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neal

Is my turbo knackered?

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[in taking the photos for this, I've already answered my question as a resounding yes! It's amazing how much better a compact camera with macro facility is than a telescopic inspection mirror and torch...]

With some dry roads finally, I was out yesterday for a spirited drive when I got a CEL. Connected up the laptop and it was P1412 - boost control. I was also getting maximum boost of 0.45 bar instead of 0.75bar. No biggie I thought, usually means one of the wastegate capsules is knackered.

But I checked today and both wastegate capsules were working fine.

Now for those not familiar, each turbo on the V8 feeds to a seperate throttle butterfly but after that there's a common chamber before the air splits off to each bank. The idea is that each turbo should provide roughly half the total airflow, but the common chamber allows a small variation to equalise so as not to cause an imbalance between the banks.

Anyway, I started digging deeper and pulled off the the intake hoses from each turbo. With the engine running I noticed that all the suction (i.e. airflow) was coming from the RH turbo - nothing at all was coming from the LH one (even with the catalyst removed).

You'll see why - these show the LH compressor wheel:

Now a new one should look look like this (off Marcus' website - hope you don't mind):

Even the RH compressor wheel shows a little damage:

Now the LH wastegate flap is fine:

As is the LH turbine wheel:

And both turbo shafts are spinning freely.

So the dumb question first - is this why my LH turbo isn't drawing any air?

And the more subjective one second - why has this happened? The LH air filter is fine:

and I suspect had any debris come through, the wheel would have shattered.

I did have both turbos rebuilt fairly recently with 12 months warranty. The LH one in Dec 06 - bugger, the RH one in Feb 07 - just okay. Is it possible to do a rebuild using a substandard compressor wheel? I would have thought they all just come from Garrett?

:devil:

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Hi Neal,

What a mess !

I can


1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Hi Mike,

Thanks for getting back to me. I was hoping you would pick up on this - I know you've been having much more serious problems in this area recently (hope the repairs are going well) and I don't know much about turbos.

It's not related to disconnecting the wastegate at Vmax - that was three years ago (i.e. before the turbos were rebuilt).

But the backpressure is interesting. While investigating this I also checked the cats and the LH one is starting to collapse. It's a metal 200cpi sports cat and the monolith is kind of pushing out rather than disintegrating completely as with a ceramic one. It still still seems to flow fine though. I don't have any dumps valves either to help. Could this be the root cause?

Can you explain how excessive backpressure can affect the compressors? It's not immediately obvious that a problem on the exhaust side can cause one on the intake side.

I presume the RH compressor wheel is also scrap?

Thanks,

Neal

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Hi Neal,

The rebuild is progressing very slowly due to other machining jobs required which were not associated to the original damage. Hopefully, the engine will be back together by the end of February.

I was referring to back pressure on the compressor side and not the exhaust side. If you have been running higher boost and without the dump valve, then you can experience this kind of distortion to the tips of the compressor blades - especially if there is use of non-Garrett replacement parts. Only your turbo refurb. contact could confirm/deny that.

Give the level of distortion, I would say that you are very lucky that the tips haven


1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Okay so the problem with the cat isn't related to the compressors?

The turbos were rebuilt at the same time as the engine was replaced since the old one had a piston with a hole through it - so obviously I've only been running standard boost since then! Also, as I said the wastegate capsules (which were replaced with the turbo rebuilds) are fine so it can't have been overboosting unintentionally either.

Therefore does it sound like non-Garrett replacement parts were used in the rebuilds, in particular they can't stand up to the V8 Esprit application?

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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The back pressure occurs when you close the throttle. For a split second, the turbo is pushing at a closed door and the inlet pressure peaks at well over the wastegate tripping point. The wastegate will open to divert the exhaust gasses away from the turbine, but because the turbine has a lot of momentum, it's not fast enough to prevent damage. The BOV discharges this excess pressure and also helps to stop the turbo from stalling. Without a BOV, you need to avoid jumping off the gas, and close the throttle slowly to limit the peak pressure.

I couldn't comment on whether the parts are genuine Garret or not, but most of the pics of failed turbos I've seen show the ends have snapped off. The fact that yours have warped might indicate that they're made from a softer metal (or you may have just been "lucky"). If they were made to the original spec, you should certainly expect more than a year's use out of them though.

If both recons were done by the same place, I think you'd have a claim against them for both, as they are clearly not up to scratch. They may have had a bad batch from Garret, so it might not be their fault. Just be nice about it rather than hurling threats and accusations and they may be willing to meet you half way on the out-of-warranty turbo.


More speed, less haste

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The back pressure occurs when you close the throttle. For a split second, the turbo is pushing at a closed door and the inlet pressure peaks at well over the wastegate tripping point. The wastegate will open to divert the exhaust gasses away from the turbine, but because the turbine has a lot of momentum, it's not fast enough to prevent damage. The BOV discharges this excess pressure and also helps to stop the turbo from stalling. Without a BOV, you need to avoid jumping off the gas, and close the throttle slowly to limit the peak pressure.

I couldn't comment on whether the parts are genuine Garret or not, but most of the pics of failed turbos I've seen show the ends have snapped off. The fact that yours have warped might indicate that they're made from a softer metal (or you may have just been "lucky"). If they were made to the original spec, you should certainly expect more than a year's use out of them though.

It's true I don't have BOVs but then none of the V8s have. With the relatively low stock boost (up to 0.75 bar) it shouldn't be necessary. Lotus didn't even fit one to the 4 cylinders and they run up to 1.25 bar.

Certainly I don't jump on and off the gas. The twin plate clutch on the V8 isn't sprung so to get a smooth gear change you need to come off the gas gently, change gear, then back on gently. Otherwise your head will bounce through the windscreen. I've had the car almost five years now so am very familiar with the feel of the accelerator and clutch. As I result I can get practically seemless gearchanges every time, even when pushing hard. Likewise for braking, off the gas gently then brake, since the clutch has no give.

As you say the fact that the blades are bent and pitted is rather suspicious. It was my impression that the metal used should be rock hard and therefore I would expect the blade tips to break off entirely if the turbo was being abused. The stuff which my wheels are made of would seem to be a lot softer. And all this after only a year (without excessive mileage - 3k for the LH turbo, 2.5k for the RH, of which 1k was spent running in the new engine on very light usage)...

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Neal,

Could have been worse! At least you didn't have fragments of the turbine breaking off and being sucked into the engine. However, after only one year and less than 3k miles I think you are very entitled to feel that you received a substandard part.

Regards,

Peter.

It was my impression that the metal used should be rock hard and therefore I would expect the blade tips to break off entirely if the turbo was being abused.

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Could have been worse! At least you didn't have fragments of the turbine breaking off and being sucked into the engine. However, after only one year and less than 3k miles I think you are very entitled to feel that you received a substandard part.

I could argue that had the proper hard parts been used in the rebuilds then absolutely no damage/distortion would have occurred in the first place. But absolutely, it could have been a lot worse and I could be looking at another new engine (and recovering that sort of money for 'incidental' damage would be practically impossible)!

But my main drive at the moment is to try to get as much opinion as possible before taking my case back to the garage who did the work.

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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