down to give a bit more air to #1.
thanks
danny
 

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Me? I'd cut the air dam off 1/4" at a time until I was comfortable with the results.

If I was building an airplane, I'd make the air dams removable with screws and nutplates to make the adjustment process easier.
 
First off, make sure the probes are in the correct places..you can warm up each one with a heat gun one at a time to check.. my O-360 didn’t have any dams, but I added aluminum foil tape to the front about as high as your left edge of the baffle. The left side is a little higher than the right side. My CHTs are within 10 degrees on climb out.
 
danny said:
I searched with no love for cutting the fwd baffle down. My CHT is high (430+) on climb out. Much higher than the other cylinders. It drops as soon as I lower the nose so I believe it's an airflow issue. I cut the baffle down maybe 3/8ths inch but since it's inspection time I haven't flown it yet.

So I'm just hoping to hear someone else's experience on cutting it down to give a bit more air to #1.
thanks
danny
Click to expand...

I don't see the 1/4 round transitions on either side of the ramp. What does the C shaped rubber lay against? If you are bleeding air to the lower cowl area, this could be part of the problem. 430 in climb seems high regardless of the dam size, so wonder if there are other issues that may be causing it. IS this a plenum setup of some type? I also don't see a front plate or rubber to seal against the cowl top. Also don't see a method of plenum attachment on rear baffle, so have to wonder.
 
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Strictly an air dam issue.

Yes, I have an SJ plenum. It seems to do the trick in every mode except on climb out when taking off. All of the probes are new and, I believe, properly installed/placed. I'm about 99% sure it's the air dam but am (cautiously) open to the ideas and experiences of others. Thanks guys.
RV9, IO-360, SJ cowl and plenum all being pulled around the sky by a Whirlwind ground adjustable prop and loving it
danny
 
Question

Where is your oil cooler? I managed to tame my #2 cylinder temps on climbout by temporarily closing the shutter on my oil cooler, which is on that side of the engine at the rear. As with your setup, everything is hunky dory with mine in cruise, it's just a climb issue.

danny said:
Yes, I have an SJ plenum. It seems to do the trick in every mode except on climb out when taking off. All of the probes are new and, I believe, properly installed/placed. I'm about 99% sure it's the air dam but am (cautiously) open to the ideas and experiences of others. Thanks guys.
RV9, IO-360, SJ cowl and plenum all being pulled around the sky by a Whirlwind ground adjustable prop and loving it
danny
Click to expand...
 
A photo with the plenum in place may be helpful, assuming that's what you're running with. There could be some type of airflow issue or turbulence created at higher AOA that's affecting that cylinder. All the other posts so far are good comments and will be helpful in narrowing down the problem. We just need a little more info.
 
High CHT's

I would not hesitate to cut them down as necessary. I recently completely removed the front baffles on a high compression 9.5 to 1 IO320 engine with two electronic ignitions. Once removed, all cylinder CHT's were balanced perfectly.

On the contrary, I have another airplane with stock baffles and CHT's are balanced perfectly.

It all depends on the airplane. Do what you need to do.
 
I can't tell from the photo what kind of engine you have but I found in the first 35 hours of testing on my io-540 that 1, 3, and 5 are always 10-15 degrees hotter than 2, 4, 6. The big problem was that 1 was as much as 50 degrees hotter than 3 and 5. I cut mine down a little bit every time I had the cowl off. It made incremental improvements.

Then around 35 hours during an oil change I removed the entirety of the #1 forward baffle. Immediate improvement. 1, 3, 5 now are always with 10 degrees of each other no matter the attitude or speed. They still run about 10 hotter than 2, 4, 6, but the 1-3 spread is now great!

I agree with the above poster about using some kind of screw set up instead of rivets to attach those baffles. If I had to do it again, that's what I would do.

I was also talking to a friend who races motorcycles about the temperature issue and he asked where my oil cooler is located (behind 6). His comment was that since 1 and 2 are the farthest from the oil pump and the oil cooler, they will pick up more residual heat over the distance and will run hotter simply because the oil will be warmer when it gets there. Apparently this is a common problem with his race engines.
 
Remove them

Hey Danny, On my 9A with the James plenum I removed the air dams completely and then used speed tape to slowly adjust how much was covered. I don't remember which but one side was completely removed and one was only about half covered.
 
Looks like you have a fuel injected engine.

The fuel line goes from the fuel injection spider down through the inter-cylinder baffle between #1 & #3. The hole the fuel line passes through has a grommet that is much larger than the hose itself. This robs the #1 cylinder of lots of cooling air.

In my case, when I RTV'ed that hole closed so there was no light showing through, the #1 cylinder quit running hot on climb out.
 
thanks for all the help

I feel validated that I'm going in the right direction. BTW...my fuel line is routed to the spider thru the rear baffle. I was a little nervous having it go in between the cylinders. My oil cooler is mounted behind #4 cylinder on the baffle. I haven't seen oil temps higher than 100 degrees. (so far :rolleyes:)
Love NE Oregon.
danny
 
Well that latest post only raises more questions. 100 degrees on the oil temp is all you've seen? Is that degrees F? That can't be right, especially in the summertime. I was just up in Washington state this past weekend--while it was certainly cooler than most of the rest of the country, that oil temp is not feasible. Either your oil temp sending unit is not correct, or the configuration needs to be looked at in the EFIS. Even if the vernatherm was sending all of the oil to the cooler, I would think you'd be well past 100 degrees F.

And referencing the post that asked about the fuel line pass-through hole on the inter-cylinder baffle between #1 & #3, did you close that existing hole off (assuming it came with a hole)?
 
Yeah, 100 can't be right. Are you sure the gauge is in F and not C?

I was getting oil temps on my io-540 of 170-180F in February in Colorado at an OAT of 20F. These days, I'm cruising around 185F at an OAT of 75-80.

I don't even do my run up until I'm sure I'm over 100F.
 
I put an air dam (1/2” x 1/2” x 3”) above and slightly forward of the #1 cylinder to create a higher pressure above the cylinder. Taped it to the inside of the upper cowling with metal tape for testing until I found the spot that had the best change in temperature. Dropped #1 cylinder temperature in the climb by around 40 degrees. #3 cylinder temperature was a little higher than it was before but I’m not cooking #1 anymore.
 
slightly below average typist

OK, you guys caught my mistake. I definitely meant "200 degrees". For my penance I'll sit in a recliner in the hangar and limit myself to drinking only one beer. :(
danny
 
danny said:
OK, you guys caught my mistake. I definitely meant "200 degrees". For my penance I'll sit in a recliner in the hangar and limit myself to drinking only one beer. :(
danny
Click to expand...

Recliner in the hangar with a beer....my favorite way to hangar fly!


KJSY, red hangar in the middle, refrigerator stocked!
 
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