Turbo on cars

Was not really sure on the right place to post it, as it is not really a maintenance question just a question I have for a car I am looking and a general question because I have not yet worked deep on a car equipped with turbo.

My first Q;

how does the turbo on a car work?

2nd Q: If the turbo on a car is “out” can it be replaced or fixed w/o much cost? Of course this will route back to first Q. My Dad (a mechanic) mentioned the possibility of re-routing the exhaust etc or something like that to make it work.

In case it matters the car I learned off is a 70’s Subaru Outback, can’t remember pacific details on the engine etc.

Any tips or suggestions is appreciated.

I got some good lies. A turbo can never be fixed cheaply. It kind of gets in the way of fixing anything else. Most of them work from exhaust gas being routed through them. It does require different exhaust manifolds or manifold. That’s about all of my “useful knowledge”.

A turbocharger works by simply compressing the air entering the engine. The exhaust spins a turbine blade which in turn spins an impeller at very high RPMs which then basically squashes the air into the intake tract faster than the cylinders can use it.

Turbocharger repairs or replacements are usually expensive. Adding a turbocharger to a vehicle that was not originally equipped with one can get VERY expensive as it entails modifying a lot of things including the intake tract, exhaust, fuel and engine management systems, and so on.

Turbocharged cars also require more frequent maintenance, especially oil changes, and the point could be made that on average a turbo car may have a shorter engine life due to stress. A lot of that could depend on how often someone is in the boost. In many normal driving situations the turbocharger is not providing any boost.

A good read on the issue of turbocharging is a Bentley publication called “Maximum Boost” by Corky Bell. The book is worth the money if you’re interested in the whys and hows of turbocharging.

A turbo charger is basically a shaft with a fan blade at each end of the shaft. One fan is moved by the exhaust gases passing by it. That fan moves the shaft and drives the fan blade at the other end which drives intake air and moves that air into the cylinders of the motor. It is in effect charging the cylinder with more air than the cylinder could suck in on its own, which is what a naturally aspirated motor does.

The pressure of the air the turbo pushes into the cylinder has to be regulated. Too much pressure (or boost) is a problem, and too little negates the effect of the turbo. So, there is a “waste gate” the opens and closes as needed to regulate the boost pressure.

Since the turbo is sitting in the path of very hot engine exhaust gases and is incorporated in the exhaust manifold (also a very hot part) the enemy of a turbo is heat. Adequate oil pressure with high quality oil (oil that doesn’t break down in the heat) is very important to a turbo’s longevity. Most turbo’s specify full synthetic oil, and relatively more frequent oil change intervals compared to a naturally aspirated motor. The turbo spins at speeds in excess of 20,000 rpm in some applications. This speed and the hot hostile nature of the envoirnment can eat up turbo bearings which have to be high quality to begin with.

The waste gate mechanism can also cause problems. So a turbo seems simple but the plumbing and actually parts are expensive and replacement can take a lot of labor depending on where the turbo is mounted and how hard it is to access. Expensive part, expensive labor, means expensive repair. Most cars do not get past 200K miles without a turbo replacement somewhere along the way.

Mhmm sounds like if the turbo is indeed the problem it maybe a no go. All in all though some good info, thank you all for the good info

As regards the last portion of the second question, it is possible to reroute and seperate the exhaust and induction path to eliminate the turbo and the engine will still run…but very poorly. Engines get sufficient power by compressing the fuel in the cylinders prior to igniting it. Turbocharged engines rely on the turbocharger to help compress the gasses when power is needed. Without the turbo boost, you won’t have enough power to pass a turtle.

Just google it, tons of info on this very popular topic, such as:

@Harland - you said you’re looking at one to buy - which make/model/year/miles?

@texases I’ll get the full details tonight if I get the callback on it, my Dad is waiting to hear back from his friend on if she still has it.

The Subaru Outback debuted in the mid-90’s. There was no 70’s Outback. What car are we talking about here that has a bad turbo?


My mistake on the outback part, might of been some miscommunication with my Dad. Like I said if I get the callback on it I’ll get the full details.

Regarding Q #1, ok4450 & Uncle Turbo explained it very well.

Re: Q #2, in addition to the reality that turbo repairs are rarely cheap, the OP has to consider the likelihood that this car has been driven to the max (as a result of the turbo), so the main bearings, piston rings, and…God only knows…what other parts have been beaten into submission over several decades. (Translation=This car should not be considered to be a daily driver or your only vehicle until all of the likely engine problems are sorted-out, at a likely high cost)

Regarding “pacific” details, I can tell you that turbochargers work the exact same way on the Atlantic coast and on the Pacific coast.

Are there any other specific details that you are wondering about?


I agree. If you avoid them, you never need to work on them. IMHO, I think you should avoid cars with them too…unless you have money to burn. I don’t think it’s a good idea for manufacturers to go this route for economizing cars by under powering them with cubes for economy and adding a turbo for acceleration. Ford seems to be doing this big time. I feel it will bite into the long term reliability both by adding moving parts and stressing the underpowered motor.


I knew it, I knew it !
I knew If I left it alone that I could count on you to show up and I was right ! Those Pacific details were just too much for you to overlook.

CSA :wink:

@common sense answer

I am glad that I have lived up to your expectations…

Glad it was lighthearted.we are common folk,we dont roast Folk for typos-Kevin

If you live in the mountains, turbos can be a great help.

While OK may be correct about shorter life spans, if it’s designed from the start to be a turbo engine, and properly cared for, then it should last just as long as a normal engine. I’d be more worried about them taking a normal engine and just throwing a turbo, and the needed plumbing, on it.

Regarding my comment about shorter engine life, there can be a tendency amongst turbocharger drivers to have a Jekyll and Hyde personality. I freely admit to being guilty of the practice.

Driving a non-turbo car I’m often accused by my wife of poking along and that’s pretty much true. I just don’t normally get in a hurry to get where I’m going.
Stick me behind the wheel of my 5 speed manual, turbo SAAB and it’s an altogether different story. There’s kind of an adrenaline rush to a turbocharger pull and I enjoy the sensation of winding it out a bit and going for the next gear…

Of course, that may or may not have anything to do with the barely noticeable top end rattle and faint 1/2 gear crunch developing… :wink:

Ford seems to be doing this big time. I feel it will bite into the long term reliability both by adding moving parts and stressing the underpowered motor.

I’m already hearing a bit of grind in the turbo of the Escape I drive for work. We got 'em 4 months ago. Quality!

That said, I have nothing against turbos. Plenty of cars run for many years with no turbo problems whatsoever - even the ones that didn’t come with a turbo from the factory. It’s all in the quality of the parts and how it’s set up.

Turbos have somewhat of a bad reputation for bad reliability because kids stick a turbo into their Honda Civic and crank it up to 14 pounds of boost without doing anything to the motor. And then they wonder why stuff breaks, and blame the turbo rather than their hare-brained install. Or they’ll put one in, and drive it hard when the engine’s cold, and turn the engine off right away after thrashing it instead of installing a turbo timer or letting the engine run for a minute or two to cool the turbo down, and then wonder why stuff breaks and blame the turbo instead of their own stupidity.

Stock turbos can last a long time, it’s the cheap aftermarket stuff or ones that have been boosted way beyond what they should in the name of high power that cause problems. The tradeoff for a little extra power with good mileage otherwise is having to replace the Turbo at some point

I think turbo’s are a good thing, but they are expensive parts to replace and repair when they go bad. In the early '80’s Saab (not the GM Saab that came later, but the real Saab) designed a 4 cylinder motor specifically for a turbo charger. Most other manufactures just added a turbo to an existing engine with much less success. Saab used more main bearings, stronger connecting rods, and designed the heads to handle the extra pressures and internal stresses that come along with turbo chargers. So, Saab turbo’s were fast, lasted well, and were about the same to maintain as a normal motor with the exception of more frequent oil changes.

Over the years the fuel injection, electronic ignition, and computer controlled engine management systems have improved the performance and durability of motors with turbo chargers. The advantage of the turbo is the motor uses the fuel of a small motor when coasting along on level ground at a constant speed, which gives good mpg. When you step down on the gas petal the turbo will push more air into each cylinder, this allows the fuel injection system to put in more fuel and the result is a lot more power. Now a small motor like a 2.4L can feel as powerful as a 4.5L motor. More power for passing and hills, towing, etc. When you are on the gas, forget about the mpg at that point. The turbo charged motor needs as much fuel as the bigger motor to generate the power. This is why some owner’s of turbo cars are disappointed with the mpg they achieve. They enjoy the feeling of the power, but don’t realize the power comes at a price, much less mpg.

There are other ways to make a big motor get the mpg of a smaller motor and one of the best is cylinder deactivation. This is basically the opposite of the turbo, a big motor cutting off fuel to 2 or 4 cylinders to use the fuel of a small motor when coasting along at a steady speed. Same result the mpg goes down significantly when the driver steps on the gas for more power. Both techniques work and we’ll see more of both in new cars.