4 replies to this topic

[freddiebakermini]

Hi Everyone,

'

Looking to purchase 'Sportex Centre Exit Exhaust System 2" Twin DTM Tailpipe' from Mini Sport and can see that there are two options. Single silencer and double silencer. Could anyone advise me on what would be best?

I want for it to sound throaty with some decent volume but not antisocially loud. 

Exhaust in question is: PHBXT17DTM2 

 

Many Thanks

 

 

[Cooperman]

Those are often known as 'power-sapping noise boosters'
A far better choice is the RC40 with either a single or a two silencer boxes.
Final output diameter is 1.75" which is exactly right for a 1275 engine.
The twin output pipes reduce the exhaust gas velocity and thus reduce power by a few bhp.

[nicklouse]

As above don’t bother.

[freddiebakermini]

Hi guys, Thanks for the replies, I do very much like the look of the twin exit centre exhausts systems are there therefore any you would recommend? And when you say a few BHP how much are we talking? Would this be noticeable?

[Cooperman]

To explain in a bit more detail: the velocity of the gas molecules down the exhaust pipe is important as the speed gives an extraction effect. The Ideal gas speed should be at the engine speed which gives max power/torque.
If the gas velocity is too low the gas pressure in the pipe increases which reduces the extraction effect. This is called Bernoulli's Effect (Google it).
For a normal to mildly tuned 1275 unit, the best pipe diameter is 1.75". This should be the diameter all the way from the front pipe junction to the final outlet.
Thus a twin final outlet needs to be two small pipes of about 1.25" diameter to give the same cross-sectional area, but that would look a bit odd and gain nothing.
A twin exhaust with big diameter pipes will lose several bhp and increase fuel consumption although how much depends on the engine state of tune. On a 1275 expect to lose around 4 to 5 bhp.
And all for what? Perceived appearance and trying to sound like a 'boy racer'.
However, everyone can do whatever they wish to their cars. I am only explaining the engine science here.