N75 valve on 2.2 DW12 2.2 HDi engine

[exec406]

Hi

Connections checked to new electrovalve (1628LQ) and OK. Still getting the flat spots on acceleration.

Could a faulty unit be causing this? I wasn't getting this happening with the old one fitted.

Thanks

[exec406]

Hi

Now getting a boost solenoid fitted - is that one of those that is on the bulkhead? This is a different part to the electrovalve 1628.LQ just fitted.

Thanks

[GingerMagic]

Yes, it's different.
By fixing one issue, you may have uncovered an underlying one - which is a pain.
Let us now how you get on.

[exec406]

Boost solenoid replacement made no difference, still being looked into...

[GingerMagic]

Okay.
Can you get the garage to bypass the swirl solenoid, this will disable the swirl diaphragm which is prone to losing vacuum.
I'm happy to have a look at it if you are local.

[exec406]

Hi

Not local but will ask them to try that.

Is the swirl solenoid part number 1628.CH?

Found the thread below from a few years ago about the DW12 Vac system.

http://www.406oc.co.uk/viewtopic.php?t=21527

Thanks

[GingerMagic]

That's a good guide, I've done many other people's 406s to simplify the vacuum system ( I also did a how-to on the Coupé forum - search for how to simplify the vacuum system )

The CH is the one that controls the swirl, it can easily be bypassed but it means the little ball and arm on the engine is floppy, so needs holding upright with an elastic band or something.

[Doggy]

The CH is the one that controls the swirl, it can easily be bypassed but it means the little ball and arm on the engine is floppy, so needs holding upright with an elastic band or something.

Agreed, but if you remove/plug the vacuum pipe for the swirl flap actuator and just leave it in place, the integral return spring does it for you.

[exec406]

Hi

Garage think the turbo may be at fault, so having it removed for an inspection. Even tried fitting a new Swirl Flap EV.

Car drove OK for a short while at speed after new Swirl Flap install then it flat spotted again. It was mentioned to me a couple of years ago that the engine note was indicative of a potential turbo issue in time. Would the fact I fitted a new Airbox EV when the previous one had a broken 'pipe', now cause turbo issues as the vacuum is back to normal?

I happened to be really close to the garage (on a slight incline) when the engine power almost went completely (about 90%) large puff of smoke out the exhaust (this soon stopped) then some 'different' noises coming from the engine. This happened before I managed to get the car to the garage for new Swirl Flap EV install.

[GingerMagic]

Okay.
The better the vacuum supply to the turbo, the better the response - so by sorting the vacuum leaks then the car should perform better.
By your description you may have a boost leak ( possibly uncovered a weak spot but as the turbo is better it's blown a pipe with the pressure )
It's very rare the turbo is at fault, and garages often diagnose a dodgy one - however there are exceptions.
If you garage can remove the vacuum pipe nearest the engine from the left hand bulkhead ev and apply vacuum, either with a pump or sucking on it, you hear a metallic ping noise when the vacuum/sucking is released - this is a good sign your turbo is fine and not choked up.

Some non-Peugeot garages don't understand this engine, as pretty much every other manufacturer uses boost supplied from the N75 valve to use the turbo waste gate - whereas the Peugeot is opposite and uses vacuum to open/close it's variable vane system.

Following on from a different thread on here, is your EGR blanked?

[exec406]

Hi

Not sure if the EGR is blanked - will get that checked. Garage think it could be a wastegate issue on the turbo but I mentioned there's no wastegate on that one (2.2 DW12 - ECU controlled turbo)

They thought car was to old for that (non wastegate turbo) but the 2.2hdi was one of the latest engines released on the 406 before the car went out of production.

Car did tow a caravan (first owner) Not sure if that would have any sort of impact on how long turbo would last.

Edit: Thanks for the info, will ask them to check that first.

[GingerMagic]

Yes, it's a variable vane set-up like the VW engines but uses vacuum to use it, not boost.

Towing a caravan should have no effect, I've pulled vans out of ditches with mine......

[exec406]

Indeed, this engine has the most torque of all the engines used in the 406 - 314 N⋅m (232 lb⋅ft) / 2000rpm.

[GingerMagic]

It over 400 Nm when remapped - it makes for effortless driving and steep hills a doddle.
I was coming back from Cornwall a few years back - me, the wife, our son and both my wife's parents, full boot and a roofbox on top - some Muppet in an X5 BMW tried to not let me past him on one of the hills by sticking his foot down, I did the same and cruised past him
Not a happy BMW owner at all, and proving to Audi and BMW drivers that there car isn't the king of the road is what a remapped 2.2hdi does best.

[exec406]

Garage is going to do a smoke test to check for boost leaks.