[makkan00]

Guys
I am doing quad exhaust conversion on N47 520d along with M5 body kit.

I am with my installer.
He suggested that I should have two small boxes on each side to keep the back pressure, otherwise there may be negative impression on engine! He stated that it is relatively new car so no point of taking risk.

Just wondering what are pros and cons of having back boxes on diesels?

Any first hand experiences?

Thanks.

[mattyrallye]

where are you getting this job done??

Also turbo you want rid of back pressure i always thought but i could be wrong.

With a derv no real advantage, without the boxes you may experience more turbo whistle but not a real sound increase.

[makkan00]

Originally Posted by mattyrallye

where are you getting this job done??

Also turbo you want rid of back pressure i always thought but i could be wrong.

With a derv no real advantage, without the boxes you may experience more turbo whistle but not a real sound increase.

At my nearest place.
So are you saying that deleting back box is good for turbo?

[mattyrallye]

well don't quote me on this... but i always thought breather mods were good for petrol turbo... perhaps diesel is different but as i see it people see gains with EGR and dpf removal and this rids all back pressure.

Sorry i just wondered where as you are local... would be interested to see result once done.

[Dan-danGT]

I'm wanting to get my centre and back box removed, just to make it flow better. I have no Dpf I do have the box but no internals. I am of the impression diesels don't need back pressure some petrol engines do like 2 strokes etc.

[wolly440]

I've had the middle and rear boxes removed on m y E92 320d. Hardly any differnce in sound, slight burble when cold and a bit more turbo whistle, but you only notice that with the windows down. As for back pressure, the most restrictive part of your exhaust is the DPF. So if your leaving that in you will be fine with no boxes

[mattyrallye]

I am glad i am not the only one that thinks this.

Perhaps the fabricator is worried about noise increase?? However if you took your car to this place you must trust the work they do... therefore i suppose why question this guys integrity?

By all accounts he should be the expert.

[mattyrallye]

Perhaps Wolly440 is the man to listen too. His post does seem to confirm my original thoughts.

[wolly440]

Originally Posted by Dan-danGT

I'm wanting to get my centre and back box removed, just to make it flow better. I have no Dpf I do have the box but no internals. I am of the impression diesels don't need back pressure some petrol engines do like 2 strokes etc.

Thats gonna get loud with no DPF

[Dan-danGT]

I'm going to drop the exhaust, fit a pipe to aim the gases down then take it on a road test. That way I can see how loud it's going to be

[makkan00]

Originally Posted by mattyrallye

I am glad i am not the only one that thinks this.

Perhaps the fabricator is worried about noise increase?? However if you took your car to this place you must trust the work they do... therefore i suppose why question this guys integrity?

Thanks.
I have heard that diesel cars can have straight pipes.
Thats normal consensus.
However this guy said that its 2011 car and no point of risking with the back box.
But then they'll be adding two small back boxes to keep the back pressure similar to oem.
Practically there is some financial implication of two small boxes so
i wondered if its worth of having those?

I was under the impression that on diesel, dpf is restricting the flow and afterwards it does not make any difference whether you have the back box or delete. Back box is silencer and perhaps reducing the noise.

I am not mentioning these guy, as just in case they are wrong and don't want to give them negative publicity.

They were highly recommended to me and have done some work on my friend's car.

I am interested to know normal consensus here and what others think.

[makkan00]

Originally Posted by wolly440

Thats gonna get loud with no DPF

I thought diesels never get loud?

[mattyrallye]

Thats a shame, was interested to find out who... so long as it isn't Elite in essex you will be fine.

Well lets go another route, if a back box wasn't important why would BMW waste money on every car they make putting them on?? Surely if that was the case they would make a straight pipe and save the money...

Im not really helping here am I!!??

[Somerset Jim]

Originally Posted by makkan00

I thought diesels never get loud?

Diesels can get loud. You can hear an unsilenced diesel boat from miles away when I'm out fishing. If it's silenced then it's a lot more difficult to hear by comparison.

I can only presume that it's the same for cars.

[makkan00]

Originally Posted by mattyrallye

Thats a shame, was interested to find out who... so long as it isn't Elite in essex you will be fine.

Well lets go another route, if a back box wasn't important why would BMW waste money on every car they make putting them on?? Surely if that was the case they would make a straight pipe and save the money...

Im not really helping here am I!!??

No mate.
Its not Elite.
Was going to consider them for springs installation but .... Are they not good?

Well you made a point as why bmw puts boxes on diesel cars?

To me difference with or without boxes is £100.
Choice was mine and guys suggested to have back boxes.
I opted to have them as can't risk the car.

There are very knowledgeable people on this forum and discussing it as if I ever ho through the same position next time, I will be more informed.
Same goes with other forum members.

[wolly440]

I got mine done at Cybox in Bromborough. They had my car for 2 days testing for a off the shelf exhaust to sell. They said that the middle section made no difference to ths sound so they removed that too. They also said that if I ever get the DPF removed, they would fit a middle box free of charge

[makkan00]

Originally Posted by wolly440

I got mine done at Cybox in Bromborough. They had my car for 2 days testing for a off the shelf exhaust to sell. They said that the middle section made no difference to ths sound so they removed that too. They also said that if I ever get the DPF removed, they would fit a middle box free of charge

Any performance gains?
Will be very difficult to say.

[makkan00]

Originally Posted by Somerset Jim

Diesels can get loud. You can hear an unsilenced diesel boat from miles away when I'm out fishing. If it's silenced then it's a lot more difficult to hear by comparison.

I can only presume that it's the same for cars.

May be jim.
Never heard a loud diesel car though (referring to e9x).

[dy63]

ive never liked the fact of remove back box. keeping them on just seems more oem to me and more factory like. without back boxes i do hear more turbo whistle which to me is very annoying. i would ask him to keep back boxes...but maybe without them your exhaust might make a little scream if thats what you want

[mattyrallye]

The way i see it BMW do so you may as well do too!

As for Elite, i believe the tyre department to be ok but i wouldn't touch them for exhausts... when my friend got his 206 gti 180 done there we ended up in the loft of the place choosing centre boxes and a back box for the fabricator. I got the impression the guy could weld but knew NOTHING about exhausts. I had my last exhaust made at wallington long life and the guy knew exactly what he was doing. Even got me the sound i wanted...

However i wouldn't go on my reviews pal, i seem to have bad luck wherever i go. AMD Essex are supposed to be a very reputable firm but they fried my ECU on my 306 Rallye and never paid for it. I seem to get bad luck wherever.

Mate have you tried PMW ltd?? i went there with my old 320d and had the swirl flap removal done. I was pretty impressed with the attitude and work done there.

[makkan00]

Originally Posted by cupraraj

ive never liked the fact of remove back box. keeping them on just seems more oem to me and more factory like. without back boxes i do hear more turbo whistle which to me is very annoying. i would ask him to keep back boxes...but maybe without them your exhaust might make a little scream if thats what you want

I would like have a bit more noise.
It is not going to make any difference in f10 cabin though but good for others.
However not at the expense of any risk to engine components.

[mattyrallye]

Good luck... would love to see pics.

Am i right in saying you are the king of coding?