Bit of fun with MK7 EGR Valve

[rossco_pb]

Interesting the underwear sharing but a little bit off topic

[andz327]

Why so serious brother Ok ok so back on topic .....just fit a new egr and get on with your life man you've wasted enough time

ANDZ

[Airthies]

Oh on the contrary dear andz boyo, if this man is willing to do some out the box thinking and tinkering then let it be, it may be the in roads to something more interesting, always nice to see some tinkering even though it may look like it's solving a problem that's been done before there's more than one way to skin a cat, and it can be satisfying to do things one's self.



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[loot]

I still maintain that everything that can be invented has been invented, it is timewasting folly i tell ya

https://rover.ebay.com/rover/0/0/0?mpre ... 3367973059

[rossco_pb]

I still maintain that everything that can be invented has been invented, it is timewasting folly i tell ya

https://rover.ebay.com/rover/0/0/0?mpre ... 3367973059

Hmmm maybe but I have a Mk7... as for why I persist, well why not. I have installed a brand new EGR and don't want exhaust gunge going into the engine, don't want a dash light on, don't want the pcm modified by deleting the EGR and hey, its technically a bit challenging so keeps the brain alive

[loot]

I still maintain that everything that can be invented has been invented, it is timewasting folly i tell ya

https://rover.ebay.com/rover/0/0/0?mpre ... 3367973059

Hmmm maybe but I have a Mk7... as for why I persist, well why not. I have installed a brand new EGR and don't want exhaust gunge going into the engine, don't want a dash light on, don't want the pcm modified by deleting the EGR and hey, its technically a bit challenging so keeps the brain alive

Indeed

Measure the output of the maf and it'll give a resistance, then get a potentiometer that will allow the current output range but will increase or decrease the output but not much.

So say for argument sake the maf range is 10k min to 100k max then you can lower it by 10% or raise it by 10%.
The maf works on wind, the more wind blowing over the hot element the cooler it gets and that changes the resistance, it has to account for different outside temps and so on.

I don't think it is that clever so maybe get it to run warmer and you'll not see the eml. The turbo does 100% of the work when the egr is blanked and that means more air flow over the maf and cooler the element and different resistance.

Possible issue with vnt feedback but the mk8 all have vnt.

You may get away with just slight change in the maf but you may not and may need to counter the egr motor demand because the egr isn't commanded uniformly, it may not work until the engine is upto temp and it may not work at 'WOT'.

Anyway, good stuff for having a play

Ps. I know yours is mk7 and there was a thread on the forum and ebay selling them but I can't find it, and I also think you know what I've said above but it's good to talk a the great Bob Hoskins used to say.

[rossco_pb]

Measure the output of the maf and it'll give a resistance, then get a potentiometer that will allow the current output range but will increase or decrease the output but not much.

The Mk7 MAF outputs a variable voltage from the thermistor for temperature, ie resistance varies relative to temperature but the air mass output is a variable frequency that is in direct proportion to the air flow so at say 750rpm (idle) frequency is about 4700hz with EGR closed but as EGR is actually open when at idle the frequency is slightly lower and so it goes up through the revs with and without the variable of additional air flow when turbo in boost. Quite interesting really but I think it is a pretty coarse measurement in ECU - well hoping that the case anyways. I assume the device you mentioned messes with the air temp value and as such fools the ECU that way, ie air mass is relative to air temp as the colder the air the denser and therefore more mass so by telling the ECU air temp is higher than it really is it does not realise more air is actually going into the engine.

[loot]

I haven't done any real world measuring, I think the voltage is 5 v that is used.
The amount of air flowing over the maf is measured by feedback so I'm proposing that changing it just enough to put it back into range should stop the melchior on.
As it is the dtc is maf in range but higher than expected. So let's lower it to expected

I did add some leds to the 2 egr motor pins to see if and when the motor is commanded to open the egr and they just sort of flashed when I revved.

Not very scientific tbh

I bought an egr from tpuk for 65 quid and it was the later black one listed as upgraded. And I cleaned my inkjet manifold out, this put an end to my egr fun really as for all the hassle I actually saw better results on my 2.4 140ps vnt system.

Bloody ford.

[rossco_pb]

Yep the EGR on the 140ps don't seem to last long, mine only around 65,000km but is a heavy camper so moving a lot of fuel and resultant carbon etc through the works. Be interesting to see how long one lasts that does not have exhaust going through it - ie just the movement of the valve...

[rossco_pb]

Little update on this now that I have managed to test this latest mod over some distance. Initially had another P1103 MAF reading high so tweaked the frequency reduction a bit more and has not shown up again and been about 400km so may have it sorted but will see how it goes with varying air temps etc.

[rossco_pb]

Well done about 1200km on current trip and finally got an EML - P0100, catch all MAF error by the looks. Happened during cooler weather with persistent strong headwind so in continual heavy boost so suspect that have tweaked frequency from MAF down too much. Will have another fiddle but looking really good so far

[winterheating]

Any flow outside the circuit will give MAF faults. That is the whole design/requirement of the Maf. For observation of egr function.

Only way is to have a direct variable feed to MAF depending on EGR position. Or have the clean air instead of exhaust, at higher pressure the the boosted intake.... then more energy would be wasted that way.

[rossco_pb]

Only way is to have a direct variable feed to MAF depending on EGR position

Trying to avoid reading EGR valve position and do not think it necessary as is a fairly coarse air measurement through MAF. EGR is pretty much open all the time from idle to around 12psi and fully closed at 15psi and above (from my observations) I have varied MAF frequency to show reduced air flow within that range, ie simulating EGR open, even though it is blanked off. Working really well so far - just tweaking the top end where boost high. Good little experiment

[winterheating]

It’s a but crude to say open all the time. Then shut. It constantly changes.

That’s how it operates, BUT the amount it opens is extremeley accurate, it will account for build up and changes in intake and boost circuit. As the MAF is so precise.
With reference to the MAF, I’m sure it has a temp sensor too, so a heating element, a temp sensor for ambient and a temp sensor after the hot element. 6 wires yes??
That is only part of it the pcm does the clever calculations.

Remember when everyone was blanking the get but drilling a certain size hole in the plate to keep the light off WTF, it just the same as having no blank plate. The Egr open position would alter to suite the restriction, as if it was built up with crap.

The reason it’s open MORE low revs and not high revs, is because that is the exact function intended. Low revs, have high combustion temperatures, so more Nox created, the Egr dilutes the oxygen to lower combustion temps, then lowering Nox.
At higher revs the combustion temps are lower no Egr required to introduce exhaust gas to dilute oxygen.

The MAF monitors this precisely, so that’s why anything out of sync, of out of the boosted circuit will be picked up on.

Would loosing boost backwards through the EGr not put more strain on the turbo?

[winterheating]

There is no separate IAt is there? So it has to be part of the MAF?