3.0TDI Back box delete!

ion2211

Registered User
Hi Guys,

I will soon be getting the back boxes removed and replaced with straight pipes to get a nicer V6 sound out of my A4.

Having done a bit of reading on this and there are numerous reports that claim a significant power gain from removing the back boxes
(claims of around + 20Bhp)

My car is stage 1 mapped and already pushing out 312Bhp & 490lb-ft

Will removing the back boxes give me even more power or do these gains apply if the car is stock?

Thanks
 

ion2211

Registered User
Personally I don't think there is that much in it at the top end, maybe a few bhp, car seems to pick up better and of course it sounds nicer.

Thanks desertstorm,

I was reading this thread which shows a +20Bhp dyno gain from just removing the backboxes.

My main reason for removing the backboxes is indeed the sound ... but if there are any power gains to be had or even just responsiveness and increased mpg , it would be a bonus.

Just wondering whether a bit more Power is a realistic expectation given that my car is already putting out decent figures..
 

And

Registered User
Hi Guys,

I will soon be getting the back boxes removed and replaced with straight pipes to get a nicer V6 sound out of my A4.

Having done a bit of reading on this and there are numerous reports that claim a significant power gain from removing the back boxes
(claims of around + 20Bhp)

My car is stage 1 mapped and already pushing out 312Bhp & 490lb-ft

Will removing the back boxes give me even more power or do these gains apply if the car is stock?

Thanks

Hi

sounds good - what are you actually having done and what are replacing the back boxes with - links et al

many thanks
 

ion2211

Registered User
Hi

sounds good - what are you actually having done and what are replacing the back boxes with - links et al

many thanks

Both back boxes including tail pipes are being cut off and replaced with straight pipes and new tips (slightly larger 3.5” inch tips)

A friend had this done on his A5 and I will be getting the exact same, see pic below:

FFEA2_FBD-6_ED7-4_D3_A-9488-_F7_E356_DF5_F5_C.jpg
 

jetty

Registered User
I would hold off on this for a while. I've heard rumors that this may be an MOT fail from May - whether it will be a minor, major or dangerous I don't know.....but it's a diesel and we all know the government no longer likes these!
 

ion2211

Registered User
I would hold off on this for a while. I've heard rumors that this may be an MOT fail from May - whether it will be a minor, major or dangerous I don't know.....but it's a diesel and we all know the government no longer likes these!

I live in Ireland, they don't even check for DPF's here ... let alone back-boxes!

The only thing tested on a Diesel is a "smoke test"
 

ion2211

Registered User
Will you go on a dyno after?
I really don't see the stock exhaust as bottle neck - I've tested it and found the back pressure totally acceptable with even 500hp.
The stock exhaust is actually very nice.

No I wont be going on the Dyno. I am just doing it for the sound... but any performance gains would be welcome :D

My friend who who got the same job done on his A5 will be dynoing his soon, so it will be interesting to see how much it puts out over the factory quoted BHP figure. (His is a 2.7 TDI A5)
 

ion2211

Registered User
Interesting update regarding removal of back-boxes..

My mate with the A5 2.7 TDI which has back-boxes removed just had his car remapped and on the "pre-remap" Dyno run, the car put out 183Bhp (I believe they are 187Bhp standard)

... So it would seem like removing the back-boxes gains you nothing in terms of BHP so it's interesting that other people are claiming gains of 20Bhp.

Either way, he got a got a significant increase in power following the Remap (246Bhp & 380Lbft) which was more than expected so maybe the backboxes being removed helped get more power out of a Remap.
 

holmefield

Registered User
i have in the last 6 weeks done the back box deletes on my A7 3.0 litre Tdi, and honestly theres VERY little difference in sound.

I did mine as i wanted different tips but didnt want to wreck mt standard back boxes, so i had mine removed and had straight pipes made with special collars made so if it comes a cropper @ mot time the back boxes just slot back in..
 

bobby singh

BSR
VCDS Map User
Gold Supporter
Interesting update regarding removal of back-boxes..

My mate with the A5 2.7 TDI which has back-boxes removed just had his car remapped and on the "pre-remap" Dyno run, the car put out 183Bhp (I believe they are 187Bhp standard)

... So it would seem like removing the back-boxes gains you nothing in terms of BHP so it's interesting that other people are claiming gains of 20Bhp.

Either way, he got a got a significant increase in power following the Remap (246Bhp & 380Lbft) which was more than expected so maybe the backboxes being removed helped get more power out of a Remap.

I'm glad you have seen yourself gutting back boxes gains nothing.
As for 246hp from a 2.7 - its average increase. I've done them to 265hp 600nm with 1756vk (stock 2.7 unit), thats with stock exhaust with dpf gutted.

Cheers
 

bobby singh

BSR
VCDS Map User
Gold Supporter
i have in the last 6 weeks done the back box deletes on my A7 3.0 litre Tdi, and honestly theres VERY little difference in sound.

I did mine as i wanted different tips but didnt want to wreck mt standard back boxes, so i had mine removed and had straight pipes made with special collars made so if it comes a cropper @ mot time the back boxes just slot back in..

MOT doesn't care for back boxes - they are concerned with dpf.
 

The Jargen

Registered User
i have in the last 6 weeks done the back box deletes on my A7 3.0 litre Tdi, and honestly theres VERY little difference in sound.

I did mine as i wanted different tips but didnt want to wreck mt standard back boxes, so i had mine removed and had straight pipes made with special collars made so if it comes a cropper @ mot time the back boxes just slot back in..

There is a notable change in sound, next time you car is regenerating. Drive under a bridge or in a tunnel. You'll notice it then.
 

ion2211

Registered User
I'm glad you have seen yourself gutting back boxes gains nothing.
As for 246hp from a 2.7 - its average increase. I've done them to 265hp 600nm with 1756vk (stock 2.7 unit), thats with stock exhaust with dpf gutted.

Cheers

Yeah that’s true. But I’m doing it for the sound as it sounds amazing with the back-boxes removed.

Will be getting the job done at the weekend :)
 

Craig Gordon

Registered User
Yeah that’s true. But I’m doing it for the sound as it sounds amazing with the back-boxes removed.

Will be getting the job done at the weekend :)

Any update on how it sounds? Looking to get this done with mine. Was going to go down the road of the whole dpf gutting but with the impending changes in MOT in May, I've opted against it.

Thanks
 

ion2211

Registered User
So, I got the back boxes removed at the weekend and also replaced the tips with slightly larger OEM style tips (3.5" instead of 3") and I have to say that I am very happy with the results!

Visually it makes for a nice yet subtle change.

The sound is just amazing with the back-boxes removed! It really brings out the purr of the V6 and there is a nice "bark" on a cold start. I always start the car with the door open and leaning out just so I can hear it better :)

From the inside, there is not much change to the sound, maybe a slightly deeper note when flooring it but it does not sound intrusive at all - its very very subtle.

The best way to describe the sound is that it now sounds more like a petrol V6 instead of a diesel.

As regards power, I'm not going to say that there has been a massive increase in power because my car is already pushing out 312Bhp - but it certainly feels less restricted and more eager to rev.

It feels a lot more responsive and it wouldn't surprise me if there are actually a few extra horses gained (maybe 2 or 3 at best).

I also seem to be getting better fuel economy ( I managed to get 6.9L/100km or 41mpg on a 30 mile round-trip by driving gently, something I never managed before)

I will try to record a sound clip but for the moment, here are some pics:

IMG_3474.jpg


IMG_3468.jpg


IMG_3470.jpg
 

LukeyC

Registered User
Love this - can you please tell me what parts are needed, and how much it cost all in?
 

ion2211

Registered User
Love this - can you please tell me what parts are needed, and how much it cost all in?

Thanks, I got this done at a specialist garage and it cost me €210 (so about £180)

Parts were supplied and fitted and old back boxes wrapped up and placed in the boot (in case I ever want to put them back on)

The garage I got this done in is a supplier of "LongLife Exhausts" and they have outlets all over the UK if you wanted to look into getting it done.
 

LukeyC

Registered User
Thanks very much, have e-mailed a few garages with a link to this thread to see whats around.

:)
 

LukeyC

Registered User
Well, I've been quoted anywhere between £300 and £500 for this, so it's going on the back burner for a while whilst I move house.

seems like you got a great deal!
 

corgiepup

Registered User
Looks great planning on doing my own during isolation after I finish work next week but am planning on doing my A6 c6 3.0tdi le mans Quattro that the back box can be put on again for MOT and then remove and put the straight through part with tail pipe on again I'll get pictures up when I get it done.
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Seanchadwick2k3

Audi A6 C6 2.0tdi 2011 Sline Special Edition
Probably the same as someone with a 3.0 TDI? I very much doubt this would do much on a TDI whether it be a 2.0 or a 3.0. Either way it's excess weight which isn't needed as those boxes are heavy and there are two and the TDI isn't much louder without anyway...
 

Willenium

Registered User
I'd like to get my rear boxes opened up and modified but so far nobody willing to do it. Could easily just have them chopped off and tips welded onto new pipework but if possible I would like to keep the boxes as the fitment is nice and it would be a stealth mod.
 

corgiepup

Registered User
I got my back box delete done yesterday turn out really good , sm well happy with that
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