How reliable are turbo engines?

Oh come on Scott !

Graham

It is wasted. A FWD cannot make use of that much power (due to the fact that as you accelerate the weight shifts to the back). Also, torque steer would be very bad.

Tell non-American car builders that !

Depends on the drive shaft length mismatch only.

Graham

There's a controller of that power: the throttle. it's really not necessary to consider the throttle as a binary device. :-)

It's my understanding that torque steer is controllable.

The extra power comes from the heat energy otherwise wasted in the exhaust. That scavanged power is used to compress the air going into the manifold, allowing more fuel to be used (but still staying within the stoichiometric ratio) thus incrreasing the power output. The increased power far overcomes any loss involved in a less efficient (? actually, more efficient) exhaust flow. The result is a net gain in output, although with more fuel use (but a more efficient fuel use). No different, really, than adding more cubes, which also allow for more air input, along with more fuel input, for a net increase in power output.

Small turbos produce less boost than larger ones, but they also reduce lag, no matter what the engine RPMs, for the same displacement engine. It's that lag they are working to reduce, with the side effect of producing more boost at lower RPMs. But, turbos do provide more power at higher engine RPMs.

One time, I conducted some 70 to 90 mph acceleration tests up a 7% grade in my Audi S4. I got the same times in 6th, 5th, and 4th gears.

Graham

Turbos are great for creating a very flat and wide torque curve too !

Graham

To avoid turbo lag. It's precisely because turbos, particually big turbos, are ineffective at low RPMs that this is done.

Because at higher RPMs, the turbo is so effective that without the valve it would increase boost so much that it would break other parts of the system. Usually the first symptom is knock.

The power in a turbo comes from exhaust heat which would otherwise be wasted. While the turbo does add restriction, it's typically not enough to significantly reduce the unboosted power of the car. A supercharger's belt drive takes significantly more.

No. Turbos do not produce power. The *ENGINE* produces power, and all engines produce more power at higher RPM. It doesn't matter whether the engine has a turbocharger, supercharger, or has none.

Ed actually got it right in his first sentence, then blew it in the 2nd.

FloydR

"Matthew Russotto" wrote

Gee, it's great that everyone knows the answers. Unfortunately, now you've given the answers to Ed, who apparently doesn't.

FloydR

Did the wastegate open? The ability to make more power with higher RPMs can be negated by systems to control that power.

"Do A Google Search"

Chris

The presence or absence of the turbo will have little effect on the longevity of the engine. Longevity will depend on how the owner uses the engine. Foremost is whether the owner adheres to aconsistent and frequent maintenance program. Next is how frequently the owner over-revs and generally uses the engine at close to it's maximum power. For tiny cars like the ones you mentioned there is no need to run the engine at its maximum, unless the owner is out to impress himself and destroy the engine in the process.

On the other hand, if the engine is seriously mismatched with the vehicle then the engine will be over-worked and wear out in short order. The only example of that kind of mismatch was a Winnebago that used a small 4 cylinder turbocharged diesel. The engine was under 75% or greater power most of the time to keep that road hog rolling. The engines died at an alarming rate, as soon as 50,000 miles.

OK. I should have been more specific. Does the turbocharger have to be replaced periodically? Those things spin so fast, it is hard to imagine that the bearings dont have to be replaced relatively often.

That's definitely not normal.

Again, I got 480,000 miles on a Chrysler Laser, with the original turbocharger.

The bearings on these are sleeves that operate with a film of oil on them, so the only time they actually wear much is when the engine first starts up and the oil film is thin because there is no circulation, or if there is a lubrication failure because the oil is cooking and varnishing inside the bearing.

The thing that wears out and has to be replaced periodically is the oil, and if you aren't very careful about that and use oil with a high breakdown temperature, the turbocharger _will_ fail.

--scott