They are designed for more stress and the internal pressures and temperatures in a supercharged or turbocharged are considerably higher when compared to a normally aspirated engine. The fact that your SAAB lasted so well is a testament to the SAAB engineers who designed the engine.

I worked for a number of years on engine management systems for a very large European company and have had first hand experience of the effects of supercharging and turbocharging on engines. There is considerably more internal stress in a forced induction engine.

My point, however, was not whether they lasted longer but that they are more complex and have more to go wrong. I too love the low end torque a well designed forced induction engine can produce and there is no doubt that with the reduced boost lag in modern engines, a forced induction engine is a genuine work of art. Modern materials and engineering technology have made the forced induction engine available to the average person, but it is no secret that they are more expensive to manufacture (look at BMW and Ford for example and at their comparative pricing for normally aspirated and forced induction engines, and yes I do have inside knowledge) and service.

From a drivers perspective the modern forced induction engine is probably better than its larger displacement normally aspirated cousin (low end torque, higher revving due to lower moving mass etc.) but they do not sound as good. I have met people who have driven BMWs latest 328i (which uses a 2 L 4 cylinder turbo) and compared it to the last generation 328i with an in line 6 and prefer the older one because it 'sounds better'. Not because it drives better. So a lot of this hype about cylinders often boils down to emotion (which is perfectly valid) and not solid objective driving observation. What is not to like about a light powerful engine that is economical?

In summary, I have biases from being around for too long and seen some of the first attempts at mass market forced induction engines and love the sound of some of the old V8s, but I know and feel the benefit of these knew engines even though they are very complex and, yes, more highly stressed.

 

I have to disagree. A four cylinder turbo has way fewer components than a V8 delivering equivalent power. Stress sounds bad to humans but engines don't care.

A turbo is a very simple and incredibly reliable device. A turbo in constant use experiences no wear in practical terms. Electronic control of supercharging ensures engine safety. Modern oils solve the heat problems facing lubricants. Turbos produce cheaper horsepower than displacement these days.

In fact, if you compare schematics with an open mind a turbocharged piston engine with the turbo engaged to the drivetrain, as for certain aero applications, is indistinguishable in principle from a jet engine. The difference is the jet engine dispenses with the inefficient piston engine gas producing pump and replaces that with a vaned compressor, combustion occurring behind that in the compressed mixture, direct injection being a feature of jet engines. Turboprops are an even more direct illustration of this similarity and are making a comeback for fuel efficiency reasons.

It is the piston engine that is unnecessarily complex, not the turbocharging system.

 

I thought this article from this weeks UK's Auto Express magazine might add to the discussion regarding the increase of diesel powered engines in the US -

US motorists turn to diesel

Demand for diesels isn't only strong in the UK. Motorists are finally warming to diesel in the US in response to rising fuel prices.
Sales of diesel cars such as the VW Passat TDI and Mercedes S-Class CDI have risen 35% in the first quarter of 2012, compared to the same period in 2011.
Sales also jumped 30% between 2010 and 2011, according to market researcher Baum and Associates. The US is still a petrolhead's paradise, though: motorists there pay the equivalent of $1.00 / 63p* per litre for unleaded fuel. (We pay about $2.20 / £1.35 per litre in the UK).

http://www.autoexpress.co.uk/

 

I guess we have to agree to differ. Your point about 4 cylinder forced induction engines versus 8 cylinder normally aspirated engines is valid. However the higher operating temperatures and pressures in a forced induction engine are more stressful whether you agree or not. New metal technology etc. have solved most of these issues, but the fact remains that forced induction engines require better metallurgy and more careful design than normally aspirated engines. Lag, waste gates, over pressure sensors,surge control etc. are required to make them work. This complexity is not solved for free. I am happy to drive a forced induction engine, but I am also aware that there is a great deal of expensive and complex technology involved. I am a ph d in computer science so understand complexity well and deal with technology a good deal more complex than this on a daily basis. I am not scared by technology, just wary of applying it where it may not be needed. We should all be aware of what we take for granted, and forced induction is not a magic bullet.

Will these engines be running after 300 KM, who knows and do we care in this world of disposable technology. I do not know and do not presume to guess, but I do know we should be careful.

 

As economics dictates there is no free lunch. And forced induction engines will pay the price sooner or later. Wear and tear, steaper power surge, higher number of parts, higher operating temps and pressures. You just can't ignore the facts. These small engines on steroids are prone to live shorter lifes. A close friend of mine had turbo problems on his GTI Golf. Turbo died and needed to be replaced. No fixing a bad turbo 3000K parts and labor.

 

Ahhh, finally someone brings up F1. In 2014, all F1 cars will have a 1.6 l V-6...
Someone should have lost their job when Jaguar did that half-fast approach, then got out.
Back on point:
I prefer the smell, sound, looks and feel of the 8, 10 or 12 cylinders myself. (Apologies for bringing up the V-10 in the Jaguar forum;-) and I must admit that I also prefer the 'feeling' of the firing order of the AJ-V8, post 2002.5.
Face it, without us supporting the oil industry, it may go bust. ;-) We are merely doing our part in support of the global economy, really.
On a related note though, have you ever tried the Tesla Roadster?? Wow!

 

$3,000,000 to fix a turbo!? WOW

I prefer superchargers. As mentioned, turbos appear to have a much shorter life span due to the extreme exhaust heat. Usually they need to be replaced under 100k. Ceramic versions that can withstand the heat are expensive.

In the biturbo Audi S4 (~2000-02) I remember reading it was well over $5k to replace the turbos. Used biturbo S4's don't sell because the car costs about $10k used and then you have to drop another $5k to replace the turbos.

Roots superchargers as used in the Jags (the M112 anyway) are relatively cheap ($500) and easy to replace/service vs turbos.

 

Turbos do not have a short lifespan. Usually they last longer than the engine they are bolted to. Internal stresses on supercharged engines (whether turbo or mechanical) are higher but only because specific output is higher. The highest stress is still at TDC on the exhaust stroke at redline, inertia load on the unloaded piston is the highest load on the weakest bearing and that is related to piston weight and piston speed, not bmep. Modern oils and water cooling have solved owner abuse problems to a large extent.

Interesting the S4 is mentioned as having unreliable turbos as that is also not the case. I have one of those also. Replacement turbos aren't particularly expensive but labour to replace is ridiculous. Then so is just about every repair on this stupid design. This is a great car but like the Porsche 911 is simply a bone headed engineering job. The engine is in the wrong place and there is no room to fix it without taking off the front bumper and radiator assembly!

Turbo failure is almost always caused by operator abuse, over driving a chipped car or, most frequently failure to replace failed exhaust gas tempersture sensors, on the S4. The V6 engine was designed as a low pressure turbo and the common modification is to make it a high pressure turbo which Audi also did. However, most chipped S4 have no other modification whereas Audi spent a ton of money to push horspower from 250 to 380 in streetable form! Drive a chipped S4 with appropriate consideration and it is as reliable as the factory engine.

 

I think this is an important point. It isn't necessarily in the interest of the car industry to build cars that will run forever. Personally I have never owned a car beyond about 50k miles and rarely owned cars that are out of warranty. The problem with car forums is that they are full of car guys who generally care about engineering, design, technology, sensory feel of a car etc. The vast majority of car buyers couldn't care less about any of this stuff. How much does the car cost? How much does it cost to run? Do I like the colour? Does it have the right image for me? That is about as far as it goes for most people. Even performance is a relative measure based on your own experience. Horse power and torque figures mean nothing to the common car buyer. So for those reasons, charged fours and sixes are here to stay.

 

Grrrrrrr!!!!!! I LOVE 911's! Porsches are just perfect cars, in my view. And I won't get into a discussion about the engine being in the wrong place, because it is undeniably in the wrong place...

The packaging of the engine and work needed to do routine maintenance is what put me off buying an RS6 a few years ago.

 

I like your Cadillac!! weegie, hehe, ron.

i would like to get one of those Jag XFDs,, i think it would be a smart move,, cruisin around Austin at 40+ MPG

 

I like how you composed your post - huge contradiction. LMAO

You say Turbos are reliable and last long time. Then you say it's failure is caused by the operator. What did you want the failure be caused by?

What you saying is, if someone beat the **** out of a NA engine, it would still last forever without problems.
If someone beat the **** out of a turbocharged engine, it will fail.

CONCLUSION: Turbocharged engine is less reliable than NA engine.

 

Coming from a steady diet of turbo'd Toyota MR2 and Supras that are dead reliable it seems obvious some of you guys have an irrational fear of turbos. The old tech 1990's journal bearing turbos routinely last 200,000 miles by just following the oil change maintenance schedule. They also stand up well when the cars are modified to run 50% higher boost, which of course they only ever have to do for short periods...unless run flat out on road courses like mine. Beyond 50% boost increase you would go to more modern designed ball bearing units that are engineered for those boost levels. I suppose if you're making 1000-1500 whp on a 3L Supra engine and the turbo blows you probably wouldn't blame the technology, but oddly enough even that isn't a problem for a properly matched turbo.

I've made about the same amount of power with my 2L 4 cylinder MR2 running a ball bearing turbo on premium grade pump gas as the Jag's 5L N.A., and run it on the road course for years. Every track day probably places the equivalent demands on the turbo as an entire year on a street driven car where the turbo only very infequently makes full boost, and only for short periods where heat is not an issue. I have no fear of turbo-charging technology, or the prospect that a turbo "might" need replacing one day. The chances of that happening on a street driven car is remote at best, and I'd be far more concerned about any one of the dozens of electric motors and electronics failing that move my seat, or raise the roof on the XKR. But that's why we have a warranty, and why we make the decision to keep or sell it when that nears expiry.

Bruce

 

Straw man argument.

I did not say that naturally aspirated engines subject to operator abuse will last longer than turbo engines subject to the same abuse.

The same types of abuse kill naturally aspirated engines also. Putting the engine under heavy load when cold, shutting down a very hot engine immediately upon stopping, failure to replace ignition or fueling components promptly and so on all kill engines before their time.

Turbos are as durable as naturally aspirated engines. In fact, because they are driven well below their performance capabilities the majority of the time they tend to be more durable than naturally aspirated engines.

 

In case you need some real-time experience, just go to your local Ford store and try out a bread and butter F150 ecoboost. In just one year, they are selling more of these than any other engine, including the very popular 5 liter v8.
23 mpg in a full size pickup that can blow the doors off most of the others out there.
Made a believer out of me, and I'm 70 and have driven v8s all my life.

 

I didn't say turbos have a short life span. I said when compared to a roots type supercharger turbos have a shorter life span.

The S4 comment is very true despite what you believe. A quick Google search will show you all the issues people have with turbo failures. Example: Audi S4 (B5) Common Problems [German Car Wiki]

 

Well, not to beat a horse but mechanical Superchargers have wear points which turbos do not. Also, the well known S4 turbo failures are attributable to Audis well known and inexplicable penchant for using cheap parts. The turbos last forever as long as the various other components are maintained correctly. Chips can overwork the turbos because of owner decisions. Chips take the turbo outside its design parameters if the owner dies not drive with that in mind. The turbo failures are slightly more common on the four cylinders because the turbo boosts a bigger engine. The V6 has two turbos feeding 2.7 liters while the four has one turbo feeding 1.8 liters.

Anyway, the facts are the facts. Supercharging a Jaguar will not make it less durable or reliable. Jaguar has been supercharging for over a decade now.

 

something to think about ,, Detroit Diesel trucks can get a Million mile warrenty, and that includes the Turbo. a lot of them have over 1mill. and going strong. i think Cummins and caterpillar has 1 mill. warrenties, on there engines!

and not to be left out,just look at what Ford is doing with the ECOBOOST engines, they got 5yr warrenty, and those are gas engines, the guys iv talked to love them.

i noticed nobody brought up MPG,, it does have some merit on this subject!

of course you can break anything if you mod it enough, but i think the turbo engines are on a new course!

superchargers VS turbochargers,, i'm sayin TURBO.

 

Uggg i hate to read this and I know this paints me as a typical american but i LOVE that my XF has a V8. It is one of the reasons I bought it. My XF will get driven 7 miles a day during the week. That's it, so I don't care a bit about the gas prices. Oh well i guess that means in three years i will have to pick up a 2012 XFR so I don't get stuck with the 6 cylinder. I know this can get political real quick but if the USA would tap into its own oil reserves we could stave off the spike in gas prices due to China's growing driving population. Regardless I enjoy my V8 rumble and would like to see it stay

 

well i still would like to get an XF 2.2D, here in the states!

also i'm a car modifier(been 60yrs modding) i'll bet i can get better mpg than the factory is allowed to do!

simply put! anyone with money can buy a car,and be ordinary, just like everyone else.

but properly modded car is like ONE of a kind! and just sometimes cant be bought!