The Student Room Group

Hollow DPF and back pressure?

I've recently had my DPF mapped out and have bashed it through; is it worth putting a pipe through it, or should I leave it as is?

I'm feeling a loss in back pressure in the high end, less torque+acceleration before the turbo kicks in, am having to shift more and drop two gears to overtake etc; but I'm not sure if this is due to the fact that the remap was from a mobile tuner, or that the now-hollow DPF is acting as an expansion chamber and messing up airflow. --- The car is astronomically faster than it was before, I just know it could be faster-er

What do you think, pipe through or leave be?

(please don't shout at me for deleting the DPF, I had no choice, thank you)
(edited 2 years ago)
Reply 1
Sounds like a dodgy map to me. My diesel cat mysteriously broke up and fell out the back and my car drives much better afterwards.

"Back pressure" doesn't really exist in a turbo-diesel. The turbo restricts/controls flow effectively enough that all the exhaust is doing is taking the exhaust gas to the most preferable exit (the back of the car).
Reply 2
Original post by Nuffles
Sounds like a dodgy map to me. My diesel cat mysteriously broke up and fell out the back and my car drives much better afterwards.

"Back pressure" doesn't really exist in a turbo-diesel. The turbo restricts/controls flow effectively enough that all the exhaust is doing is taking the exhaust gas to the most preferable exit (the back of the car).

oh okay!! I agree on the dodgy map front. What's weird is when I had the exhaust system fully removed (engine > turbo > Flexi > out) the car ran way better on the low end. I had no high end acceleration, but I could do twenty in fourth gear and be okay, found myself not needing to shift whenever I reached a hill etc, engine braking was way better too. Might give the mapper a call and see if he's willing to re-do it.
Reply 3
Sounds like a good way to get a fine.

Also “no choice” that’d be like I had no choice to run my car with an MOT? Or no choice but not to throw out potentially carcinogenic fumes out into the environment....

How very Volkswagen of you.

Of course you had a choice - it just seems you didn’t like the choices and decided you put yourself in front of others.

YSK that should your mapper get caught the DVSA may well be looking through the records to find their “customers”.
Reply 4
Original post by roo02
I've recently had my DPF mapped out and have bashed it through; is it worth putting a pipe through it, or should I leave it as is?

I'm feeling a loss in back pressure in the high end, less torque+acceleration before the turbo kicks in, am having to shift more and drop two gears to overtake etc; but I'm not sure if this is due to the fact that the remap was from a mobile tuner, or that the now-hollow DPF is acting as an expansion chamber and messing up airflow. --- The car is astronomically faster than it was before, I just know it could be faster-er

What do you think, pipe through or leave be?

(please don't shout at me for deleting the DPF, I had no choice, thank you)


You did have a choice. You chose to gut it.
All ill say is there's no way i'd let some dodgy walloper in a van with a mob number 'tune' my car and I wouldn't screw with my exhaust/legality like this.
Reply 6
Original post by IWMTom
You did have a choice. You chose to gut it.

Fair

My engine burns an insane amount of oil - about a L a fortnight, which then catches in the dpf and forms this sticky tar-like substance that won't burn off. It was delete the DPF, engine swap the car, or spend £250 a year, or so getting the DPF cleaned out
(edited 2 years ago)
Reply 7
Original post by virgil1
Sounds like a good way to get a fine.

Also “no choice” that’d be like I had no choice to run my car with an MOT? Or no choice but not to throw out potentially carcinogenic fumes out into the environment....

How very Volkswagen of you.

Of course you had a choice - it just seems you didn’t like the choices and decided you put yourself in front of others.

YSK that should your mapper get caught the DVSA may well be looking through the records to find their “customers”.

I'll just write what I've already said to Tom -

My engine burns an insane amount of oil - about a L a fortnight, which then catches in the dpf and forms this sticky tar-like substance that won't burn off. It was delete the DPF, engine swap the car, or spend £250 a year, or so getting the DPF cleaned out.
Reply 8
Original post by roo02
Fair

My engine burns an insane amount of oil - about a L a fortnight, which then catches in the dpf and forms this sticky tar-like substance that won't burn off. It was delete the DPF, engine swap the car, or spend £250 a year, or so getting the DPF cleaned out


So fix the root cause instead of doing dodgy **** to work around it...
Reply 9
Original post by roo02
I'll just write what I've already said to Tom -

My engine burns an insane amount of oil - about a L a fortnight, which then catches in the dpf and forms this sticky tar-like substance that won't burn off. It was delete the DPF, engine swap the car, or spend £250 a year, or so getting the DPF cleaned out.


So instead of fixing the issue you are content with screwing up the env even further with not only carcinogenic particulates but oil fumes?

I stick by what I said previously - you had a choice, you just didn’t like the proper options (ie is IWMTom says fix the car)!

It’s not often I say this - but I suppose all we can do is hope you get caught on your next MOT.

Quick Reply