Turbo's, how do they work -is there an emergency air intake?

[draper3000]

Hello to all bongonauts.

Ok todays problem....The Turbo.

Back Story:
Been working on my bongo for last 4 and a bit months, replacing cylinder head, gaskets any broken tubes and bits myself to avoid the scary price quoted by the local garage. Its been an education at the very least but honestly if you have the money pay the garage to do it, as it takes some time time gather the needed tools and know how.

The van is now up and running nicely except 1 thing, it would seem the turbo is not kicking in (well that's the current diagnosis anyway.)


Symptoms:
When the van is running as soon as it goes over around 2000 revs you get loud loud humming, from the front end of the engine, and there is not much power to the engine. It turns out that a lot of air is being sucked in through the small air intake on the left side of the engine (drivers side, just in front of the battery). And not much air is going through the airfilter under the drivers seat.

Questions:
Is the air intake at the front of the engine an emergency one that kicks in if the turbo has failed?

Does this sound like a turbo problem?

Could someone very simply explain the layout of the turbo and how it works...(I know where it is in the engine and that's about it).

Many thanks for any help.

1 week 2 days and counting:
I've just booked the van in to have this looked at plus an MOT but its not in till next week, so if I can sort this myself it should save me some money and maybe take away any fear of them telling my I need a new Turbo simply because I don't understand them, when really all it needs is a new bit of wire somewhere. Cynical yes, but garage bills always seem to add up very quickly...that state if mind is whats making the idea of learning my way around an engine more beneficial.

Goodbye Bongo Hello Baby:
All this to fix our van and sell it to then go and buy something newer, and something my wife will happily drive when our first baby arrives in January....

[scanner]

The simple answer is no - if induction air is being drawn in other than through the intake behind the grille just under the front edge of the bonnet something is wrong.

Is anything blocking that intake? It's not unknown for folk to leave bottles/rags/bits of paper there, that then get sucked into the intake.

[bigdaddycain]

If you mean the air intake below the front cross member, then that is the cold feed to the intercooler. The Intercooler does what it says on the tin, it makes the intake air cooler via a small rad,the cooler the intake air,the denser the air,the more fuel can be added = more power.

A turbocharger is a small radial fan pump driven by the energy of the exhaust gases of an engine. A turbocharger consists of a turbine and a compressor on a shared shaft. The turbine converts exhaust to rotational force, which is in turn used to drive the compressor. The compressor draws in ambient air and pumps it in to the intake manifold at increased pressure, resulting in a greater mass of air entering the cylinders on each intake stroke.

[draper3000]

...thanks for that.

does my problem sound turbo related? any ideas?

[munroman]

Hi. From what I understand, and please correct me if I am wrong.

There is lots of air being sucked through the air intake, under bonnet just in front of the battery.
You don't think much is getting past the air filter.
If lots of air is being pulled in, the only thing which can be pulling it in is the engine, via the airfilter, therefore I suggest this area is not where you should be looking, but it can do no harm to check that there are no bags or debris in the intake ducts before the air cleaner.
The 2000 rpm is possibly significant, the turbo should be building up pressure by this speed, perhaps there are leaks in the pipes, or bad connections where they go to the intercooler at the front as BDC has described, this loss of pressure will make a noise, and greatly reduce performance.

Can you get the Bongo running at 2000 rpm, safely, and get out and listen more precisely as to what you hear, e.g. hissing/whooshing, or if you can feel any big draughts of air from the hoses or connections, then perhaps report back?

Derek

[bigdaddycain]

Good idea Derek.. It's that rumbling sound too that's getting me thinking... I've heard of it with bongo's suffering failed waterpumps, but that wouldn't affect the performance... Till it overheats of course...

[draper3000]

hmmm....I can get the van out and drive it, it can get up to around 50 mph...but no more.

The sound is definitely loud humming like something is vibrating alot.?

Maybe the air intake at the front always takes in the amount of air it is now, I just never noticed it before.

I guess I can check fuses and hoses leading to the turbo and thats about it.

[dave_aber]

When you are driving along, and get the revs up above 2000, do you see any black smoke in the rear view mirror?

I had a collapsed air filter on my 2.5TD audi recently. No 'go' above 2500 rpm, and a lot of black smoke (I do mean a LOT!).

Things to look for - Collapsed air filter (I couldn't believe it was possible, but the filter was being sucked down the intake pipe towards the turbo....), collapsed pipework between the filter and the turbo (this bit can get 'sucked' flat if it's very old), disconnected air piping from turbo to intercooler, or from intercooler to manifold (this bit is under positive pressure, and can pop open), leaking / split / collapsed or otherwise damaged intercooler.

All this is generic advice, not Bongo specific. I have no idea how likely or unlikely any of these could be on a Bongo, since mine's not here yet.

Since I haven't got my Bongo yet, I can't comment on the "small air intake on the left side of the engine".

However, here's a thought - is the humming / vibrating possibly a flattened induction pipe (in the section from the filter to the turbo, under suction), and you are hearing the air farting past the flat section? Or, possibly, you are hearing post-turbo pressurised air escaping at a joint or a damaged intercooler before it gets to the manifold?

[bigdaddycain]

and you are hearing the air farting past the flat section? manifold?

You certainly have a way with words Dave! Bloody good suggestions though... I was just gonna post summat along the same lines! I have a feeling that the intake pipe, or a breather, or some of the pipework to the turbo has been loosened/damaged during the engine rebuild... Seems a bit of bad luck for the turbo to go at the same time as the head, unless of course there was a complete loss of coolant upon C/H failiure,causing the water feed to the turbo to deplete,thus fubarring that right up too!