GTI - Removing opf/gpf but staying with the cat

[Rasmus_GTI]

Hi

Does anyone know if its possible to remove the opf but not the cat - or is it one combined unit?

I heard milltek is coming up with an opf delete solution just like what they have for the fiesta ST, but I am really confused if this solution removes both the opf and the cat - and replaces with a 200 cell cat?

Hope someone could help - pretty desperat to get rid of that sound killer opf but want to stay with the original cat if possible.

Thanks!

[phillos]

Purely physically, it's absolutely possible. The OPF/GPF is a completely separate device from the CAT.
I have first hand experience with this, as I did a resonator delete on mine.
Technically however, I'm pretty sure its a dead end. There are sensors before and after the OPF/GPF that measure 'stuff'. Pretty sure the Engine Management will be quite confused if all sensors report the same amount of particles before and after the GPF/OPF.

[Dark_cze]

yep ecu will throw out error maybe even go to criple mode

[l3rady]

Pretty much what others are saying, physically possible but the ECU will complain.

Currently, on diesel model cars many tuners offer a DPF delete service which involves removing the DPF and software modding the ECU to remove the DPF functions on the ECU.

As both a none GPF and GPF version of the Polo GTI exist I'm sure it will only be a matter of time when some brainiac figures out how to software mod the ECU to remove the GPF and offer it as a service.

[ryanponti]

Whats the "legal" standing on doing this, i know its against the law to drive around with a DPF removed if one was installed when the car was sold. Does the same apply to OPF?

[SRGTD]

Whats the "legal" standing on doing this, i know its against the law to drive around with a DPF removed if one was installed when the car was sold. Does the same apply to OPF?

Based on the content of the article at the link below, it’s illegal in the UK if the car is used on public roads, and could invalidate your insurance too.

https://www.hypermiler.co.uk/gasoline-p ... it-illegal

The legal position may be different in other parts of the world though.

[ryanponti]

Where abouts is the OPF located? Would it be easier to create a bypass pipe?

[monkeyhanger]

Not sure if it's clear cut illegal to remove the GPF in all cases.

If your car was sold as being WLTP compliant and made after it was compulsory to be WLTP compliant (Sep 18) then I'd sat it almost certainly is illegal or an MOT failure at the very least.

However, the MK7.5 Golfs had GPFs fitted from around the end of 2017. It might not be illegal to remove those as they are NEDC compliant.

There were people drilling through their DPFs until sometime in 2013 when they became compulsory fit.

If EGRs worked on recirculating post DPF/GPF gases, we'd not have any EGR issues down the line. Too complicated to do or too much back pressure to do that?

[Rasmus_GTI]

I managed to find a 2018 downpipe for my 2020 GTI.
That downpipe has 2 cats and no gpf and I hope it will be a straight swap.

I think the only sensors on the gpf is differential pressure - so planning to install two pressure ports on the 2018 downpipe on each side of the second cat, and fit the sensors to that to hopefully keep the ecu happy

[ad_182_uk]

Bumping an old thread but an owner on here recently had a cobra full system. Sports cats, GPF removal, straight pipe to the tips.

The car was already REVO stage 2 so just required some VAGCOM tweaks. Been going a few thousand miles now and no issues.

Its significantly louder than mine that is just a straight pipe from GPF back, sounds nice on the DSG shifts.

So totally do-able it seems. May need a nice MOT place though.

[RinDman]

Each time you do a opf/gpf delete, you need to flash the ECU, either to cut the sensor warning or to tell sensor how to see the value from the gaz temp without the opf/gpf ...

If you only want the pop from the orignal phase 1 without opf/gpf natively, you better find the old ones from 2017-2018 ...

[johnpolo2]

Until they bring in noise cameras , which some areas have or are testing. Although the Polo has never had an over the top exhaust sound.