[Diesel Flash]

Ive recently decided to go for a quad tailpipe setup on my 2011 520d, i thought i would just go through my experience to try and help others as couldnt find much on the subject.

Really not rocket science to do what i did however, by prepping the rear underside to accomodate a second silencer will save the custom exhaust fitter time and me money in the process.

unfortunately i wished id of taken more pics but its generally quite a simple process.

1. first i began by popping out the 5 clips on the underside of the Oem diffuser this is done by prying the center of the clip out/downwards, some do take some force to shift but will eventually come free. pic attached of offending clips.



2.Once all five clips are out you should be able to pull oem diffuser off, with a firm pull. note diffuser is still retained by several short tabs around edge but they will just pop out when abit of brute force is applied.



3.Next is to remove the underside plastic covering directly behind the rear wheel, drivers side, this needs to be removed to allow access to fit the custom second rear silencer, sorry i cannot recal the exact nut sizes but they are something like m6, and there are four of them. again sorry i did not take pic of location but from memory there were 3 toward the front of car and 1 bolt securing it to the rear bumper support. here is the panel in question.


4. Next up is the cubby box that is found in the boot drivers side, and it drops down behind rear wheel here it is

there are 6 rivets holding it into place, you can either drill these out however space is limited or i chose the chisel and hammer option from below, but please bare in mind i had car up on a ramp so again which ever option works best for you, with these rivets gone the box is free to move around, and you may think you would be able to just slide up and pull out from within the boot, this was not the case i spent a good half hour taking components off from within the boot to allow cubby box to slide out, it just wasnt playing ball. i ended up cutting my loses and cut box out as i didnt intend on keeping. it is actually quite brittel and once i taped with a hammer a few times i persuaded it to come free...'apologies for the butcher moment but if anyone manages to do it without breaking im all ears'.

5.I then went on to make a template out of 1mm thick galvanised plate not to tricky just use an old bit of cardboard and when desired size just cut metal and mark holes from underneath, drill them out and then either rivet back in or nut and bolt, i chose the rivet option also appling a generous amount of automotive silicone to the edges and outerlip.

once in i left silicone to set for over an hour and coated the underside with red oxide paint to prevent any corrosion, shultz underseal etc will do the same job.


6. Finally whist waiting for silicone to set, i fitted the new diffuser, I chose an frp wrapped in carbon fibre jobbie from good old taiwan £220 delivered, as i personally thought it complemented my sophisto grey f11 and i also have the Vorsteiner rep carbon front splitter.
Now its pretty much a case of reverse the removal, however if like me your diffuser isnt 100% the right curvature of the bumper you have to improvise a little, instead of added the plastic clips back in i chose to sandwich rear diffuser and bumper mount with m6 bolts and large washers, this also provides better secuirty in my opinion and every bolt can be easily tightened as shown

i also cut down some large washers to retain the very edge of the diffuser and prevent it from popping out, and yes my car is stinking and yes it all looks heath robinson but the end result you cant see them.


Overall im pleased with the outcome and have done over 200miles in bad weather and everything has held up, exhaust is booked in to be done next week and shadow chrome tips to be fitted as shown




Hope this will provide someone some help if attempting a quad conversion. please note i imagine the f10 to be the same but cannot confirm.

[MrPogle]

Nice job. Looks very neat.

Your second pic still has your registration visible.

[Diesel Flash]

Originally Posted by MrPogle

Nice job. Looks very neat.

Your second pic still has your registration visible.

Thanks, yes did notice, ill let it slide this time.

its abit of a sketchy write up to be honest and apologies its my 1st proper post so had a couple of teething probs.

Looking back i wish i had taking better pics, but i guess its a start.

Ive used the forum so much over the last couple of years and never contributed anything to it so thought id start, somebody might find something usefull in there lol.

[mobilejo]

Good writeup.

I want to go quad on my 535d but its much easier for me than it was for you

[Diesel Flash]

Originally Posted by mobilejo

Good writeup.

I want to go quad on my 535d but its much easier for me than it was for you

Yes i imagine you have no cubby box to blank, or lower panel to take off, which will definately speed things up.
The guy im using has quoted around the 180 mark for back box and custom fabricated pipework, im providing the tailpipes which were 85pound. As soon as its done i will upload a few pics

[mobilejo]

Yes I have dual backboxes but with single exits, so all I need is 2x single to twin tailpipes. I was actually looking at those same ones that you have posted so i'll be keen to see the end results!

[M5TouringFan]

Great work and very interesting about the RHS storage box. I was wondering how to deal with that!!!

[Diesel Flash]

Originally Posted by M5TouringFan

Great work and very interesting about the RHS storage box. I was wondering how to deal with that!!!

Thanks, just covered a liitle over 400miles and seems all ok, no leaks, plate still secure etc however for extra piece of mind i think i may use some flashing tape from internally just to really make it water tight, abit overkill-but dont fancy a damp fuse box

[eliw]

Have you had the quad pipes fitted ? I want to do the same thing but not quad just 1 pipe on each side as in the 535 .... Any advice as to where I can take it in the SW London/M3 area ??

[Diesel Flash]

Originally Posted by eliw

Have you had the quad pipes fitted ? I want to do the same thing but not quad just 1 pipe on each side as in the 535 .... Any advice as to where I can take it in the SW London/M3 area ??

Car is going in thursday so will hopefully get some pics on thursday evening of conversion as long as all goes to plan.

By the way, just a note, you do not need to remove cubbybox if you do not want a second silencer, which may i add you do not need as it is only purely cosmetic. Straight pipe may be the way i go as funds are dwindling at present.

Sorry from wales havent much idea about london garages, someone will know of a place on here im sure

[eliw]

Without the second silencer it will look unbalanced methinks. So will definitely add one to the right hand side as well.

[brad850csi]

off topic slightly, are those F10 M5 wheels? how do they fit at the front?

[DutchM550d]

Thanks for the write up, I played around with this idea for a while but due to lack of time I didn´t research the whole cubby thing so thanks now by adding another backbox do you have any loss of performance? can you post some pictures from underneath with the finished product

[remmib]

Originally Posted by brad850csi

off topic slightly, are those F10 M5 wheels? how do they fit at the front?

They're Avantgarde M5 replicas.

[Diesel Flash]

Originally Posted by remmib

They're Avantgarde M5 replicas.

Yeah around £6k cheaper

[lsturbointeg]

Awesome write up!