Oversquare ops

[unreal]

I've noticed that the old rule of "never operate with a higher MP than RPM divided by a hundred" is still alive and well, both at my current school, and apparently at others as evidenced by the thread about power reductions after takeoff.

This never made a whole lot of sense to me to begin with, simply because turbocharged engines are almost always operated oversquare, and normally-aspirated engines often takeoff oversquare, and even have cruise power settings that allow for oversquare operations. Now, I have two questions:

1) Are turbocharged engines typically built to handle a higher loading compared to normally-aspirated engines, or is the oversquare fear on NA engines just a kickback to that "old rule"?

2) On a typical NA engine found a light aircraft (we'll say anything up to an IO-550), does operating the engine oversquare even really do anything that'll cause a reduction in service life? My understanding is that the old oversquare rule had more to do with old radials than anything else.

Just curious about all of this. I've found that my school is chock full of "old rules" that someone came up with years ago and nobody ever questioned. Unfortunately a lot of that has seeped into my own training, so it'd be nice to get to the bottom of this as to get out some of those bugs.

 

[CA1900]

I've noticed that the old rule of "never operate with a higher MP than RPM divided by a hundred" is still alive and well, both at my current school, and apparently at others as evidenced by the thread about power reductions after takeoff.

It amazes me, too. You have two entirely separate readings, in different units, measuring different things. Why in the world would they be related? What if you measured centimeters of mercury instead of inches? What if the prop tach were in "Thousands of revs per hour" instead of "Hundreds of revs per minute"? 2400 would all of a sudden be 144, but would be the same speed. Would that mean I could then go to 144 centimeters of mercury? What about 144 inches?

There's only one "guideline" for operating an engine, and it's found in the operating handbook for it. I'm not sure where that "oversquare" idea originated, but I'd venture that very few engine models are actually restricted that way.

This never made a whole lot of sense to me to begin with...

Go with your gut! Because you're absolutely right.

1) Are turbocharged engines typically built to handle a higher loading compared to normally-aspirated engines, or is the oversquare fear on NA engines just a kickback to that "old rule"?

Depends entirely on the specific engine. Some simply use turbocharging to maintain sea-level manifold pressure to a higher altitude. Others allow pressures higher than sea-level pressure, and of course that would require a sturdier engine (or shorter engine life).

2) On a typical NA engine found a light aircraft (we'll say anything up to an IO-550), does operating the engine oversquare even really do anything that'll cause a reduction in service life?

Quite the opposite, actually. Assuming you stay within the pressure limits of the engine, let's say you're presented with two possible power settings for a given percent of power: One is a higher-RPM, lower-MP setting, and one is lower-RPM, higher-MP. I'd contend that the more revolutions you put on that engine, the more you're wearing it out. Every time it goes around, each valve is getting cycled, each bearing is wearing, etc. I'd go for the lower-RPM setting for the same reason I do it in my car by going to the highest gear possible: a quieter airplane (inside and out), less engine wear, and better fuel economy because of reduced engine friction.

My understanding is that the old oversquare rule had more to do with old radials than anything else.

It's another bit of "knowledge" that was never correct. Take the F4U Corsair's R2800 engine: Rated-power climb was 42.5" of manifold pressure on 2600RPM.

Just curious about all of this. I've found that my school is chock full of "old rules" that someone came up with years ago and nobody ever questioned.

That's the beauty of teaching people to fly: You're motivated to find real answers, not conjecture, and you'll often find that the things you thought were true--like the "oversquare" myth--really aren't. If someone refuses to believe that it's a myth, ask them to show you in the aircraft manual, a flight training manual, or any kind of definitive source. I'll bet you they can't.

 

[USMCmech]

1) Are turbocharged engines typically built to handle a higher loading compared to normally-aspirated engines, or is the oversquare fear on NA engines just a kickback to that "old rule"?

First off, there are two kinds of turbocharged engines on airplanes.

Turbonormalized engines with automatic wastegate turbos should maintain no more than 31" no mater what you do with the throttle. In this instlation the turbo does nothing for you at sea level. It gradually adds in boost to offset the lower pressure as you gain altitude.

Turbocharged engines with fixed wastegate turbos will have a maximum allowable MAP, useually about 40". If you add full throttle at sea level you will overboost it and poossibly cause a seal to blow on the intake manifold. The engines are built to handle the added pressure, therefore as long as you don't exceed the limits, you're OK.

2) On a typical NA engine found a light aircraft (we'll say anything up to an IO-550), does operating the engine oversquare even really do anything that'll cause a reduction in service life? My understanding is that the old oversquare rule had more to do with old radials than anything else.

Operate your engine by the figures in the POH and you'll be fine. 2100/23" is no problem on most engines. The slower speed may actually reduce vibrations which wear on your accesories. All the old radials ran oversquare, some racers at Reno run about 2500 RPM and 70" MAP!

Now, don't get stupid. It's apropeller not a paddelwheel! 1800/29" on most engines is not published in the operating handbook, and will proabaly break soemthing eventually.



I too learned most of these false myths about piston engines as I was training at a large flight school with glossy ads in Flying. My time at A&P school cured quite a few of them.

Read the articles from Avweb by John Deakin.

http://www.avweb.com/news/pelican/list.html

Best tutorial on engine operation I have seen.

 

[pilotyip]

undersquare bad

On round engines, R-1820's etc. Oversquare ops are not a big deal if done within the limits specified for the RPM and MAP. Used to launch off the boat in the C1A, no cat 59.5" 2800 RPM. But on round engines undersquare is to avoided if at all possible. Undersqaure causes the prop to drive the engine and reverses the loads throughout the drive gears and increases the likely hood of premature failure.

 

[midlifeflyer]

Open a piston POH. Look at the power setting table. Then look at the engine manufacturer's operating tips on its web site (Lycoming generally recommends the highest MP and lowest RPM combination in the table for smooth operation).

 

[avbug]

Correct responses on all accounts. Oversquare operation is a myth.

You asked if there's a difference between a boosted engine and one that isn't, with respect to construction...in most cases, no. The same engine that's normally aspirated vs. one that's boosted (turbocharged, supercharged, turbonormalized, turbocompounded, whatever) usually involves the same part numbers. For example, an O-520, IO-520, and TSIO-520 may use the same cylinder part numbers. Same construction, same material, same workmanship...but for different engine designations. This isn't always the case, and you need to refer to the specific engine...but the truth is that blown engines (boosted) often use the same parts that normally aspirated engines do. The increase in pressure isn't so much stress on parts due to pressure, but due to head, and decreases the margin approaching detonation in cylinders...which tends to do more internal damage than external...which is part of the reason that in many cases the same cylinders are used for both engines.

If you think about it, a normally aspirated engine operating at sea level will be showing nearly thirty inches of manifold pressure before any ram air rise at high power settings. Your RPM is typically 2500 to 2700 rpm at the prop, which means your takeoff manifold pressure is already "oversquare."

As was previously stated, you need to look at your manufacturers power tables and limitations to determine what's applicable to your aircraft, and you should always stay within those limitations. Many more issues apply to a power setting than oversquare...oversquare is a non-existant theory without any backing, which has been passed down from instructor to student in what I like to call the heritage of inexperience...one statement of ignorance passed from an inexperienced instructor who was told it by another inexperienced instructor who was told it by another inexperienced instructor, ad nauseum.

Other issues affecting takeoff power setting are the compression ratio, propeller limitations, type of drive and gearing, crank shaft design, harmonic issues, and a host of other reasons that a given limitation or power combination is provided by the manufacturer. The manufacturer has subjected the engine to very expensive and extensive testing...the manufacturer does not explain why the limitations apply in most cases, but you should always abide by the power schedules, fuel flows, temperatures, RPM's, and other criteria established by the manufacturer.

Pilotyip touched on the issue of undersquare operations...operating undersquare, per se, won't necessarily cause harm to your engine. But operating undertorque can...the potential for damage is greater in some engines than others. As a general policy, operating when the propeller is driving the engine isn't a good policy and it's a matter of poor airmanship. You'll find some in aviation who disagree with this...Avweb publishes a list of "Aviation Myths" which include this among others. I disagree, and I've had discussions about it with the author and many others...the particular type of engine is a big consideration, but even simple direct drive engines as a rule shouldn't be descended for prolonged periods of time at idle at high airspeeds, when the prop ends up driving the engine.

"Undersquare" operation is okay, to a point...only when you hit a point of zero torque when the engine isn't driving the prop, can you run into potential problems. In piston engines, and reduced power settings, thermal issues can become a concern, which is another reason to avoid prolonged operations at reduced power, too.

Operation "oversquare" isn't so much about overboosting anything or lifting heads, but more about detonation...but again, the "oversquare" issue is a mute point...nonexistant becuse it presumes a relationship or rule which simply does not exist. As always, refer to the manufacturer recommendations, proceedures, schedules, and limitations.

 

[Huggyu2]

"Undersquare" operation is okay, to a point...only when you hit a point of zero torque when the engine isn't driving the prop, can you run into potential problems. In piston engines, and reduced power settings, thermal issues can become a concern, which is another reason to avoid prolonged operations at reduced power, too.

I'm trying to understand, since I'm very new to all of this. Is the zero torque issue a problem because everything is sort of "floating", e.g. the prop isn't driving the engine and vice versa?
And in your second sentence, are you referring to "shock cooling", or something along those lines?

 

[avbug]

This depends on the engine. Geared engines vs. non geared engines, size, drive, make up etc. Floating isn't really a correct analogy, though backlash, especially in geartrains, can be an issue. Torque is reduced or reversed, with a reverse loading on bearing journals, crankshafts, etc. Pressure, wear, and fit is brought to bear opposite and out of sync in gear teeth, and on bearing surfaces. (Some argue this, saying the engine is still turning in the same direction and therefore this cannot be...but they're incorrect).

Thermal issues can include shock cooling, though that discussion is beyond the scope of this thread. Shock cooling is a controversial subject. A primary means of temperature control and cooling in an aircooled engine is airflow, as well as power management (to include power settings, engine RPM [and subsequently propeller RPM], mixture setting, etc).

Suffice it to say that one should treat one's engine as though one's life depends upon it, becasue surely it can do. The ignorance with which engines are often treated, as a function of the heritage of inexperience (particularly in the training arena) means that many pilots are scarcely aware of the proper operation of the powerplants under their control...a lot of abuse takes place. One can get away with it in some powerplants, but not in others. Fostering good habits is best done when both taught properly, and practiced properly, and good airmanship dictates that one properly treat one's equipment, even when the equipment is forgiving enough that one may get away with poor behaviors.

 

[Big Dog]

I have done a little research on the topic. As it turns out, 25" - 2500RPM is about 75% on most IO type engines, which is recommended for climb in many A/C. 23" - 2300rpm is about 65%, which is good for cruise in many A/C. I would imagine many operators told there students to operate the engines at those settings to 1. Give them a starting point & 2. Help control wear and abuse.

In short, operating over square is a myth. One should always consult the POH to find the proper power setting. In general, pick the percent power that is appropriate for the operation (high speed cruise/climb power - 75%, reduced wear/normal cruise - 65%, extended endurance - 55%, holding power - 45%, ect.) I can't stress how general that all is. The C402B (large bore, turbo charged) recommends no more than 70% power where the C172R can be run at 80%. Then use the combination of RPM/MP that gives that percent power. In general, higher RPMs will give you higher CHTs (increased friction heating) and higher fuel burns. I tend to use the higher MPs with 2300rpm w/ most normally asperated engines to get the best combination of KTAS/engine wear/fuel burn as opposed to incresing the RPMs to 2400-2500 rpm, although according to most POHs either is allowed. Of course this will all vary slightly with specific atmospheric conditions and altitudes.

Again, I can't stress how general that all is and how important it is to read both the A/C and engine POHs and to read, understand and follow the power charts and recommended procedures. Also remember that many older A/C have STC's and the books may not reflect what is actually in the A/C, for example, older C172s w/ O-360 180hp Lycomings or BE58s w/ IO-550s. But that's another kettle of fish...

 

[Wiggums]

What aircraft POH recommends you climb at 75%? Always climb at max continuous at the recommended airspeed from the POH.

 

[DC8 Flyer]

What aircraft POH recommends you climb at 75%? Always climb at max continuous at the recommended airspeed from the POH.

If I remember correctly, the seminole POH called for 25" and 2500 RPM for climb and the baron called for 2500 rpm (full throttle) for the climb. IIRC.

 

[avbug]

Most aircraft have a variety of climb schedules, just as they have cruise schedules. Climbing at full power may or may not be necessary...again, according to your mission. If you're doing pattern work, for example, carrying full power to one thousand feet or fifteen hundred feet may not be reasonable...you may be making a power reduction right after takeoff just to keep it slow and keep the rate of climb reasonable...all depends what you're doing.

The subject of operating at reduced power has been mentioned as a way of saving wear on the engine. Operating at a reduced manifold pressure does not necessarily save anything...reducing RPM does, but sometimes at other costs...and may still result in more wear. You need to look at your specific mission--what you're hoping to accomplish with the aircraft on a specific flight--to determine what schedules you want to fly.

Takeoff thrust or power is not necessarily the same as climb thrust or power. Use what you need, and what you have planned. Using maximum takeoff power when it's not needed is just as ridiculous as not using enough when you need more. Use what you need.

 

[orcfi]

There's only one "guideline" for operating an engine, and it's found in the operating handbook for it. I'm not sure where that "oversquare" idea originated, but I'd venture that very few engine models are actually restricted that way.

This is 100% correct

Quite the opposite, actually. Assuming you stay within the pressure limits of the engine, let's say you're presented with two possible power settings for a given percent of power: One is a higher-RPM, lower-MP setting, and one is lower-RPM, higher-MP. I'd contend that the more revolutions you put on that engine, the more you're wearing it out. Every time it goes around, each valve is getting cycled, each bearing is wearing, etc. I'd go for the lower-RPM setting for the same reason I do it in my car by going to the highest gear possible: a quieter airplane (inside and out), less engine wear, and better fuel economy because of reduced engine friction.

This is incorrect with the respect to pressure issues. At a given manifold pressure, higher RPM's are easier on the engine. However, pressures only come into play at higher MP settings. A normal piston aircraft engine (non FADEC) has fixed timing. The cylinder usually fires about 20 to 25 degrees prior to the piston reaching top dead center. The mixture does not just explode, it burns with a flame front progressing from the plug to the center of the cylinder. Ideally, peak pressures within the cylinder happen as the piston is travelling back down, producing optimum mechanical advantage (peak power). If the piston is travelling slower (slower RPM), then the pressures are higher because the mixture is firing closer to top dead center, meaning that it has to overcome the position of the connecting rod, producing more pressure within the cylinder (bad) and less power.

 

[Fedora]

Try investigating Charles Lidburgh's efforts in the western Pacific in WWII.
He played a major part in teaching American pilots how to fly the P-38!
Oversquare was what he preached, and he increased the range of the aircraft by almost twice, without damaging the engines. Good story, really!

 

[Rally]

I've noticed that the old rule of "never operate with a higher MP than RPM divided by a hundred" is still alive and well, both at my current school, and apparently at others as evidenced by the thread about power reductions after takeoff.

This never made a whole lot of sense to me to begin with, simply because turbocharged engines are almost always operated oversquare, and normally-aspirated engines often takeoff oversquare, and even have cruise power settings that allow for oversquare operations. Now, I have two questions:

1) Are turbocharged engines typically built to handle a higher loading compared to normally-aspirated engines, or is the oversquare fear on NA engines just a kickback to that "old rule"?

2) On a typical NA engine found a light aircraft (we'll say anything up to an IO-550), does operating the engine oversquare even really do anything that'll cause a reduction in service life? My understanding is that the old oversquare rule had more to do with old radials than anything else.

Just curious about all of this. I've found that my school is chock full of "old rules" that someone came up with years ago and nobody ever questioned. Unfortunately a lot of that has seeped into my own training, so it'd be nice to get to the bottom of this as to get out some of those bugs.

Its a bunch of crap.....I have a Cessna 172 that is 1956, it just happens to have a manifold pressure guage. (don't know why) guess what you will be running over square until you reach about 5000 msl. Follow the POH, otherwise people are trying to reengineer or make up procedures that really have no basis. Its pretty dumb, yes most turbo a/c cruise over squared. Does'nt seem to TEAR them apart. The other thing that kills me is the BIG hurry to get the power pulled back, just relax pull it back lesiurely at 1000 agl or so, no big deal or hurry. Geez.

 

[RedGuy]

Actually running high pressures do take their toll on turbo charged engines. I fly 310's and 402's they both use identical engines, Continental IO-520's. But the 402 is turbocharged and always cruses over square. The 310's run to 2200hr TBO, and the 402's only get 1800hr TBO. On the 310 you can't tell the difference between a 200hr engine and a 2200hr engine. On the 402 you can feel her getting tired when it's getting near TBO, CHT's start running high, oil turns black quickly, uses more oil, has less power, and use more fuel. So running higher pressures definitely cause more wear.

 

[avbug]

Higher pressures don't cause more wear. More heat causes more wear, higher RPM causes more wear, inconsistant operation, heating and cooing differences...these cause more wear. The engine doesn't know, and can't tell about cylinder pressure...the fuel air mixture knows about it, and responds with detontion under very specific circumstances...which does reduce engine life. But higher pressures of their own accord do not reduce engine life.

Two entirely different airplanes. Same manufacturer of the engine, but not the same engine. Not the same fuel system, delivery system, operating parameters, cooling, induction..different engines. Apples to oranges. Poor comparison, and one cannot draw conclusions with any degree of accuracy as you've done there.

Nice try, though.

 

[RedGuy]

Higher pressures don't cause more wear. More heat causes more wear, higher RPM causes more wear, inconsistant operation, heating and cooing differences...these cause more wear. The engine doesn't know, and can't tell about cylinder pressure...the fuel air mixture knows about it, and responds with detontion under very specific circumstances...which does reduce engine life. But higher pressures of their own accord do not reduce engine life.

Two entirely different airplanes. Same manufacturer of the engine, but not the same engine. Not the same fuel system, delivery system, operating parameters, cooling, induction..different engines. Apples to oranges. Poor comparison, and one cannot draw conclusions with any degree of accuracy as you've done there.

Nice try, though.

Your right higher heat does cause more wear. With higher cylinder pressures you will get higher temps, you'll also get more blowby which breakes down the oil faster. The planes while they may look entirely differant, they're not, they share many systems and from the wing root out they are identical to a turbo 310. And actually they are the same engine, same fuel system, and same fuel delivery, induction and cooling are the only differences. The 402 is turbo charged, and has additional cooling via cowl flaps. The 310 is generally operated at 2300rpm and 23 inches MP, the 402 is run at 2300rpm and 30 inches of MP. This isn't apples to oranges, it doesn't get any closer than this.

 

[avbug]

Again, nice try. Two entirely different airplanes. Make very small changes, such as small holes or positioning of baffles, or sizes or shapes of inlets, you have completely changed the thermodynamic cooling process of the engine, and you can make zero comparisons between the two...mount even identical engines (these are not, despite what you may think) on two different airplanes, swinging different propellers, at different speeds under different conditions in different cowlings with different baffles with different inlets, different inductions, different cowl openings...you have different engines and most certainly you do have apples to oranges comparisons.

Same spark plugs and timing? Same cooling inlet area, outlet area, and shape? Same baffling, same fuel flow, same airflow? No.

Moreover, operating at 30" isn't much of a boosted pressure...certainly not enough to cause excess wear and damage. Think about it...the airplane at sea level when normally aspirated runs at that value, paricularly with ram rise in flight. That's not highly turbocharged, that's turbonormalized...and yes, there is a difference. You're boosting to sea level pressure only...no different than what the normaly aspirated airpalne is capable of seeing. Blowby isn't increased, nor is it really an issue. I believe you mentioned darkening of the oil before, which is a ridiculous measure by which to assess wear in an engine...color is irrelevant and meaningless. You appear to believe this is a result of blowby and evidence that one engine is experiencing more wear, which puts your observations squarely in the realm of those of a housewife understanding her car. You can do better than that.

During a standard compression check I flow 80 psi or greater to the cylinder, and some of it may or may not leak past the valves or the piston. An engine close to TBO may have nearly perfect compression, or it may not. TBO is a reference number, and other than some legal implications, it's largely imaginary. Further, an overhaul may be nothing more than verifying that parts are within tolerance and putting them back...laying some lack of creditiblity to the idea that engines wear out at TBO...TBO doesn't mean much, and overhaul means even less.

W(h)eather you believe it or not, you have two different engines there, in two different aircraft, under two different circumstances and two different operating parameters. Apples to oranges. Examine two identical 402's, operating one at the lower RPM and manifold pressuree setting, and the other at the higher power setting, and if operated properly, you won't see much difference, if any. Especially at those minimal power settings.

Of course, when you're running 30 inches, you're running the same induction pressure as you get with the normally aspirated engine at sea level, when the normally aspirated engine is SHUT OFF...that's barometric pressure, and that's what your manifold pressure gauge will read when the airplane isn't even running...think about it. What you have are thermal differences which are not a consequence of the manifold pressure, but the combustion process and your mixture and power settings, being operated by different pilots at different times.

I ran a fleet of nearly 30 airplanes that all had the 0-520's, some turbocharged, some not. Most everything made it through TBO without worries, and most could have gone far beyond, very few problems, because we looked after them. They were regularly used, regularly inspected, some coming in for 100 hours two times a month. When I flew the boosted airplanes, I seldom used much boost because I didn't need it, but operationally, we had better value with the normally aspirated because they weighed less and were a little less complex and did the same job.

When you shut down your turbocharged models, are you running them for five minutes to cool the turbo and help eliminate coking in the turbo bearings? your black oil is the result of residual oil in the case following a change, and thermal differrences. Blowby does contribute to darkening of oil, but may be considered inconsequential, becuase to some degree you're always getting it, and if it's enought to be causing breakdown of the oil, you're already low enough on your compressions (and cylinder pressure isn't the cause) that you need to be doing something about it. Regular oil changes are the order of the day. If you're not operating the engine properly, you're going to see more wear. Adequate warm up and cooling periods, as well as preoiling, will make a lot of those problems and the wear you're seeing go away.

As far as running at 30" being the cause of excessive wear...it's good for a laugh, but not very realistic.

How do you suppose we could run 45" or more inches of manifold pressure and still have engines left? How do you suppose the normally aspirated engines run all day long at the same 30" hg. of turbonormalized induction pressure as your 402, without a hiccup? Truth is that you're not providing anything to that engine that it doesn't see sitting on the ramp cold and quiet...other than heat and pilot abuse.

Again, nice try.

 

[RedGuy]

Look I know I could go on an on and you would always have some sort of counter because you know everything. But comparing there 2 are not apples and oranges. Are these two exactly identical circumstances, no, but relevant to this conversation since no one else has given any other comparisons, including you, it's the best that we've got. Comparing these to are like comparing green apples to red apples. Also the fact that you say the 402 is turbo normalized leads me to believe you don't know a dang thing about the 402. They are not turbo normalized, 30 inches is just the cruise setting that we use, you can use 32inches and 2300rpm and they go up to 34.5 inches and 2700rpm for max power in the B models and 39.5/ 2700 in the C, BUT the C DOES have a different engine, still a 520 but a different model, where as the B's use the same model 520. The inlets are the same, the baffling is different and the outflow are different to allow MORE cooling on the 402, which should make the engine last longer. Also they are swinging the same propeller and both A/C go the same speed. So again for the purposes of this discussion this is as close as it gets, since no one has come up with a better example.

Also I never said it causes excessive wear, it increases wear. Blowby IS increased, anytime you put more pressure into a cylinder you will inevitably get more gases that pass by the cylinder rings (more blowby), they teach you that in basic auto shop! Also color of oil is not irrelevant, if your oil is dark you have more particulates in it, which will break the oil down chemically or cause it to form sludge blocking oil passages, again basic auto shop here, nothing earth shattering. If blowby and oil color was meaningless and irrelevant then we wouldn't have systems to remove blowby or change our oil. Why do you think you can drive 100,000 miles on your transmission fluid (which is just oil) but only 3,000 on your engine oil? It's because blowby breaks the oil down, since there's no blowby gases in the transmission the oil doesn't break down.

You also keep referring to the fact that when you cruise in the 402 at 30 inches it's the same as a N/A engine at sea level. This is true, but a N/A engine is only going to be at that pressure for a few seconds because even at full throttle the instant you break ground the pressure will drop. No N/A engines cruise anywhere near 30inches and in most cases you don't even get 30inces on takeoff since the air is restricted slightly through the induction system and filter. Also I still don't understand your rationalization that an engine not running on the ramp showing 30in is the same as a running engine at any MP, that just doesn't make any sense.

We run or engines far past TBO through approval from the FAA, the 402 goes from 1400hrs to 1800hrs and the 310 goes from 1600hrs to 2200hrs. The 402 still gets a lower TBO because of the simple fact that they do wear out faster. Why because we're running higher pressure through them, which produces more power, which produces more heat, more blowby and just generally causes things to wear out alittle faster over the long term. Is it excessive wear no, but it is increased wear.

And yes, we use adequate warm up, cool down and cool the turbo's before shut down.

The end.