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Escort Cosworth Tuning

The original big turbo T34 Escort RS Cosworth was built for homologation purposes to allow to compete in the WRC. When then required quota of 2,500 cars were built for homologation purposes Ford starting build the Escort RS Cosworth with a smaller turbo, the T25 as opposed to the T34 that was supplied for homologation. The T25 turbos had a lower boost threshold and felt more responsive for road use. However these smaller turbo cars are less tunable, read on for more details.

Escort RS Cosworth T25 Tuning Guide

The original Motorcraft clutch is not famous for it’s strength and when you put 50% more power through it, its going to have problems. Helix and Alcon both make upgraded items which will cover all all most the extreme outputs.

A common problem with the cossie is the nearside driveshaft popping out due to it being slightly too short. An XR4x4 shaft will cure this.

Escort Cosworth Engine Bay – Image source:

Escort RS Cosworth – Engine Management

Older generation Cosworths used Magnetti Marelli management whereas the T25 models came with Ford’s in house EEC-IV ECU, which, unfortunately is suited to big power upgrades. Owner looking for 300+bhp usually opt for the older L8 ECU. This could be argued as a backward step which is why the T25 cars don’t usually get tuned beyond the usual turbo back exhaust system and induction kit,

see also:
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Escort RS Cosworth T25 Tuning Guide

There are 305bhp “chips” on the market but these are usually a disappointment as the EEC-IV turbo map cannot be altered and therefore limits power to 265bhp. Given that the car has got 230bhp to start with, the cost of the extra 35bhp isn’t really worth it. The injectors are also application specific meaning the cannot be simply swapped out for bigger items.

It is possible to get around the EEC-IV problem but it involves throwing it and installing an aftermarket ECU. MA Developments can do the job and replace the standard ECU with an Autronic item which opens up a whole new world of tuning possibilities. After this the usual T34 methods are the same for the T25 so basically the fundamental problem with the smaller turbo items is the ECU which can make the initial steps on the tuning road relatively expensive which is why the big turbo models are more popular.

Escort Cosworth engine upgrade – Image Source:

Escort Cosworth – Suspension Tuning

When replacing the factory dampers the most common route is to upgrade to coil overs . Coil overs are available from the usual players such as Eibach, Spax & Bilstein. Uprated bushes are not a necessity.

Escort RS Cosworth – Brake Upgrades

Standard brakes are quite good but there are many upgrades available from AP Racing, Brembo and HiSpec to name a few.

Related links

RS Cosworth Breakers


Find performance parts on ebay

This page was last modified Jun 24, 2018 @ 6:16 pm

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