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Does anyone have any "real world" documentation or figures about the aftermarket K&N filter system sold by IAP?
My experience with Dyno results on Formula Ford motors back in the 80's showed that an increase of 2-3 hp was typical.
An increase that small on a production engine might give one a "psycological feeling" of being quicker, but in fact would be inperceptible except to the stopwatch. (Sort of a clean car runs better syndrome.)
Experiences anyone? Any dyno figures available?
Please let me know...I hate to spend $150 for a "feeling."

..Keeth Lawrence
84 Spyder

...."horsepower sells motors........torque wins races!"
 

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Keeth:
My only direct experience is on my 6 Cylinder Mitsubishi engine where I installed something very similar. There is a perceptible difference in throttle response, it ain't anything overwhelming and certainly not worth $150. The biggest improvement comes from the elimination of the stock Mitsu air box which is very restrictive. The Alfa one is much better.

I want to do something similar on my 92 spider but I wouldn't buy the one from IAP. The filter is a vailable from K&N for about $40. You just need an adapter to attach it to the MAS.

The other thing that I'd like to do is have the filter be situated low in the engine compartment, away from the engine heat where it will hopefully pull colder, denser air.

The thing is, with the way the series 4 air box is engineered, with a tube that sucks air in from the front of the car, I'm not sure that eliminating the air box would generate an improvement.

So all of that typing results in "I don't really know, but I've been thinking about it a lot myself" Okay, I'll shut up now.

PS - The mitsu does sound cooler with the K&N, there's a kind whoosh sound when you get on the gas and when you shut the engine off.
 

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I did this mod on my '85 Spider, but I made my own adaptors and brackets. I mainly did it because the stock filter is hard to find and expensive, and the cone filter is of course reusable. Also, you can get at your oil filter from the top with the big airbox gone.

With the mod I get a "throatier" sound and perhaps a slight, barely perceptable boost in acceleration - but certainly nothing worth the $150 price tag from IAP. I agree with Paradiso that the cone filter mainly draws in the hotter engine bay air versus the stock airbox which draws only cooler, fresh air from an inlet at the front of the car. My next project will be to fabricate a shield of sorts which will direct air from the original air inlet to the cone filter.

If you want to make your own adaptor, you can do so using an old fuel filter and a flat aluminum pot lid. It just so happens the original bosch fuel filter is aluminum and the perfect diameter for a 3" cone filter. Just cut the ends off, pull out the filter media and save the tube. Using the original airbox to MAS adaptor, you can trace the hole pattern onto the pot lid and then cut that out. Weld the resulting flat plate to the tube using a propane torch and those "magic" weld sticks (as advertised on TV!). You will also need to get some flat aluminum bar stock to hold up the MAS - but they are easily bent into the right shape to do this. This may sound like a lot of work but the filter tube was free and the pot lid was 25 cents at the thrift store - and you can get cone filters identical to the K&N type at Autozone for about $20.

If anyone is interested in this mod, let me know and I will post some pictures.
 

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John,

Bear with me as I don't know how to attach multiple images to these replies. This first picture shows what you need: old fuel filter, the new cone filter with 3" connector, pot lid, and the stock airbox to mass airflow sensor connector (which you dismantle from the airbox). By the way, this mod is easily reversible to stock as you don't modify any stock pieces.
 

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This picture shows how to trace out the adaptor plate pattern. After you drill the bolt pattern and cut it out of the pot lid - you can then weld it to the fuel filter tube. I cut the tube in half so I would have a back-up in case my first attempt failed. I used a product called "Mightyweld" which I bought at a gun show. The stuff "welds" using a regular propane torch and works with any non-ferrous metals. I've seen the same product advertised on TV under various other names. I suggest you weld on a concrete floor with a weight holding the tube onto the plate. This way the plate will stay flat when heated. I did mine in a vise and managed to warp the plate slightly forcing me to fabricate a gasket to keep a tight seal.

The last picture shows everything installed with aluminum bar brackets attached to stock airbox mounting holes to hold up MAS.
 

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Final picture.

If you have any questions, let me know. This is really shop class technology at it's best!
 

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Rick, thanks for the pix.
To me, this is the pinnacle of working on cars as a hobby. A little bailing wire, some JB weld and a little ingenuity. (and a yard sale pot lid) Awesome.
 
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