Question about turbos

[acediac]

Hi folks,

I've been reading about turbos blowing up, and I'm trying to get more details:

1) How do you tell if a turbo is blown? What kind of noise is there? Or is it just no power, with no boost showing on the boost gauge?

2) If you don't use the car "in boost" often (ie. keep below 3-4000 rpm, hardly anything showing on the boost gauge) does that help the turbos' longevity? (My understanding is that they spin regardless whether you're "in boost" or not, right?)

3) How many k's are turbos expected to last, assuming I use factory boost settings, and change oil regularly and cool it down properly after hard driving?

4) How do you tell a turbo is on the way out, apart from actually inspecting it physically? Does a worn turbo smoke? (why?) Does it make some kind of noise? Will it just blow up without warning?

5) Is the car drivable when turbos are blown? Will I risk further damage if I drive it? As I understand, most of the Japanese R33 turbos were ceramic, and someone told me that this means they could shatter and be sucked into the engine causing major damage... true or false? If true, why weren't the stainless steel ones that were made for UK used instead? Cost savings?

Thanks in advance for imparting your experienced wisdom.

[JimX]

1) It would depend. Damaged compressors or exhaust wheels could be hitting the housing, bearings could be making a noise, or the whole thing could not be spinning at all in which case it will just make no power (probably even hideously restrict it). Your boost gauge will still go up and down with the manifold vacuum, but not past 0 (ie, no positive pressure)

2) It will definitely help the turbo last longer, because although the turbo is always spinning, it's only really under strain when on boost. Also exhaust temperatures increase with revs which will cause it to wear out quicker. That said, as long as you take care of it by allowing it to cool down and doing regular oil changes with good oil even a plain bearing turbo can last quite a long time. Ball bearing turbos will last even longer.

3) I don't have enough experience with this, but I've had my plain bearing turbo for over 20000km now, and I don't know how much it had done before I got it. I give it some stick fairly often, but it's still like new. There's no axial shaft play whatsoever. If it does die, a rebuild is around $350. I also run it at 14.5psi (1 bar).

4) Sometimes the seals will leak causing oil to be blown out in the exhaust, but if you are thinking of buying a turbo or turbo car the best way is to just check the axial play on the shaft. If it moves in and out at all, it's either toast or in need of a rebuild very soon. There will be some side-to-side play even on a brand new turbo, but check it anyway to make sure it doesn't hit the housing. It shouldn't, if there is no axial play. You can also check for pitted blades, they're a sign that a good air filter was not used and can also indicate an engine in bad condition. The bearings may make weird noises before they go but it's not a guarantee. Too much boost can also kill them without warning.

5) If you don't mind filling your engine with chunks of ceramic, sure Personally if I had a ceramic turbo that blew its compressor wheel I would immediately pull over and get a tow. Ceramic is used for (a) cost savings (I believe, not 100% sure), (B) quicker spool up than steel, and © planned obsolescence. They're obviously designed to last a very long time, well outside the warranty period. So sometime after that if they blow, the shattered wheel may write off your engine and hey presto, another customer for Nissan when you rebuild your engine and buy the new parts from them (well that's their plan anyway).

I hope the above answers your questions ok and doesn't contain too much misinformation! (I apologise for anything I've got wrong)

[acediac]

Thanks JimX for your very informative and thoughtful response!

As you can guess, this is the first time I'm actually owning a turbo car, and I knew there were more things to look out for, but I'm now finding out just how much!! Oh well, part of the fun I guess

I had also been planning to take it out on a few track days, but now I'm reading about sump baffles and oil coolers being mandatory for ANY track work at all... sheesh, my wallet is really dreading the worst now !

[Duncan]

lol acediac, unless you've got a GTR, slicks, and big balls, don't worry about the sump baffle and oil cooler for track days.

Come along to Eastern Creek on 2/10 and check it out, there will be a big crowd there.

A track day is a great day out and a top opportunity to get to know a new car Just don't push it like a schumaker and everything will be fine...

[Zensoku]

Guys, on skylines, the only ceramic part is the exhaust turbine. And when this lets go (a condition i like to call Shaftus Separatus) it will either get lodged in the dump pipe, or further down near (or in!) the catalytic converter. This is due to the massive amount of exhaust back pressure pushing it downstream. I haven't heard of a turbine making it's way past the manifold and anywhere near the exhaust ports on the head.

Rarely, ever, rarely will you see a turbo that also has a ceramic compressor wheel as well.

If i had a digital camera, i'd take a photo of the back of one of the GTR T28's i pulled off my motor. "Where's the wheel?!" LOL

On another note, i have heard of stories of race teams not running blow-off valves on their drag cars at all, (in the quest for power, no leaks!) and when they've just hit WOT, and lifted their foot off the throttle, the amount of pressure now slowing down the still spinning turbos has caused the compressor fins to bend and eventualy snap off and head into the intake! Although, i think this was the case on the old school turbos and their lack of knowledge back then...

[strutto]

But if the turbo bearings seize or shatter you are more than likely to get metal particles in your oil. Not the best place for em....

My .22c

[Mase]

here's an example, my rb20 turbo went recently, on minimum revs it would start whining (not spooling), it got to the stage that with any acceleration it would whine until it boosted up, wasn't too miuch of a noticeable difference in power but maybe a bit over time.

[acediac]

Mase, when you say your turbo "went", did you eventually find out what was wrong with it? Did the turbine scrap against the housing? or the bearings started siezing?

I guess yours was a gradual failure, but did you keep driving the car when you noticed that??

Duncan,

Actually I do have an R33 GT-R which is why I'm dead broke now Hence my paranoia about not breaking anything. I have driven Eastern Creek before, but in my previous cars (only N/As), and that first kink is damn fast with a long period of sustained G's... just the ticket for oil starvation even on road tyres, don't you think? And what's the point of going on the track if you don't try reasonably hard?

Wish I could go to EC, but I'm not around Sydney anymore, for the moment.

[Sydneykid]

Hi guys, my experience has been that any GTR that sees a race circuit should have a larger sump with baffles fitted. It matters not what tyres or how hard you are running it. I have seen a standard GTR (exhaust only) with standard suspension and road tyres run a big end bearing in 3 laps.

In my opinion it's simply not worth the risk, circuit = sump & baffles.

[benm]

How much are sump baffles ?

[Mase]

Quote:

Mase, when you say your turbo "went", did you eventually find out what was wrong with it? Did the turbine scrap against the housing? or the bearings started siezing?

End Quote:

Acediac when i took the turbo off to replace it, it had no up and down movement (well none that signified a buggered turbs)however, it did have a whole heap of back and forth movement. Im guessing this was the problem and it may have been rubbing on the housing. That's all i can tell you sorry. If u were in brissie u would be welcome to come check it out as i have it sitting in the garage still waiting for someone who wants to hi flow one or if i do.

Jayson

[Simonster]

Zensoku,

I have all the DVD's that HPI put out and in an interview with the Boss of Veilside, he says their drag cars don't use "ancilliary" equipment like BOV's etc. So the turbo's don't last very long with the massive changes in pressure from WOT to fully closed. So no, it's not just old style turbo's. Just some food for thought

[blind_elk]

Originally posted by Zensoku

...This is due to the massive amount of exhaust back pressure pushing it downstream. ...

WTF!!!! It's called back pressure because it's pushing back towards the engine. So it's quite possible for a shattered ceramic exhaust wheel to find its way back into the cylinders - where it will perform a fine job of de-glazing the bores.

[JimX]

Back pressure does not kill ceramic wheels, spinning too fast is generally what does it.

Back pressure does not push anything back into the engine either.

[blind_elk]

Originally posted by JimX

Back pressure does not kill ceramic wheels, spinning too fast is generally what does it.

No-one said it did. The comment was made that backpressure operates to cause things to move towards the back of the car.

Back pressure does not push anything back into the engine either.

With all the fluid dynamics happening in the exhaust pipe, with valve overlap, scavenging, etc, who's to say that a shattered (ie powdery) ceramic won't end up back up in the cylinders.