cylinder temperature

[rwarre]

I have on my RV7A a Lycoming O320 with ECI cylinders. It now has 180 hours and has been running fine. The number 1 cylinder in the cold weather weather runs about 100 degrees while the rest of the cylinders run about 215. I have checked compressions every fifty hours and they all have been 80/80. Spark plugs are clean. The engine runs strong and here in Colorado I see speeds from 140 to 150 knots. Should I be concerned with the low temp on number 1 cylinder? Thanks

[DanH]

Randy, if it runs well on all four, there's something wrong with the #1 CHT probe.

[vic syracuse]

Randy, those temps are all too low. I would check your indicating system configuration/connections. And for a well running engine, a 100 degree difference between cylinders is not usually feasible.

vic

[Noah]

I would swap CHT probes for 1&3 and see if the problem persists (they are easily removed). You could also test them (water boils at ~206F in Wray) while they are out of the cylinder heads. If the problem is not the sensor then you may need to install an air dam at the front of cylinder 1 as shown in Vans baffle plans.

[mike newall]

How I wish I had low temperatures............

Our 7 with a TMX IO-360 has only 10 hours on it.

#4 is running around 400 in the cruise (23/23)

#1 is running around 300.

OAT around 40f.

Now, after much looking and searching, we didn't have temperature dams on the front of the inlet ramps, so today's project was to fit them. Made them up, rivetted them onto 032 rolled angle, took out 4 rivets from the original set up and fixed them with Monel pull rivets.

I have seen several people with up to a hundred split between 1 & 4 - mainly due to #1 being forward and the oil cooler being behind #4 but haven't seen that split between 1 & 3.

We also moved the blanking plate from the back of the oil cooler to the front and went round everywhere with high temp silicone to seal even small holes.

In your case - I would look at fitting the dams in front of at least #1 to raise it's temp, as well as checking the probes.

I won't be able to fly to check ours for maybe a week but will report back.

[N941WR]

Start by using aluminum duct tape for temporary dams. Once you know what size you need, fabricate replacements out of aluminum.

In my case, I put platenuts under the baffle ramps so that I can easily swap out the dams in front of cylinders 1 & 2.

[rwarre]

Went flying yesterday and verified the numbers. #1 and #4 were reading 100 and #2 and #3 were 315 not 215. I suspect bad connections or something simple, I will remove the probes first and make they work ok.

[mike newall]

Further to last post and after some minor fiddling we have stable temperatures.

Got good advise from some guys directly - thanks.

The dams evened the temps across the engine and helped reduce the high#4 CHT.

What finally nailed it was realising that where the oil cooler is mounted - a lot of rather hot air goes past the cylinder and into the cooler.......

I blanked between the baffle and the cooler, all the way from the bottom - left about 1" at the top of the matrix and then step drilled 2, 1" holes near the top of the baffle. Now we are getting no leakage of air behind the cylinder - it is being forced down through the fins - Thanks Dan for pointing that out.

A quick seal around with silicone and we now have a well balanced engine.

It is amazing to see how sensitive the whole set up is to relatively small changes.

[blueflyer]

Originally Posted by mike newall

Further to last post and after some minor fiddling we have stable temperatures.

Got good advise from some guys directly - thanks.

The dams evened the temps across the engine and helped reduce the high#4 CHT.

What finally nailed it was realising that where the oil cooler is mounted - a lot of rather hot air goes past the cylinder and into the cooler.......

I blanked between the baffle and the cooler, all the way from the bottom - left about 1" at the top of the matrix and then step drilled 2, 1" holes near the top of the baffle. Now we are getting no leakage of air behind the cylinder - it is being forced down through the fins - Thanks Dan for pointing that out.

A quick seal around with silicone and we now have a well balanced engine.

It is amazing to see how sensitive the whole set up is to relatively small changes.

Mike
What are you calling "dams"?

Also, I dont follow when you say you "blanked between the baffle and the cooler, all the way from the bottom - left about 1" at the top of the matrix and then step drilled 2, 1" holes near the top of the baffle."?

It sounds as if my CHTs match yours before your fixes, but I cant visualize what you are saying you did to correct the high temps.

[mike newall]

The air dams are the two blanking plates in front of the two front cylinders. They mount onto the lower inlet ramp reinforce angle and cover the upper portion of the cylinder to partially blank it and to throw some air over those cylinders.

They were always mentioned in the baffle instructions, but only seemed to be included in the last 4 years or so.

We have a rear mounted oil cooler - hangs off the back of #4 cylinder. The cut-out in the rear of the baffles matched what Vans showed, however, as we are in a cool climate - UK - we don't need that much cooling air and, with hindsight, the location isn't particularly good as it affects the cooling flow past the fins of #4. Also, the fact you have a large hole, bleeds high pressure air out the back of the baffles.

I experimented with speed tape initially, then made up a thin ali plate which completely closed the exit into the cooler. I made it large enough to fit onto the existing mounting holes - don't make the holes too snug, you are only trapping it between the back of the baffles and the front of the oil cooler.

I then trimmed it down at the top and put the two holes in. These were placed in line with free air, not air that has been past a cylinder.

If you don't have the sketches for the dams, PM me with an email and I will send some drawings and snaps.