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Discussion Starter #1
Hi,

Today, when travelling around 60 KMPH, pressed the pedal & car moved little faster but seems something is holding it back. Went home, got the Nanocom connected. stationary car, idling.
At idle the boost pressure is at 102 Kpa ,
at 2000 RPM 109 Kpa :?:
and at 2500 RPM 76 kpa.8-0=
At 2500 RPM there is an unusual noise from turbo charger area with a slight whistling. Some whitish smoke from exhaust too.

Can someone explain how come the boost pressure go below the 102 Kpa pressure at 2500 RPM?

Thanks in advance.
 

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1995-2002 Range Rover P38A
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Hi Kapila,

I have got a Faultmate, I guess it is similar to the Nanocom.
Boost pressure is measured as absolute pressure, not gauge, so 102 KPa at idle is normal. It is at atmospheric pressure.
There is zero boost at idle, I have found it only starts to kick in from 2000 rpm. At 2500 rpm I would expect to see 200 KPa (which is 100KPa gauge or 1 bar g).

I would check the hose from the turbo into the intercooler first to see if it has a split or the clip has come off. It has happened to me more than once. Whistling sounds like a split.
I would also expect the exhaust to be smokey if the turbo wasn't up to pressure. It is going to be over fuelling.
76KPa at 2500 rpm is less than atmospheric. It may be that the turbo is delivering bugger all and the inlet manifold pressure drops as normally aspirated engines do?
 

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Discussion Starter #3
Thanks Dave.
No splits but slightly loose hose clips. Yes , above normal smoke whitish but not a lot. ( Once I had a oil leak in the turbo & it was clouds of smoke behind me.)
Going below atmospheric pressure, I presume. is a vacuum. Is it the turbo turning other way around? is it possible?
This vacuum acts as a engine brake not allowing flow of air into the engine & hence the feeling of something pulling back.
Anyway, turbo removal & inspection is called for.
 

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I would double check for hose splits. I had one that was facing the engine and difficult to see.
It could be your turbo has blown.
 

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Don't measure boost on an engine what isn't working, give the engine a good load, and then measure boost.
 

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Check the wastegate. If that is opening too much/too early, you'll lose boost. Though actually getting vacuum is strange.
As Reinhoud says, you need to check boost with the engine under load. Just sitting there you'll never get much boost because there aren't enough exhaust gases to get the turbine up to full speed.
 

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Discussion Starter #7
You both are correct. What I experienced on the road may be due to vacuum forming in the intake.
No boost can be due to reasons sited by you all but how can there be a vacuum.
Anyway I will remove the turbo this weekend.
Is there any shortcut method to remove the turbo? I normally remove the exhaust manifold first to remove the turbo.
 

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Are you trying to do it from the top? Take the RH wheel and wheel arch liner off. It gives good access from the side.
 

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Discussion Starter #9
I thought the RH air spring would interfere.
 

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Before taking stuff apart, go for a ride with the nanocom and get some readings. It doesn't sound like the turbo is the problem, more like a control issue. So wastegate or fueling. You did check the MAP line, sensor and electrical connector?

Filip
 

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Discussion Starter #11
Turbo makes a noise around 2500 RPM , hence assumed something is wrong with it. Checked MAP air line , no blockage but slight oil there. sensor wiring intact, no faults in Nanocom.(except my life long fault- injection timing out of range)
Can't check the waste gate, unless I remove the turbo. Will do a test run with Nanocom connected.

What are you suggesting by saying " fueling"? Could fueling issue give a vacuum in the manifold?
 

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Smoke would indicate the fuel/air ratio is wrong. Not enough air for the fuel quantity because the turbo is not delivering.
I have had split hoses in the past and it was down on power and making strange noises due to air escaping through the split. The hose has also flown off a couple of other occasions followed by dense smoke from the exhaust. I replaced my hoses through the wheel arch. Access is good.
 

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Turbo makes a noise around 2500 RPM , hence assumed something is wrong with it. Checked MAP air line , no blockage but slight oil there. sensor wiring intact, no faults in Nanocom.(except my life long fault- injection timing out of range)
Can't check the waste gate, unless I remove the turbo. Will do a test run with Nanocom connected.

What are you suggesting by saying " fueling"? Could fueling issue give a vacuum in the manifold?
You can check the wastegate, you need a compressor with an air gun, it's not exact science, but it can give you some kind of indication.
 

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Smoke would indicate the fuel/air ratio is wrong. Not enough air for the fuel quantity because the turbo is not delivering.
I have had split hoses in the past and it was down on power and making strange noises due to air escaping through the split. The hose has also flown off a couple of other occasions followed by dense smoke from the exhaust. I replaced my hoses through the wheel arch. Access is good.
Does it smoke continuously, or only that period the turbo is spooling up?
 

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As Reinhoud says, you can check the wastegate with an compressor or such. A while ago I had a customer with a Defender that lost power on full chat. Turned out the wastegate wasn't opening and as soon as the boost got above 2.2bar (absolute) the ECU cut fueling to save the engine. Which of course also resulted in the boost dropping to below atmospheric.

I did miss the part about the noise around 2500rpm, that could point to the turbo. But a mechanical failure would likely be present across the range, not cause a sudden drop around 2500rpm.

Filip
 

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Discussion Starter #16
It does not smoke but only when the manifold pressure drops below atmospheric pressure.

I'm going to run it today with Nanocom connected. will revert with the recordings.
 

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Discussion Starter #17
Test drove the car today. Prior to that noticed two things.
One is that the heat shield above turbo input hose was loose & that could have resonated at 2500 RPM. The other was that intake hose from intercooler to intake manifold has moved out about 1/2 inch, but not loose. Anyway attended to both & cleaned the turbo output to intercooler hoe/pipe which had some oil but not any visible internal damages.
Though could not go above 2000RPM due to traffic conditions , the sudden drop in power was not observed. As said, the turbo pressure was seen when the car is runniing not when stationary. Here is the Nanocom record ;

hopefully, the matter is resolved without any expense. Thanks to everyone.
 

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You both are correct. What I experienced on the road may be due to vacuum forming in the intake.
No boost can be due to reasons sited by you all but how can there be a vacuum.
Anyway I will remove the turbo this weekend.
Is there any shortcut method to remove the turbo? I normally remove the exhaust manifold first to remove the turbo.

How there can be a vacuum when you have no boost?
Well that’s totally normal for a naturally aspirated engine. That’s how vacuum operated brake servos are operated and other things run on vacuum. For instance fuel pump shutoff on old Mercedes W123 diesels.

But with overboost a vacuum pump is needed for those things.
 

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Discussion Starter #19
When I tested the car initially, the manifold pressure dropped to 76 Kpa, much below the atmospheric pressure. That' s why I said forming vacuum but unable to explain. At that moment car behaved like it's been pulled from behind suddenly.
 

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It is still very hard to explain how a partial vacuum can occur in the inlet manifold on a turbo charged diesel engine.
The pressure control system on the turbo is just a simple mechanical blow off valve operating under spring pressure. It is straight through.
You also have no EGR that can have a build up inside. Assuming your turbocharger is OK, maybe you have a partial blockage somewhere.

........... intercooler full of oil? Needs cleaning out.
........... delaminated hose that you can't detect externally?
........... air filter blocked? or even collapsed? (I have had a Fram filter collapse on mine under suction)
 
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