Mike M Posted October 9, 2006 Share Posted October 9, 2006 Sorry to see this mate, least you have a set waiting to go. Kinda makes me wonder what state mine are in at 70k. Quote Link to comment Share on other sites More sharing options...
JohnA Posted October 10, 2006 Share Posted October 10, 2006 Interesting pictures. So #1 had already managed to shatter bits of the blades. I wonder if they go to heaven by shattering bits off, then breaking off completely because of the resulting imbalance. Up to now the prevailing theory was that the whole wheel comes unglued from the shaft, but your pics indicate that it ain't necessarily so. Nice one. Quote Link to comment Share on other sites More sharing options...
Kranz Posted October 10, 2006 Share Posted October 10, 2006 Where steel turbine blades would take some abuse and just have a small chip or ding out of them it looks like ceramics just explode! Its shocking to see the #2 turbine completely gone. The forces on the turbine must have been instantaneously massive. Number 1 turbine has obviously seen lower impact forces, possibly due to a small imbalance at speeds beyond the design speed, causing the blade to vibrate excesively and fracture or chip against the housing. The greater damage to #2 its possibly to do with the spooling of #2 while on high boost to even higher boost. The acceleration forces on the turbine blades may have caused one to fail, putting the whole wheel out of balance at RPM beyond the design speed, causing the wheel to self destruct against the housing with the intense vibration. Quite a messy outcome! Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 10, 2006 Share Posted October 10, 2006 That first turbo has had debris through the turbine section, very recently indeed. Maybe the same debris killed the second turbo, or the debris was *FROM* the second turbos demise? You should check all the piston tops for sign of anything having been through a combustion chamber. Quote Link to comment Share on other sites More sharing options...
Bob Posted October 10, 2006 Author Share Posted October 10, 2006 That first turbo has had debris through the turbine section, very recently indeed. Maybe the same debris killed the second turbo, or the debris was *FROM* the second turbos demise? You should check all the piston tops for sign of anything having been through a combustion chamber. I'm hoping it's nothing sinister and that my engine is otherwise fine and dandy, but now you've got me worried! Nothing but ceramic bits came out the cat though, which is a good sign. I hope. How would you suggest I go about inspecting the piston tops without forking out £300 for a bore scope and / or removing the head? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 10, 2006 Share Posted October 10, 2006 Pay someone witha medical quality endoscope to have a look down the plug holes, but I assume the car's now in bits? You'd have to either find someone willing to come to you, or wait until it's running again and hope you don't have to undo all your good work to fix anything it may show. Quote Link to comment Share on other sites More sharing options...
Bob Posted October 10, 2006 Author Share Posted October 10, 2006 Ah well, Google and Ebay it is Quote Link to comment Share on other sites More sharing options...
uk-rich Posted October 10, 2006 Share Posted October 10, 2006 jesus bob, hope you can sort it soon. Quote Link to comment Share on other sites More sharing options...
JohnA Posted October 11, 2006 Share Posted October 11, 2006 ... Maybe the same debris killed the second turbo, or the debris was *FROM* the second turbos demise? ... But is it possible for debris to move from turbine #2 to turbine #1? Of course if he had bits going through the engine, then it's anyone's guess what else is damaged. Find a friendly proctologist and try to use his tools of the trade:d What sort of airfilter have you got Bob? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 11, 2006 Share Posted October 11, 2006 If you come off the throttle, ceratainly on RB26 engines, the turbine wheel fragments can go back in through the exhaust ports (as the cylinder is in vacuum), and out again, so I guess it may be possible. It may also be that the engine injested something that went out via both turbos. Quote Link to comment Share on other sites More sharing options...
Kranz Posted October 11, 2006 Share Posted October 11, 2006 It may also be that the engine injested something that went out via both turbos. Its a possibility Chris, but then the compressor wheel(s) should be showing damage from impacting the same object... unless its a spark plug tip or similar? Another possibility is overspeed due to high boost peaks? Excessive overspeed (and probably over temp pre-turbine due to the high boost pressures) could cause vibration/harmonics/shaft resonance/bearing flutter (and associated loss of oil film)/turbine blade stresses; any one of which could causeone blade to brake off or chip, further imbalancing the turbo and leading to a chain reaction of total destruction? Quote Link to comment Share on other sites More sharing options...
Mcgoo Posted October 11, 2006 Share Posted October 11, 2006 Those turbos in the pictures look identical to mine when i took them off a couple of weeks ago. No. 2 completely gone shaft and all, No.1 with chipped blades. I,m pretty sure I chipped the blades on No.1 when splitting the turbo as they didn't come apart easily. Could this be the case here? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted October 11, 2006 Share Posted October 11, 2006 This is why i said *VERY* recently damaged, see that there is ZERO carbon build up on the chipped edges? Quote Link to comment Share on other sites More sharing options...
Kranz Posted October 11, 2006 Share Posted October 11, 2006 Sounds very possible, especially when the photos show absolutely no carbon or soot buildup on the fracture lines. Edit - Chris beat me to it Quote Link to comment Share on other sites More sharing options...
JohnA Posted October 11, 2006 Share Posted October 11, 2006 If you come off the throttle, ceratainly on RB26 engines, the turbine wheel fragments can go back in through the exhaust ports (as the cylinder is in vacuum), and out again, so I guess it may be possible. ... Crickey, I didn't know that:blink: Yeah, I guess the strong vacuum can suck bits back in. Live and learn. Thanks Chris. Quote Link to comment Share on other sites More sharing options...
Bob Posted October 11, 2006 Author Share Posted October 11, 2006 What sort of airfilter have you got Bob? Standard air box and a Blitz panel filter. Standard boost too I've had a look around the turbo housing and there's no little bits of ceramic there - in fact, the 1st turbo came off fairly easily once the v-band clamp was off. I gave it a few medium taps with a dead-blow hammer (rubber head) and it slid off no problem. Just done a quick(ish) compression test (many thanks to Bijal for lending me his kit and talking me through it! ). Everything seems okay, if a bit high. Readings from front to back ('cos I don't know the proper firing sequence! ) 1 - 180 2 - 165 3 - 178 4 - 170 5 - 165 6 - 180 And joy of joys, I've managed to find somewhere that will lend me an endoscope this weekend for £60. It's for inspecting cavity walls but is small enough for use through the spark-plug hole Quote Link to comment Share on other sites More sharing options...
Kranz Posted October 12, 2006 Share Posted October 12, 2006 Your compression readings are fine at 180. The thing about compression checks is that they are what they are! Ideally they need to be within 5%, so if 180 is the top reading you want 170 as the lowest. But 165 is fine, no worries. just shows its not a brand new engine. With the endoscope you want to check each cylinder with the valves open so you can see there's no pitted or burned valves. Check the bores for vertical scratches. You should be able to see honing cross hatch marks, which is normal. Also check the piston crown especially at the edges (ring land area). Hopefully its got good clean optics and a bright light. The bendy end one is best, but the rigid one can do a good job too. Have fun! I'm sure it'll all be ok. Quote Link to comment Share on other sites More sharing options...
JohnA Posted October 13, 2006 Share Posted October 13, 2006 .. 1 - 180 2 - 165 3 - 178 4 - 170 5 - 165 6 - 180 180-165 = 15psi spread, which is quite a bit. The upper end of the recommended range in fact. Quote Link to comment Share on other sites More sharing options...
Bob Posted October 14, 2006 Author Share Posted October 14, 2006 Right then. Had a gander at the insides of the bores today. The pistons look okay, though very black. All valves were a manky rusty colour, but no obvious damage, with the only slight bit of pitting to #2 cylinder though it didn't look like it had been done anytime recently. There were a few very faint vertical scratches in cylinders 4, 5 and 6 but not so much that they were instantly noticeable. The problem, it would seem, is cylinder #2. Much as I wished he wasn't, Chris was correct in that something has passed through recently. There are 2 deepish scratches (deep enough to snag a fingernail, for example) 1 of which I managed to get a crap picture of (below). It would also appear that something has twatted the spark plug as there is scratching to the edges of it. Though that may just be my hamfisted removal of them So, will 2 scratches (1 reaches about 1/3 of the way up the bore, the other about 1/4 way up, from roughly BDC) mean a head-off and costly engine work? Or can I get away with sticking the turbos on and turning to prayer? Piccies: General state of my spark plugs (Denso Iridium IK20's) #2 spark plug top: dodgy photo of the scratch to bore #2 (runs about 10 degrees from horizontal in the picture - didn't bother rotating it!) :edit: Also noticed a fair bit of black oil around the head gasket area inside the bore - is this normal? Quote Link to comment Share on other sites More sharing options...
Kranz Posted October 14, 2006 Share Posted October 14, 2006 The pitting on #2. Is it pitting to the top of the piston??? EDIT - If whatever went through and scratched the bore & dinged the piston then went out of the turbo & knackered that I'd say your problems are mostly over.... as long as there's no more bits to come through! The bit of ???? that got sucked into #2 cylinder probably rattled around in there a few times before it finally found its way out of the exhaust valve and into #2 turbo. Those scratches will probbaly not cause a piston to pick up or ring trouble (I bet you already had that when the turbo went pop!!). As long as there's no more to come through then you'll be ok. A prime candidate for catching bits, then releasing them at full chat is the intercooler. May be worth taking it out & checking/flushing it. Quote Link to comment Share on other sites More sharing options...
Bob Posted October 14, 2006 Author Share Posted October 14, 2006 The pitting on #2. Is it pitting to the top of the piston??? My bad, I meant to say it's pitting to a couple of valves in there. Looks more like general wear-and-tear tbh - certainly not recent. As far as I can tell the pistons are completely un-damaged. Quote Link to comment Share on other sites More sharing options...
Kranz Posted October 14, 2006 Share Posted October 14, 2006 If something had passed through it would have taken its anger out on the top of the pistons... and as the softest metal in there they'd have had little dents in like the surface of the moon! Its very rare for something to come in through the inlet valves & then straight out through the exhaust valves... unless you're running huge amounts of overlap? Is the pitting of the valves on the seats or the combustion chamber faces?? Quote Link to comment Share on other sites More sharing options...
Bob Posted October 14, 2006 Author Share Posted October 14, 2006 pitting was just on the faces of the valves in the combustion chamber. Quote Link to comment Share on other sites More sharing options...
Kranz Posted October 14, 2006 Share Posted October 14, 2006 That's normal where the carbon flakes off I think. Leaves an uneven surface, but not little dents into the metal. Quote Link to comment Share on other sites More sharing options...
Bob Posted October 14, 2006 Author Share Posted October 14, 2006 Checked the intercooler - a bit of oil and crappy flaking fins, but no debris came out when I gave it a good shake. Would the scratch in the bore cause excessive ring wear? Quote Link to comment Share on other sites More sharing options...
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