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Engine guides and mods

451 Euro4 Exhaust Retrofit

The Euro4 and Euro5 exhausts are very different but it's easy to retrofit.

Modification Details




Euro4 And Euro5 Exhausts

The emissions standards in Europe get tighter and tighter every few years.
Each standard is given a number to supersede the previous.

European Emission Standards call for better, cleaner engines. Generally this involves adding
more filtering on the exhaust in the form of DPF's for diesels and more CATs for petrol engines.

However, this does NOT make the Euro5 exhaust worse than the shorter Euro4.
Quite the opposite in fact. Site reader Thomas found that fitting a standard (non Brabus)
Euro4 exhaust to his Euro5 car caused it to go into safe mode. So whether the standard
Euro4 exhaust is more restrictive and causing in increase in boost or less restrictive and
allowing the turbo to spool up for a higher boost, you don't want your car going into safe mode.

Currently we have no proof either way.

What Is This Page Showing Then?

It is just proving that the Euro4 Brabus exhaust can be fitted to a Euro5 turbo 451.
I fitted this exhaust as an upgrade to the standard exhaust and have had no issues.
This is just to show you what parts you need to fit a Brabus Euro4 to a non Brabus Euro5.

The older Euro 4 exhaust manifolds was on the right but the Euro 5 exhaust manifold is on the left.

Euro4 Exhaust

You can see the very basic flow pattern for the Euro4



Euro5 Exhaust

In the Euro5 exhaust the gasses have to travel 50% further and pass through more filters.



Power Increase From The Factory

All Euro5 turbo 451 smarts that are documented as leaving the factory with 84bhp actually
contain the Brabus remap so output closer to 96bhp. The 45bhp diesel is closer to 50bhp,
the 54bhp diesel is closer to 60bhp. The non turbo fortwo don't see much of an increase.

Fit A Euro4 Exhaust To A Euro5 Smart 451

The idea is to take off the Euro5 exhaust as I managed to pick up a cheap Brabus Euro4 exhaust.

This is a Euro4 Brabus exhaust. Not that much better than standard and cheaply made.



I sandpapered the body and sprayed it with several coats of VHT (very high temperature) paint.


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