Here is the stock 111R paper air filter next to the K&N drop-in option PN 33-2252. The filter was purchased for about 45 dollars over the counter. Our airbox appears to derive from one of the Toyota Matrix models using our engine, and not the Toyota Celica GT-S. Celica air filters are a couple inches smaller in the long direction.
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It's a bit harder to close the box on the K&N as the flange is a hair less compressible than the stock piece, but it can be done after a few attempts. You have to use one arm under the hood and one under the wheel arch to make it happen. You also have to be careful that the composite air tube that leads to the vent on the side of the Elise stays pressed onto the airbox entry tube. So check that before you wrap things up. It might be easier for some to close the box if you detach that tube...it is fastened to the top of the airbox with one plastic screw-exanded fastener.
I like to test stuff using onboard dataloggers so I ran the car up a slightly uphill onramp starting from the same spot twice. I had the meter measure me from 40-60 MPH in 2nd gear. About 45 minutes later I did the same thing but with the K&N in place. Same clear weather but a few degrees warmer. Same pre-drive conditions before the tests. The K&N seemed to help a small amount. At least in this test it helped over a broad RPM range and added about 1-2 HP. I used a Race Technology AP-22 for this test. You can read about them at their site.
Second Gear Speed To Speed Test, Stock VS K&N
Run#--------------Stock--------Stock-------K&N--------K&N
40-50sec/feet----1.39/91------1.37/90----1.37/90-----1.37/90
50-60sec/feet----1.21/189----1.21/188---1.20/187---1.20/187
40-60sec-----------2.60---------2.58--------2.57--------2.57
Notice how when you set the meter up to do a speed to speed run there is little run to run variation. The launch and shifting are out of the picture as the car was in 2nd gear in this speed range. In fact you just drive off normally but briskly in such a test so there is no extra wear and tear going on and noone knows you are doing anything. If a stock and a K&N car were next to one another it looks like the K&N version could very slightly pull on the other car.
It's a bit harder to close the box on the K&N as the flange is a hair less compressible than the stock piece, but it can be done after a few attempts. You have to use one arm under the hood and one under the wheel arch to make it happen. You also have to be careful that the composite air tube that leads to the vent on the side of the Elise stays pressed onto the airbox entry tube. So check that before you wrap things up. It might be easier for some to close the box if you detach that tube...it is fastened to the top of the airbox with one plastic screw-exanded fastener.
I like to test stuff using onboard dataloggers so I ran the car up a slightly uphill onramp starting from the same spot twice. I had the meter measure me from 40-60 MPH in 2nd gear. About 45 minutes later I did the same thing but with the K&N in place. Same clear weather but a few degrees warmer. Same pre-drive conditions before the tests. The K&N seemed to help a small amount. At least in this test it helped over a broad RPM range and added about 1-2 HP. I used a Race Technology AP-22 for this test. You can read about them at their site.
Second Gear Speed To Speed Test, Stock VS K&N
Run#--------------Stock--------Stock-------K&N--------K&N
40-50sec/feet----1.39/91------1.37/90----1.37/90-----1.37/90
50-60sec/feet----1.21/189----1.21/188---1.20/187---1.20/187
40-60sec-----------2.60---------2.58--------2.57--------2.57
Notice how when you set the meter up to do a speed to speed run there is little run to run variation. The launch and shifting are out of the picture as the car was in 2nd gear in this speed range. In fact you just drive off normally but briskly in such a test so there is no extra wear and tear going on and noone knows you are doing anything. If a stock and a K&N car were next to one another it looks like the K&N version could very slightly pull on the other car.
