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Petrol Turbo Reliability? - meldrew

HJ advises against buying a second hand turbo diesel car on the grounds of reliability and subsequent expense. I wonder now if the same rules apply to petrol cars with a turbo?

Modern BMWs and Fords now have petrol turbo engines and we normally buy two or three year old cars with modest mileages. Is it still safe to do so or does one need to shell out for a proper dealer warranty every year? Its getting a bit like old televisions that were rented because they went wrong so often!

Petrol Turbo Reliability? - thunderbird

HJ advises against buying a second hand turbo diesel car on the grounds of reliability and subsequent expense. I wonder now if the same rules apply to petrol cars with a turbo?

Modern BMWs and Fords now have petrol turbo engines and we normally buy two or three year old cars with modest mileages. Is it still safe to do so or does one need to shell out for a proper dealer warranty every year? Its getting a bit like old televisions that were rented because they went wrong so often!

Don't panic. Buy what you want (petrol or diesel - turbo or not) but buy it carefully just like you should always buy a car or any other large purchase).

Cars have never been better than they are today. Considering how many more there are on the road the hard shoulders and verges are not littered with broken cars.

Its a fact that there are reports of certain brands having problems but on forums like this you only ever hear about that tiny minority, the vast majority just keep fueling up and driving and never visit a forum to say how great and reliable their car is.

Petrol Turbo Reliability? - Cyd

20+ years ago I prefered to drive a large capacity normally aspirated motor (I had a 220hp 3500 SD1). Back then, early petrol turbo's tended to have lag and be quite unreliable.

Nowadays I'm a huge fan of petrol turbos. My current car is a 07 Saab 9-3 Aero 2.0T with a Maptun tune to 260hp/360Nm. I've had it just on 2 years now. My previous chariot was a 96 Rover 800 Vitesse Sport, the 200hp version (a completely different car to the old 820 turbo).

I had the Rover 11 years and took it from 88k at 3 years old to 167k at almost 15. It never missed a beat and took quite a pounding I can tell you. It went to an enthusiast from the ROC.

My advice:
# try and buy with a good service history - especially oil changes
# give it a full service shortly after buying.
# fit the best oil of the correct grade,
# drain thoroughly from the sump plug and use flushing oil at least every other change
# change oil at least twice a year
# thoroughly flush the coolant system at 4 year intervals and use 25% OAT coolant and a bottle of water wetter (most petrol turbos are water cooled - don't let the system sludge up).
# warm up gently from cold, avoiding high throttle & revs till the engine is properly warm (5 miles+)
# cool down gently for the last few miles of any journey. Leave it idling for up to 10 minutes if it's stinking hot (I raise the bonnet too).
# if you can see the turbo glowing do not shut down untill the glow has completely gone.
# try and avoid repeated full throttle / shut throttle transitions (the accelerations on the turbo shaft really strain it under these conditions)
# clean out the intake system (including compressor and intercooler) occasionally
# keep an eye on the state of the throttle plate and keep it clean.

The Rover had a front mounted turbo (the Saabs is at the rear) which meant that the heat from the turbo went past the HT leads. In the first couple of years it went though several sets of leads (couldn't take the heat) untill I fitted a set of Magnacor KV85s, which were still like new 10 years later.

Enjoy!

Edited by Cyd{P} on 09/04/2013 at 20:37

Petrol Turbo Reliability? - gordonbennet

Thats the difinitive list of what to and what not to do Cyd, excellent stuff, should be made a ''sticky''...hows about that Avant?

I knew several people who had petrol turbos in the 80's, nearly all failed at some point, in all cases when i asked about their extra servicing regimes or warm up cool down procedures they looked at me blankly as a sheep would.

People with turboDiesel cars would do well to take heed of much of your list too, better than shelling out up to £1500 each time (if no resulting damage) and then looking here for guidance or to complain long after the event.

Petrol Turbo Reliability? - brum

Thats the difinitive list of what to and what not to do Cyd, excellent stuff, should be made a ''sticky''...hows about that Avant?

Only if it has the disclaimer that a large number of these points is considered by many to be twaddle

Oil change at least twice a year? Flushing Oil?? Clean out the intake system (including compressor and intercooler) occasionally???keep an eye on the state of the throttle plate and keep it clean??????

Hey, welcome to the 1990 guide to maintenance.......

Petrol Turbo Reliability? - gordonbennet

is considered by many to be twaddle

And they'll be posting here for guidance how to get the maker to stump up for their blown turbos, sheared timing chains and ruined engines in due course.

Petrol Turbo Reliability? - Avant

I can't think of any reason why a turbocharger should be any more or less reliable in a petrol engine compared with a diesel.

Despite cars in general being more reliable than they used to be, turbos can still fail, and surely any reasonable steps to prolong theor life, as suggested by Cyd and backed by GB, make sense. Like many, I'm suspicious of the modern fashion for extended intervals between oil changes.

I am no engineer and may be talking through my hat here, but isn't the engine oil in my current 200 bhp Skoda doing more work than the oil did in my first car, a gentle old 50 bhp Austin?

If there's general agreement on the care of turbos I could ask HJ if it would be a possible answer to a FAQ.

Petrol Turbo Reliability? - unthrottled

I can't think of any reason why a turbocharger should be any more or less reliable in a petrol engine compared with a diesel.

I can. Heat. Petrol exhaust gases are considerably hotter than diesels. When industrial diesels are converted to gas engines (sorry, designed from a clean sheet of paper-ha ha!), the big issue is cooling the exhaust gases to maintain acceptable turbocharger lifespan.

Petrol Turbo Reliability? - brum
I am no engineer and may be talking through my hat here, but isn't the engine oil in my current 200 bhp Skoda doing more work than the oil did in my first car, a gentle old 50 bhp Austin?

The oil in your 200bhp Skoda is as similar to the oil in your old 50 bhp Austin as chalk and cheese.

And yes, most of the time the oil in your 50bhp Austin did work much harder than your 200bhp Skoda, if only because the mechanical efficiency was so bad that the engine had to be constantly thrashed just to get the one ton brick up to 50mph.

Not to also mention the pathetic fuel and thermal management that meant the oil was constantly being contaminated with petrol, water and all sorts of other pollutants

But on the other hand, a lot of the advice advocated in this thread is appropriate for a 1950's pushrod engine.

Edited by brum on 10/04/2013 at 01:39

Petrol Turbo Reliability? - john farrar
I agree with Brum. I have run a turbo petrol Audi A6 to 150,000 miles with nothing more than the standard oil change regime(10,000miles)using fully synthetic. I also have a mate who has run a turbo petrol Saab for 130,000 miles using the makers service schedule.

I drove the Audi in the same way as a normally aspirated engine with no special consideration for the turbo. I have also run diesel turbos in the same way to over 100,000 miles and have never suffered from any turbo, or indeed other engine, problems.

In my experience most modern engines are remarkably reliable and tolerant of abuse. Long gone are the days when 60,000- 80,000 miles was considered a normal life for an engine before a complete overhaul was needed - and that was with 6,000 mile oil changes.

In my view engines (and cars) have almost become ' white goods' and/or fashion statements, depending on to what use they are put.
Petrol Turbo Reliability? - Cyd

I can't think of any reason why a turbocharger should be any more or less reliable in a petrol engine compared with a diesel.

Despite cars in general being more reliable than they used to be, turbos can still fail, and surely any reasonable steps to prolong theor life, as suggested by Cyd and backed by GB, make sense. Like many, I'm suspicious of the modern fashion for extended intervals between oil changes.

I am no engineer and may be talking through my hat here, but isn't the engine oil in my current 200 bhp Skoda doing more work than the oil did in my first car, a gentle old 50 bhp Austin?

If there's general agreement on the care of turbos I could ask HJ if it would be a possible answer to a FAQ.

Diesel exhaust temps are typically around 850C, whereas petrol will be around 1100, possibly more on a HOT motor.
This is why most petrol turbos are water cooled whilst most diesels turbos are not.

It doesn't take me much hard driving to get my Saabs turbo glowing a bright orange!

Petrol turbos also have much more shaft accelerations / decelerations as the throttle is opened and closed which places more stress on the whole assembly.

Brums snide comments don't really help his case much, do they? After 20+ years in automotive R&D, years building rally cars and much contact with engine engineers I know that oil is an engines best friend. Long service intervals are a sop to the fleet buyers who are consumed about "cost of ownership" and have been pushed to the max. Not forgetting cars are designed for a 12 year 125k lifetime. So if you want your car to last and perform like new with 167k on the clock, then follow my way. If you're not that bothered, well, you do as you please. A little preventative maintenance is way cheaper and less inconvenient than failure. Whilst there are no gurantees, you can stack the odds. I for one am not about to risk my expensive motor to short term marketing strategy.

Petrol Turbo Reliability? - coopshere
Interesting reading from both sides of the argument. However the bottom line would seem to be don't buy a turbo engined car that was previously fleet owned, had extended service intervals or does not have a very comprehensive service history. It would seem the only alternative if you want to run one long term is to buy new so that you know it's been treated correctly.
Petrol Turbo Reliability? - meldrew

Perhaps when I made the original post my thoughts were that I don't want any car with a turbo that might fail. Just a plain vanilla petrol engine for modest mileages. It seems that if I want a "nice" car I no longer have the choice!

Buying new used to be a good idea but I just can't afford £5k a year depreciation on a new BMW! Bit like buying boat - If you have to ask the price you cannot afford it!!

Petrol Turbo Reliability? - SkodaIan

A fleet owned (single driver) highish mileage turbo petrol car is probably actually a very good value option second hand.

It will have spent most of its life with cruise control set to 80 on the motorway, probably barely bothering the turbo (my Octavia 1.8TSI only really comes on boost up hills in this situation). The oil will spend most of the miles running at the correct temperature and suspension, clutch etc will have below average wear for the mileage.

Obviously all these would equally apply to a turbo diesel, but the big draw for an ex fleet turbo petrol is that it will have been owned by someone interested in cars as they will have taken a big tax hit because they wanted that car rather than the boring diesel. Most likely they will have looked after it well and been a relatively mechanically sympathetic driver.

Petrol Turbo Reliability? - concrete

Hello Cyd, interesting comments about turbo cooling. With a water cooled turbo, how does the water cool it when it is glowing hot? Will it not just boil the water? Would really like to know.

My diesel PD130 TDi has done 165K miles. Manufacturers variable service regime means average service at 18/19K miles or about 9/10 months with fully spec'd synthetic oil. No problem from new and engine sweet as a nut, economy average 48/50 mpg. I live a couple of miles off the motorway so my turbo gets a chance to warm up and cool down getting to and from, so I guess this has served it well. Interesting comments in general and I shall take some advice from them. Thanks. Cheers Concrete

Petrol Turbo Reliability? - unthrottled

With a water cooled turbo, how does the water cool it when it is glowing hot? Will it not just boil the water? Would really like to know.

The water passes through the CHRA (Centre hub rotating assembly), not the turbine housing. The water does boil, and this removes vast amounts of heat and stops the oil in the bearing assembly from coking.

Industrial gas engines have long used water cooled exhaust manifolds to reduce the temperature of the gas entering the turbine. Car manufacturers have started to followed suit.

Petrol Turbo Reliability? - galileo

The company I worked for used to supply turbos for marine applications which had the turbine housing watercooled - a very desirable feature in cramped engine rooms and favoured by insurers for reduced fire risk.

Petrol Turbo Reliability? - concrete

With a water cooled turbo, how does the water cool it when it is glowing hot? Will it not just boil the water? Would really like to know.

The water passes through the CHRA (Centre hub rotating assembly), not the turbine housing. The water does boil, and this removes vast amounts of heat and stops the oil in the bearing assembly from coking.

Industrial gas engines have long used water cooled exhaust manifolds to reduce the temperature of the gas entering the turbine. Car manufacturers have started to followed suit.

Thanks unthrottled, satisfied my curosity. Obviously a sealed system under high pressure. I did have this picture of a huge water jacket surrounding the turbo, but then thought how could it glow? Many thanks. Concrete

Petrol Turbo Reliability? - BenG

Cheers for the comments about turbo reliability.

I guess the advent of water-colled turbo bearings since the '80s would have helped make turbos a bit more tolerant to abuse, particularly hot shut-downs, along with better-quality oil.

As for the extended oil-change intervals, I guess it still makes buying a seconhand turbo car a bit of a minefield if it's previously been on a hire car or company fleet, or owned by a private buyer who thought the standard oil changes were OK?

Also, how important is it to allow time before driving off for oil to circulate around the turbo bearings? I have a turbodiesel which I drive maybe every week or two, and usually idle for 20-30 seconds before driving off in case the oil has drained away from the turbo feed pipework. Being a diesel with a VNT, it's not really possible to drive 'off-boost' until the engine has warmed up a bit...

Cheers,

Ben

Petrol Turbo Reliability? - Cyd

Cheers for the comments about turbo reliability.

I guess the advent of water-colled turbo bearings since the '80s would have helped make turbos a bit more tolerant to abuse, particularly hot shut-downs, along with better-quality oil.

As for the extended oil-change intervals, I guess it still makes buying a seconhand turbo car a bit of a minefield if it's previously been on a hire car or company fleet, or owned by a private buyer who thought the standard oil changes were OK?

Also, how important is it to allow time before driving off for oil to circulate around the turbo bearings? I have a turbodiesel which I drive maybe every week or two, and usually idle for 20-30 seconds before driving off in case the oil has drained away from the turbo feed pipework. Being a diesel with a VNT, it's not really possible to drive 'off-boost' until the engine has warmed up a bit...

Cheers,

Ben

A good point Ben. Some parts of an engine are lubricated by splash and drain back. Cam lobes, valve guides and timing chains for example.

It's extremely bad for an engine to be driven off the instant it fires. All those parts mentioned above will be lacking proper lubrication and cooling.

As you say, allow about 15 seconds (perhaps a shade longer if it's not a daily driver) before driving off. I do this by starting up, then putting my seatbelt on.

 

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