If you're worried about using carb heat on landing approaches, for fear of forgetting to remove it during a go-around, develop the habit of selecting carb heat "cold" on very short final. Do that religiously, and it'll develop into a habit, and helps to do the right thing when things actually get a little stressful.

For you folks with O-470 or O-520 engines who might fly in fairly cold temperatures, take a short piece of foam pipe insulation, the split stuff, and wrap it around the forward induction cross over tube. Tie-wrap it in place. That cross over tube is exposed to a cold blast of air coming into the cowl, and significantly cools the iduction air going into the the front cylinders, causing the engine to run rough. My old C-180 wouldn't run for beans at temps lower than about +10 F without that pipe insulation. And, as noted by others, partial carb heat will help to even out induction temps on these installations as well.

MTV

mtv wrote:If you're worried about using carb heat on landing approaches, for fear of forgetting to remove it during a go-around, develop the habit of selecting carb heat "cold" on very short final. Do that religiously, and it'll develop into a habit, and helps to do the right thing when things actually get a little stressful.

For you folks with O-470 or O-520 engines who might fly in fairly cold temperatures, take a short piece of foam pipe insulation, the split stuff, and wrap it around the forward induction cross over tube. Tie-wrap it in place. That cross over tube is exposed to a cold blast of air coming into the cowl, and significantly cools the iduction air going into the the front cylinders, causing the engine to run rough. My old C-180 wouldn't run for beans at temps lower than about +10 F without that pipe insulation. And, as noted by others, partial carb heat will help to even out induction temps on these installations as well.

MTV

Thanks Mike, I'll look into the induction cross over tube issue.

And that's the habit I'm into, pushing carb heat in (off) on very short final. During my training (go-arounds), that was the one item I kept forgetting to do (for what ever reason).

I remember reading about some of Max Conrad's bladder - busting record - setting endurance flights in the PA24-180. He used carb heat and leaning, way before those fancy electronic worry meters they have now. Seems like it should be a valid technique.

Me, I can't sit that long!

mtv wrote:For you folks with O-470 or O-520 engines who might fly in fairly cold temperatures

And for the REALLY cold stuff, -40 and below, especially at sea level with DA's about 4,000 feet BELOW sea level, you gotta use carb heat to keep from cooking cylinders as you're gonna be way too lean with the mixture. The O-470's just don't want to run unless you warm and thin the air.

Think lower you go with the DA, the further you push the mixture control forward. Problem is, with the below sea level air, the mixture control knob hits the panel and can't go any further. So if you can't make the carb richer, you heat up the air to raise the DA.

Gump

GumpAir wrote:

mtv wrote:For you folks with O-470 or O-520 engines who might fly in fairly cold temperatures

And for the REALLY cold stuff, -40 and below, especially at sea level with DA's about 4,000 feet BELOW sea level, you gotta use carb heat to keep from cooking cylinders as you're gonna be way too lean with the mixture. The O-470's just don't want to run unless you warm and thin the air.

Think lower you go with the DA, the further you push the mixture control forward. Problem is, with the below sea level air, the mixture control knob hits the panel and can't go any further. So if you can't make the carb richer, you heat up the air to raise the DA.

Gump

Dat's what I gotta do to keep EGT's managable

mtv wrote:I believe that most of the carb air inlet temperature probes are GENERALLY located UPstream of the fuel nozzle. I doubt you'll see much difference in temperature associated with fuel vaporization with a Carb temperature gauge.

Try it when you're up high. You'll see the needle wander down a bit almost immediately.

I'm not sure where the throat is precisely on mine, but the probe is buried in a threaded mount just above where the throttle plate shaft appears to be (O-470).

When we bought our Maule M5 235 the seller said to add a little carb heat in cruise and it will run better. I thought that was wrong but later tried it and found we could always even out the egts and cut fuel flow by aprox .5 gal per hr. I could never detect a noticeable change in MP. Doesn't make sense but it works. Have any other Maule drivers with carbs found this to be true? I doubt it would work on injected.

cross arrow wrote:When we bought our Maule M5 235 the seller said to add a little carb heat in cruise and it will run better. I thought that was wrong but later tried it and found we could always even out the egts and cut fuel flow by aprox .5 gal per hr. I could never detect a noticeable change in MP. Doesn't make sense but it works. Have any other Maule drivers with carbs found this to be true? I doubt it would work on injected.

This is pretty much the technique the GAMI guys suggest to even out EGTs sufficiently to be able to run lean of peak in a carbureted engine. And, it does work, though I follow Lycoming's admonition NOT to run their engines lean of peak EGT.

But, if you have a multi probe EGT, and you apply carb heat gradually, you'll see those very uneven EGTs even out considerably as you apply carb heat.

And, you're right that it won't work on injected engines, since they don't have a carb heat control.....

MTV