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WR 4" and 6" Sport Air Filters

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  • Optional plate to relocate voltage regulator for clearance.
  • Optional plate to relocate voltage regulator for clearance.
5.50 LBS
Calculated at checkout

Product Description


WR 6" Sport Air Filters

These are the newest air filter kit for the Weber 40 and 44IDF from WR.  The base and top are machined from 6061 aluminum and the screen is an aluminum stamping that gives a look very similar to the original Knecht filters, but that's the only similarity. The WR filters use a K&N type inner filter element which is far superior to the original oiled wire mesh of the Knecht, and they incorporate a set of 4" tall air horns to optimize the resonance length of the intake on the 356 and 912. This optimum length has been dyno proven to increase power in the mid range. The spread of this increase is between 3000 and 5000 rpm depending on the camshaft and engine size

 The dyno test shows the results on a 1720cc engine that was built by a local SoCal repair shop. We tested the engine on our Superflow 902S engine dyno and the results are impressive. The first run was with adapters and the stock SC/912 Knecht filters; the second test used our new WR filters but with the shorter 2.25" air horns; the final test was after switching to 4" air horns. We checked the fuel curve at each test, and the two tests with air horns actually required a slightly larger air corrector jet because the fuel stand-off was being captured better by the air horns. Oil temps and head temps were also identical. 

The test driving in the car also confirmed an increase in throttle response and power in the mid range. Often, an increase will show up on the dyno but is not really noticeable in the car...the WR filters give a noticeable improvement in power. They also give a more throaty sound to the intake. 

The WR 6" Sport Air Filters are standard on our WR 1.9 and WR 2.2 engines, but this was the first time we tested them on a stock 1.7. The results are equally impressive.

They fit perfectly on any 356 Coupe with Webers, either 40IDF or 44IDF, even when using the WR Insulators. They also fit on all T6 Cabs and Roadsters with the optional voltage regulator relocation plate. On early Cabs, Roadsters and Speedster they require elimination of the WR Insulators and the relocation plate.

We also now offer a 4" version that still outperforms the stock Knecht filters, and works easily on all models including 912.







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Product Reviews

  1. An excellent finishing touch 5 Star Review

    Posted by on 16th May 2019

    After a total engine rebuild complete with new Webers it didn't make sense to compromise on the air filters. The WR 6" filters fit perfectly and let the engine breath the way it was meant to. And they look great too! That's why I always trust Willhoitt's. Thanks to Mike for the great service too!

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