How reliable are turbo engines?

223rem > wrote:
>It would seem that a high RPM, small high-output engine (for ex. Subaru
>WRX STI or Mitsubishi Evo) cannot last too long. The stress on its
>components is
>just too much. Can such an engine last, say, 150,000 miles without
>major repairs?

I got 480,000 miles on a Chrysler Laser without any real engine maintenance.
It took five transmissions to get that far, though. I never got it up to
500,000 because I got fed up with the constant transmission work.

>Is there any special, expesnive maintanance that a turbo engine
>requires?

Not if you drive it gently. For the most part, modern engines are designed
carefully with proper reinforcement of parts that need to take a lot of
stress. The engine is designed to work with the turbocharger. But if you
abuse it, it'll be wrecked. A lot of folks who drive fast cars abuse them.

I will say that _some_ turbocharged cars have a particular issue where the
turbocharger remains hot after the engine is shut down, but oil stops
circulating through it. As a consequence, it tends to bake the oil into
varnish which clogs the turbo bearings up. Idling the car for a little
while before shutting it off can reduce the problems, as can using synthetic
oil that has a higher breakdown temperature.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

> wrote:
>Saabs are quite unrepresentative ot turbos too. Low pressure,
>relatively low performance (compared to a Scooby) and mainly not
>tending to be driven by hooligans either.

It's the "being driven by hooligans" factor that most strongly reduces
the lifespan of engines.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Ed Pirrero" > wrote
>> The whole point of turbos is to avoid the need for high revs.
>
> Uhh, no. The point of turbos is to recapture lost energy.
>
> The more revs you run, the greater the volume of air you can push, and
> the more fuel you can burn. High revs is where the turbo does its best
> work.

So, why do designers use small turbos, or multiple turbos so that full
boost is attained at low rpm (1500 rpm in the new BMW engine, for instance)?

Also, why do turbos have a pop-off valve to limit boost at higher rpms?

Methinks your statement doesn't accommodate those facts.

FloydR

mobil 1 synthetic, even more often than recommeded if you drive hard.
Also a good filter, and never forget your Air filter. follow the above
and you will get many trouble free miles on your car.
2005 PT GT 2.4. Also most people idle thier cars for a while after a
good run. This includes low spped of 30 mph which is sufficient to cool
it down. It will last like any other engine.
Just a dad, Wayne


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wrote:

> 223rem wrote:
>
> > It would seem that a high RPM, small high-output engine (for ex. Subaru
> > WRX STI or Mitsubishi Evo) cannot last too long.
>
> True, but that's more to do with the drivers they attract, not the
> engineering. In a UK city, you actively avoid Subarus when driving,
> simply because of the mouth-breathing Burberry-clad oiks they attract.
>
> Saabs are quite unrepresentative ot turbos too. Low pressure,
> relatively low performance (compared to a Scooby) and mainly not
> tending to be driven by hooligans either.

The LPT Saabs aren't the only ones they do ! Check out an Aero.

Graham

223rem wrote:

> > Small ? Like how small ? My own experience is limited to Saab engines of 2.0 -
> > 2.3 litre displacement. In 'hot' factory tune these can develop up to 300 bhp.
>
> 2 liters is small.

Only to Americans.


> 300 horses on a FWD car? That's a waste of
> horsepower.

Apparently not.


> > Race tuned ones are good for up to 400 bhp but you have to be careful not to
> > melt the piston crowns.
>
> AFAIK, nobody races in FWD cars.

http://www.btcc.net/html/home.php for example

Saab did exactly that when they introduced the 9000 actually and won trophies for
several years just to make the point !

Graham

Scott Dorsey wrote:

> > wrote:
> >Saabs are quite unrepresentative ot turbos too. Low pressure,
> >relatively low performance (compared to a Scooby) and mainly not
> >tending to be driven by hooligans either.
>
> It's the "being driven by hooligans" factor that most strongly reduces
> the lifespan of engines.

100% agreed. Crappy drivers can trash *any* car in fact.

I've never known anyone claim that 300 bhp from 2.3 litres was relatively low
performance btw !

Graham

"Scott en Aztlán" wrote:

> Eeyore > said
>
> >> > The whole point of turbos is to avoid the need for high revs.
> >>
> >> Uhh, no. The point of turbos is to recapture lost energy.
> >
> >No it isn't.
> >
> >It's to 'push' more fuel-air mixture into the cylinder.
>
> And it does this by recapturing energy that would otherwise have been
> lost out the tailpipe.

It's actually a 'drag' on the exhaust compared to a free flowing one. The power
has to come from somewhere. I'm intruiged by the new interesting in
supercharging in fact.

Graham

"Scott en Aztlán" wrote:

> "Floyd Rogers" > said in rec.autos.driving:
> >"Ed Pirrero" > wrote
> >>> The whole point of turbos is to avoid the need for high revs.
> >>
> >> Uhh, no. The point of turbos is to recapture lost energy.
> >>
> >> The more revs you run, the greater the volume of air you can push, and
> >> the more fuel you can burn. High revs is where the turbo does its best
> >> work.
> >
> >So, why do designers use small turbos, or multiple turbos so that full
> >boost is attained at low rpm (1500 rpm in the new BMW engine, for instance)?
> >
> >Also, why do turbos have a pop-off valve to limit boost at higher rpms?
>
> Because they sound cool?

Oh come on Scott !

Graham

Eeyore wrote:

> > 300 horses on a FWD car? That's a waste of
> > horsepower.
> Apparently not.

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.