Graham contacted us to discuss adding a set of Throttle Bodies to his Caterham Seven 310 which is powered by a 1.6 Litre Ford Sigma Ti-VCT engine.

The first port of call before diving into this Caterham Sigma Throttle Body Conversion, was to install the Caterham on the rolling road to see what power the car produced. Graham keeps the car in impeccable condition and it had very low mileage so we expected the engine to be on the money with its claimed power and torque outputs.  After the initial power run, the car produced 155.7HP and 123.1LB/ft which was slightly above the Caterham quoted standard.

We then got to planning and agreed with Graham to build the car a bespoke engine wiring loom to go with a new ECUMaster Classic engine management system and a set of Jenvey Throttle bodies. Graham also wanted us to install a lightweight flywheel and new performance clutch.

Engine Management

This Caterham Seven came equipped with an encrypted version of the MBE 959 ECU as standard. We opted to move away from this ECU due to the desire for an engine management package with complete freedom and due to the limited support available with the encrypted MBE ECU. We opted for the ECUMaster Classic ECU with a bespoke engine wiring harness which we designed and hand made in house. The main benefits of the ECU Master Classic  lie in its extensive list of standard features such as on-board wideband lambda control, knock control, engine protection and monitoring strategies, Drive by wire and switchable maps to name a few.  This ECU also has the ability to be expanded and can work with other ECU master accessories such as Dash displays, PDUs, Data Loggers plus many other accessories.  More crucially the open software on this ECU meant that we could offer graham remote support should he ever need it which was just not possible with the encrypted MBE unit.

Throttle bodies:

Graham wanted to upgrade the stock inlet manifold for a set of Throttle Bodies and the Jenvey 42mm Direct to Head Throttle Body kit was the perfect solution. As Graham did not want to cut the bonnet, we opted to run a shorter trumpet than is normally supplied with the kit. Along with the shorter trumpets, we also ran a set of medium length flow matched Bosch 350cc injectors to give us the required clearance between the fuel rail and air filter back plate. Even with the shorter trumpets, we still didn’t have a lot of clearance under the bonnet so we opted for a slim line ITG Air filter & back plate.

The final two pieces of the jigsaw were the coolant pipes and fuel lines. An adaptor was purchased to allow the original fuel line to connect to the Jenvey fuel rail.  The top coolant pipe which runs between the top of the radiator and thermostat housing  fouled  the newly installed throttle bodies so a new pipe was fabricated and installed running neatly along the side of the chassis rail and giving plenty of clearance to the throttle bodies.


By adding a lightweight billet steel flywheel, you reduce the rotational mass of the engine which allows the engine to rev more freely improving throttle response. We have experienced issues before with super light flywheels affecting the idle stability so opted for a TTV Racing flywheel which weighted a total of 4.3KG (compared to the original at 7.1KG). This Caterham had an AP Racing organic clutch as standard but these have since been discontinued. We opted to install a Helix Autosport equivalent clutch kit with a new replacement slave cylinder.

Caterham Sigma Throttle Body Results:

We saw a peak power increase to 175.7BHP and 132LB/ft with improvements throughout the rev range from 3600RPM to 7800RPM in power and torque. Along with the power improvements, we were also able to achieve a more stable idle, a proper cold start strategy and general improvements to the driveability. The graph below shows the initial power run in red and after the tuning and throttle bodies’ in blue.

We are able to reproduce this kit for any variant of Caterham, Westfield or Kit Car with any variant of engine and level of Tune. Please Contact Us for more information, prices and potential gains.

Caterham Seven Sigma Throttle Body Conversion Results from Northampton Motorsport