Debunking Downpipe Myths

We all want bang for our buck,  pounds for our pennies and miles from our cars. 

Many of us are also after more umph and roar from our exhaust.

So what’s the perfect part for both?

A downpipe is a good place to start, more sound, more roar and more power, means it definitely sounds like a good way to go.

The question is, how?

In this blog we will look at what a downpipe is, how it works and common assumptions made about downpipes.

What is a downpipe? 

A downpipe for your car is a part that connects to the turbine housing and the catalytic converter; unless it has a decat.

In which case it will connect to the decat pipe, and has a primary job of directing gasses from the vehicles turbine housing into the exhaust system.

The downpipe is made to move exhaust gasses throughgthe system in the most effective way possible.

This is by minimising obstructions and collisions.

They can also increase the sound of your car and the pitch due to more effective gas flow.

EP Adam S, Corsa & Astra J 1.4T Decat Downpipe

What does a downpipe do? 

Its job is to move the gasses through to the exhaust system as efficiently as possible to improve the performance of the vehicle.

The more gas that leaves the turbine housing, the more air the engine can breathe in.

This equates to more power.

A turbo charged car typically will benefit from an aftermarket downpipe due to the  improvement of the flow of gasses into the exhaust system and consequently gaining a potential 10-20bhp.

So, how does an aftermarket downpipe work?

If the exhaust downpipe isn’t smooth inside and a consistent diameter then this can obstruct the flow of gasses and reduces the effectiveness of the downpipe.

With smoother pipes there are less restrictions on gas flow, this means the turbo can spool up faster which equates to more power and/or better fuel economy.
Our downpipes are TIG welded and back-purged to ensure the most efficient transition of gasses to produce maximum power.

Do downpipes make a car louder?

Exhaust downpipes are a great addition to your car for more power and when made with meticulous design in mind can improve the performance.
Fitting a downpipe will almost always increase the sound of your car and will usually result in a more aggressive sound.
This is due to the reduction in back pressure in the exhaust system which allows the sound to travel without interruption or collision.

This is when you can hear that roar and feel that rumble coming from your exhaust.

Will an after market downpipe fail an MOT?

Depending on many factors, including your car, exhaust system and the downpipe you purchase impacts on whether or not a downpipe will cause an MOT failure.
Fitting a stainless steel decat downpipe will almost always bring on your engine management light, this is an MOT failure.
This is due to the smoother extraction of gasses from the turbine housing into the rest of the exhaust system without processing through the cat which reduces emissions
Smoother and more efficient gas removal results in more power. 
But, as a result your car can produce higher emission levels that take them over the legal limit which will cause an MOT failure.
Buying and fitting a lambda spacer may prevent the light coming on but to ensure that the light stays off you will need to have a remap done.

If more power is what you are after and a downpipe doesn’t feel like it will give you enough growl and enough power, then you may be looking at a full exhaust system.

There are a few to choose from such as catback exhausts that connect to the catalytic converter or turboback that connects to the turbo.

To find out more about which exhaust could be for you and what the differences are, check out our After Market Exhaust Blog here.