Oil vs. Dry intake

[MissingtheMrs.]

I have searched (both google and C5) and am having a hard time finding the pros and cons of an Oiled Air Filter vs. a Dry Air Filter. Can someone help me? The RotoFab intake has a Dry intake option for $12 more. Why is it more? Would one need more maintenance than the other? etc.

Any help would be appreciated...

[EDIT] ALSO... would using polished stainless steel instead of a plastic tube make a difference other than aesthetics?

[BlackinBlack]

I asked Roto-Fab these exact questions and here is the response I got.

Oil is better flowing but does not filter as well as there dry filter. IE Oil = HP and Dry = cleaner air to the motor.

In a stock car the difference is about 1-2HP. With a supercharger the difference can become more noticeable. The CAI is the same so you can switch from dry to oiled or the opposite just by buying the other filter.

The dry filter requires less steps to clean due to not oiling the filter and has no chance of fouling the MAF sensor. Which there is not a huge chance of happening if an oiled filter is properly cleaned.

Stainless Vs Black plastic. Plastic = more power due to less heat soak. Stainless = Good looks. Again the performance difference is minor.

I personally have the dry filter. I ran oiled filters in my other cars and noticed dirt on the "clean" side of the filter from time to time. And for me oiling the filter was a PIMA. So I am giving the dry filter a try.

If it comes from Roto-Fab you cannot go wrong. It is a very nice CAI.

[MissingtheMrs.]

Wow. Thanks for the info. Answered all my questions!

[eddie SS]

I was wondering the same. Thanks for clearing it up for me.

[HaveBlue]

Here is some info I've posted else where.

Originally Posted by HaveBlue

"First. All cotton gauze filters are not the same. Sounds simple but the term "K&N" is like "Kleenex", and gets applied to the category. There are cheaper versions and more modern versions (the basic K&N filter dates back to the early 70"s). Very cheap & offshore versions are easy to identify. Hold them up to a light. If you can see pinpoints of light then dirt will get thru those holes. Any filter is a compromise of Flow vs Filtration. A normally aspirated engine (air pump effect) has a set demand it needs. Lets say 300 cfm. If a filter has a higher airflow rating of 350 cfm, than you are giving up filtration. The motor will pull no more than 300 cfm. If a filter allows less than the 300 cfm, then it would be considered "restrictive" but probably "filters' better. OE's want to make power, long life (100,000 warranty) and keep noise down. They spend lots of engineering money to get an acceptable (in their eyes) balance.

"Wet vs Dry"
The dirt released from the filter comes from cleaning the oil off, which the dust clings to. It's the "release agent". A dry filter is put in a bucket and agitated. You will get the surface dirt out but not the deep dirt. So each washing leaves the filter less efficient that it was new. Think vacuum cleaner filters. It will never be 100% efficient again, a oiled gauze filter is. Again it's Flow vs Filtration. Dry filters have come into vogue due to the great "Oil on Mass AF sensor" debate. Foam filters are synthetic not natural fiber. Oil will not penetrate the foam, it sticks to it. Foam filter manf use a thicker sticky oil to cling, but it WILL shed off. Did we use foam for years on powersports and trucks? Yes, when they were carburated and the motor wasn't affected by ingesting a little oil.

MAF Fouling.
Oiled Mass Air sensors is pretty much an urban myth. Check out the K&N website for the actual scientific testing they had done.
http://www.knfilters.com/MAF/MAFTestresults.htm
A lot of dealers make a big deal about this because they've been scared into it by the warranty techs. Keep this in mind. A GM dealership has NO way to test a mass air flow sensor. The book tells them to put the MAF on a same year vehicle to see if it's bad. !!
Can it happen? Sure. From over oiling. If a cheap offshore filter has oil on the inside of the bag wrapping the filter than it's over oiled. Don't use it. The biggest culprit is the owner reoiling the filter after cleaning. Ever read the instructions before doing it? You oil a small area and let it wick thru the filter for 30 min. You DO NOT try to get the cotton all red in 30 seconds
Several manufacturers now list the amount of oil they put on their filters from the factory. It's done by a computerized sprayer. The amount averages 0.6 oz. Very little.

Current manufacturers of filter (vs re-packers) spent a lot of time and engineering to get the correct configuration to achieve the best Flow vs Filtration AND correct MAF air signal. Number of pleats per inch, pleat depth, all play apart in "straightening the air" as well as filtration. This is an area that very few kit builders (vs filter manf) spend any time. It's usually what fits in the space. IMO it's very important to know who's filter a kit has in it. Did they cut corners there?

There are lots of hype, myths and legends out there on the errornet. Also some facts. Do your research from multiple sources."
__________________

[IPS Brandon]

The biggest difference in maintenance. The dry flow filters that many company's produce now, will not require any cleaning at all , while still maintaining a very high filtration rate. This is by far the single biggest advantage, because we all know how the dirt and grim clogs the pores on a oil filter, an then requires cleaning, and the oil solution.

As for the plastic and stainless, the thermal characteristics of the two are the difference, as mentioned prior, but you will not see any noticeable difference in performance, for most applications.

Also if you have not already purchased your roto-fab, shoot me a PM and we would be happy to help save you some money on shipping, and use our member discount!

Regards

[HaveBlue]

Originally Posted by MissingtheMrs.

[EDIT] ALSO... would using polished stainless steel instead of a plastic tube make a difference other than aesthetics?

Yes, but not for the reason you might think. It not so much heat soak as it is the ability to make complex shapes. Air flow managment is critical on the new vehicles. You need to make sure the MAF "sees" the correct airflow and you can make smoother transitions. Air flow does not like 90° turns. It's fluid dynamics. As an example look at the tube on the Airaid post. It sweeps up and around to the throttle body. Nice transition.
BTY-there is now such thing as "ram effect", unless you have a jet or rocket engine.

[HaveBlue]

Originally Posted by IPS Brandon

The biggest difference in maintenance. The dry flow filters that many company's produce now, will not require any cleaning at all , while still maintaining a very high filtration rate. This is by far the single biggest advantage, because we all know how the dirt and grim clogs the pores on a oil filter, an then requires cleaning, and the oil solution.

So the dry filter vaporizes the dirt? They still need cleaning. The oiled filter will have a higher flow rate when dust loaded than a dry filter. If filtration is your concern use the Airaid. It has an addtional layer of synthetic material added to the cotton.
There are new filter media on the horizon that may give us everthing we want. But we need to find new terminology, a "dry filter" can be anything from a paper to a synthetic fiber mesh. Just like there are crappy cotton guaze filters, there are, and there will be more variations of "dry filters".

I hope one the the actual filter manufacturers can chime in on this.

[scrboy2002@aol.com]

bringing this back.
Opinions? dry or oiled?
Im installing the rotofab, dynatech long tubes, and a 2.5 corsa catback. ss M6