Air flow in a turbodiesel

[vrsmxtb]

Could someone run through the air flow stages of a turbodiesel with an intercooler and egr valve for me please, from cold air intake to exhaust pipe - thanks!

[jbi]

Filter - Turbo - intercooler - intake - cylinder - exhaust manifold - turbo - exhaust pipe

The egr takes some fumes from the exhaust and injects it back into the cylinder, reducing combustion efficiency and increasing soot levels.

[vrsmxtb]

Thanks, that's what I wanted.

So if air was leaking from the intercooler would it make sense to be down on power but running more efficiently, ie better mpg?!

[deadtom]

wouldnt have thought so, surely the engine would be over fuelling if that was the case?

[varsas]

deadtom said:

wouldnt have thought so, surely the engine would be over fuelling if that was the case?

If it is overfueling you'll have black smoke, especially at high loads. I doubt the car will overfuel, the MAF is on the other side of where you think the leak is so it will compensate.

Edited by varsas on Sunday 17th July 18:28

[heebeegeetee]

vrsmxtb said:

Thanks, that's what I wanted.

So if air was leaking from the intercooler would it make sense to be down on power but running more efficiently, ie better mpg?!

Underfueling/ accelerator cable issue would cause this, I think. Have you checked that at full throttle the injection pump is being opened fully?.

[spats]

vrsmxtb said:

Thanks, that's what I wanted.

So if air was leaking from the intercooler would it make sense to be down on power but running more efficiently, ie better mpg?!

I had a pipe that came loose at the intercooler end, it caused a whoosing noise and the ECU picked up the loose in boost from the actual reading, to what it had requested and then went into limp mode and seemed to stop boosting at all.

Another TDi had a similar pipe split and there wasnt any issues with boost, but it made a racket when on boost.

do you suspect a leak? what car?

[hebbhog]

As a previous poster has suggested a split pipe could account for a suspected air leak.

Another possibility is that O rings may have warped. this has happened to a couple of my diesels in the past with the worst offender being the intercooler to EGR hose.

[vrsmxtb]

What happened was that a garage had noticed a hissing noise from the intercooler while it was in for a new rad. Whilst driving around in the spell of warm weather with the window open I also noticed quite an audible hissing noise that matched the turbo speed. I just had it replaced today it turns out part of the plastic duct shroud that covers the intercooler is in contact with the core itself, and it rubbed against it eventually causing a hole in the core hence the hissing. It wasn't enough to kick up any boost faults on the ECU or really to have much noticeable drop in power. It seems to be a design flaw and on the new intercooler they have put a piece of thin rubber between the plastic and metal so it doesn't happen again. The car is a Fabia VRS so if any other owners have their intercooler off or replaced this is recommended when refitting.