Theory:

The theory here is to increase air-flow to the turbo inlet. The factory air filter box is a pretty descent part even though it looks like a little garbage can. The inlet from the box to the turbo however is terrible. Lumpy accordion hose is not the key to smooth airflow! Can you imagine the flow characteristics of the air racing through the stock pipe?—Bernoulli would turn in his grave!

The open element filter gives a bit more intake sound and flows more air than the closed box. The filtering effect of these filters is advertised as "superior to traditional paper elements" as well. In addition, these filters last a lifetime and don’t need to be cleaned or changed.

Type:

I have a K&N filter with high-flow inlet pipe installed by Top End Performance since May 1998. They also offer the same pipe with an ITG filter instead—take your pick! There are numerous companies that offer open-end filters; but according to Steve, at Top End, these 2 are the best.

Cost: from Top End Performance:

K&N filter with high flow inlet pipe $175.00

ITG filter with high flow inlet pipe $199.00

You can check your local speed shop for filter pipe options. Many pre-fab filter-and-pipe units exist for other cars, but you will likely not find a better price and risk it not fitting right unless it is custom-made like the Top End job. The pipe can be custom color powder-coat painted for a few more bucks too!—otherwise it comes gloss black.

Installation:

The Top End package includes the choice of filter mounted to a custom-made metal pipe. This metal pipe replaces the lousy stock lumpy rubber hose that travels from the air filter canister housing to the turbo inlet. It is simple to install with merely a screwdriver. You must remove the old rubber pipe and "garbage can" housing and then affix the new pipe with a screw clamp on the end. It’s that easy!! The garbage-can is held in place by 4 bolts whose heads are beneath it. There are 2 sensor hoses that connect to the pipe as well, and they are easily affixed. Should you choose to purchase an air filter set-up somewhere else, you will need to make sure it fits into the engine bay area and has attachments for the sensor lines.

Use:

This is a passive device, just hook it up and you are in business.

Review:

I believe the filter and pipe to be an excellent upgrade for the Elan! Understanding aerodynamics, it helps me sleep easier knowing that terrible lumpy hose has been removed from my Elan. The air can now shoot straight in through the filter into the turbo. I believe (but did not do any scientific data gathering) that the decreased resistance afforded by the open-element filter and straight pipe translates into air-flow improvements significant enough to increase turbo response and therefore reduce turbo lag.

With the open filter installed I can actually hear the air being sucked into the turbo as it spools up under hard acceleration. Clearly you want the least flow resistance in this situation. The question has occurred to me, "Won’t the intake air be warmer flowing in through the engine compartment to the open filter than it is through the stock tunneling?" I cannot answer this for sure but I have done some crude measurements: Even in the heat of Summer with the engine running ‘hot’, if I stop the car and put my hand on the filter or inlet pipe, they feel ‘cool to the touch’, and the surrounding engine bay air is not hot either. We owe this to the superior heat-conductive characteristics of fiberglass over metal! The open filter sits on the stock intake tunneling as well and does have fresh air access this way. For those still not satisfied, there is a concrete way to test this question, which no one has done yet: hook a laptop computer up to the ALDL port and monitor the "intake air temp" sensor (MAT sensor) under driving conditions, first with the factory set-up and then with the open-element filter and straight pipe.

If you raise the boost on your Elan, enhanced air-flow is even more essential to be sure the turbo gets all the air it needs. It is impressive to hear the amount of air used by our little engine under high boost conditions. Even if you don’t opt for the above filter set-up, I’d recommend changing your factory paper air filter element to a Drop-in K&N Air Filter replacement filter—it will give better flow and will last a long, long time.

All and all, I feel the superior filtration and flow characteristics of the open-ended pipe set-up are well worth the expense for the improved boost response and mileage reaped from it.