Engine wear during a cold start.

gismo

gismo

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At the beginning of an article on preheating in this month's Plane&Pilot magazine the author made an incredible statement:

Plane&Pilot said:
Starting a cold engine can give it the equivalent of 500 hours of cruise wear and tear, according to engine authorities.
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While it is reasonable to assume that cold (defined in the article as below freezing) starts cause more wear than most other operations, this obvious exaggeration would have you believe that four such starts are all that's necessary to require the overhaul of a recently broken in engine. Even if you subscribe to the unproven popular notion that a normal (above freezing) start causes as much cylinder/ring wear as an hour of flight and an average flight time of as little as one hour, a 2000 hr TBO engine's life would be cut in half by four cold starts.

Why do they publish such nonsense?
 
That is really hard to believe. Does that mean hot starts are good for the engine?
 
lancefisher said:
At the beginning of an article on preheating in this month's Plane&Pilot magazine the author made an incredible statement:



While it is reasonable to assume that cold (defined in the article as below freezing) starts cause more wear than most other operations, this obvious exaggeration would have you believe that four such starts are all that's necessary to require the overhaul of a recently broken in engine. Even if you subscribe to the unproven popular notion that a normal (above freezing) start causes as much cylinder/ring wear as an hour of flight and an average flight time of as little as one hour, a 2000 hr TBO engine's life would be cut in half by four cold starts.

Why do they publish such nonsense?
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That sounds extremely far-fetched to me. But, if it is true, would an engine preheat solve this "problem?"
 
lancefisher said:
At the beginning of an article on preheating in this month's Plane&Pilot magazine the author made an incredible statement:



While it is reasonable to assume that cold (defined in the article as below freezing) starts cause more wear than most other operations, this obvious exaggeration would have you believe that four such starts are all that's necessary to require the overhaul of a recently broken in engine. Even if you subscribe to the unproven popular notion that a normal (above freezing) start causes as much cylinder/ring wear as an hour of flight and an average flight time of as little as one hour, a 2000 hr TBO engine's life would be cut in half by four cold starts.

Why do they publish such nonsense?
Click to expand...


That's the same mag that when talking about runway incursions had a diagram with the taxiway hold short lines backwards (implying that you could freely enter the ry but couldn't exit without ATC clearance)!
Umm. Because it's Plane & Pilot, Lance? ;)
 
RotaryWingBob said:
That's the same mag that when talking about runway incursions had a diagram with the taxiway hold short lines backwards (implying that you could freely enter the ry but couldn't exit without ATC clearance)!
Umm. Because it's Plane & Pilot, Lance? ;)
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I remember that one... made me do a double take, scratch my head and go "Huh?"
 
RotaryWingBob said:
That's the same mag that when talking about runway incursions had a diagram with the taxiway hold short lines backwards (implying that you could freely enter the ry but couldn't exit without ATC clearance)!
Umm. Because it's Plane & Pilot, Lance? ;)
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Seems like they need Ken to straighten them out.
 
Essentiallly P & P's story is correct however how they quantified the wear as similiar to 500 hrs of normal operation is a bit far fetched. Gawd I'd be at TBO by the time I'd done the breakfast and $100 hamburger run!

The gist of the statement is that engine lubrication (which minimizes wear -naturally) is minimal at cold start up. It is also not terrific at hot start up either but in the cold condition more oil has run off of the parts that need lube and the parts themselves have contracted to their cold state, therfore parts that need lube don't have it and the parts themselves are not yet at their optimun running temperatures for operating clearances. This means high wear. Of course it's going to be at a higher rate than "normal runnng" but what can you do? Got to start it "cold" every time.

Even "hot" starts have higher than "normal running" wear since oil has also run off the parts and it still takes time for oil pressure to build. but again what can you do, got to sart it hot too.

All you have to do is understand that "start up" phase wear is higher than "normal running" wear in every case , hot or cold. Your job as the owner/operator is to simply understand the reason and then operate the engine in a way to minimize it. It can't be eliminated entirley but it can be minimized.

NEAR "elimination" : Plug a pre-oiler in that has warm oil circulating through the engine, then start the engine as soon as possible after disconnecting it. Even still there will be start up wear until there is sufficient oil pressure and parts that rely on splash lube get splashed.

Start up wear minimizing:

Cold. Pre heat if really cold. THis at least gets the parts closer to their normal running clearances and gets some heat into the oil. Start the engine and keep the RPM as reasonably low as possible for as long as possible. IF no pre heat is used then this is agonizing since you need to balance the idle speed with the warm up time. Oil pressures can get too high quickly when its cold & thick. This is nearly as bad as too low. Pre heat helps mitigate this problem but there will still be "start-up wear'-just for a shorter period and thats what it's all about: keeping the start up phase as short as possible and at the lowest "engine stress" level.

I hope this helps. Magazine articles uggh! Sometimes the writers are looking at too low a common denomitator!
 
I know! The solution is to never power down your engine, just don't do it!
 
bbchien said:
I know! The solution is to never power down your engine, just don't do it!
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We Have 4, T-56-401Ds running a rice thrashing mill/powerplant that went on line in 1954, they have never been shut down or been off line ever.

They operate on NG, and have a huge airfilter that is two stage, two section, when the PSI differental across the filter element on section 1 gets above 5 psi drop, the filter automaticly changes to section 2. the oil is Mil-23699, synthetic, and never needs changing when on 3 micron filitering. We expect these engines to run forever, because they have 1 cycle on them. they have no bleed air system to fail, they have no accessories to fail, they have no air errosion to contend with.

Remember the heat cycle is what causes wear, and metal fatuge.

90% of engine wear is during the time of start and normal run temps, specialy in the cylinder and hot section of the engine..Cranks and bearings not so, they love cold oil it is thicker, highly loaded gear trains, which allow the oil cushion to drain off, run dry during start, and thus will wear until the oil cushion is returned.

Lots to be said for not powering down, (shutting it off), but to power down during let down, well........ cooling cylinders below operating temps at any time is as bad as a start. cylinder gets cool and shrinks around the piston which stays hot and swelled, and skuff skuff goes the cylinder wall to piston fit. any your oil will look like metal flake paint at next oil change..

Give me an engine that has done long cross countries over an engine that has been doing touch and goes all its life.

I tell all my customers, " It ain't how well they are built, as much as how well they are operated".
 
lancefisher said:
At the beginning of an article on preheating in this month's Plane&Pilot magazine the author made an incredible statement: "Starting a cold engine can give it the equivalent of 500 hours of cruise wear and tear, according to engine authorities."
Click to expand...

By that standards, four starts and the engine is ready for overhaul. Who are these "authorities"? And how do they define "cold"? What rubbish.
 
lancefisher said:
Why do they publish such nonsense?
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Why do pilots, even learned folks such as yourself, continue to read such tripe as P&P?

That magazine is dangerous.
 
Richard said:
Why do pilots, even learned folks such as yourself, continue to read such tripe as P&P?That magazine is dangerous.
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It sure is. More like "redneck Fly'in". I remember an article that discussed whether, after having busted "B", the best strategy was to shutoff the transponder, go for the deck and fly away....or.... all I could think was "Ja_sus".
 
Richard said:
Why do pilots, even learned folks such as yourself, continue to read such tripe as P&P?

That magazine is dangerous.
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The subscription was acquired as a favor to a high school student as part of a promotion to raise money for his swim team. It won't be renewed.
 
Lance:


I've read that mag. a few times and when I know more than authors, watch out!! I've had the same issue with Flying, but have gotten where I just read articles by some authors.

BTW, I was speaking to a mechanic at an FBO shop on my home field that really wanted to do some work for me. In the course of him talking through an oil change with me, he said if I drained my oil and left it out over night, my turbos could lock up.

My point is, there are mechanics out there at the P&P readership level!!

Can you guess how quickly I left?

Dave
 
Dave Siciliano said:
he said if I drained my oil and left it out over night, my turbos could lock up.
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maybe he means if you start it up with all the oil in a drain pan!
 
No, it was pretty clear Dave. Told him when I changed my oil, I come in from a flight, poke a hole in the top of the oil filter, open the quick drain, take an oil sample and leave. Come back the next day, change the filter, fill it up and do a run up check

He pretty much said, leaving the oil out overnight could lock up my turbos. Course, I've been doing this for five years now in the A-36 and this is right out of what ABS recommends. (Not the overnight, but punching the hole in the filter and letting it drain for a sustained period).

Dave
 
Dave Siciliano said:
No, it was pretty clear Dave. Told him when I changed my oil, I come in from a flight, poke a hole in the top of the oil filter, open the quick drain, take an oil sample and leave. Come back the next day, change the filter, fill it up and do a run up check

He pretty much said, leaving the oil out overnight could lock up my turbos. Course, I've been doing this for five years now in the A-36 and this is right out of what ABS recommends. (Not the overnight, but punching the hole in the filter and letting it drain for a sustained period).
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Total BS. First, in many applications the oil drains out of the turbo every time you shut down as the oil from the turbo must return to the oil supply and this is usually gravity assisted. On top of that, an oil film remains for a long time after draining, certainly more than a day. Finally, a perfectly dry turbo would be OK as long as oil reached it before the engine RPM reached much above idle.
 
lancefisher said:
Total BS. First, in many applications the oil drains out of the turbo every time you shut down as the oil from the turbo must return to the oil supply and this is usually gravity assisted. On top of that, an oil film remains for a long time after draining, certainly more than a day. Finally, a perfectly dry turbo would be OK as long as oil reached it before the engine RPM reached much above idle.
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There are a couple things that will harm you turbo

High RPM starts, turbo is spun up before the oil pressure is stable.
quick shut down, oil pressure is removed before the turbo is stopped spinning.

Quick temp changes, setting take off power with one jab of the throttle. etc.
 
lancefisher said:
Total BS. First, in many applications the oil drains out of the turbo every time you shut down as the oil from the turbo must return to the oil supply and this is usually gravity assisted. On top of that, an oil film remains for a long time after draining, certainly more than a day. Finally, a perfectly dry turbo would be OK as long as oil reached it before the engine RPM reached much above idle.
Click to expand...

There are a couple things that will harm your turbo

High RPM starts, turbo is spun up before the oil pressure is stable.
quick shut down, oil pressure is removed before the turbo is stopped spinning.

Quick temp changes, setting take off power with one jab of the throttle. etc.
 
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