Diesel engine testing

merlin

merlin

merlin

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This is work related but maybe some engine geeks can help me understand.

3 weeks ago a car manufacturing plant got a little upset as they were testing an engine which failed before it should have failed.

In a nutshell, this engine was set up to run at 7,500rpm constantly. It blew apart after 1140 hours. It should have lasted 1200 hours.

Reason for the failure isn't really relevant - I just can't get my head around why/how this engine was being run at 7,500rpm because it's actually a Diesel engine.

I've no idea whether the engine was just free revving or under load.

Twice now I've asked for confirmation of the set rpm for the test and twice I've been told 7,500rpm so there's no way I've misheard.

Data protection & all that rubbish so I can't give any more info on who is involved etc but maybe someone can explain why the engine was running at 7,500 rpm?
 
Sounds like a stress test tbh. That sort of speed would show accelerated wear over standard operating speeds and therefore reduce the length of time the test would take, or alternatively act as a worst case scenaro. It's fairly standard to test things well outside their usual operating range to see what happens.
 
I should explain - it's not a race engine and the capacity is 2.0 and it goes into family type cars.

It's your regular dull diesel engine for your regular dull family type car.
 
Dolph said:
Sounds like a stress test tbh. That sort of speed would show accelerated wear over standard operating speeds and therefore reduce the length of time the test would take, or alternatively act as a worst case scenaro. It's fairly standard to test things well outside their usual operating range to see what happens.
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Yes, they say it simulates 100,000 miles.
 
I know you can't go into details J, but I find this really bizzare. Surely a test is just that, a test. Why did they 'get upset' when it failed the test? A test, by it's very nature, is going to involve either passing or failing :confused: :confused:
 
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As some of you may know I spend my days sitting in the middle of an engine test facility. Never heard of doing overspeed tests (assuming it is actually operating outside it's normal range) to that kind of extent though.

1200 hours pretty much sounds like a full engine life durability test where the engine would usually cycle over it's full range of speeds and loads. If they were testing the effects of inadvertantly running at 7.5k I wouldn't expect the test to last any longer than a few hours.
 
DreXeL said:
I know you can't go into details J, but I find this really bizzare. Surely a test is just that, a test. Why did they 'get upset' when it failed the test? A test, by it's very nature, is going to involve ether passing or failing :confused: :confused:
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They said it was "unacceptable" the engine did not hit 1200 hours.

Their engineers have calculated that 1200 hours = 100,000 miles.
 
kaiowas said:
As some of you may know I spend my days sitting in the middle of an engine test facility. Never heard of doing overspeed tests (assuming it is actually operating outside it's normal range) to that kind of extent though.

1200 hours pretty much sounds like a full engine life durability test where the engine would usually cycle over it's full range of speeds and loads. If they were testing the effects of inadvertantly running at 7.5k I wouldn't expect the test to last any longer than a few hours.
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I can't really comment on whether the test is a reasonable durability test, i'm not clued up on that sort of stuff, I just know they equate 1200 hours @ 7.5k to be 100,000 = pass, but the engine failed.

What I don't understand (because again I'm pretty clueless on these things) is whether the engine would have just been free revving @ 7,500 or whether it would have been under load? Diesel doesn't burn quickly enough for 7,500rpm & this is just a bog standard 2.0 D engine.
 
Is there any chance that the engine was just being used as a mule to test a particular component (piston rings, bearings etc)?

In that case it may be that the engine was being motored (ie driven by the dyno in a similar way to when you coast down a hill) in order to increase engine speed and reduce the time taken to put a certain amount of wear on the relevant components.

Edit, having though about it you couldn't test rings in this way as they would need to see realistic combustion pressures for the test to be valid. They could concievably be testing bearings though.
 
kaiowas said:
As some of you may know I spend my days sitting in the middle of an engine test facility. Never heard of doing overspeed tests (assuming it is actually operating outside it's normal range) to that kind of extent though.

1200 hours pretty much sounds like a full engine life durability test where the engine would usually cycle over it's full range of speeds and loads. If they were testing the effects of inadvertantly running at 7.5k I wouldn't expect the test to last any longer than a few hours.
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I want your Job! :eek:
 
Is it just me who thinks that sustained 7500rpm on a diesel engine without exploding until it had covered a simultated what.. 95,000 miles, is damn good?
 
merlin said:
No, they just test one, then they start production.
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Any of the big players would be running a lot more engines that that before going to production. Even if an existing design is put into a different vehicle there'd be at least 2-3 validation engines to ensure that changes to the ECU calibration haven't caused any issues. An all new design would go through anything up to a couple of hundred engines.
 
kaiowas said:
Is there any chance that the engine was just being used as a mule to test a particular component (piston rings, bearings etc)?

In that case it may be that the engine was being motored (ie driven by the dyno in a similar way to when you coast down a hill) in order to increase engine speed and reduce the time taken to put a certain amount of wear on the relevant components.

Edit, having though about it you couldn't test rings in this way as they would need to see realistic combustion pressures for the test to be valid. They could concievably be testing bearings though.
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It was an "engine test", so I guess they were just expecting no problems up to 1200 hours. They intended to simply run it for as long as possible but so long as it hit 1200 hours it's a pass.

The top end failed.

Engine being "motored" to 7,500 rpm makes sense!
 
kaiowas said:
Any of the big players would be running a lot more engines that that before going to production. Even if an existing design is put into a different vehicle there'd be at least 2-3 validation engines to ensure that changes to the ECU calibration haven't caused any issues. An all new design would go through anything up to a couple of hundred engines.
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These are big players! Huge in fact.

Bear in mind I only have the information that's been fed to me though. This test could have been one in a series of tests. I just don't know the absolute full story.

Certainly I know for an absolute fact that they were ready to start making engines, then they had the failure, then they were not best pleased as the track stood still untill a revision was made and finally the engine let go AFTER 1200 hours.
 
[TW]Fox said:
Is it just me who thinks that sustained 7500rpm on a diesel engine without exploding until it had covered a simultated what.. 95,000 miles, is damn good?
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Yes and no.

Yes in that 7,500 rpm in a diesel is impressive as it's waaaay outside usual trim.

No in that it failed at 95,000 miles, well, that's if you agree that 7,500 rpm over 1200 hours = 100,000 miles. Their engineers have always worked to this formula.
 
We're all assuming it was actually running on diesel. Is it possible they were using some alternative fuel in it, which could burn fast enough to make 7500rpm possible?
 
Merlin, give Simon a call, you know he does this thing for a living, so he's the one to speak too.

Though, with the higher revs it's used to simulate wear and tear on the engine. My RVS red lines at 4500rpm, and limiter kicks in at 5000.
 
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