406oc.co.uk

New question about turbo - is there variable geometry on HDI 2.2 or not? Technician at local service assures that there is no variable geometry on this engine.

Variable yes, geometry no.
Technically it's a variable nozzle turbo designed to allow a controlled amount of the exhaust gasses to bypass the turbine blades.

If your mechanic is trying to tell you the turbo is non-adjustable, he's wrong.

Doggy wrote: ↑Wed Jul 19, 2023 7:44 am Variable yes, geometry no.
Technically it's a variable nozzle turbo designed to allow a controlled amount of the exhaust gasses to bypass the turbine blades.

Are you sure? I think there are two systems:

• HDI 2.0: variable nozzle
• HDI 2.2: variable geometry

See also https://www.youtube.com/watch?v=RqXBUESgQ90&t=761s (12:41 Le turbo compresseur à géométrie variable)

Not sure what is variable nozzle. There is some bypass (switch air flow here and there) controlled by diaphragme (#12) from scheme below. The explanation was that it works like simple variable geometry:

On the HDI 2.0, the turbo is controlled by a vacuum-operated relief valve. It can be seen in this picture: https://i.ebayimg.com/images/g/VSQAAOSw ... -l1600.jpg .

On the HDI2.2, the turbo is controlled by the vacuum pressing the scoops further into the air chamber, see: https://i.ebayimg.com/images/g/SiIAAOSw ... -l1600.jpg

486 wrote: ↑Wed Jul 19, 2023 10:01 am Not sure what is variable nozzle. There is some bypass (switch air flow here and there) controlled by diaphragme (#12) from scheme below. The explanation was that it works like simple variable geometry:

22.png

That's the swirl flap system to blank of half of the inlet valves at low engine speeds to increase intake air velocity and improve fuel/air mixing, nothing to do with the turbo, (though the vacuum diaphragm that operates the swirl flaps is a common source of vacuum leaks which can affect turbo control).

See the link frog posted which clearly shows a similar diaphragm assembly on the turbo, used to regulate boost. Most common issue is vacuum loss elsewhere preventing the turbo actuator working as intended resulting in too much boost.

Doggy wrote: ↑Wed Jul 19, 2023 10:55 am See the link frog posted which clearly shows a similar diaphragm assembly on the turbo, used to regulate boost. Most common issue is vacuum loss elsewhere preventing the turbo actuator working as intended resulting in too much boost.

In other words - there is variable geometry? I guess one of the 3 valves on pictures above is for turbocharger but not sure which one. I don't like to dig in such engine/vacuum/etc. topics but it is hard to find competent service here.

486 wrote: ↑Wed Jul 19, 2023 11:01 amIn other words - there is variable geometry? I guess one of the 3 valves on pictures above is for turbocharger but not sure which one. I don't like to dig in such engine/vacuum/etc. topics but it is hard to find competent service here.

Yes, your 2.2 HDI has a variable geometry turbo. It uses vacuum to relieve boost. I.e., loss of vacuum can lead to overboost.

HDI 2.0 turbo uses vacuum the other way, so for that engine (not yours), loss of vacuum leads to loss of boost.

Have a look at this post: viewtopic.php?t=21527

There are 5 electrovalves in total, 3 on the bulkhead and two nearer the front of the engine.
The turbo control valve is No. 8 on the diagram entitled "Air Supply Function", posted by jonsowman
Can't honestly remember where it's located.
Suggest following the vacuum pipe back from the turbo.

FWIW
No. 1 is Air doser control
2 is swirl flap conrol
4 is the egr control
10 is the intercooler bypass

I think they're all interchangeable apart from No. 2

Note that No.s 2 & 8 get their vacuum from the reservoir tank (6) and are least likely to work if there's a leak anywhere

frog wrote: ↑Wed Jul 19, 2023 11:08 amYes, your 2.2 HDI has a variable geometry turbo. It uses vacuum to relieve boost. I.e., loss of vacuum can lead to overboost.

Is it possible to switch/move geometry by hand? The conclusion after diagnostic at Peugeot dealer was that geometry does not move for some reason and causes overboost. I guess overboost is measured and the reason (geometry) is found logically. But if vacuum leak can be a reason for overboost then the problem can be in non-working valve or cracked pipe. Months before this diagnostic I had another issue with ckeck-lamp-on when driving at 3500 rpm for more than 4-5 seconds. The diagnostic then said that problem is in eletro-valve but I did not replaced it and have refrained driving above 3000 rpm. Unfortunately they didn't point me the exact valve, only the oem code 1628HC (which is same for 3 valves). Original valve is about 100 euro. I see METZGER and other brands for 50 euro and below but not sure how long they will work.

You almost certainly have one or more vacuum leaks, but tracing can be difficult.
It's worth checking all the rubber push-on connectors carefully, you may find some loose, split etc.
If you find a suspect connection and fix it, don't assume it's the only issue.
Don't ignore the connections to the vacuum pump.

If that doesn't work, disconnect and plug the vacuum supply pipe on the egr solenoid valve, (not the pipe going to the egr valve), leaving the electrical connection in place. Check the engine is unaffected, it almost certainly will be fine.
You can now swap this electrovalve with either of the other two identical valves in order to eliminate a faulty valve.

Next, I would temporarily disconnect as much of the vacuum system as possible, leaving only the turbo actuator, its control valve and of course the brake servo connected to the vacuum pump. This will disable the egr, swirl flaps, air doser/intercooler bypass, it will not prevent the engine running virtually as normal, but it will eliminate a very large proportion of the vacuum system pipework and most of the potential leaks. Don't leave the vacuum reservoir in circuit for this test as they have been found to leak on occasion.

If this works, reconnect the other vacuum circuits one at a time until you find the problem(s).

The easiest way to provoke an overboost fault is to accelerate hard in a high gear from say 2000 RPM, ideally up a hill.

For information, the effect of disconnecting those systems is:

EGR disable prevents some of the exhaust gases being recirculated into the inlet manifold under idling or overrun conditions

SWIRL FLAPS shut off one of the two inlet valves on each cylinder at low engine speeds

AIR DOSER/Intercooler bypass used to increase inlet air temperature to shorten engine warmup period and during DPF regeneration