what is the worst that could happen if a turbo lets go? the reason i ask is that im planning on using a turbo out of a junk yard without rebuilding it. what should i look for in junk yard turbos? i know to wiggle the impeller up and down and back and forth (I assume play in the shart should be nill).

P.S. thanks to all you guys. i registered just the other day and you guys have helped alot.

 

On a journal bearing turbo, some shaft play is normal. I would look for Nissan turbo's primarily but i'm biased towards the standard garret flanges because of my HKS mani. DSM turbos are also available off eclipses and...

 

I guess the worst that could happed is peices of you turbo get sucked into your motor and blowing it up.

 

The pieces would hopefully get stuck in the intercooler, the smaller pieces will go through the motor come out the valves and get recycled through the turbine housing thus destroying the rest of your turbo that might have survived.

 

shaftplay would mostly be the in and out movement of the impeller which would mean its about to go...

 

This is isn't likely to be a problem on a Miata but on a Turbo Diesel Citroen Xantia I used to own the oil seal in the turbo failed whilst I was driving... oil got sucked into the inlet and the engine started to run on oil alone.

I pulled the key out of the ignition but the engine continued to run and revved straight up to the redline...it sat there at the redline for about a minute in a cloud of smoke before it cut out.

I assumed the worst (new engine) but in actual fact I fitted a new turbo, some new glowplugs and a new cambelt (just for safety) and it was fine!

As I said, not likely to happen on a low compression petrol engine like the Miata but thought you'd want to hear about a turbo failure...

 

Well, the turbine casing explodes, shredding the brake and steering lines. You car crashes into another vehicle, killing the Director of the CIA and his family. Conspiracy theories and political infighting paralyze the agency, causing America’s already troubled intelligence capacity to grind to a halt.

Meanwhile, hard-line extremists rise to power within Russia and their charismatic ways reunite the old empire under the Soviet banner. Seeing America’s military paralyzed, Russia (with the support of the African and middle-eastern nations, who are tired of the US and its colonialist tendencies) launches an aggressive campaign to seize control of the West and ensure the future economic stability of their fledgling nation.

Defenseless, and with western Europe cautiously refusing to cast their lot in what could ultimately trigger a Third World War, the US turns to China for aid. In a desperate bid for survival we mortgage our future to the Chinese, who ultimately betray us to our aggressors in order to strengthen the heretofore secret negotiations in a new Sino-Soviet alliance. And within five years we’re all living under the iron thumb of Communism.

That’s pretty much the worst that could happen.

 

jokes aside; could the turbo granade under the hood and realistically take something out? would it be a good idea to put a skatter sheild around the turbo just incase?


joe: if the sino-soviet alliance took over, do you think they would bring some lada or yugo turbos over here.

 

I have never seen a scatter shield on a turbo, just heat shields. That goes for cars running 30 psi even. If you are running a turbo under conditions that you are afraid it might "grenade" then you need to change something because it's obviously not safe.

 

so the worst that could happen is my $50 junk yard turbo goes up in smoke and I go get another, right?

 

I doubt seriously that an automobile turbocharger could ever grenade in the same way as an aircraft engine. The turbine wheel itself is fairly stout, and the pieces that might actually tend to break off would have very little mass (and thus very little inertia) relative to the strength of the housing. I've heard of engines ingesting hardware and people finding bits of the turbine blades stuck in the catalytic converter, but never an "explosive" failure of a turbocharger.

And I doubt seriously whether we would see any Ladas or Volgas here. If our benevolant overlords permitted us to own private vehicles, it'd more likely be Chery QQs or some other Chinese brand. Which already seems pretty likely to happen...

 

You don't need to worry about the turbo physically exploding, allowing shrapnel to scatter into the engine compartment. You may need to be concerned with the internal parts of the turbo fragmenting and following the intake charge into the motor. That could cause substantial damage to the motor.

 

Though worrying about an oil line breaking and catching the vehicle on fire is valid.

 

If the car has an IC I doubt that the turbo coming apart would get to the engine, there just isn't a path for anything big through the IC is there?

 

Even if a piece of the turbo broke off, it would have to get down the tubing (not very difficult), through your intercooler (difficult), back UP into the intake manifold (very difficult), through the throttle body (WOT: not hard, no throttle: near-impossible), and then make it into the engine through the intake valves, and THEN it has to be a big enough piece to either wedge in a valve or dent a piston. If it's not, it goes right back out the exhaust valve and eats the rest of your turbo.

As long as you have less than 1mm of shaft play (some turbos come stock with up to .75mm of shaft play) you are good to go.

 

how much wiggle is acceptable: in and out? up and down?

 

savington mentioned 1mm of play, that sounds reasonable.

 

LOL - nice post!