turbos in diesels why are they percieved as a problem?

danlightbulb

danlightbulb

danlightbulb

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Friday afternoon ponderings whilst waiting to finish work.

Turbos are often cited as a reason to choose a petrol over a diesel car.

I acknowledge its a potential failure point, thats not my question.

I am wondering why they are considered so costly to repair? All it is is a cast metal part that bolts onto the exhaust manifold somewhere. Why isnt this just a simple bolt on, bolt off part?

Turbo fails, bolt it off, bolt a new one on. Why is it not this simple?
 
Doesn’t matter how simple to fit, the part cost of it is significant with a highly engineered turbine, compressor and bearing inside the housings.
 
The problem is a decent quality turbo replacement is £300 alone as although there's not much to a turbo, it's a very high precision part that spins in excess of 80,000rpm. Plus various other gaskets and oil feed pipes to add to that cost, and due to the nature of where they are often located on the engine, makes them quite a pain to remove, therefore a good few hours of labour.

However turbo failure is pretty rare really, and it's nearly always cause by lack of maintenance.
 
They are (at least in most transverse applications in smaller vehicles) pretty inaccessible, usually wedged in somewhere between the exhaust manifold and the bulkhead! That tends to add significant labour costs.

I've only ever had a single turbo failure, and it was due to coked up variable vanes (the bearings were starting to get some play also), at 166,000 miles. Cost me £400 for a reconditioned turbo (part-exchange), and a weekend to fit. Fortunately the E46 330d is pretty accessible, being on the drivers-side of a relatively open engine bay.
 
To me it should be as simple as changing an air filter.

The intake and exhaust manifolds are both near the top of the engine, and the pipes feeding them are pretty big.
 
To me, as an engineer who stuffs things into engine bays, it’s nothing like a service item, nor should it be. Turbos tend to need to as close to the catalyst as possible to descrease the warmup time of the cat and the exhaust goes down and out under the floor.

Only the hot V engine give hope to any reasonable access if you want to swap a turbo on a recent engine.
 
Choking up and then things starting to go wrong seems to be what kills them at high mileage. Diesel is a really dirty fuel.

You often find with them that a turbo blows up, it gets replaced and then a couple of years later blows up again. Because the root problem that killed the original turbo is still there.
 
Jonnycoupe said:
Only the hot V engine give hope to any reasonable access if you want to swap a turbo on a recent engine.
Click to expand...

Just looked this up. Its the obvious place to put them, why was this just not done by everyone? Its like someone designed it wrong on purpose or out of stupidity.

If i was designing an engine, id put the turbos in the place that made them easiest to access and shortest pipe length. Should be simple really.

Id do the same with power steering pumps, water pumps, oil pumps. any sort of rotating item should be made easy to swap out.
 
danlightbulb said:
Id do the same with power steering pumps, water pumps, oil pumps. any sort of rotating item should be made easy to swap out.
Click to expand...

So you want the engine bay to be 8ft tall to accommodate all of the ancillaries you think need to live on top of the engine?

I'm glad you have nothing to do with automotive design.
 
danlightbulb said:
Just looked this up. Its the obvious place to put them, why was this just not done by everyone? Its like someone designed it wrong on purpose or out of stupidity.

If i was designing an engine, id put the turbos in the place that made them easiest to access and shortest pipe length. Should be simple really.

Id do the same with power steering pumps, water pumps, oil pumps. any sort of rotating item should be made easy to swap out.
Click to expand...

Do you not realise how much a knot you'd tie yourself in? You've listed virtually every ancilliary part of engine as needing to be the easiest to access, your theoretical engine bay would be about 15feet long and a completely inefficient mess lol
 
danlightbulb said:
To me it should be as simple as changing an air filter.

The intake and exhaust manifolds are both near the top of the engine, and the pipes feeding them are pretty big.
Click to expand...

One of the last turbos I replaced was on a 2014 Ford Kuga 2.0TDCI. Trust me it was not a simple job. The wipers have to be removed along with all the trim below the windscreen, exhaust downpipe, intercooler pipes, oil feed pipes, coolant pipes, manifold bolts.. and the engine has to be removed from its mounts and pulled forward to even allow room for the turbo to come out. And most of the job is done laying on top of the engine, with your arm around the back of the engine at maximum reach, there's no space on top.

They're not designed to be easy to change at all, because, my design, they're not really meant to be replaced.
 
danlightbulb said:
Just looked this up. Its the obvious place to put them, why was this just not done by everyone? Its like someone designed it wrong on purpose or out of stupidity.

If i was designing an engine, id put the turbos in the place that made them easiest to access and shortest pipe length. Should be simple really.

Id do the same with power steering pumps, water pumps, oil pumps. any sort of rotating item should be made easy to swap out.
Click to expand...

Need a V engine for a start and typically only sensible for petrol with vehicle proportions preventing the array of DOC/DPF somewhere to put a urea injector sufficiently upstream of the SCR.

Mercedes have moved from a V6 to I6 for the efficient gains it offers in terms of thermal and friction benefits.

If you need to design things to be serviceable it’s better to put the engineering effort into preventing it being a frequent event than to compromise everything else...
You won’t see power steering pumps very often either ;)
 
it's because it's a big bill, and compared to not having a turbo it does shorten the lifespan of the whole system as it's a big bill on an old car that's at the stage folk are looking to change anyway.

i also suspect the current fashion of making tiny engines with big turbos as a stand in for where an older car would have a bigger engine (for example the 100bhp diesel fabia option went from a 1.9 to a 1.6 to a 1.4 over the mk1-3) isn't helping matters.

of course these days it's less about the turbo itself and more the tonnes of emission control equipment that's popping up everywhere.
 
andy_mk3 said:
One of the last turbos I replaced was on a 2014 Ford Kuga 2.0TDCI. Trust me it was not a simple job. The wipers have to be removed along with all the trim below the windscreen, exhaust downpipe, intercooler pipes, oil feed pipes, coolant pipes, manifold bolts.. and the engine has to be removed from its mounts and pulled forward to even allow room for the turbo to come out. And most of the job is done laying on top of the engine, with your arm around the back of the engine at maximum reach, there's no space on top.

They're not designed to be easy to change at all, because, my design, they're not really meant to be replaced.
Click to expand...
^this ,
they're designed to last average/mileage age, discard buy new car

edit: built to last length of warranty period, why should they engineer anything thats lasts longer, no profit in it
 
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danlightbulb said:
Friday afternoon ponderings whilst waiting to finish work.

Turbos are often cited as a reason to choose a petrol over a diesel car.

I acknowledge its a potential failure point, thats not my question.

I am wondering why they are considered so costly to repair? All it is is a cast metal part that bolts onto the exhaust manifold somewhere. Why isnt this just a simple bolt on, bolt off part?

Turbo fails, bolt it off, bolt a new one on. Why is it not this simple?
Click to expand...

A turbo in a diesel:
* if the oil supply seal fails the engine can run off the oil.
* if the turn fails the engine cylinder has more work to get to detonation pressure.
* if the air/diesel mix is out due to failing then it may drive up NOx and particulates etc destroying the DPF.
*diesels need the turbo to because the performance without sucks!
 
NickK said:
A turbo in a diesel:
* if the oil supply seal fails the engine can run off the oil.
* if the turn fails the engine cylinder has more work to get to detonation pressure.
* if the air/diesel mix is out due to failing then it may drive up NOx and particulates etc destroying the DPF.
*diesels need the turbo to because the performance without sucks!
Click to expand...

I get they are potential failure points.

Here is what I would do:

4 cylinder transverse engine, viewing from the front of car:
*exhaust manifold comes out the top rear
*it turns to the side and runs to non drive belt side, rhs, of engine.
*here sits turbo.
*exhaust downpipe continues down from turbo and then turns under car exiting to rear as normal.
*intake comes in front right side, up from behind front grille, through air filter located rhs of engine bay
*intake runs through turbo, out to intercooler, and then straight into intake manifold front of engine.
*lhs of engine is drivebelt side
*power steering pump, alternator and water pump all in a row near the top sitting front to rear, connected by drive belt.
*battery in boot to free up space
*front bumper clips off easily with some screws
*located front bottom of engine is oil filter and sump drain plug, no need to even jack the car up for oil change

easy peasy.
 
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