The standard (donought with a hole in the middle where the SU carb sat) housing had a more than large enough volume between the outside of the filter and the case, so the result was that until really clogged (which didn't happen in eight years), the engine would still always breathe enough air as the filter got dirty. The K&N filter I fitted had more surface area by having more zigs and zags in the same diameter than the Unipart paper filter. Perfectly, in a real life test more representative, especially in duration, than any accelerated bench test. I have seen the data you refer to as well, Ben, but as always, I speak as I find. It look slike we will have to agree to differ untill i find the evidence. Did you run an engine for 90k on a different filter in the same conditins as a control.Īs i have said i will post the data if i can find them showing flow and filtration properties of commonly available air-filters. How can you possibly conclude negligible wear was due to a filter, surely other factors would be rather more important.
Further to that if the filter filtered properly why did it not get covered in dirt- where else could all the muck possibly go? You could even use the same argument to suggest leaving a paper filter in for 90k miles. If the air filter was fitted in the standard case, and was therefore the same size and shape as the original, how did it have much more surface area. I am used to common cars where i can get air-filters for a few quid. I accept your point regarding reduced costs. ITG filters on the other hand were significantly better. If i could find the web-page i would post the link here that shows under decent lab tests that filtration from the K&N filter was significantly worse than the standard Mann paper filter in the test. Again this may give you a few more mousepower, but the biggest benefit will be that you'll never buy another replacement so over about 4 years or so it will work out cheaper. K+N do a range of 'replacement' elements where you replace the paper filter with a K+N but leave the air box alone. In this instance the wrong choice of filter could have a disatrous effect on engine performance. On the other hand if you have a finely tuned rally or race engine then you would definately need something like a K+N to get the best from it. Even if airflow is improved, your engine may not be able to make use of it depending on the design of the fueling and ignition systems.
Simply changing the air filter may give you a few more mousepower, but the biggest noticeable difference will be noise (if you're using a direct intake type). There's the valves, inlet tract, throttle body etc etc. In standard road car, the biggest restriction to air flow is not generally just the air filter. What is highly unlikely is whether one will make any difference to your car.