Amsoil Air Filter Page

We have had custom made hi-flow air filters made for the Lotus Esprit V8. As yet there is no alternative to the very restrictive paper filter that is provided from stock. They completely eliminate flow problems associated with the original filter units. They are fully "plug and play", fully oiled and ready to go. Just drop them into your original filter boxes, no cutting or compromizing retro-fitting required.

Our filters use a very high quality "racing" oiled foam core. It is designed as a one time replacement for street applications. They use a standard commonly available high grade Air Filter Lubricant, similar to the K&N variety. However, when the filter itself is compared to K&N, ours provides a lot more engine protection. The manufacturer recommends that they be cleaned and re-oiled after 25,000 miles of normal use. However, we recommend that you follow the standard Lotus maintenance periods for the stock air filters, as defined in your owner's manual, but instead of replacing them, simply inspect, clean, and only re-oil as necessary. They should be wet to the touch, but no saturated.

It has been determined that these filters do increase power by an as yet unmeasured amount. We originally installed them for their superior filter characteristics. The higher flow turned out to be an added benefit. After only 2000 miles with the original filters in Southern California under normal driving conditions, we noticed the original filters were cracking round the edges.

General Information

Oil-wetted foam improves performance and fuel efficiency by trapping more dirt and allowing better air flow. Washable and reusable for thousands of trouble-free miles. Reapply Foam Filter Oil after every washing.

Oil-wetted foam air filters keep oils and engines cleaner for longer periods with the most effective air filtration available today. They provide superior performance in all three critical areas of filtration: efficiency (dirt-stopping), capacity (dirt-holding) and resistance (air flow). These air filters are uniquely designed to hold wear-causing dirt while allowing only clean air into the engine for better performance, better fuel economy, lower exhaust emissions and longer engine life. Also, foam air filters are washable and reusable for thousands of miles of trouble-free service. Tests prove AMSOIL foam air filters have up to 350 percent greater life expectancy than competitive air filters.

These are "full-depth" filters that trap and hold much more dirt than do conventional "surface-type" filters. The polyurethane foam used in them is much thicker than the thin layer of paper used in conventional filters. The foam’s thickness allows for more filtering area and more capacity to trap dirt over a longer period of time.

Oil-wetted foam air filters allow more air into the engine than conventional air filters do and better maintain their air flow over the life of the filter. The intake surface of conventional paper filters quickly becomes obstructed with dirt, which impedes air flow. Foam air filters distribute dirt throughout the foam depth, allowing unobstructed air intake to the engine.

The flexible polyurethane foam provides a consistent, tight seal between filter and housing. Unlike conventional filters, which often fail to seal properly due to their hard rubber seal, the foam conforms to irregularities on the bottom and top of the housing, forming a tight seal when the housing is secured. Intake air must go through the filter before reaching the carburetor.

Service Life

The service life of these air filters can be extended indefinitely when the following procedures are performed. For normal driving conditions, AMSOIL recommends servicing the filters every 25,000 miles or one year, whichever comes first. We recommend following Lotus's normal maintenance program for the stock filters, but instead of changing them, simply clean and re-oil.

We have been running various prototypes for over 6 months now, and when they are removed for inspection, they are always still like new. The noise level is no different than that of the stock filters, and completely unnoticeable as far as we are concerned. Some individuals with standard filters do notice a difference for the better. I am told that the car "growls" a little more when accelerating from a standing start. The difference apparently can only be heard from outside the car. I personally cannot tell.

They are designed to be a direct replacement for the stock filter assemblies. This has actually proved a bit of a challenge from a design standpoint, as the V8 Esprit's very unique size and tolerances have to be replicated PRECISELY for an exact and effective fit. The is no room for error. There is a very small sealing area that has to be replicated exactly. So cutting up an off the shelf filter could be detrimental to your engines health. One cannot take any risks what so ever with air filtration to this very high tolerance V8 engine. We were very concerned when we read the filtration characteristics of other so called hi-flow filter systems, obviously forfeiting some filtration for flow!

Here are some photos of the prototypes and the Esprit V8 Filter Box for your inspection.

As you can see here there is a very small ridge that secures the filter to the main housing in the cars firewall. any filter designed must use this ridge to create a perfect seal from outside contaminants.

Notice the ridge that corresponds to the cover (shown in previous photo). This is only 1/4 of and inch wide. Not much room to work with.

This photo shows the snug fit of the filter to the cover. This ensures a good seal and optimum filter position in the firewall filter box. (This filter has been run for 3 months and is still like new)

This photo shows the zero tolerance fit required for the filter to be sealed in place. The sealing ridges for the cover can just be seen in this photo around the edge of the filter.

The production filters have a less dense metal backing support for maximum flow and a 1" core. The foam ridges have been removed for an even air surface to reduce turbulence. The sealing foam on the outside of the filter is 5/8" for maximum flow with a good air seal. Please refer to Figures 1 - 4 below.


Production Air Filter Figure 1	Production Air Filter Figure 2

Production Air Filter Figure 3	Production Air Filter Figure 4

We hope you find this page interesting. I think now they have to be specially manufactured by Amsoil using Part Number: S1984. They are well worth the effort.

Provide Full-Depth Filtration

Improve Air Flow

Form Tight Seal

Service Life