Felix

Where in the rev range does that boost level happen?

JBL930

I'm not entirely sure Felix, i think it's between 3000 and 4000rpm, I guess we'll see at the dyno tomorrow, i take you're still coming?

Felix

I think my engine runs that sort of boost level but only above 5000-5500 rpm. At 3-4000 rpm you're in the peak torque area and sustained boost may cause problems with the con rods and/or head sealing.

JBL930

Just got back from the dyno, engine is pulling boost, not entirely sure why, could be that it is running a bit lean and it's sensing knock, i'd like to see it at 0.82 or less, if it was dead flat at 0.80 i'd be very happy.
It will go back up on Monday to get sorted out, when it's on boost and running it's really strong! Now for the funny part, i know Jean and Toby will love this, check out the torque!!! HOLY ****!! roughly 630ftlbs or 854nm, crikey!!

JBL930

Well as usual nothing seams to go right, i set off for Le Mans and get 4 miles down the road and no boost, then loads of smoke and i mean LOADS of smoke!
I manage to get the car towed and set off to Le Mans in the BMW instead, gutted!

It turns out that the right hand turbo dismantled itself, the nut came off the end of the shaft and the hot side impeller ended up in the CAT, the nut then got sucked around the the back of the engine through the intake and destroyed the left hand turbo!

I'm led to believe that the only way the nut can come off the shaft like that is with a sudden stall of the turbo, and that a dodgy BOV is the usual culprit? I had new Turbosmart adjustable BOV's fitted only a day earlier! Is there any other reason that a turbo might dismantle itself like this other than what i've described, i want to have all the available info so i don't get lied to if you catch my drift, cheers chaps

eclou

wow. Very sorry to hear. I find it impossible to believe that the impeller nut made it across the intake to kill off the other turbo though. That is impossible if the left turbo was still making boost and the right turbo was dead. More likely both turbos were overboosting and the center bearings failed/seized.

MOD500

Sorry to hear of your trouble Jon, hope you get sorted quickly.

JBL930

It is a bit of a mystery how the nut got round there but it did, it was obvious the right hand turbo had failed because the smoke was only coming out of the left pipe, the garage called me to tell me what had happened and that they were puzzled as to where the nut had gone. I asked them to send back both turbos and it was only when they took the left hand one off they found the nut.
The symptoms i experienced would confirm it too, one minute there was boost and the next there was none, i mean absolutely zero boost, if the left hand turbo was still working i would have seen something on my boost gauge.
I pulled over and started checking the intercooler pipes, at this point there was no smoke, i got back in the car to drive it home and as i set off the smoke came, i guess the nut had come off and been sucked round almost instantaneously, therefore zero boost from either turbo, then as i pulled away and the right hand turbo tried to spool up the shaft just came out sending the impeller into the CAT and then burning all of the oil.

I can also assure you that there was no over-boosting, i was driving on a slowish back road following a small convoy of cars as we headed off to Le Mans. I did at one point have a very short blast, not even 2 seconds with my foot to the floor in 2nd gear, didn't even go above 5500rpm. Then i continued on until we came to a junction, i pulled away from the junction expecting to feel the turbos spool up but there was nothing, the rest is history.

If the right hand turbo seized why would the nut come off, surely a seizure wouldn't be sudden enough to cause that??

JBL930

Cheers mate, hope yours isn't serious either, maybe some ear wax has worked loose and your hearing is now more sensitive

Carrera GT

I don't know the project (is there a thread? I can't find one) but the situation depends more on who did the work, why the engine has BOVs instead of diverter valves, maybe the turbos are old, maybe they're freshly rebuilt, etc. etc.

I think I see where your suspicions are leading you, but you really don't need to be a forensic mechanic -- it seems to me, the person who built the turbos is up for getting you another pair of turbos.

Their business insurance should cover any consequential damages and costs (including the tow back) but you never know where their ethics intersect their wallet and for the most part, the overall "warranty" on a project car like this is zero. The only warranty I would expect is that each individually built part or component would live up to reasonable expectations.

It's interesting to follow through on failures like this to understand what went wrong.

Well, good luck with the next steps and hopefully the people who built the turbos will just admit to a quality problem (lack of loctite on the impeller nut?) and that's that.

The "local" turbo expert on Rennlist is "Kevin" so you might post him a PM to get his perspective.

Felix

How would the nut have made it through the intercooler?

JBL930

It didn't, it was sucked back round the turbo air feed pipes around the back of the engine and into the other turbo, you can see the piping on this picture



The turbos were basically new, they started life as K16's and were sent off to be modified to K16/24 spec, here are some shots of them, as you can see they were basically new








There are two threads running about this project, this one and the one on the 930 board, here is a LINK

I really hope that it does all get sorted out easily, i just wanted to ask for as much info and opinion so i was well informed. Cheers

JBL930

The BOV's, or recirculation valves or whatever they are called are these ones, supposedly top notch!?!

They are the top ones on THIS page under the name "Plumb Back"

TB993tt

Jon
Gutted for you mate, you are having some abysmal luck

FWIW I posted before, RS use stock Bosch valves and imply the aftermarket ones are pointless....

If your remanufactured turbos have let go then I agree with Carrera GT above, it sounds like you are owed some new ones at the very least ?

Carrera GT

I wouldn't say "sucked," I'd say the nut was thrown off the compressor shaft -- at what, 50,000 rpm? -- and had enough energy to get up to the intercooler then fell down into the turbo and thankfully didn't proceed through the plenum into the engine ... luck of a sort. : )

It would be great to see the turbos as soon as they come off the engine.

It sounds like the company that did the turbo rebuilds should accept responsibility. Every time I've seen new or old turbos there's been a paint mark or some sort of indicator on the nut on the cold side showing the correct torque on that compressor wheel nut. Maybe not relevant, but curious. Maybe these photos are before the rebuild?

I was going to ask how someone got the engine out without removing the mufflers ... the photos in the other thread explain ... : )