I remember reading a post over on Edmunds re filters, with a link to a Volvo (!!!) board wherein several posters had sent eninge oil for analysis before and after use of K&N, and then again, after they had gone back to stock filter.

The upshot was that silicates (eg, dirt) numbers went up with K &N, went (back) down with stock.

And I have great respect for John L., but I suspect he isn't trying to build a 100,000 mile motor, either.

 

Willard - Thought I stated that it was a "shadetree" test? Even if U had the car strapped to a dyno it wouldn't be worth the trouble to try a duplicate the testing parameters to 100% accuracy. Also, if the generally accepted estimate of it taking roughly 10 additional horsepower to drop a tenth off a 0-60 run ( old drag racing rule of thumb, for U youngsters! ) applies here, I seriously doubt that all the variables U mentioned totalled together would account for the improvement. As far as a "control" test, my baseline runs with the factory filter were to taken as such. The 'Vette is a bottom-breather & no one in his right mind would dare run the car w/o an air filter as it could potentially pick up debris which could find themselves into the MAF or it's screen ( for those of us who removed ours ). Worse yet, the plenum isn't the place for those particles to go either!When we start talking about the viscosity of the engine oil when making street horsepower, even though I have a Bachelor's in Petroleum Engineering, man, it's time for me to find another hobby!!:eek:

 

Thanks a lot for your responses so far.
Few more details:
- I bought K&N for its "better filtration" not better performance. If it helps the latter, that's fine with me, but its effect on the stock housing is probably undetectable.
- When I cleaned the filter with just 5K miles on it, it was all black and dirty, similar to the OEM I replaced (with the same 5K miles), so it should be doing a similar job, at least.
- It's entirely possible to have better filtration AND better flow than the OEM filter with better technology than paper. I know K&N have better flow (I don't particularly care about that) because I can hear the sucking at idle that I didn't hear before (and bench testing as well), but I question the better filtration issue, which is my main concern.

Hey MeanGene, I was relieved to read your post, but I have a question for you. I can see light thru some of the pores of the filter media when tilting the filter sideways (not very reassuring), but not much when held straight, as the "supposed" direction of air flow. Obviously the pleads must disturb air flow in some way, but probably not enough so the air hits the filter media at 90º, so unfiltered particles get thru those tiny holes (but much bigger than dust particles, right?).
My question is this: can you tell if the filter is letting in more particles than it's supposed to by how dirty the oil gets before each oil change? I change mine every 3K miles, and I haven't seen any difference (good, huh?) in oil color before changing it than when I had the OEM filter: still yellowish (except at the bottom of the dipstick) on my GS. However, my Navigator gets the oil dirty in a hurry (black by 3K miles), even with OEM filter (probably more tolerance on piston to wall, huh?).

Final question: on my GS, where I don't use it much, should I just re-oil at 5K without cleaning every year, or clean and re-oil? Is re-oiling a dirty filter a good idea?

Thanks guys.

 

Juan - Remember the mention of excess oil contaminating the downstream MAF's? By re-oiling a dirty filter U increase the chances of that happening as there's less pleated filter area to absorb the new oil ( the pleats R trapping the dirt ). Supposedly the K&N filters better ( up to a point ) the dirtier it gets but I'm not taking a chance. An oil analysis ( as was mentioned earlier in this thread ) would tell ya how much dirt's getting by the filter but the old eyeball method U are currently using will do in a pinch. The pleats not only are designed to stop dirt but to straighten out the airflow. We discussed turbulant airflow ( great in the combustion chamber ) versus laminar ( perfect for the intake system ) a few months ago ( I think up in the Engine/Tranny section of this Forum. I wouldn't worry too much about being able to see light thru the pleats - that's the old school way of checking a standard air filter for replacement needs & it still applies, IMO. The weave of the K&N pleats should stop 99% of the particles - Hey, nothing's perfect!!

 

Mean Gene when you bought your new K&N filter for the Corvette did you also buy a brand new Corvette filter and then conduct the test?
Most people compare a brand new K&N with their old filter - I haven't heard of any that buy both and compare. How does a new Corvette filter compare to a new Lexus filter for flow?

A dirty Lexus filter has twice the pressure drop across it as a new one - an new one is heaps better than an old one.

0.1 of a sec can be measured but seat of the pants it isn't much.

There is no doubt that a K&N flow better than a standard Lexus filter - I have measured it and it is so. (a new standard Lexus filter flows great - no problems there )

There is plenty of doubt whether a K&N filters as good as a standard Lexus filter. There is only annecdotal evidence and opinion around. Only a certified accredited lab can answer the filtration question.

I get my oil analysed for contaminants every change. This is cheap to do. The analysis only picks up very small particles - it won't tell you if you got all the metal shavings out of the sump when you put in that oil return line for instance.

I suggest that if any body is worried about contamination of their engine, rather than try to pin down the effectiveness of filtration of different filters, go and get your old oil analysed - it doesn't cost much and then you will now for sure. It is the outcome that is important - not the method.

It may be that a K&N provides suitable protection for your car in your area with your driving style.

My first oil analysis is on my webpage - the second one is due in a month or so (every 5000 km for me - 3100 miles). I just filled up a clean bottle with a sample of the old oil - took it down to the autoparts store which buys/sells heaps of Castrol products, they gave it to the oil rep who gladley took it away to get analysed.

Got the results back in about 2 weeks.

My Dad has worked on large Earth moving equipment in dusty areas - oil analysis is standard procedure every service - they can't afford to get it wrong - too much money involved. Filtration is number one priority - they protect their massive engines as best as possible - and their isn't no oiled cotton filter anywhere in sight.

 

I appreciate all the responses on this debate; very informative.
Lots of knowledge on this board; I'm proud to be part of it.

Have a great day guys.

 

Peter - Well, the factory air filter had less than 100 miles on it so it was close enough to new for me. As U can tell, I couldn't wait to start modding the 'Vette! Heck, it had 15 miles on it when I put it in the install bay for the stereo - straight from the dealership to the shop!! !00% in agreement about oil analysis being a terrific tool for engine wear & diagnostics. Working for an oil company has it's advantages as I get mine done for free but Dexter found some others that charge a nominal fee ( depending on how comprehensive an analysis U opt for ). I think they're posted back a few pages in this Forum for those that R interested.