Freeflow exhaust

[Peter Connan]

And compared to a freeflow, is it much louder or similar in sound?

Difficult to answer, as you must realize there is no "standard" for a free-flow. It can be whatever you ask for. It will definately be louder with no silencer, but how much depends on lots of factors.

[JoshJ]

SJC,

Why don't you start with the low cost approach to get to where you want to be. start by removing the catalysts and silencer boxes in your current exhaust. and replace them with pipe. then you have a straight pipe. if its to noisy then a bigger straight pipe wont work. ad 1 free flow box and see from there. when you got more or less what you want then you can go and redo the whole exhaust.

[ricster]

I disagree with what Peter said. For game viewing yes the diesel is noisy.... BUT its not the exhaust that is the noisy bit..... Its the motor itself. If I idle my motor the distinctive chugga chugga of the motor is heard over the noise out the exhaust.... even when I stand behind the Patrol. Is it noisier than a petrol motor .... oh yes, but idling along at 20-30Km/h on a game drive at 1200 rpm my Patrol is no louder than a stock 4.2 turbo diesel. If you want to quieten down the TD42 motor you will have to fit some additional Dynamat or similar material to dampen the sound.

[SJC]

The straight pipe conversion is defnately on my "to do list".

[Kagiso II]

Manne -- dis nou so belangrik, ik gaat in Ingrish skrywe:

When you change the exhaust on your vehicle, the LENGTH OF THE BRANCHES AND THE LENGTH BEFORE the "into one" is VERY importyant. If you have it too short yoiu loose oodles of TORQUE and you will NOT be a happy chappie.
If you want true low down the choke must be well designed.
Speak to a lot of manufacturers before you decide.
Make sure SAC Boksburg an VIPER Exhaust are on that list. The down pipes [branches] should be 76mm and then you choke down to 63 mm on a turbo diesel .. 4 cyl.
The guys with the Lexus engines with no torque [for a V8] .. that branch-to-combine is TOO SHORT

[Wilkie]

Hi guys
Kagiso,you are absolutely right,
With all my dealings and doings in the rally and racing cars ,the length of the header pipes is where the horsepower and torque curves lies,
I would advice people to phone Shaun or Etienne van de Linde or Freddie Pretorius from the BMW racing team ,if they want expert advice .These guys have paid there school ..!!!

[ricster]

I have branches on my Iron Maiden. Does it make a difference compared to a standard cast iron manifold?..... I have no clue. But my branches are no where near 76mm, in fact I doubt if they are even close to 63mm. At a push they are probably 50mm, and then they all meet into one cluster with the flange to mount the turbo onto. Is my set of branches correctly made .... I have no clue. The 6 lengths all look identical.

Maybe on a 3L, 4 cylinder the exhaust ( not down pipes )can be a 76mm reduced to a 63mm. Personally a cannot see why though, other than creating sufficient back pressure to prevent the turbo over boosting/spinning. But on a 4.2L, 6 cylinder the motor doesn't rev enough to overspin/boost.....hahaha.... and currently my turbo has a 2" outlet on the outlet side of the turbo which then increases to a 3" pipe and stays that diameter all the way.

Petrol motors work VERY different and need a little back pressure to gain the efficiency needed, but a diesel motor needs to breathe, but definitely a good balance needs to be achieved!!!

[Peter Connan]

Cedric, it's my turn to disagree with you. Petrol motors don't need backpressure, that's an old wive's tale.

I also don't think the individual branches should be anywhere near 76mm, they are talking about the downpipe,which is after the collection point.

[David M]

I am afraid I need to agree with Mr Connan here Cedric.

Recently installed 42 mm unequal length ceramic coated branches with 64 mm pipe with only 2 much smaller freeflow silencers fitted further back than normal.

The idea being to scavenge the air as quickly as possible and keep the temperatures as cool as possible.

Since doing it I keep looking for a 6th gear and fuel consumption is 11% lower even though I have been driving like a hooligan just to listen to the glorious sound.

On the equal vs unequal length branches - google it - it is still a bit of a dark art and not an exact science.

[Michael]

This is a topic that can last for weeks
In my opinion the branch length is really only relative to a natural asperation engine, on a turbo engine.....and specifically a diesel turbo I dont think it makes a noticable differance.

I also agree about the back pressure needed......its a myth. The faster air can get out the better, whether its a turbo, na, diesel or petrol.....