Turbos

[Skylark]

I still don't know what the downsides are other than a vague notion of complication. I presume almost everyone has reasonably complicated engines and are not all running single cylinder things 'for simplicity' so why is the Turbo a step too far? Am I right that the turbo essentially boosts the engine but if it failed you would simply have a non-turbo engine, so the risk from failure is low or would the engine stop working if the turbo failed.

Any internal combustion engine has its power output limited by the amount of air available to burn the fuel. It's very easy to add more fuel but not so air. Turbochargers provide air (oxygen for combustion) at above ambient pressure therefore more oxygen becomes available for the combustion process. Quite simple really.

I'm ever so slightly biased towards them as I spent almost 20 years working for the world's largest manufacture of such products. By way of example, across three European sites we would assemble approx. 20,000 per day. A typical warranty provision in the budgeting process was usually less than 0.2%. They are incredibly reliable products.

As I posted previously, there is a practical limit to small size. There is also a huge cost of development which is not such a big deal when amortised over a million engines a year. Not quite the same finance model for a 40 bhp sailing boat engine derivative.

There's nothing to fear about a turbocharger.

Doubtless some people also have strong, equally ill-informed opinions about many other things in life and in sailing (keel configuration and number of hulls to name just two :encouragement

In the unlikely event of a failure, a couple of things spring to mind. Given that the average passenger car turbo will be spinning at approaching 200,000 rpm, failure can happen quickly. Foreign object damage through either the intake or exhaust can be a problem. Coking, thermal degradation of the oil, in the bearing housing leading to scoring of the bearing journals, ultimately to failure, was a problem in the 1980s -90s but has long since been solved. Any abnormal noises should be investigated.

Saab was at the forefront of turbocharging gasoline engines. At first, their marketing department ensured that the cars were badged "Turbo" (who could forget the 99 EMS Turbo of the mid 1980s). By the 1990's they took the decision to turbocharge their entire range of vehicles and took away any reference on the badge.

 

[nickd]

The obvious advantage of a turbo or twin turbo engine in a boat would be much better power to weight ratio than a conventional.
A turbo does not need any fancy eletrickry it can work entirely mechanically.
A twin turbo is not two identical turbos's but one small one and one big one, the small lightweight one gives modest boost at low revs and the bigger heavier one kicks in when the revs go up to give a higher boost as the unit requires more O2. The point of a turbo is merely to act as a fan and shove more oxygen into the cylinders thus allowing more fuel to to be burnt thus producing more power.
I would have no real problems with the added complexity of a turbo, just that in a sailboat the cost benefit on a small horse power engine is probably not there, I think that it is generally considered that the cost benefit starts to arrive at around 50hp although I have no figures to back that up.

 

[teredo]

I'd have thought supercharging was a pretty special case on sailing boats. If more power is needed there is almost always room to fit a more powerful donk - cases when there simply isn't enough won't be too common, and cramming a white hot turbo into a tight engine compartment may not be the most prudent way to go anyway...High speed motorboats are another matter with their almost insatiable appetite for horsepower and sensitivity to added weight where supercharging really does come in useful.

For my money I'd prefer the simplicty of a normally aspirated engine and fit a bigger one if I needed more oomph. Easier to maintain, less to go wrong,

 

[pvb]

I'd have thought supercharging was a pretty special case on sailing boats. If more power is needed there is almost always room to fit a more powerful donk - cases when there simply isn't enough won't be too common, and cramming a white hot turbo into a tight engine compartment may not be the most prudent way to go anyway...High speed motorboats are another matter with their almost insatiable appetite for horsepower and sensitivity to added weight where supercharging really does come in useful.

I hope you realise that supercharging is rather different from turbocharging. As for the "white hot turbo", they don't get any hotter than the normal engine exhaust components. My old boat had a 24 year old Volvo 2003T engine, and the original green paint on the turbo was still green.

 

[RichardS]

Any internal combustion engine has its power output limited by the amount of air available to burn the fuel. It's very easy to add more fuel but not so air. Turbochargers provide air (oxygen for combustion) at above ambient pressure therefore more oxygen becomes available for the combustion process. Quite simple really.

I'm ever so slightly biased towards them as I spent almost 20 years working for the world's largest manufacture of such products. By way of example, across three European sites we would assemble approx. 20,000 per day. A typical warranty provision in the budgeting process was usually less than 0.2%. They are incredibly reliable products.

As I posted previously, there is a practical limit to small size. There is also a huge cost of development which is not such a big deal when amortised over a million engines a year. Not quite the same finance model for a 40 bhp sailing boat engine derivative.

There's nothing to fear about a turbocharger.

Doubtless some people also have strong, equally ill-informed opinions about many other things in life and in sailing (keel configuration and number of hulls to name just two :encouragement

In the unlikely event of a failure, a couple of things spring to mind. Given that the average passenger car turbo will be spinning at approaching 200,000 rpm, failure can happen quickly. Foreign object damage through either the intake or exhaust can be a problem. Coking, thermal degradation of the oil, in the bearing housing leading to scoring of the bearing journals, ultimately to failure, was a problem in the 1980s -90s but has long since been solved. Any abnormal noises should be investigated.

Saab was at the forefront of turbocharging gasoline engines. At first, their marketing department ensured that the cars were badged "Turbo" (who could forget the 99 EMS Turbo of the mid 1980s). By the 1990's they took the decision to turbocharge their entire range of vehicles and took away any reference on the badge.

I understand all that ...... but let me pose a "simple" hypothesis:

Take a standard internal turbo combustion engine, petrol or diesel. Set it up on a bench and run it continuously at 2/3 redline and then just watch and wait .........

Now, all other things being equal, which part do you think will fail first?

Richard

 

[Malo37]

Generally there is no requirement for a turbo charged yacht engine. A turbocharged engine may deliver a higher power to weight ratio and therefore be advantageous in a high speed motor yacht but in a yacht where HP rarely exceeds 100hp, and is usually much less, there is no need for the added complexity.
Furthermore turbocharged engines do not like running on low load or at low speeds which can cause problems with carbonisation and valve burn.

 

[stuartwineberg]

Few yacht auxiliaries die of hard work, most die of corrosion. I doubt if the precision engineering and high grade steels in a turbo would take kindly to the damp salt laden atmosphere of a small boat. Particularly if left standing idle for weeks or months at a time! Fe bikes in the under 500 cc class bother with turbos, as they are simply not cost and weight effective. Turbo charging anything much under about 30hp is probably just not worth it for the marginal gains in size an weight. In any case, turbos need a fairly fast running engine to be effective. Most smaller donks are just that - slow revving (3 -3.500 rpm) plodders.

Relate to that. Another member of the forum on the mobo side lost a turbo on his Yanmar while it was laid up through damp air seizing it. Wouldst have happened if it had been constantly in service

 

[teredo]

I hope you realise that supercharging is rather different from turbocharging.

pvb, actually, I can only assume you don't realise what your extraordinary statement says about your knowledge of supercharging.

Er, turbocharging IS supercharging. .... ! What on earth did you think it was?

OK, maybe the white hot bit was a little ott but I'd be highly suspicious of a turbo that ran cool enough to retain a paint finish. If it's running that cool where's it getting it's energy from?

Wikipedia provided the table below and a bit of research suggests that commercial vehicular diesels typically run a max EGT at turbo inlet of up to 1200C but more commonly 900 - 1000C.

Paint ????? Wow!


Colour Temperature [°C]
From To From
Black red[2] 426 593
Very dark red 593 704
Dark red 704 814
Cherry red 815 870
Light cherry red 871 981
Orange 981 1093
Yellow 1093 1259
Yellow white 1259 131
White 1315+ 2309+

 

[Skylark]

I understand all that ...... but let me pose a "simple" hypothesis:

Take a standard internal turbo combustion engine, petrol or diesel. Set it up on a bench and run it continuously at 2/3 redline and then just watch and wait .........

Now, all other things being equal, which part do you think will fail first?

Richard

I don't understand your point. I suspect that any engine running at 2/3rd of its max speed would run for 10,000 hours without a problem. I don't imagine any component would fail under those circumstances. Perhaps the engine may die from boredom.

In my career, I've seen many, many engines tested on dynamometer. It's rare to see a turbo fail.

Now I'm intrigued. Why do you think a turbo will be the first component to fail on an engine test at 2/3rd max speed?

Turbine inlet temperature will probably be in the region of 700 deg C and it's material is good for approaching 1000. Delta P across the two stages would be quite small so very little thrust. Constant speed, providing the firing frequency doesn't give rise to any resonance, means almost perfect harmony for the bearings. Assume no problem with oil supply. So what's the issue? Please tell.

 

[RichardS]

That extraordinary statement shows you don't seem to know much about supercharging then.

Er, turbocharging IS supercharging. .... ! What did you think it was?

This has got to be a wind-up ...... surely?

Richard

 

[davidej]

Er, turbocharging IS supercharging. .... ! What did you think it was?

It think most people mean supercharging to mean an intake compressor run by a belt from the engine while a turbocharger compressor is run from an exhaust turbine

 

[Bobc]

I still don't know what the downsides are other than a vague notion of complication. I presume almost everyone has reasonably complicated engines and are not all running single cylinder things 'for simplicity' so why is the Turbo a step too far? Am I right that the turbo essentially boosts the engine but if it failed you would simply have a non-turbo engine, so the risk from failure is low or would the engine stop working if the turbo failed.

I think you're actually right on this. I don't think there are any "real" downsides, just perceived ones. The reality is that you're more likely to have a water pump, cambelt, or intection pump go than have a turbo let-go.

 

[RichardS]

I don't understand your point. I suspect that any engine running at 2/3rd of its max speed would run for 10,000 hours without a problem. I don't imagine any component would fail under those circumstances. Perhaps the engine may die from boredom.

In my career, I've seen many, many engines tested on dynamometer. It's rare to see a turbo fail.

Now I'm intrigued. Why do you think a turbo will be the first component to fail on an engine test at 2/3rd max speed?

Turbine inlet temperature will probably be in the region of 700 deg C and it's material is good for approaching 1000. Delta P across the two stages would be quite small so very little thrust. Constant speed, providing the firing frequency doesn't give rise to any resonance, means almost perfect harmony for the bearings. Assume no problem with oil supply. So what's the issue? Please tell.

Ah .... I see that you didn't answer the question. Let's go past 10,000 hours and perhaps let's vary the revs up and down from idle. I'll ask again, which part, statistically, do you think is most likely to fail first? It's not a trick question .... just an engineering question.

Richard

 

[teredo]

It think most people mean supercharging to mean an intake compressor run by a belt from the engine while a turbocharger compressor is run from an exhaust turbine

People "taking" something to mean what it doesn't can be very misleading, especially for them!
I thought everyone knew - well, those who are interested in such things that supercharging is the name given to using a compressor to force extra (hence "super") charge into an engine. We all know there are various ways to drive the compressor but all are supercharging whether you use a turbine, ram air effect in a duct if you're going fast enough or drive the thing mechanically. Mechanically doesn't have to be a belt, modern ones are usually gear driven, and the motive power doesn't have to come from the subject engine either - it could feasibly be horse driven - but all the above are supercharging.

A turbo is thus correctly called a turbo-supercharger, a mechanically driven one is usually referred to as a mechanical supercharger. Assuming a "supercharger" is mechanically driven is either a pretty fundamental misunderstanding or misnaming of the process.

Windup indeed. Petard. Hoist??

 

[davidej]

All true but just being clever-clever.

Most people use the common parlance.

 

[Malo37]

Supercharging is the name given to using a compressor to force extra (hence "super") charge into an engine. There are many ways to drive this compressor but all are supercharging whether you use a turbine (perfectly possible for this to be exhaust, electric or even horse driven if you wish), use ram air effect if you're going fast enough or drive the thing mechanically. Mechanically doesn't have to be a belt, modern ones are usually gear driven, but all the above are supercharging.

A turbo is correctly called a Turbo-supercharger, a mechanically driven one is usually referred to as a mechanical supercharger. Assuming a "supercharger" is mechanically driven is a pretty fundamental misunderstanding of the process.

Pedantic but incorrect. As previously stated a turbocharger is driven by an exhaust gas turbine whereas a supercharger is driven through direct mechanical connection to the engine. Obviously this results in a totally different mechanical configuration and different design of the engine manifolding etc. i.e. they are NOT the same.

 

[RichardS]

Supercharging is the name given to using a compressor to force extra (hence "super") charge into an engine. There are many ways to drive this compressor but all are supercharging whether you use a turbine (perfectly possible for this to be exhaust, electric or even horse driven if you wish), use ram air effect if you're going fast enough or drive the thing mechanically. Mechanically doesn't have to be a belt, modern ones are usually gear driven, but all the above are supercharging.

A turbo is correctly called a Turbo-supercharger, a mechanically driven one is usually referred to as a mechanical supercharger. Assuming a "supercharger" is mechanically driven is a pretty fundamental misunderstanding of the process.

This thread is discussing turbochargers and turbochargers are only ever driven by exhaust pressure. If you wish to bring supercharging into the debate you are welcome to do so but absolutely no-one will think you are talking about exhaust driven supercharging so it's going to be a rather lonely debating strategy. :encouragement:

Richard

 

[teredo]

All true but just being clever-clever.

Most people use the common parlance.

Why is using correct terminology in a technical discussion "clever clever"? Is it somehow "clever" to use misleading and incorrect language as people are doing here or perhaps worse to defend incorrect usage or mechanical misunderstandings even when they are explained? I don't think so. Do you carry this sloppiness over into your navigation for instance?

Malo. Pedantic? Read the above, it applies to you as well.

As previously stated a turbocharger is driven by an exhaust gas turbine

Who can disagree with such wisdom?

[whereas a supercharger is driven through direct mechanical connection to the engine.

Clearly you need to re-read what I wrote as what you have put is completely incorrect. Both are superchargers. A gearbox has a direct mechanical connection but is not a supercharger. If a supercharger were driven by an external electric motor, or indeed a horse would it cease to be a supercharger merely because of a lack of mechanical connection? Mechanical connectons have nothing to do with it. If it compresses a charge it is a supercharger. Add descriptives at will to define it further. Turbo charger or (perhaps a little pedantically) turbo-supercharger or mechanically driven supercharger - all fine. Just don't assume that a supercharger is necessarily mechanically driven. It isn't.

Do try to get basic facts right, it's pretty simple really! Just go and look up definition of Supercharging, there's a good chap.


ps. Just for the record it most certainly was not I that brought mechanically driven superchargers into this discussion.

 

[RichardS]

Why is using correct terminology in a technical discussion "clever clever"? Is it somehow "clever" to use misleading and incorrect language? Do you carry this sloppiness over into your navigation for instance?

Malo. Pedantic? Read the above, it applies to you as well.


Who can disagree with such wisdom?



Clearly you need to re-read what I wrote as what you have put is completely incorrect. Both are superchargers. A gearbox has a direct mechanical connection but is not a supercharger. If a supercharger were driven by an external electric motor, or indeed a horse would it cease to supercharge because of a lack of mechanical connection?

Do try to get basic facts right, it's pretty simple really! Just go and look up definition of Supercharging, there's a good chap.

Wow! Real bitchy sarcasm from a newbie. I don't think Teredo is going to last very long on the forum! :encouragement:

Richard

 

[pvb]

Wow! Real bitchy sarcasm from a newbie. I don't think Teredo is going to last very long on the forum! :encouragement:

Richard

It's a bit early in the day to find such, err, zany views.