Help needed - xantia lots of black smoke!!

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MikeT
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Post by MikeT »

Hi Mike, my immediate though is a blocked air intake? I don't think you've got a fuel restriction as black smoke means too much.
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Post by Peter.N. »

Try disconnecting the air intake pipe from the manifold, if it runs OK you have an obstruction in the air intake somewhere. If its been standing, mouse nest?
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Post by CitroJim »

Hi Mike,

Came into this one a bit late :oops:

First thoughts is that one of the oval rubber pipes to/from the intercooler is collapsing under suction and effectively cutting of the air supply.

You can tell if the turbo is Ok by running with the manifold inlet pipe disconnected and feeling for a breeze coming from it as you rev the engine. Even if the turbo was seized (very unlikely) it should be able to pull sufficient air past it for idling and slow speed running.

Have you checked all pipes and the airbox for obstructions, including the air inlet hose from the front of the car to the airbox?

The intercooler is unlikely to be blocked. It may have a drop of oil in it but that should suck out with the engine running.

Basically, the route is airbox, turbo inlet, turbo outlet, intercoler in, intercooler out, inlet manifold.
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Post by MikeT »

superloopy1 wrote:....Could I have knocked against something, i have had the air filter box off when I was putting in a couple of new front brake pipes but that was only for access to the ABS block
You may have perhaps inadvertently misplaced the air box where it sits on the inlet feed taken from the grille area?
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Post by Peter.N. »

Try disconnecting the pipe from the airbox, if that doesn't improve matters work your way around the system, disconnecting one pipe at a time.
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Post by Peter.N. »

Are you getting a really good blast of air from the turbo? Because it would seem as though the engine is sucking harder than the turbo is blowing. Try disconnecting the intercooler 'in' pipe, if the out pipe still collapses it would seem that you have a blocked intercooler.
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Post by Peter.N. »

You should have sufficient pressure from the turbo to overcome the vacuum from the engine, so indications so far are pointing to the turbo or its associated piping. Could anything have got sucked into the turbo inlet from the airbox? The only real test is to disconnect the pipes actually form the turbo, a pain I know but I can't think of any other way of proving it - unless anyone else can - Jim?
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Post by Old-Guy »

Mike

Possible turbo failure is a red herring. Even if the turbo has seized, an engine will run and rev on no/light load.

There must be a physical blockage upstream from the collapsing (intercooler out) pipe. Rather than working your way connection-by- connection back from this point, you could make life easier with a 'binary chop' approach:

1. Open a connection in the intake systemat a convenient point about halfway (in terms of the number of connections) between the intercooler-out connection and the intake at the front of the car.
2. If the engine runs properly, the fault lies upstream; if not, then downstream of this open point.
3. Close the open point.
4. Open the blocked part of the intake system at a convenient point near its middle.

Repeat steps 2, 3, 4 until you've isolated the location of the obstruction.

To (perhaps) pre-empt any jokes, the 'binary chop' technique is used in the electronics and software industries to isolate faults in the fewest possible steps.

Oh, nearly forgot: In answer to your question "What does the Intercooler do?"

Air is sucked in by the engine through, in turn:
- the air filter to remove debris/dust,
- through the compressor side of the turbo-charger (where it gets hot),
- through the inter-cooler (an air-to-air radiator) to cool it down again,
- and into the inlet manifold.
When the engine is revving, the hot exhaust gas from the exhaust manifold has enough energy to spin the turbine (hot side) of the turbo which is directly coupled to the compressor side. The spinning compressor raises the pressure of the in-coming air so instead of the engine have to use suck, it's force-fed air at up to 1.7 bar. Compressing the air makes it hot, but the cooler the intake air, the greater its mass at a given pressure. More air going into the engine means more fuel can be burnt (cleanly) giving more power.
The turbo reclaims some otherwise lost heat energy from the exhaust and feeds it back into the engine.
Turbos 'whistle' because of they run at high (10s of thousands) revs.

Good hunting

Guy
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Post by uncle buck »

I would take the in side pipe of the intercooler off & rev the engine & feel how much air is coming from the turbo....then put the In pipe back onto the intercooler & remove the inlet manifold pipe...rev the engine as before & see if the air flow is the same....it should be.

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Post by MikeT »

Did you check the airbox IN feed? They require force-fitting as you're pushing it against rubber bushes. I misfitted mine last time it was off, it's easy to do and as there's a flimsy, flappy collar down there, I can imagine that getting pinched and causing the obstruction.

Study the underside of the airbox and you'll see what I mean.
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Post by Peter.N. »

Rain :shock: where on earth are you. 8)

Yes the intercooler would appear to be OK because its passing enough air for the hose not to collapse, the problem must be further upstream.
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Post by myglaren »

Peter.N. wrote:Rain :shock: where on earth are you. 8)
I'm ten miles away from superloopy and can confirm that it has been torrential here on and off over the past week, including today.

I have never pulled any turbo bits to pieces (yet) but I do seem to recall a warning not to put your hands near the turbo pipes with the engine running as some have serious suction and others sling out a lot of heat.
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Post by uncle buck »

Pipework air flow.....
(I'm only going from the photo as I don't have a Xantia)

It looks to me that.....

The Blue line is the airflow to the Turbo.

The Pink line is the airflow from the Turbo to the intercooler.

The Green line is the airflow from the intercooler to the inlet manifold.


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Post by uncle buck »

That fits in with my understanding but what i an't work out is why i'd expect to get a blast of air from an inlet manifold pipe when i disconnect it from the intercooler, surely there should be suction at this point ie pulling cooled air through the intercooler and presenting it to the manifold or am i way off beam in my thinking?
You won't...you will get a blast of air from the end of it if it is still connected to the intercooler tho...assuming the intercooler isn't blocked.

The air is sucked through the air filter & through the light blue pipe into the Turbo

The air is blown from the turbo down the pink pipe through the intercooler up the green pipe to the inlet manifold.

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Post by uncle buck »

Disconnect the pink pipe where it meets the intercooler & rev the engine, there should be a lot of air flow as this pipe is coming directly from the Turbo so the air will be being blow through it....put this pipe back on then.....

Disconnect the green pipe where it joins to the inlet manifold & rev the engine there should be a lot of air flow as this pipe is coming from the intercooler.

The air flow should be exactly the same from both of these pipes...if it is not & less is coming from the end of the green pipe where it joins to the inlet manifold there is some sort of blockage in the intercooler.

You said in a earlier post that you had the air filter housing off the car, you didn't stuff a rag or something in the end of the pipe from the air filter & leave it in when you put it back on or anything silly like this?

I think you need to stop & start again from the beginning with this problem as I think things could be being assumed....you should never overlook the simple things when fault finding.


Cheers.
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