Anyone ever try and adapt a shop vac filter for their car or truck? I was looking at the filters at Sears yesterday, especially the Gore teflon ones which are Hepa rated (97% @.3µm). Those big shop vacs move a lot more air than a car or small truck would. I think these would actually work and would probably give some pretty good used oil analysis and the teflon ones would be washable and reusable.
Hepa filter for car?
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Interesting idea. I do wonder if enough air would flow through something small enough to fit under the hood.
Does anyone have any CFM(Cubic Feet per Minute) figures for any shopvac models using HEPA filters?
Hmm... for a small engine at modest RPM it seems it would work. Assume a 2.0 L engine with 100% volumetric efficiency- that is, for each full intake cycle it actually draws in a full 2 liters of air.
At 3000 rpm(a good 5th gear cruise in my car, ~72 mph), that engine inhales [(3000*2000)/2] cc of air. (Why divide by 2? Because it's a 4-cycle engine.
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Now, 3,000,000 cc/minute of air translates to 105.944 ft^3/minute. I think 106 cfm is close enough, for a nice safety factor we could bump it to 120 or 125 cfm.
I'm probably missing something, but it seems if you could plumb it, it should work.
Now we wait for the experts.
Does anyone have any CFM(Cubic Feet per Minute) figures for any shopvac models using HEPA filters?
Hmm... for a small engine at modest RPM it seems it would work. Assume a 2.0 L engine with 100% volumetric efficiency- that is, for each full intake cycle it actually draws in a full 2 liters of air.
At 3000 rpm(a good 5th gear cruise in my car, ~72 mph), that engine inhales [(3000*2000)/2] cc of air. (Why divide by 2? Because it's a 4-cycle engine.
Now, 3,000,000 cc/minute of air translates to 105.944 ft^3/minute. I think 106 cfm is close enough, for a nice safety factor we could bump it to 120 or 125 cfm.
I'm probably missing something, but it seems if you could plumb it, it should work.
Now we wait for the experts.
I called Gore, the HEPA filters do not flow enough for an engine.
Nobody that I have seen makes a HEPA filter for air conditioner/furnace usage. (Even 3M Filtrete filters aren't HEPA). I assume it is because they don't provide enough airflow for that application.
But it is interesting that they do have HEPA vacuum cleaner filters since those produce a lot of airflow through a small filter that will have a high dirt flow rate.
It might be worth a try in a car.
But it is interesting that they do have HEPA vacuum cleaner filters since those produce a lot of airflow through a small filter that will have a high dirt flow rate.
It might be worth a try in a car.
I like your calcs Stuart. 125 CFM is not much at all. A vacuum cleaner is a lot more and the filter isn't even pleated.
Something doesn't make sense here. If I had to guess, I would say the vacuum manufacturers may be exagerrating their claims.
Something doesn't make sense here. If I had to guess, I would say the vacuum manufacturers may be exagerrating their claims.
Flow numbers mean nothing without specifying the pressure drop. Sure, a small filter can flow a HUGE amount of air BUT with a HUGE pressure drop. Pressure drop is not good for an engine.
Ah, there's the rub!
OK, so it needs to flow the required amount of air, at 1 atmosphere input pressure, with very little to no pressure drop. I suspect that to filter fine enough for HEPA specs will require a pretty big filter.
See, I *knew* I was missing something!
See, I *knew* I was missing something!
At 125 CFM you would have to have a very restrictive filter indeed to give you very much pressure drop.
I am thinking of regular upright Hoover vacuum bags, which are available in a HEPA variety. At least that is the claim.
Something definitely doesn't make sense. I'm quite certain that if a HEPA filter could be used in an automotive application, somebody would be doing it.
I am thinking of regular upright Hoover vacuum bags, which are available in a HEPA variety. At least that is the claim.
Something definitely doesn't make sense. I'm quite certain that if a HEPA filter could be used in an automotive application, somebody would be doing it.
You are right, when I called Gore, they said if it could be done, they would be selling automotive engine air filters. I spoke with their applications engineers.
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