Another Possible Turbo Failure???

[tarmac terror]

Similar to the thread below by Dean J, I have a similar kind of problem.......

When, say, accelerating from a standstill, the car will spool up fine then at approx .35-.40 (ish) bar the whole car just bogs down completely, misfires very badly and produces lots of black smoke

Car idles fine, although not as smoothly as before TBH, and will rev cleanly up to 5k+ when sat in neutral and revved progressively without any boost. Vacuum is a normal -0.60 - -0.70bar at idle.

Suspecting some sort of boost leak I removed ALL hoses and pipework and meticulously reseated them all (have had a boost leak ages ago and know how elusive they can be) although I must admit the symptoms are different.

The cruncher for me is the fact that all this only happens when I hit approx .35-.40 (ish) bar and car is perfectly behaved off/on light boost. I suspect some sort of turbo trouble but need someone to tell me what symptoms would appear if one (or both) turbo's are knackered. A lot of water has passed under the bridge since I was a mechanic and TBH I never had much exposure to turbo cars apart from the theory and a brief squizz at a 205/309/405 TD (which was Peugeots only turbo cars at the time). I can take a guess at the probably symptoms but I thought it would be easier and more accurate if you guys could give me an idea of what happens when turbos are on the way out.

Many ta's in advance.

TT

[xaero1]

TBH it sounds like you've checked every other logical possibility. AFMs? Coilpacks? Spark plugs?

If it's still causing problems then the turbos need looking at. They may not have exploded, but I'd hesitate to drive the car until you know for sure. You may be lucky and they've blown the exhaust wheel down your exhaust. Unlike me where the blades got sucked into my cylinders...!

I'm sure you'd be able to remove them if you give yourself a few hours one Saturday morning.

[dean j]

If you havent checked the bottom intercooler hoses, then check them before anything. I think mine has still popped off. My turbo problem is another problem altogether (i think).

Hope thats your only fault mate. Easy fix really

[tarmac terror]

well I'm pretty sure I can discount hoses as they aint coming off!!Use Mikalor clamps on all boost hoses and all are seated fine.
AFM's are new Nismo items.Coil packs are new splitfires,plugs are new trust iridium 8's, ignitor is new, coil loom is new.All the above have only about 1500miles on them.
I think possibly the rear turbo has perhaps stuck!!.What symptoms would that produce??

TT

[Cornhoolio]

Have you investigated the possiblity of one of the BOV's leaking?

Split hose that only opens up on boost?

I would imagine a "stuck" or seized turbo would effect the running of the engine at all conditions not just when coming on boost. It would be like restricting the exhaust massively on the rear 3 cyls at all RPM'S, not good

If the car runs fine off boost at all revs, to me, this would point to an air (boost) leak. Black smoke = unburnt fuel.

Remove the AFM's and blank off holes, pressurise inlet system with compressed air to 15psi and use Snoop or Fairy Liquid/water mix in a sprayer and spray it all over the inlet and turbo pipework, check for leaks that way.

Just my thoughts

Are the turbo's ceramics?

Hope this helps

[tarmac terror]

BOV's have been removed and car ran fine after this was done. I suspected the split hose idea as well but have gone over them all with a fine tooth comb but NO splits in any of the hoses......
Now the car has been playing up for a while now where it would stutter as it transitioned from vac to boost but keeping the foot down it would pull through this and boost well to normal levels. Now upon reaching aforementioned levels car completely bogs and WILL NOT pull through this AT ALL!!!. Bizzarely, since this new problem has reared its head there is now NO hesitation at vac boost transition point any more!!Work THAT out!!
I cant figure out if its an escalation of the first problem or something completely different.

Turbos are std ceramics with about 68k on them so probably in the zone for getting past their best although last time I checked, around 500 miles ago, there was still very little play in the shafts.

I just cant seem to get my head round this one unfortunately....And to say its pissing me off is an understatement and a half.

TT

[dean j]

Does it smoke at all? What colour is it? I dont know, but maybe the exhaust wheel has gone on one of em. Check the front turbo (clean side) at least. Maybe that could give some clue.

As i said before. Hope it dont go the way it is for me mate

[tarmac terror]

Originally Posted by dean j

Does it smoke at all?

Not really, only black when I hit this 'barrier' which would point to unburnt fuel. I fully believe the block/head/internals to be in GWO so it must be some ancilliary component. Having thought about it I changed the std intercooler to a monster trust item. Car ran very well after the swap but perhaps this has shown up some shortcomings in other components causing them to fail. Not one of the more plausible theories I admit but still something to consider.


Just wish it would go away so I could enjoy my car once again.

TT

[mp302007]

your symptoms do suggest massively overfuelling - black smoke and misfire. if you've eliminated ignition (and assuming the injectors haven't started to misbehave) then you have a lack of air, compared to what the ecu is expecting.

do you have anything that allows a monitor of the AFM voltages? if one of the turbos is not working, i'd expect to see a big difference between the AFM outputs when you go on boost. you say the AFMs are new - are they a direct replacement or have you an ECU that allows differences (and therefore have been programmed accordingly)?

i'd have thought that if a turbo "sticks" with turbine and compressor wheels complete, the restriction that would cause significant running problems even before transition btwn vacuum and +ve pressure (since 3 cylinders would be receiving less air than the others). i imagine the force of the exhaust gases is quite high and the standard oil film bearings fairly robust, so can't think this would happen. if the ceramic wheel were to come off, it'd be left in the exhaust housing. since nothing is driving the compressor end, that would spin due the air being pulled be induction. idle would be ok but as pressure increases, since only one turbo is supplying compressed air, there will be a point at which the consumption becomes less than demand (the transition point) and air flow would take the easiest route and (might) reverse the flow back out of the knacked turbo. again, the AFM voltage would clearly show this.

if you're happy all the pipework is sound, i'd think the only thing left to do is remove exhaust elbows and check the turbines. i don't think your problem is electrical, symptoms sound mechanical.


good luck,

[tarmac terror]

Yeah, I agree that its something mechanical and more than likely turbo related. The injectors are also new sard 700's. ECU is PFC which was all mapped by Abbey when the Nismo AFM's and injectors were fitted. Fuelling provided by new Nismo pump.
Have pretty much replaced all fuelling and ignition components/wiring with new OEM or uprated parts. Only bits left to do are CAS, Injector Resistor Pack and a possible upgrade to HKS Twin Power.
I shall check the PFC commander on the way home from work and see if the AFM voltages are within reason. TBH, I'm highly suspicious of the turbo's and might whip off the downpipe and have a look to see if anythings amiss. There have been no strange sounds etc which would indicate a turbine wheel has separated but I suppose if it was stuck somewhere in the turbine housing or elbow then it wouldnt be making much in the way of noise.

Keep the helpful comments coming....

TT

[uglymother]

Timing?

[mp302007]

i'd have thought that if the timing was an issue, the idle and other bits of the rev range would be affected, not only when on boost. as the engine builds revs, the ecu retards the ignition (or reduces the amount of advance) from 20 degrees before tdc towards tdc (and beyond??). i assume that the ecu would throw a fault code if its timing adjustment was faulty. check this link RB ECU - ECCS Fault Codes.

[GarethK]

Sorry mp302007, I have to disagree with most of what you've said!

The GTR does not 'feed' 3 cylinders with one turbo and 3 with the other, they join just after the turbos, share an intercooler and share the inlet plenum. There would be a difference in exhaust restriction if one had a problem but not to a level that should cause such a sudden / violent reaction.

Timing is also not retarded as revs build, in fact the opposite is true.

TT - Monitor AFM voltages as you've suggested, it's unlikely that both turbos have gone at the same time so if there are big differences between the two readings then i would start pulling off pipework and turbo elbows to check. I guess it might also be worth swapping afms around to see if the problem moves before you start pulling it to bits. In any case, do the minimum amount of running you possible can in this state!

[Cornhoolio]

Originally Posted by dean j

Does it smoke at all? What colour is it? I dont know, but maybe the exhaust wheel has gone on one of em. Check the front turbo (clean side) at least. Maybe that could give some clue.

As i said before. Hope it dont go the way it is for me mate

This was going to be my next suggestion, reason for asking if they were ceramics. I once lost a turbine wheel, no serious noise when they go, just a bit of a muffled kind of "whump" sound It was the rear turbo, wheel completely disintergrated into small gravel like pieces and went out the exhaust.............some remained in the tailpipe as a tell tale. Car still ran fine apart from where you expected boost there was none, no oil smoke etc, I drove it 6 miles home after his happened. I dont recall any missing or associated carry on as you are having though, but would not rule this out

Have you recently de-catted the car by any chance? This is what caused my turbo calamity........... de-cat, cold morning, no turbo...........

It is an ar5e of a job to get the turbo's off too

[mp302007]

i didn't mean to imply that a turbo feeds one group of three cylinders. what i was thinking was since the turbos feed a common "rail", if one is producing no boost then the other will be pressuring the inlet tract but at some point the air will force its way back out the side which isn't doing any work.

i accept your point on the timing. so does the ecu advance it even more "ahead" of tdc? this, presumably, allows more time for the compressed charge to drive down the piston on the power stroke. the ecu then takes knock sensor input to avoid pinking?

think i'm going off thread somewhat now.