Blow off valve

[Parksy10]

Hi can anyone tell me how to change the diverted valve I can’t seem to find it without taking too much apart. Any idea if I can do it or will I be better to take it to a garage. It’s a 2015 c250 coupe. Thanks

 

[LostKiwi]

What do you mean diverter valve?
If you mean wastegate I'm pretty sure you don't have one as your turbo is variable vane.

 

[Parksy10]

What do you mean diverter valve?
If you mean wastegate I'm pretty sure you don't have one as your turbo is variable vane.

No it’s the blow off valve on the intake side

 

[Lee Edwards]

I see some people describe the engine crankcase breather as” blow off “ . the breather is an easy change if you wish to attempt yourself. There are lots of videos of this on the web. Can you say why you think you need to change it ?

 

[Parksy10]

Do it’s the same as a dump valve. I read that it increases boost by forcing air back in to the turbo

 

[LostKiwi]

No it doesn't.
Boost is controlled by the ECU operating the variable vanes on the exhaust turbine.
The valve you're referring to as s blow off valve actually operates as a priority valve and only becomes effective when the throttle pedal is suddenly released. It then dumps boost pressure back into the inlet to prevent boost on the inlet stalling the compressor thus enabling the turbo to maintain shaft speed and spool up quicker.
This only happens when the throttle is rapidly closed such as on a manual gearbox when changing gear or when coming off and on the pedal quickly while driving in a spirited manner (but even then if you're a fast smooth driver those changes in throttle are usually slower).
Fiddling with it will do 2 things - make it louder (like some chavved Halfords turbo rice burner that goes pssst psst psst at every gearchange) and make the turbo lag increase.
One is annoying for everyone outside and the other annoying to you as a driver.

If you have an automatic gearbox messing with it will have next to no effect at all other than introducing lag.

You won't increase boost or performance.

 

[Parksy10]

Thanks I have seen mixed reviews I just thought for £90 and three screws it wouldn’t hurt to try since it can easily be returned to stock but I can’t even find the thing

 

[LostKiwi]

I really wouldn't bother.
Just to add to the above, if you vent boost to atmosphere you're venting air that has already been through the MAF sensor. When you lift off and then put your foot on the accelerator again the air the ECU has seen go through the MAF sensor is no longer there, so when the ECU injects fuel it runs very rich which can screw with plugs, valves, pistons and catalytic converters. Often you'll see a big puff of black smoke as a result.
I'd put the £90 to a decent remap if you want more power.

 

[Parksy10]

Thanks much appreciated i was wanting to make a few other mods before having a map so they could be taken in to account. I’ll take your word for it and just take it back. Thanks for taking the time. This is the first car i have owned that’s worth doing anything to and it’s the first Mercedes I’ve owned

 

[V6Matty]

In all honesty other than a good stage 1 map there is little worth doing to a diesel, unless your going to upgrade the turbo, injectors, fuel pumps, exhaust and then map your really just throwing money where it could be better spent on a more powerful 6/8 pot anyway

 

[LostKiwi]

In all honesty other than a good stage 1 map there is little worth doing to a diesel, unless your going to upgrade the turbo, injectors, fuel pumps, exhaust and then map your really just throwing money where it could be better spent on a more powerful 6/8 pot anyway

I think it's a CGI Matty.

 

[V6Matty]

I think it's a CGI Matty.

I was going by his previous thread on remapping

 

[LostKiwi]

I was going by his previous thread on remapping

Ah - well spotted!
In that case a blow off valve/dump valve has even less effect!

 

[Srdl]

I think it's a CGI Matty.

I was going by his previous thread on remapping

It’s CDI
https://forums.mercedesclub.org.uk/index.php?threads/c250-cdi-remapping.180780/

 

[Parksy10]

To be fair I’ve just spent 17k on it so I won’t be getting a 6/8 pot any time soon.

 

[flowrider]

I thought this was going to be a thread about flatulence