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HDI Air Doser

UncleBen

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Hello to all.
Well I'm writing this in the hope that someone who understands the induction circuit might read it and be able to explain how it works.

My engine has the twin doser, with one hose coming from the intercooler outlet and the second one coming from a bypass Y piece which leads to the intercooler inlet side.
Both butterflies have what look to be the same actuators, however only the side which comes from the intercooler outlet side has an electronic and vacuum connection, which weans this butterfly is controlled by the ECU. The bypass butterfly has neither connection, meaning it has no control and is static, the butterfly is sprung in the open position, meaning that the engine is always drawing in air that has not passed through the intercooler. Now isn't that defeating the object??
Obviously there is a reason why it is like this. If anyone knows how this system works please could they explain.
 

RCZIain

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From my very rudimentary understanding (from previous Peugeot HDIs) the air doser copies the EGR.
EGR open = doser closed.
EGR closed = doser open.

I assume you're getting codes/running faults?
 

UncleBen

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Hi.
Yes had a whole bunch of codes, lost the use of cruise control and was having intermittent power loss. I'll post the codes. After investigating all the codes and doing some searching I discovered that my loss of power was due to the turbo solenoid valve being faulty, once I replaced it everything including cruise control went back to normal and all codes remained gone.
I just don't get why the bypass is open all the time, drawing air in before the intercooler??
After all the above issues were dealt with I had a remap and egr delete which has made a fantastic difference to the driving experience.
I'm wondering now if I could block off the bypass side of the doser.
Screenshot_2020-07-29-06-48-21-530_com.miui.gallery.jpg
 

Pedro

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You should never delete the EGR on a diesel it will just make the whole system filthy
 

UncleBen

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You should never delete the EGR on a diesel it will just make the whole system filthy
I cant see how that would happen when there is a plate planking it off. Anyhow I would gladly suffer some gunge to stop all that soot being pumped into the engine and contaminating the oil and creating more wear.
 

George123

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I cant see how that would happen when there is a plate planking it off. Anyhow I would gladly suffer some gunge to stop all that soot being pumped into the engine and contaminating the oil and creating more wear.
Has the egr made any difference to the feel of the car at all? And how is sunny Limassol?
 

Pedro

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I cant see how that would happen when there is a plate planking it off. Anyhow I would gladly suffer some gunge to stop all that soot being pumped into the engine and contaminating the oil and creating more wear.
High pressure EGR valves divert the high flow high soot exhaust gas Before ! it enters the DPF filter the soot can combine with oil vapour to create sludge
Low pressure EGR valves divert the Gas After! it has passed through the DPF filter this gas has a lower flow but is almost free from soot so if your car has had it deleted why is it fitted to your Engine? I know a way how to cut down on the problems with the sludge & soot etc but you don't need me to ell you how to go about it judging from your post
 

UncleBen

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Has the egr made any difference to the feel of the car at all? And how is sunny Limassol?
I cant answer your question in all honesty, because I did the stage 1 remap and deleted the egr at the same time, it has changed the whole feel of the car. The idle has remained really good, the car is much more responsive in its power delivery and generally a lot more enjoyable to drive. Also there is a small improvement in economy.
 

UncleBen

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High pressure EGR valves divert the high flow high soot exhaust gas Before ! it enters the DPF filter the soot can combine with oil vapour to create sludge
Low pressure EGR valves divert the Gas After! it has passed through the DPF filter this gas has a lower flow but is almost free from soot so if your car has had it deleted why is it fitted to your Engine? I know a way how to cut down on the problems with the sludge & soot etc but you don't need me to ell you how to go about it judging from your post
The reason I started this thread is to understand the way that the twin air doser works and its effects. I haven't as yet.
 

UncleBen

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I cant answer your question in all honesty, because I did the stage 1 remap and deleted the egr at the same time, it has changed the whole feel of the car. The idle has remained really good, the car is much more responsive in its power delivery and generally a lot more enjoyable to drive. Also there is a small improvement in
Has the egr made any difference to the feel of the car at all? And how is sunny Limassol?
Limassol is great thanks a bit too sunny. When did you last visit?
economy.
 

George123

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I cant answer your question in all honesty, because I did the stage 1 remap and deleted the egr at the same time, it has changed the whole feel of the car. The idle has remained really good, the car is much more responsive in its power delivery and generally a lot more enjoyable to drive. Also there is a small improvement in economy.
The only reason I ask is because I’ve read conflicting information on deleting the egr. Some people do the stage 1 as you have while others say it’s a ‘bad’ thing to do. I am planning a remap after some point, when funds allow, so I guess I have time to hear others experiences and decide from there.
 

UncleBen

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I researched quite a bit before going ahead with the map, I even spoke with a couple of the tuning companies. The performance benefits of deleting and blanking the egr were negligible. I decided to do away with it purely to stop the carbon contamination in the engine and the additional wear that go's with that. I have also read that this mod in its self can return slightly better MPG.
HDI tuning are a good source for info. But there is so much out there on the subject.
The key for me is always trying to understand as much as possible what I am are planning to do, not just going ahead because I have seen it done.
 

tm2204

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I've a 156 THP petrol RCZ now but my previous car was a 406 Coupe 2.2. HDi. I removed both air dosers with a 'Nico' pipes upgrade. I removed & blanked the EGR. I removed the FAP from the exhaust flow. I upgraded the ECU on the car with a generic 180 remap that also mapped out the dosers, EGR & FAP, it also added about 44 HP & a chunk of torque to the car.

I also greatly simplified the vacuum system in the car by eliminating a lot of the un-needed vacuum electro valves including the ones controlling the EGR and the air dosers.

The difference was literally incredible 😁 Great pull through all the gears, great power & torque, greatly reduced EML warnings over 120k miles I had this setup. Vastly cleaner inlet manifold due to EGR being removed.

Was literally like driving a different car 😁 (sorry I know this is OT :))
 

UncleBen

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Yes its clear to see that all this wizardry on the HDI is there for emissions mostly. But how the heck does this air doser system work??:confused:
Cannot find an explanation anywhere!

tm2204, after removing the doser did anything change with the idle or shut down/start up?
 

tm2204

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Yes its clear to see that all this wizardry on the HDI is there for emissions mostly. But how the heck does this air doser system work??:confused:
Cannot find an explanation anywhere!

tm2204, after removing the doser did anything change with the idle or shut down/start up?
Believe the air dosers switch the flow of air to the inlet manifold depending on engine temperature, also something to do with dpf regeneration air flow.

Nothing at all changed when I removed my 406 Coupe HDi air dosers as it was all handled by the ECU remap which was done to 'map out' the removal of the dosers, EGR & FAP. You can't just remove these without remapping (telling the car to forget about them) or you'll have EML's all over the dash 😂
 

UncleBen

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Believe the air dosers switch the flow of air to the inlet manifold depending on engine temperature, also something to do with dpf regeneration air flow.

Nothing at all changed when I removed my 406 Coupe HDi air dosers as it was all handled by the ECU remap which was done to 'map out' the removal of the dosers, EGR & FAP. You can't just remove these without remapping (telling the car to forget about them) or you'll have EML's all over the dash 😂
Interesting. I'm not planning on removing the dpf for now, so I will not be looking at getting rid of the air doser. However I'm still puzzled as to why there is a bypass when it is not ECU controlled, has no vacuum or electrical connections to its actuator and is always in the open position, this means its always drawing air from before the intercooler resulting warmer induction? I'm I correct in this thinking? If anything I would like to block the bypass off.
 

tm2204

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Interesting. I'm not planning on removing the dpf for now, so I will not be looking at getting rid of the air doser. However I'm still puzzled as to why there is a bypass when it is not ECU controlled, has no vacuum or electrical connections to its actuator and is always in the open position, this means its always drawing air from before the intercooler resulting warmer induction? I'm I correct in this thinking? If anything I would like to block the bypass off.
Don't understand that one myself mate, seems strange alright 👍 I have a petrol 156 now so I've left DPF's & air dosers behind me 😂
 

UncleBen

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Don't understand that one myself mate, seems strange alright 👍 I have a petrol 156 now so I've left DPF's & air dosers behind me 😂
Whaaaat! petrol, that horrible smelly stuff.....:D
Thanks for all your feedback pal.
 

tm2204

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Whaaaat! petrol, that horrible smelly stuff.....:D
Thanks for all your feedback pal.
Absolutely no problem mate. I've picked up a lot of knowledge over the years on Peugeot HDi engines and I'm happy to pass on what I can as it was passed on to me mainly over on the 406 Coupe Club Forum 👍
 

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Well as most people who have seen my previous posts I have two Hdi RCZs in my garage and would not swap them for any other 😎🤠🙃😉all drive safe and stay lucky 🍀
Les n Karen n Co
 
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