H2 Motorsport Wiring Loom

The Factory Loom Cannot Come With You

This is the point at which a large proportion of H2 conversion projects stall — usually with the engine already in the car and the budget already spent.

The motorcycle loom and ECU expect to see a motorcycle. The immobiliser and security integration will not permit the engine to run without motorcycle-specific components present. Throttle actuation is ride-by-wire and has to be correctly reproduced. Motorcycle sensors and connector standards are not always appropriate to a car's vibration, heat and moisture exposure. And none of the things a car actually needs — cooling fan control, fuel pump control, dash feed, warning strategy, data logging — are provided for in any usable form.

Removing the factory electrics entirely is not a shortcut taken to save effort. It is the only route that produces a car that starts reliably, runs predictably and can be diagnosed when something is wrong.

Built to Your Installation

Every loom is made to order. Rather than supplying a fixed harness with generous slack coiled up behind the bulkhead, we build to the distances in your car: you specify where the ECU sits and where each ancillary lives, and the tails are made to those lengths.

That matters for more than tidiness. Excess loom length adds weight, creates chafe points, complicates fault-finding and gives you somewhere for water to collect. A loom cut to the car is lighter, easier to route, easier to diagnose and considerably better looking — which, on a car where the engine bay is on display, is not a trivial consideration.

ECU choice is yours. Tell us what you are running, or discuss it with us first via our ECU options, and the loom is built to terminate correctly for it.

Launch, Paddle Shift and Traction Control

The engine harness, at £2,220 +VAT, is complete in itself: everything required to run the engine, terminated for your ECU. It also carries three dedicated connectors, ready to accept the launch, paddle shift and wheel speed harnesses. Each of those is a separate plug-in harness, so none of them has to be decided on the day the loom is ordered.

Retro-fitting functions to a finished loom normally means splicing into a harness you paid to have made properly, or building a second one. Here it means plugging in a connector. Order the options with the loom, or add them later as the car develops.

The paddle shift harness (£420 +VAT) brings shift control into the same loom rather than running as a separate parallel system — fewer connectors, fewer failure points, one harness to diagnose. The launch harness (£336 +VAT) plugs into the main loom in the same way.

The wheel speed harness (£360 +VAT) is what makes full traction control possible, and what makes launch control meaningful rather than nominal. On an engine with this much torque in a light car, that is not a luxury feature.

Engine Variants

Looms are built for the supercharged H2 family. Confirm your engine variant when ordering — the variants differ in specification, and the loom is built for the engine you actually have rather than for the family in general.

If you are unsure which you have, our H2 engine reference explains how to identify one properly. The engine number prefix alone will not tell you, because it is shared across the whole family.