Twin Turbo Engines as reliable as naturally aspirated engines?

[mtech8]

Really stupid question.

Are naturally aspirated cars more reliable than one that have forced induction?

I'm buying a X5 4.8i and planning on keeping it for a while (buying not leasing). I believe eventually BMW will put the new XDrive35i and XDrive50i engines into the X5. Just not sure if it will be as soon as 2009 model year or later.

The increase in power from the twin turbo engines would be great! But would that also make the car less reliable? ie: faster engine wear, more potential parts breaking down, etc?

Obviously, if the TT engines aren't making it into the 2009, the choice of the naturally aspirated 4.8i would be fine. But if it is, then it's really a hard choice of whether I should wait or not is definitely a tougher choice.

Example. If I bought the last year of the 330i vs getting the 335i. Pretty big difference.

Guess I'm just looking for justification on getting the 4.8i vs waiting for the twin turbo engines.

[SpeedR]

There is always a trade-off between higher performance and reliability. Turbo has more moving parts to break, and creates reliability's worst enemy - lots and lots of heat.

Also, this is a new engine to BMW, as compared with the 4.8 which has been used several years in the 6 & 7 series.

I just ordered my X5 4.8i and would do it again, even if the TT was an option, since this is my daily driver. If it was my weekend toy, my choice would be TT.

[vinuneuro]

Originally Posted by SpeedR

There is always a trade-off between higher performance and reliability. Turbo has more moving parts to break, and creates reliability's worst enemy - lots and lots of heat.

Also, this is a new engine to BMW, as compared with the 4.8 which has been used several years in the 6 & 7 series.

I just ordered my X5 4.8i and would do it again, even if the TT was an option, since this is my daily driver. If it was my weekend toy, my choice would be TT.

LOL are you going to be endurance racing with your TT X5?

BMW has plenty of experience with turbcharged engines from the many diesel's they've produced. They're just as reliable.

[SpeedR]

Originally Posted by vinuneuro

BMW has plenty of experience with turbcharged engines from the many diesel's they've produced. They're just as reliable.

While I like turbo and supercharged engines, any manufacturer's turbo charged engines - gas or diesel - are not a reliable as their normally aspirated engines. This is a fact.

Does this mean BMW does not have a reliable TT V8; NO. It just means, relative to a normal aspirated engine, it has a higher probability of problems.

BTW, most problems with turbo charged cars are not with the engines or even the turbo units - its the cooling systems that usually fail, both water and oil.

[vinuneuro]

Originally Posted by SpeedR

While I like turbo and supercharged engines, any manufacturer's turbo charged engines - gas or diesel - are not a reliable as their normally aspirated engines. This is a fact.

Does this mean BMW does not have a reliable TT V8; NO. It just means, relative to a normal aspirated engine, it has a higher probability of problems.

BTW, most problems with turbo charged cars are not with the engines or even the turbo units - its the cooling systems that usually fail, both water and oil.

Higher probability? That's fine if you want to think about it like that. You also have a higher probability of dieing by leaving your house v. remaining inside forever. You already mentioned it in your post. It's all about reliability.

As far as your probability idea, I'm sure it's far from the truth. That might have been the case decades ago, but modern fi engines are just as reliable. If they were so unreliable, basically all diesel engines wouldn't be turbocharged by manufacturers, and if they were so unreliable consumers wouldn't purchase them, which would lead back to automakers not using them.

So what part of the lubrication system fails because an engine is turbocharged..the oil pump, because that's the only moving part of that system. Cooling system is less reliable because the engine turbocharged? lmao. You realize it's not that hard to make a oil or cooling system more efficient right? And you also realize that these automakers aren't idiots right?

Be clear about this: you can design and develop around ANY constraint. Oils are spec'd, developed and validated for turbocharged engines just as they are for na. Etc etc. Every component that's affected by the effect of an engine being turbocharged, rev'd high, pulling heavy loads, whatever. It's all accounted for. You'd shit your pants if you knew how much went into producing an engine, and how specialized engineers are who come up with individual and even what you may think are mundane components.

[SpeedR]

I'm done...vinuneuro doesn't get it

[jimsaq]

I agree with vinuneuro

There's countless examples of turbo diesels not only working many many times harder their entire running life than naturally aspirated gasoline engines, but often for more than double the miles

And the 3.0 twin turbo is not a brand new engine, it's been available in 3, 5 and X3 (maybe others?) for at least 12-24 months

[Wagner]

The only way you will screw up that TT engine is if you start chipping it and changing boost levels You'll be fine.

[FSETH]

You can probably count on the 4.4 TT winning some form of the International Engine award. The TT 3 litre engine from the 135i and 335i won Best new engine of 2007, Best 2.5-3 litre engine and International Engine of the Year in 2007. It was BMW's 3rd straight International Engine of the Year award. The 3.0 litre TT probably wouldn't have won this award if it wasn't going to be reliable. A lot went into creating this engine and it is not a Turbo of the past. BMW should have all overheating issues from the 3.0 TT worked out by the time the 4.4 TT is introduced. My only question would be the cooling system. BMW are notorious for having the plastic components break and crack after about 5 years. If the heat from the TT is any higher than the NA engines I wonder in the higher temps will heat cycle the plstic componets are cause them to fail even earlier than typical. Otherwise the TT does have more parts, so maybe that does increase your chance of a part failure, but overall I would immagine that this engine will be pretty reliable. Acording to LeMansX5 BMW may be transitioning away from NA engines to a total TT lineup. I am sure they ar egoing to want to get the 4.4 right if that is the case.

[mtech8]

Thanxs for the inputs!