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      09-10-2008, 03:19 PM   #45
swamp2
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That data will still not establish cause and effect to the extent that one can say one configuration is inherently more reliable than the other since there are other significant variables such as quality of the engineering design, build quality, usage behaviours/consumer base, etc. Engines from the same manufacturer using similar design expertise and manufacturing processes would need to be tested in a controlled fashion which simulates an acceptable life cycle. Even then, one can argue some manufacturers have more expertise in designing a specific type of engine, but are not necessarily as effective when dealing with another configuration.
Very true - engineering effort increases reliability and often cost can as well. However, this would be about as real world as we could hope to get. I think you actually want these effects (all human factors type things) included. If turbos have way more engineering (which they do in part just because of the additon of the turbo itself) thay may be enough to push the overall turbo reliability numbers higher. Again I doubt they would be pushed higher than NA, but this could absolutely be an effect. Specifically if we could drill down to engine reliability the data may be useful in this discussion.
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      09-10-2008, 03:54 PM   #46
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This might interest you but I know a few years back Topgear did their own JD Power type exercise and on one occasion the Imperza came top. Now that is a turbo charged car that proved to be the most reliable that year.

Also something that needs to be considered if you are to use the JDP data is that turbo and FI powered cars in general will be more likely to be tuned, causing additional stress and possible failure. I still believe that when designed with the power that the manufacturer intended the turbo engine is just as reliable as any N/A engine.
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      09-10-2008, 07:52 PM   #47
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This might interest you but I know a few years back Topgear did their own JD Power type exercise and on one occasion the Imperza came top. Now that is a turbo charged car that proved to be the most reliable that year.
One year of data is not sufficient.

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Also something that needs to be considered if you are to use the JDP data is that turbo and FI powered cars in general will be more likely to be tuned, causing additional stress and possible failure.
One of potentially dozens of confounding factors.

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I still believe that when designed with the power that the manufacturer intended the turbo engine is just as reliable as any N/A engine.
We will continue to disagree. Again not that they can't be made so, just that through history they have not been.
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      09-10-2008, 08:12 PM   #48
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...Again not that they can't be made so, just that through history they have not been.
Swamp, how about some examples. I gave you Subaru and Volvo, could've thrown in Saab, who's probably been doing it longer and better than anybody else, and I'll even throw in a high performance example. The '86 - '87 Buick Grand Nationals were absolutely bulletproof - with stock internals - even when running enough boost to get the Princeton Plasma Physics guys interested and turning low to mid 11-second quarter miles at over 120 mph.

I'm coming up a little short when trying to compile a list of factory stock forced induction grenades. Help me out.

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      09-10-2008, 10:42 PM   #49
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Very true - engineering effort increases reliability and often cost can as well. However, this would be about as real world as we could hope to get. I think you actually want these effects (all human factors type things) included. If turbos have way more engineering (which they do in part just because of the additon of the turbo itself) thay may be enough to push the overall turbo reliability numbers higher. Again I doubt they would be pushed higher than NA, but this could absolutely be an effect. Specifically if we could drill down to engine reliability the data may be useful in this discussion.
Engineering expertise might be considered to be a "real world" consideration in a specific context. However, human factors issues should not be. You might be running into really strange population effects. For instance, what if people who buy "high revving" engines are somewhat pre-disposed to running them much harder? Those types of effects would surely bias the data in the sense that one would not necessarily be talking about the effects of the engine configuration on reliability anymore, but more about how people treat them.
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      09-11-2008, 01:02 AM   #50
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Swamp, how about some examples.
All we both will likely provide are anectdotes not evidence, which I already admitted would be the case. You can name turbo cars all day and make claims about their robustness, you may be right, you may be wrong. Without evidence we are both engaging in a lot of speculation. However, my speculation has a basis in basic principals of engineering and reliability. Just to appease you with some anecdotal evidence though I heard many stories about blown turbos in the Third gen RX-7. That was a Wankel, but I am not talking about a blown engine, but a blown turbo. One in particular was my good buddies girl, she lost her turbo with less than 100k miles, might have even been closer to 60k. Both he and her knew of similiar losses at similar mileages. Other anecdotal reliability evidence can be found online about Mitsubishi, Renault, Toyota, Ford, etc. Much of that evidence seems focused around 80-early 90 vehicles and I don't doubt for a moment that turbo reliability has improved substantially since then.
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      09-11-2008, 02:06 AM   #51
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swamp,

Subaru have continually been in the top ten for reliability for as many years as I can remember, likewise Honda who are renowned for making high-revving engines.

Of course you can name more N/A engines cars that are reliable, mainly because there is more produced in the world but if you look at the JDP rating you will see certain brands are continually high, regardless of what type of engine is their preferred choice, it's their engineering skills which come into play. BMW are renowned for N/A engines, VAG for turbo-diesels, Mercedes for large capacity, Honda for small capacity high revving, etc, etc. Each have their own philosophy on how to get the desired results but it's your own personal opinion which you feel is the right way about it.

All I know is that VAG turbo diesel and petrol engines are as reliable as any non-turbo engines. My TTMk1 225hp which produced 125hp/ltr has covered 180,000 miles without any major repairs, and the reason I know this is I happened to see the car the other day and got the talking to the new owner, third one in the books.

As Bruce has already said it all down to how the engine is designed that determines it's reliability, push the boundaries by it high revving or increasing the boost pressure and you will reduce any engine's reliability......FACT.
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