What happens if you regularly shutdown a diesel engine with the throttle wide open?

[GManBart]

I'd just like to be able to say, here is why no one should be doing this, and if we continue to do so, these problems will likely crop up.

I think you'll find it hard to find specific failures that can be directly tied to high RPM shutdowns, for a number of reasons. It's not the kind of thing anybody would think to test and document, for one. Second, most of the problems it causes are the kind that take a while to develop...essentially increased wear and tear.

Generally speaking, high RPM shutdowns will cause accelerated wear to a number of engine components. You probably won't see the problems for a while, and when the do start showing up, you can't be sure of the cause. Have a cylinder head gasket fail at 3,000 hours? Well, maybe it was faulty, or maybe it was because the engine was repeatedly shut down without a brief temperature stabilization period, and the cylinder head temps got too high over and over...that sort of thing.

If I've been running an engine under light load I reduce the throttle to idle, and wait a couple of seconds before shutting down. If I've been working it for a while (like the 3hrs of brush hogging I did yesterday), I let the engine idle for at least a minute or two before shutting down, and a couple of minutes more is even better to get the temperatures stable...more than that is probably a waste.

Expecting employees to use that sort of judgement is asking an awful lot, so it might be easier to just tell them to always let the engine idle for 20-30 seconds before shutting down (other than in emergency situations).

 

[JDgreen227]

I may be wrong here, but from my understanding shutdown from full speed will cause numerous problems, ESPECIALLY with a turbocharged engine. I have no idea why any moron would be stupid enough to do this...have to wonder, when they park their personal car or truck do they shift to neutral or park, then floor the throttle and rev it up then shut the engine off? DUUUHHHH

 

[Gary Fowler]

It is just common sense to let an engine idle for at least a few seconds or longer if it has been working very hard. Everything and everybody needs a cool down cycle prior to shut down. Why to athletes walk around a bit after a run? Why do we walk a horse around after a run? Why do Indy cars make a couple laps after the race is finished? Read the OEM manual, why do they all say to let engine idle for x minutes prior to shut down.

Same with start up, even railcar dragsters idle up to the start line and allow a bit of warm up before putting the 4000+ HP to use. Whether it is a push lawnmower, riding lawnmower, tractor, car or locomotive they all need a few minutes to warm up prior to loading them. The smaller the engine the less time it needs to warm up and cool down but they do need that time to stabilize the temps to keep bad things from happening. Engines with turbochargers are even more particular about startup and shut down with shutdown being a critical issue with longevity of bearings in the turbo. Starting at WOT is a no no with any engine. I know some lawnmowers only choke with a notch past full throttle (I have one of them) but I immediately yank back the throttle as soon as it catches. These are just mainly cheap design and save a buck or two in not have an extra cable to run the choke and usually they are harder to start. My no choke cable B&S engine spins and spins prior to cranking while my Kawasaki engine with choke cable rarely needs more than 1 second to start.

Whether you are talking a $500 engine or a $50,000 engine, it pays to start easy and stop easy to make them last longer.

 

[chopped]

. I have no idea why any moron would be stupid enough to do this...have to wonder, when they park their personal car or truck do they shift to neutral or park, then floor the throttle and rev it up then shut the engine off? DUUUHHHH[/QUOTE]
DUUUHHHH[/QUOTE] DUUUHHHH[/QUOTE]
LOL:laughing::laughing:

 

[SPYDERLK]

. I have no idea why any moron would be stupid enough to do this...have to wonder, when they park their personal car or truck do they shift to neutral or park, then floor the throttle and rev it up then shut the engine off? DUUUHHHH

LOL:laughing::laughing:

I dont know why anyone would do it either ... just impatient laziness I think.

-- The analogy to flooring the throttle prior to shutoff is not accurate however. Thats a full power condition on a non governed engine - and it can rev way hi. Best way to wash the cyl walls down with gas. Oh the irony -- investing extra time to do an action that harms the engine. DUH is right. :wink:
... Hi idle is a lo power, lightly fueled, condition because the engine is just spinning at steady moderate speed and not working against an outside load or to spin up its inertia.
larry

 

[GManBart]

I have no idea why any moron would be stupid enough to do this...have to wonder, when they park their personal car or truck do they shift to neutral or park, then floor the throttle and rev it up then shut the engine off? DUUUHHHH

Some people do just that...blip the throttle just before turning off the key. I've seen a famous British race car driver do that over and over on one of those shows where they drive famous vintage race cars....he's shutting down a multi-million dollar Ferrari and blips the throttle before shutdown. Guess he doesn't realize it has like four timing chains (prior to all gears) that can skip a tooth doing that (inertia of the chain wants to keep it going when the cams and crank stop) and possible cause valve/piston contact....just stupid.

 

[SPYDERLK]

What do you think happens when you catch a gear? Every shift.

 

[GManBart]

What do you think happens when you catch a gear? Every shift.

The engine rpm slows, but doesn't stop...different scenario and loading.

 

[SPYDERLK]

.. No.

 

[jim44]

Interesting question. I can see this happening if the workers involved are government employees, but on a "family farm" (mine) it would happen no more than ONE TIME. I would not be paying a worker to be stupid.

Seems that the main question should be WHY? .