This is a long shot but I thought I would ask.
Is anyone or has anyone worked in engine development testing before ?
Are engines tested to destruction and if so is it to find weak points in an engine ?
Are they tested without coolant / oil to see what breaks ?
How do the car makers perform accelerated life testing (i.e put 1 million miles on an engine) ?
Like I have previously said, this is a long shot but I have always wondered what testing was carried out.
Or is the above irrelevant as we are all testers for the car makers (much like computer software) ?
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A work colleague of mine used to work at Ricardo in the early 90's and tells great stories of blowing up various Ford and Volkswagen engines in the name of research!
What a job.
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I haven't worked in engine testing, but, based on other types of engineering testing I have done, I can answer some of your questions;
>>Are engines tested to destruction and if so is it to find weak points in an engine ?
Not routinely. It would be much more likely to find an engine being tested against a fatigue life specification (so many hours at so many revs, at a certain load, under certain environmental conditions). It will be reasonably common for tests to be extended an agreed percentage beyond the spec to make sure there are no "cliff edge" failures just beyond the spec.
The test spec, and over plan of tests is manufacturer specific.
Testing to destruction tends to be a very poor way to gain experience, it is costly in terms of time, test facility use, and engines.
>>Are they tested without coolant / oil to see what breaks ?
Why should they be? The outcome is obvious, and there's nothing to be learnt or proven by such a test.
>>How do the car makers perform accelerated life testing (i.e put 1 million miles on an engine) ?
There are many methods for calculating load and speed factors for accelerated life testing, and they are all a bit of a bodge. However, it's just a case of running faster, under more load, and under worse environmental and usage (i.e., frequent stop starts) conditions than you expect to see.
For complex built up parts like engines, most of the testing is already carried out on component level, meaning that there are fewer expensive engine level tests (dust tests for air filters, for example) - the skill in this approach is in applying the correct testing to the sub-components to minimise the risk of it failing at engine level without going over the top, and over testing, and over-specifying every part in the engine.
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minimise the risk of it failing at engine level without going over the top, and over testing, and over-specifying every part in the engine.
And similarly without under-testing and under-specifying some part or parts in a way that will only show up in a percentage of cases around the time of warranty expiry, as with the famous Corsa camshaft bearing cap bolts NC...
It occurs to me that test units are likely to be correctly assembled - what they used to call 'blueprinted' - in a way that production engines may not be even with robots replacing unreliable and ham-fisted bolshy workers with hangovers. No doubt some early production units are given thorough road testing (anyway they should be). But perhaps due allowance isn't always made for slapped-together mass-produced units as opposed to engines made as they are designed to be. Perhaps these margins are best addressed by an intuitive element in the makeup of a decent production engineer...
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I don't think the Corsa problem would have been found by this type of testing Lud - but, as neither of us knows the true root cause of the failure, we are just speculating.
But, yes, it's important to make sure component and sub-assembly testing, and the following complete engine testing plan doesn't leave any gaps.
Some degree of over-testing at component level is actually not that bad, because it happens earlier in the life of the project, and removes risk from the final engine level testing.
>>It occurs to me that test units are likely to be correctly assembled...
I know that here automotive practice does differ from the aerospace practice which I know a little more about. For flight qualification testing, the qualification units must be built using exactly the same materials, processes, and conditioning as will be used for the flight build. Any change during the flight build run - for example a bought in part becoming obsolete - may mean that the unit needs to be re-qualified to allow the use of the different part, material, or process.
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aerospace practice
Very different of course when all the engines are assembled meticulously by skilled fitters. Rolls-Royce who are a name in aerospace engines used at one time to make their car engines like that and run each one in, first on an electric motor with special lapping oil in the sump and then for some hours at varying speeds and loads with running-in oil.
Lenin (among others) swore by the product...
Edited by Lud on 28/04/2009 at 18:09
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The real difference in practice is that what you qualifiy is what you have to supply, wheras most automotive testing is being done for less rigorous reasons.
Of course, in automotive practice, what is tested for type approval, mpg, emissions and other regulatory tests *should* be what's actually put into production.
>>used at one time to make their car engines like that and run each one in, first on an electric motor with special lapping oil in the sump and then for some hours at varying speeds and loads with running-in oil.
Sounds good, but was actually used to cover up some pretty shoddy dimensional tolerances - they also used selective assembly to reduce similar mis-matches.
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selective assembly to reduce similar mis-matches.
...like traditional gunsmiths before Colt and Springfield invented Fordism during the American civil war... the point was surely that today's levels of large-scale precision were difficult to maintain with early 20th century equipment, and fettling by hand was a way of producing a pretty fine result despite that. Of course it was quite expensive. But I bet a real lemon of a RR Phantom 1 was still a desirable car by the standards of the day.
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War-time experience in the aircraft industry echoes NCs point. The Merlin engine showed how Packard improved on RR hand-assembly techniques, whilst using semi-skilled production line workers. Not to mention GM Pontiac division re-design of main bearings. Snippet here: www.bookrags.com/wiki/Rolls-Royce_Merlin
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Slightly off topic but are there any truly fully hand assembled engines being made any more. I normally take Jeremy Clarkon with a pinch of salt but he had me wondering when he made the point that AMG sell thousands of cars, are production line built now and yet each engine has a "handbuilt by" label like the old Aston Martin engines. I wonder if that is a gimmick?
There must be some sort of durability testing surely, though, as suggested the dismal record of the 1.2 Vauxhall/Opel engine raises questions as to how much?
Edited by mattbod on 28/04/2009 at 18:24
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>>It occurs to me that test units are likely to be correctly assembled... I know that here automotive practice does differ from the aerospace practice which I know a little more about. For flight qualification testing the qualification units must be built using exactly the same materials processes and conditioning as will be used for the flight build. Any change during the flight build run - for example a bought in part becoming obsolete - may mean that the unit needs to be re-qualified to allow the use of the different part material or process.
Sounds pretty much the same as in telecoms where I only do HALT & environmental testing on units built with production intent materials and processes, much the same with changes during production as well.
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Correct me if Im wrong.
I read somewhere in a newspaper that Ford have their own testing lab somewhere in Essex.
They said they tested a transit engine to see how it can stand being left idling for hours on end.... etc.
I can also remember reading about at one lab a few years back, a brand new Jag (either S or X type) was tested to see how it coped with a "Granny run", basically a short run every week nothing else (about 1 mile each week), to test how the components cope.
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Correct me if Im wrong. I read somewhere in a newspaper that Ford have their own testing lab somewhere in Essex.
They certainly used to, with its own test track. I went there years ago because the DB7 under development at the time was overheating at 160mph....
Whatever engine testing is done, I suppose there's no way of knowing if an engine will behave the same with all "worst case" tolerance parts in it, whatever analysis is done at component level.
One thing to bear in mind with testing, is it's very expensive. Much cheaper to let the first few thousand customers do your testing for you ;-)
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Dunton? I worked there nearly 20 years as a student. They used to loan out test/development cars over the weekend if you would promise to put lots of miles on.
Could sometimes be.....entertaining....
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From my experience of durability/development testing of automotive air compressors, engine durability testing will be aimed at checking that the engine will continue to perform satisfactorily up to an acceptable life. Failure to meet the required standard will usually be judged by an inability to meet required performance parameters, not catastrophic destruction of components.
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I have worked in engine testing.
As NC suggests, testing to destruction is of little value - I've never done this for a whole engine. In practice, an engine manufacturer or a major user such as the MOD will have their own test schedules which incorporate the evaluation of parameters of interest.
So, on a test bed and coupled to a dynamometer an engine will be run in for a defined number of hours, given scheduled maintenance and set to work. The work cycle will probably consist of periods of constant speed, idle, ramping up and down the speed/load range and and short periods at max output. For a large customer, the determination of the maximum rated output of an engine might be part of the test itself.
At defined periods within the test, parts will be examined either non intrusively (borescope) or the engine may be partly or fully dismantled. Any known weaknesses of an engine will be examined closely and testing may be modified to highlight problems.
Thus there is no simple answer to "How do you test engines" but there are some interesting quirks. My favourite is the MAN diesel thermal shock test. Roughly speaking, you get the engine really hot by prolonged running at maximum output, stop engine and drain coolant. Then fill it right up quickly with cold water. These engines do not usually suffer gasket problems - I suspect the designers know all about thermal cycling and thermal shock.
659.
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659FBE, that is an interesting test.
I wonder if the engine designers perform a run at max output from cold.
It would be something that most peopel do not do with their cars but there are plenty of 'boy racers' (I use the term very loosely) out there that rag their car before it has even warmed up.
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My wife's aunt used to warm her Fiesta up in winter by flooring it at rest under choke for about a minute and a half. I used to hear the poor little thing yelling miserably and gently advise her not to do it. She used to nod, and continue doing it. She had never taken a driving test having learned to drive before tests were needed. She was terrifying on the road, and that was (in its later life) one rough and sorry Fiesta.
I can't help thinking it may have fallen into Rattle's hands eventually.
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A retired Church of Scotland Minister used to live near my childhood home. He drove ( loosely speaking ) a battleship grey Vauxhall Viva. Not the slightly swoopy final model but its box shaped predecessor.
He never went far in it and in as much as my then untutored ears could tell, always drove it on full choke. Clearly not satisfied with that he also seemed to keep the throttle buried to the floor at all times and must have moved the thing with what can only have been a highly complex clutch slipping technique.
The poor car was regularly to be seen being loaded on to a trailer to be taken away for repair. It must have gone through numerous clutches and goodness knows what the other internals suffered.
Even then I decided that this otherwise charming man must have been using the wretched car as a safety valve for his dark side.
Some years later, a school friend was proudly describing his newly aquired car bought with money from a summer job. He went on to describe it as a bit of a find. A one owner Vauxhall Viva, a retired Minister, low mileage..........
I never did have the heart to tell him what I knew about his car......
:-)
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