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Side Exhausts

I used to drive a Caterham and was given the following advice about side exit exhausts.

1. They are not an MOT issue. MOT is only concerned with how effective the silencer is and that it is suitable for the car i.e. a loud exhaust on a Caterham is OK, but not on a Sierra (unless you know a good MOT test centre).

2. Technically side exit exhausts without a heat shield is illegal as someone can burn themselves on it.

WRT a Caterham, if the car has cycle wings and no heat shield it is illegal i.e. people must be protected from being able to brush against the exhaust.

Info from Chris 28 12 02.


From memory the RC40 has an OD (outside diameter) of 1.75" and an ID (inside diameter) of 1.625".

Some have an ID of 1 7/8"; the end flanges are wider.

The angle between the boxes seems to match the standard exhaust (side exit RC40) as the tail pipe on mine fits up to the little cut out in the rear valence where the standard exhaust fits near to.

If the LCB outlet has a 2" OD and a 1.875" ID, it would fit inside a 2" ID link pipe. Apparently pipes with 1.75" ID's should have an OD of 1.875", so they should fit into an LCB.

Exhausts, theory of stainless steel increasing power

Yes, stainless steel exhausts are worse heat conductors than other metals, therefore keep the temperature of the gases trapped in, increasing the gas speed. That's also why its a good idea to have a cromed finished inlet manifold, it conducts heat poorly hence the exhaust manifold doesn't heat it up as much and the shiny surface helps reflect the heat too. Further more the very smooth surface eases the gas flow. I don't know how much HP can be gained, but who would throw away even just a few... A few + a few + a few = a lot...

NOTE: Since this article has been posted there has been comment about whether a smooth inner surface is advantageous.

Exhaust wrap

It may help to keep the hot air away from the carb intake, but that isn't why they wrap LCBs.

They do this to keep the gas temp/volume up so that it travels faster down the exhaust (more momentum).

My bonnet scoop was fitted to get cold air to the carb and force the exhaust heat downwards.

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