turn up the boost to cure black smoke?

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Well, my boost gauge has arrived safely from Taiwan and is now plumbed in.

The most I can get it to read is just under 0.5 bar - and I think the 200tdi is supposed to run 0.7 bar as standard?

I've plumbed in the t piece on the pip that leads to the pump.

So; possibilities are:

1. It wasn't boosting at all before

2. The gauge under reads

3. Plumbing it in in the pipe to the fuel pump gives a low reading.

Any thoughts?
 
You mean the other small pipe - the one that goes to the wastegate? Could be...

I know that, strictly, you should drill and tap the inlet manifold, but I don't need that degree of accuracy. But I'm surprised it's so low. It would be easy to move it to the wastegate pipe if that works better - perhaps I should just try it and see if the readings different.
 
I cant see it making much difference which end of the plastic pipe you have the gauge t piece fitted as i have tried a gauge in several places over the years and they all read pretty much the same.


Lynall
 
Lynall

It's not which end, it's where.

Mine's in the line that goes to the diesel pump.

There's another that goes to the wastegate.

And then there's the main circuit - in the intercooler pipes or on the inlet manifold.

Where did you try mounting the gauges and was there any difference at all?
 
Years ago i had one at the inj pump end then that failed so i remade it at the turbo end and it read the same, bear in mind 0.5 bar is still 0.5 bar no matter where your measure it.
A good example would be a bicycle tyre its 60 psi at the tyre valve so its got to be 60psi all around.
The only reason people say to measure it at the actual manifold is due to volume drop.
Another good example of this would be at where i work if you pump up a truck tyre at the outlet near the compressor its much quicker than on the other side of the workshop where the air has had to travel 200 feet to get there its still 150psi just not the available volume.
Google intercooler pressure drop.
But in a nutshell 0.5 bar is not enough.


Lynall


Lynall
 
Lynall, I'm with you on that and follow your logic.

Personally, I'd have thought that the inlet manifold would read the same pressure as the wastegate, but it seems others disagree.

I've been googling about how accurate my gauge is likely to be. It's a mechanical gauge made by an outfit called 'Autogauges'. Halfords apparently sell them, and it seems that if anything they tend to over read.

Incidentally, I'd have expected it to show a slight vacuum going down steep hills using the engine braking in 2nd and 3rd, but it doesn't drop below 0.

If I do this again I'll spend the extra on a Stack gauge!

So, it looks like I shall have another go at increasing the boost.
 
You should NEVER get a vacuum in a Diesel engine!

Having said that there are some crazy systems (I saw one on a Vauxhall a while back) which do close a butterfly valve on the air inlet for some reason. The V X one had failed SHUT, so I took the vacuum pipe off, opened the valve (which stayed open) and the car was perfect ever after.

It is quite easy to test the gauge - do it against a tyre inflater but do it SLOWLY or you will blow the gauge up!

1 BAR should be about 15 psi, 2 Bar about 30 psi

0.5 BAR isn't enough. You should have almost twice that, but check the gauge first.

Remember the flying golden rule - always believe your instruments, until there is proof positive that there is an error.
 
Some old n/a diesels had a flap in the inlet this was to generate a vacuum for the brake servo
Ive seen this on an old merc van and i believe s3 had a similiar set up
When i test drive the trucks at work i always have the boost pressure up on the dash only time it gets to zero is when exhaust brake is on

Lynall
 
One reason I'm slightly suspicious is that the gauge does seem reluctant to move off the zero, whereas on other boost gauges they seem to respond very quickly. Almost as if it's too damped. Perhaps there's a kink in the hose somewhere.
 
Does anyone by any chance know the name/part number of the wee black pipe that goes from turbo to injection pump?

Only mine has sort of melted a little bit, guess it doesn't like being wrapped around the exhaust manifold too much :rolleyes::D
 
Any motor factors 6mm od plastic tubing or 4mm id rubber tubing not screen washer pipe!


Lynall
 
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