Honda S2000 EVAP System Delete with Fuel-Tank Vent Valve

The delete depends on a single specific part: the Newton TPV8 in-line pressure-relief vent valve. It is sold under several retailer brands, most commonly Mocal, but every version is stamped Newton and functions identically; only the printed markings have changed over the years. Expect to pay roughly $70 to $90 shipped from UK suppliers. Avoid US resellers that mark the identical valve up to nearly triple that price. The valve has an 8mm (5/16 inch) nipple on its atmosphere side that will accept a breather filter.

A modified tank can hold significant pressure. Before pulling the final line off the tank, loosen the fuel filler cap to bleed off any built-up pressure; owners who skipped this reported a loud hiss of pressurized vapor when the last line came free. Work in a well-ventilated space away from any ignition source, since fuel vapor will be released during the job.

In the engine bay, locate the purge solenoid bolted to the driver-side frame rail. It connects by hose to a T fitting on the intake manifold and to a hard line that runs along the underside of the car to the rear. Unbolt and remove the solenoid and its hoses. Cap both now-open ports on the intake manifold using 3/8 inch or 5/16 inch ID vacuum caps. The hard line will be open at both ends once the rear components are gone and does not strictly need capping, though a cap on the front end keeps debris out.

Raise and support the rear of the car on jack stands. Remove the charcoal canister along with all of its hoses, solenoids, and brackets. Also remove the black metal heat shield beneath the canister, which bolts to the canister bracket and the rear subframe cross member. Keep the removed parts if you may want to reinstall the system later; the full assembly weighs roughly 10 to 15 pounds with a dry canister.

With the canister gone, two lines remain coming off the fuel tank. The wider plastic hose, the one using push-lock fittings, serves as the vacuum feed: it only admits fresh air into the tank to replace consumed fuel. The narrower rubber hose is the tank vent line, which expels excess vapor and pressure. Note which is which, because the check valve goes on the vent line only. The rubber vent hose is the one retained by a factory spring clamp rather than the thin push-lock clips.

Connect the TPV8 to the end of the rubber vent hose where it previously joined the EVAP system, reusing the factory spring clamp. Orientation is critical: the end whose groove sits closer to it goes toward the vent line, and the opposite end faces atmosphere. Installed backward, the valve will not regulate tank pressure. Fit a K&N 62-2470 breather filter onto the valve's 5/16 inch atmosphere nipple so the outlet stays clean while still venting freely.

The corrugated plastic vacuum hose that admits air into the tank should be left open to atmosphere but shielded so nothing can be drawn inside. Fit a K&N 62-1370 breather filter, which has a 1 inch flange ID, over the plastic shell at the end of the hose. As a low-cost alternative, wrap foam around the opening and secure it with a zip tie. Do not seal this hose closed; the tank relies on it to draw in replacement air.

Anchor the assembly using two of the four now-vacant bolt holes that the charcoal canister once occupied. Secure the valve with a 1.25 inch ID stainless cushion clamp and the corrugated vacuum hose with a 9/16 inch ID cushion clamp. Supply your own stainless bolts, because the factory canister bolts and washers are too wide to seat on the cushion clamps. Route the hoses so the filters point downward or sideways, away from road spray.

A separate plastic nipple on the subframe once carried vented pressure away from the canister by hose. Its outside diameter is approximately .700 inch. Cap it with a Dorman 02251 coolant bypass cap, which is advertised as 3/4 inch but measures about .690 inch ID and seats snugly over the nipple. This step is cosmetic finishing rather than functional, since the nipple only ever released pressure, never liquid.

Three connectors are freed by removing the solenoids. For a tidy result, unwrap the factory loom tape, de-pin the connectors so the wires pull out of the factory grommet without cutting it, cover the exposed pins with heat-shrink tubing, bundle the wires, and push them back into the body cavity. Blank the empty 1.5 inch ID grommet hole with a Caplugs BPFE-39MM plug to seal the body and keep the wiring out of the weather. A quicker option is simply to bundle and zip-tie the harness to a hard fuel line.

Start the engine and let it run. As fuel is drawn from the tank, air enters through the vacuum hose and pressure slowly builds until the TPV8 opens to relieve it, then reseats; this shows up as a faint intermittent hum lasting several seconds at a time and a light vapor haze at the filter. Any fuel smell at the outlet should be minimal and dissipate at once. After shutting off, loosen the filler cap: a small pressure release confirms the valve is holding the intended slight positive pressure, and a brief vacuum sound from the underside confirms the tank drawing air back in through the vacuum hose.