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Quote:

Originally Posted by powers1

BACK PRESSURE.You have noticed that the 3.0D exhaust system is straight through from the Turbo,Cat to the rear silencers!At the rear silencers,Bmw have installed a "back pressure" loop,meaning that you have a pipe entering
the silencer and this pipe does a 180 degree turn inside the silencer and comes out on the same side as the pipe entering,and then you see your downpipe.Now if one is to install a silencer that is more straight through ,which has a pipe entering one side and exiting on the other side ,you will loose "back pressure". Your car will feel like you have lost power at lower revs but you may gain at the top end because your exhaust gases will be flowing better.
The 4.8 silencers I fitted on mine do have a pipe entering on one side and then you have the tips on the other side.However,the pipes inside the silencer do a few turns before leading to the end tips,so although the design is different from the 3.0D silencers ,the Back pressure should be similar!
Another thing that effects back pressure is the pipe diametre.This is easiest perhaps to explain back pressure to you!....If you have a narrow garden hosepipe ,when you open your tap ,water flows with more pressure than a larger diametre hose!Its the same with exhaust gases,these flow quicker with a narrower pipe!If you increase the pipe diametre they will loose "back pressure".Here is the reason why I cut as much of the 63mm pipe of the 4.8 and used as much as possible of the 3.0D oem 51mm pipe.
Exhaust diametre is relative to engines size/power.If you increase your horsepower,you should also increase exhaust pipe diametre.Theres a formula for this.

Ok.Now its time for you to have a laugh at my photo editing skills( first time I did this and I am tired now).You asked me,why not on the twin ovals tips from your downpipes,well have a LOOK.................................... :D

Good info! I was unaware that the 4.8 mufflers had pipes inside which make a couple of turns, hence establishing some backpressure. I assume you have no performance loss then at all ?

Dont think anyone knows for sure what the internals of the 4.8 mufflers look like,unless of course,BMW!iI really would like to open one up and see for myself

I also dont know why Bmw changed the design of the 4.8 muffler in relation to the 4.6??The 4.8 muffler is much bigger,taller!
I can follow the flow of gases inside the muffler from the outside by touching the muffler and feeling which parts of it are hot!

the car actually feels "looser" and the sound at the back is very V8´s!!!!

Quote:

Originally Posted by powers1

the car actually feels "looser" and the sound at the back is very V8´s!!!!

looser = more vivid ?

Here is an idea for those wanting to add tips to your downpipes!They might also fit the 3.0i??.........................

http://cgi.ebay.com/ebaymotors/Merce...QQcmdZViewItem

Quote:

Originally Posted by Hans_ACS

looser = more vivid ?

quicker,swifter.........faster....

Ok been to the exhaust centre.
3.0D to have tips exposed they have to be welded on to the back box.
Can not extend the downpipes through the OEM hole.
Powers1 you were correct all along.. not sure why i doubted you ha.

anyway if you want to get tips showing they will be none functional and will be "tacked" on to the back box.

couple of queries.
1) what the hell is tacked on?
2) remember seeing somone with a pic of this done?
3) would it look silly?
4) been quoted £200 surely you can buy some chrome tips from ebay for £40 each and get some garage to "tack" them on?

anyone shed any more light on this would be much apprieciated

Thanks

Quote:

Originally Posted by demondali

Tacked on in their context means that they will weld the tips to the end of your back box with some metal brackets(tacks!).Providing they weld it properly, straight and dont leave the tips siticking too far out,it wont look too bad or silly because from most angles you will just see the end of the tips.
Because your oem pipes point down you will still have some exhaust gases around the area where you are going to weld the tips,so although your tips will be non-functional ,they will be somewhat realistic!
In fact,as I mentioned before,I now get a lot of condensation smoke with my 4.8 mufflers(didnt realise this before on my 3.0D because of the oem downpipes)!Should this continue to bother me,my only option is to do what your are contemplating!This way you have the looks but your still being ecological.

One more thing!Make sure that you are present when they align the tips?Thus making sure they are done to your preference.

Make sure you get the oem rubber trim for around the cover holes!
These shouldnt cost more than 20 quid and they add a nice finishing touch.
The part nos. are.51 12 7 010 123 and 51 12 7 010 124

power1, what exactly do you mean by 'condensation' smoke ?