OK... Glad you're not worry about my car. Perhaps you just think I'm unintelligent and need some guidance. Much appreciated. My "theory" is that the oil may not even be necessary to provide the same level of filtration that is present in the stock filter that doesn't even seal all that well against the duct. The first time I looked at it I thought, "that thing is definitely letting dust through." Based on the gaps I see when I look at it I would say that it's there to get about 90+ percent of it the dirt but because of the design it can't seal well enough to get it all. The K&N with a rubber seal and no oil may actually do a better job. I'll let you all know how it works out! If the darn thing doesn't fit well enough I'll chalk it up to a learning experience and toss it. Still worth a try...

 

It's been done successfully before. There was an earlier thread (maybe by gpsman1) about how to slightly trim the K&N to fit perfectly.

I'm on my 2nd paper filter, and just continue to blow it clean with compressed air. Seems like the main purpose is to keep big stuff out like tree leaves.

Let us know how it goes.

 

First things first - Thank you to gpsman for this great tip and for the K&N part number reference!

OK - I just installed the K&N filter in the rear traction battery duct. Piece of cake... But I do have some tips for those who might want to go this route.

First, the filter comes pre-oiled with a fairly liberal amount of oil. It was mentioned earlier in this thread that the oil could be a problem if it were to drip or otherwise get through into the ducting. After opening the K&N I could tell there was a pretty good saturation of oil in the element; enough to be of concern for this application anyway. I took the filter to the shop and placed a shop towel behind it while blowing 100PSI of compressed air through it from a distance of about 2-3 inches away. I did this a few times while turning it over. It left a pretty good stain of oil on the towel. While the velocity of the air going through that duct is nowhere near what I did with the air nozzle, the oil present on the filter might have been enough to "mist" into the ducting and possibly get to the battery. As Bill Winney pointed out, this could potentially cause a fire. I think that's a bit of a stretch considering the small amount of oil we're talking about here, but safety first. The filament still has oil in it enough to function quite well as designed after removing the excess.

Then I trimmed away the flanges of the filter to remove the majority of the excess and come close to the size of the original. I learned years ago as a machinist that to accurately cut rubber, you can't cut it with a blade. The best way is to grind it. After trimming it close, I used my bench grinder with a course wheel to grind the silicone in small increments to get it exactly the right size. The shorter side (see pictures) has to be trimmed to 9cm +/- .5mm or so. That side of the filter is actually pretty thick and would be difficult to cut with scissors or a blade, so I definitely recommend grinding it to size. The grinder peels away the silicone with ease and leaves a nice smooth edge. The filter is already within a millimeter of the correct thickness as made. The thickness is also the least critical dimension as the rubber sits beautifully flush against the surface of the duct, sealing it better than the original filter ever could.

From Left to Right:
Original Untrimmed filter - top view
Original filter - side view
Partially Trimmed filter with towel showing excess oil removed
Fully trimmed (ground edges) filter exactly the correct size
Installed Filter

 

My thought on oil in the traction battery was not after just one filter. Rather it was after, say, your 5th or 10th filter.

It is possible to have some oil entrained in the air flow, virtually undetectable, that after several filters does leave a residue inside something like the traction battery. Your test shows that oil comes through. So the issue is how much and for how long.

Using these filters for the engine does wonders as the oil assists in trapping very,very fine dirt and what gets to the cylinders is burned.

 

Thanks Corey for all the information on the K&M battery filter.

My concern about using the K&M filter has not changed however. I use the Motorcraft filters because they are designed for that application. The filters have a maintenance inspection and replacement schedule spelled out in the manuals by Ford. Also, when I had relays go bad in my FEH, Ford was concerned about a DTC that meant my HV battery was bad. Ford's hotline was looking for any excuse they had to void my battery warranty and the first place they had the Hybrid Tech check was my battery filter. The Tech told me when he check the filter, he told the hotline folks it was new and clean.

I take no chances when it comes to expensive warranty replacements such as the HV battery. My concern about the K&M filter is that it looked soaked with oil for its intentional use to filter air. Removing that oil reduced its effectiveness to filter the air.

I would use a aftermarket battery filter made similar to the OEM filter if I could not get the OEM filter. Today, we can shop around for price on the internet, so price is not an issue for me. My dealer and Walmart gives me the best price where I live, so that isn't a issue for me.

GaryG

 

Interesting that Ford might be looking for an excuse to void the traction battery warranty. Would have thought better of them. This is a nicely engineered car.

I use the NAPA Gold filters and change them as specified.

 

Admittedly this is somewhat of an experiment. I'm normally as particular as anyone with regard to OEM quality parts... As in, I really don't like to use anything else if at all possible. Consumables is one area where I will sometimes stray. I will be checking the duct just below the filter frequently within the next couple of weeks. If anything looks suspect at all I'll be pulling that thing out. My feeling is that it may actually do as well if not better than the original at filtering considering the fact that it actually does seal better than the original. I've done some extensive reading recently where there are plenty of naysayers on the K&N filters even for the intake. I've used them for many years with no issues including my '97 explorer with 190K on it. I don't live in an area that is considered "rough service" though either. Folks who live on dirt roads have reported finding dust that didn't get caught by the filter.

I will say without a doubt that the filter is flowing more air than the dirty filter was. I haven't looked to see what the recommended interval is for replacement but I was surprised at how dirty my filter was... This is kind of contradicting my previous statement about rough service I guess. The filter that was in there was a little over a year old so obviously it was due. I was experiencing some delays in the ICE shutting down and all seems to be back to normal now with a free flowing filter.

 

Corey, I've never had a dirty battery filter prevent or give me any delays in going EV. If outside air is not cooling the battery, the Aux A/C will provide cooler air. Now, I've had my battery so hot, the A/C could not cool it down fast enough with heavy regen charging. In this case, I had to use the brake pedal tap in "N" to prevent further regen heating to go EV.

In general, I drive clean roads and don't have problems with early dirt before the 20,000 mile replacement. However, my '09 FEH had a real dirty battery filter after a short time after changing it. After thinking about it, my FEH was in the body shop a few days having the carpet and seats replaced because of a chlorine spill. All that sanding and body work being done in that shop must have been the problem. I just checked the filter a week ago and the new filter is still very clean.

GaryG

 

It seemed odd to me too that the battery filter would cause delays in the ICE shutdown but all I can say about that is that the filter change has definitely made a difference. I only looked into it because of a suggestion on another thread where we were discussing problems with ICE shutdown.

I started experiencing some intermittent delays a few months back. I use some hypermiling techniques that will heat up the battery but I really hadn't changed my habits at all when I started experiencing the delays. Changing the filter definitely made a difference but I wouldn't say it completely cured it. I still get some occasional delays that I'm pretty sure weren't happening before. I'm suspicious that something in the system might be bordering on being out of normal parameters and, if so, the free flowing filter may have helped that. I was able to confirm the behavior change by pulling the filter out for one 35 mile round trip commute cycle. That's when I discovered that the filter was dirtier than I expected it to be... By the way, yep, that was well over 20,000 miles of driving on that filter. Oops... Should have read the owners manual on that one.

I'm also somewhat disappointed in the ability of the battery to cool itself when using regeneration. I live in a very hilly part of the country. I find that the battery is typically only good for about 2-3 percentage points (SOC) before the system fades out charging very quickly on a steep hill; I have to assume due to heat build up. I try to limit high charge rates by not riding the brake pedal but some hills just don't give you a choice. It's difficult to monitor the amount of regeneration to keep the battery from getting hot and still take advantage of all that energy. What goes down must go back up! It would be nice to be able to store more of that energy than the system will allow due to heat. I'm sure you've lamented on this yourself Gary as you probably try to maximize your energy storage.

I don't have my scangauge set up (yet) to read battery temperature. I need to get that X-Gauge input so I can get a better feel for what is actually going on in there. That might tell me more...

 

To answer your concern Bill - The idea with the K&N is that you should never have to replace it. K&N actually advises that the filter works better the dirtier it gets and you should really never need to clean it either, but if you insist on cleaning it they provide instructions anyway. So far I've followed their advice with good results on my other vehicles. It's counter intuitive that the filter is OK to let it get dirty but the "claim" is that a filthy K&N filter still flows better than a brand new paper filter. Sorry if I'm telling you stuff you already know. It sounds like you're familiar with the K&N but I was curious as to why you were suggesting that there might be a need to replace it.

Ideally there would never be any more exposure to oil in the system than just after installing a new filter. If the theory of never changing or cleaning the filter is followed (and successful) then the oil should stay in the filter.

After blowing the excess oil out of that filter I had to admit that I was glad you brought up the issue. The oil was on there pretty thick... Thicker than necessary (in my opinion) to allow the filter to function in this application. I will be monitoring this little experiment closely...