Hi all,

I have a mk6 with the 1.4 TDCi engine, its currently on only 144k miles - have driven it for around 50k miles so far with various mix of driving in terms of motorway/town/A roads etc and have been trying a few different intake setups on the engine to improve its performance.

ECUs usually self adjust the fuel trims and can usually fuel to a slightly different part of the ECU map when additional airflow is going through the engine so I just wanted to see if there were a few simple changes I could do to help out this engine without remapping.

I have tried various setups but here are the main parts I have tested:

EGR blanking

Intake snorkel to air box

Airbox vs cone filter

Doser valve

 

The car currently has an EGR blanking plate fitted (although this might be reversed due to new MOT laws coming up), but after getting a spare intake for testing which has had the EGR plugged in for all its life the sludge that builds up in the intake is horrific!

Anyway, back to some testing, below are a few setups from 'worst' to 'best' - there are some trade off which are noted:

• Stock airbox with snorkel, Doser valve standard and EGR blanked - car felt spongy on the throttle and felt fairly slow, took this as a baseline
• Stock airbox, snorkel removed,  Doser valve standard and EGR blanked - improvement in some throttle response, slight increase in induction noise especially when letting off the throttle
• Stock airbox, snokel removed, Doser valve unplugged and EGR blanked - quite a noticeable improvement in throttle response, engine is still fairly quiet, no real gain in power but nicer to drive
• Modded airbox (base cut away). doser valve unplugged and EGR blanked - improvement in performance due to additional airflow, issue being is that the air filter now gets dirtier quicker so not recommended
• Stock airbox, snorkel removed, Doser valve butterfly removed and EGR blanked - a noticeable improvement in throttle response with a slight bump in power by simply removing the butterfly valve from the doser valve setup (2 screws) - the butterfly is spring loaded so is open when unplugged but doesn't sit flat giving a fair restriction to airflow. The check engine light might come on at some point due to higher airflow (much like the cone filter) but the engine is fairly quiet on the motorway
• Cone filter (3" pipework), doser valve unplugged and EGR blanked - considerable improvement in throttle response and power, I found that the all the air the engine gets through the stock airbox has to go through a thin slot then around a bend, a cone filter does improve performance. The cons for this setup is that engine noise on the motorway is increased, the check engine light might come on due to high airflow though the MAF and the injectors are slightly noisier due to the adjustment of the fuel trims to keep up with the airflow.
• Cone filter (3" pipework) doser valve butterfly removed and EGR blanked - this is the setup for the best throttle response and power, no restriction in air for the engine (MAF is a tiny 60mm tube), no restriction going through the doser valve either. This setup does increase both power and throttle response as the ECU does adjust fueling for the additional airflow, the downside to this is that you might get a check engine light due to high airflow detected, engine noise is increased on the motorway, the injectors are also slightly nosier especially at slightly higher RPMs owing to the fuel trim adjustments etc.

My recommendations for anyone who feels that their 1.4 TDCi is slow but don't want to get too involved is:

• Remove the snorkel from the stock airbox
• Unplug the doser valve

For those who want a bit more of an improvement but don't want an induction kit I would suggest to:

• Remove the snorkel from the stock airbox
• Remove the butterfly from the doser valve - its amazing how much difference just this makes

Its worth noting that although the car was fitted with an induction kit, because the engine is a diesel and therefore has no vacuum you don't get the usual 'induction roar' - more of a constant noise as that's due to the turbo pulling in the air under load.

Its also worth noting that some models of 1.4 TDCi engines don't actually have a doser valve in the intake, so far for me, simply unplugging the doser valve hasn't caused any check engine lights to come on - whereas if you remove the butterfly there will be - just shows how much restriction that butterfly valve has in terms of airflow!

I would also suggest anyone to start with a full oil and filter change (including the fuel filter) and run some 'diesel purge' neat through the injectors (connect up the can to the feed lines to and from the pump into the can).

For me I am currently running with the stock airbox, no snorkel with the doser valve unplugged, this has mean that the ECU has readjusted fueling so that the engine is quieter and no check engine light has come on in a while - throttle response and power isn't as good as having the cone filter and no butterfly but less to worry about.

Also worth noting that its worth resetting the ECU fuel trims - its fuse 16 (3A) behind the glove box, relearn procedure after its pulled/reset is to get the car up to operating temp and then hold it at high idle for around 2 minutes. I have however found that the fuel trims do self adjust as I have noticed that they are much quieter now I have put the doser butterfly back in (which means less airflow etc).

 

 

The EGR valve is the devil for engines. When I was doing the injectors on my 1.6 tdci I looked at the intake manifold and that was caked in carbon. I used oven cleaner and a pressure washer and that opened it up. I think you should still look at a remap. You can check out HDI tuning. @TomsFocus used them and has had no issues. They charge £150 for a map and specialise in just the peugeot Citroën PSA Hdi engines. I'm thinking of using them in the summer. 

On 15/02/2018 at 7:30 AM, m1tch said:

Hi all,

I have a mk6 with the 1.4 TDCi engine, its currently on only 144k miles - have driven it for around 50k miles so far with various mix of driving in terms of motorway/town/A roads etc and have been trying a few different intake setups on the engine to improve its performance.

ECUs usually self adjust the fuel trims and can usually fuel to a slightly different part of the ECU map when additional airflow is going through the engine so I just wanted to see if there were a few simple changes I could do to help out this engine without remapping.

I have tried various setups but here are the main parts I have tested:

EGR blanking

Intake snorkel to air box

Airbox vs cone filter

Doser valve

 

The car currently has an EGR blanking plate fitted (although this might be reversed due to new MOT laws coming up), but after getting a spare intake for testing which has had the EGR plugged in for all its life the sludge that builds up in the intake is horrific!

Anyway, back to some testing, below are a few setups from 'worst' to 'best' - there are some trade off which are noted:

• Stock airbox with snorkel, Doser valve standard and EGR blanked - car felt spongy on the throttle and felt fairly slow, took this as a baseline
• Stock airbox, snorkel removed,  Doser valve standard and EGR blanked - improvement in some throttle response, slight increase in induction noise especially when letting off the throttle
• Stock airbox, snokel removed, Doser valve unplugged and EGR blanked - quite a noticeable improvement in throttle response, engine is still fairly quiet, no real gain in power but nicer to drive
• Modded airbox (base cut away). doser valve unplugged and EGR blanked - improvement in performance due to additional airflow, issue being is that the air filter now gets dirtier quicker so not recommended
• Stock airbox, snorkel removed, Doser valve butterfly removed and EGR blanked - a noticeable improvement in throttle response with a slight bump in power by simply removing the butterfly valve from the doser valve setup (2 screws) - the butterfly is spring loaded so is open when unplugged but doesn't sit flat giving a fair restriction to airflow. The check engine light might come on at some point due to higher airflow (much like the cone filter) but the engine is fairly quiet on the motorway
• Cone filter (3" pipework), doser valve unplugged and EGR blanked - considerable improvement in throttle response and power, I found that the all the air the engine gets through the stock airbox has to go through a thin slot then around a bend, a cone filter does improve performance. The cons for this setup is that engine noise on the motorway is increased, the check engine light might come on due to high airflow though the MAF and the injectors are slightly noisier due to the adjustment of the fuel trims to keep up with the airflow.
• Cone filter (3" pipework) doser valve butterfly removed and EGR blanked - this is the setup for the best throttle response and power, no restriction in air for the engine (MAF is a tiny 60mm tube), no restriction going through the doser valve either. This setup does increase both power and throttle response as the ECU does adjust fueling for the additional airflow, the downside to this is that you might get a check engine light due to high airflow detected, engine noise is increased on the motorway, the injectors are also slightly nosier especially at slightly higher RPMs owing to the fuel trim adjustments etc.

My recommendations for anyone who feels that their 1.4 TDCi is slow but don't want to get too involved is:

• Remove the snorkel from the stock airbox
• Unplug the doser valve

For those who want a bit more of an improvement but don't want an induction kit I would suggest to:

• Remove the snorkel from the stock airbox
• Remove the butterfly from the doser valve - its amazing how much difference just this makes

Its worth noting that although the car was fitted with an induction kit, because the engine is a diesel and therefore has no vacuum you don't get the usual 'induction roar' - more of a constant noise as that's due to the turbo pulling in the air under load.

Its also worth noting that some models of 1.4 TDCi engines don't actually have a doser valve in the intake, so far for me, simply unplugging the doser valve hasn't caused any check engine lights to come on - whereas if you remove the butterfly there will be - just shows how much restriction that butterfly valve has in terms of airflow!

I would also suggest anyone to start with a full oil and filter change (including the fuel filter) and run some 'diesel purge' neat through the injectors (connect up the can to the feed lines to and from the pump into the can).

For me I am currently running with the stock airbox, no snorkel with the doser valve unplugged, this has mean that the ECU has readjusted fueling so that the engine is quieter and no check engine light has come on in a while - throttle response and power isn't as good as having the cone filter and no butterfly but less to worry about.

Also worth noting that its worth resetting the ECU fuel trims - its fuse 16 (3A) behind the glove box, relearn procedure after its pulled/reset is to get the car up to operating temp and then hold it at high idle for around 2 minutes. I have however found that the fuel trims do self adjust as I have noticed that they are much quieter now I have put the doser butterfly back in (which means less airflow etc).

 

 

Hi m1tch when you say you removed the snorkel from the airbox, do you mean every pipe or do you leave the one that goes under the fuel filter to the airbox just bnecause with that one off it makes a deep rumble which I hate, also if your using a panel filter I would personally suggest using a Green Cotton Performance filter, I did have one for my car and it was fantastic, better than the k&n panel filter I have but had to send it back as the girlfriend got me the k&n one and was not happy with my using another but ether is much much better than the standered filter, anothing thing is when I had my EGR blanked you could hear the air in the EGR pipe and it was so irritating do you get that?