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Keeping EGR on when adding boost?

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Old Jan 9, 2023 | 01:07 PM
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S203 C200 CDI 2006
Question Keeping EGR on when adding boost?

Hi there!

I've been looking into making some slight performance mods to my OM646 C200.
I know the car isn't worth much nowadays, but I still would like to do this for fun.

One potential change I'm considering is to switch to the bigger turbocharger that comes with OM642 engines.

I noticed people mentioning in various posts in forums that the EGR valve has to be blocked off when making this change because of the extra boost.

Namely, in

You must block the EGR pipe, when boost is higher than EGP.
Otherwise the boost pressure disappears among the EGR pipe straight to exhaust manifold.
from https://mbworld.org/forums/diesel-fo...ml#post2742893

and

If the EGR valve is not blocked, the boost pressure escapes from the intake manifold back to the exhaust manifold, with the exhaust gas recirculation system working in the wrong direction.
from https://web.archive.org/web/20150507...00-220cdi.html (Translated from Finnish)

That being said, I already live in a city with a lot of pollution and I am reluctant to just bypass emissions control devices.

So, I was wondering what exactly is it that makes it possible to have a functional EGR valve on the cars where the more powerful turbo comes as stock?
Is it something in the exhaust system that makes the difference? Is it something in the EGR valve itself?

Could someone (ignoring whether it's worth it or not) adapt these changes so as to keep EGR functional when fitting the bigger turbo?

Thanks in advance for any answers!

Last edited by bencieshtebenc; May 31, 2023 at 03:20 AM. Reason: remove theatrics
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