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Do high performance air filters increase engine power in marginal tow vehicles?


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If one asked me this question a year ago, I would have said probably not.  I have a different opinion today.  Depending on the vehicle, I have anecdotal evidence that some vehicles may benefit from a high performance air filter when towing.  This includes my vehicle. 

By way of history, I have used a washable K&N air filter in my tow vehicle since I purchased it in 2004, only substituting a stock pleated air filter when removing and cleaning my K&N.  I switched to the K&N only to save money on replacement air filters.  I never really believed in the claims of more engine power.  I was somewhat concerned in the beginning that the K&N wouldn't protect my engine as well as the stock air filter but I was wrong.  My decision paid off as I went almost 200,000 miles on my first  K&N filter.  I now have 225,000 miles on the engine and the engine still burns less than 1/2 quart of oil every 5,000 miles between oil changes.  I have saved $100s of dollars over the last 20 years by being able to periodically wash my air filter rather than buying a new one.  But I never bought into the "more engine power" hype.  Until recently. 

Almost any tow vehicle rated to tow the weight of an Ollie will perform acceptably on flat highways at sea level.  Where the marginal vehicles like mine struggle is climbing hills and performance can decline rapidly as ambient air temperatures rise and/or altitude increases.  This is simply due to the fact that warm air is less dense than cold air and air density  (i.e., air pressure) drops as altitude increases.  Less dense air means less oxygen in the combustion chamber and lower combustion temperatures.  Of course, no air filter will compensate for lower air density (that is where turbochargers come in).  However, if the air filter is at all restrictive of airflow required to achieve the full compression ratio in the cylinder, then that engine will lose even more power on top of the power loss due to the air being less dense. 

In most driving situations, even a clogged air filter will still pass all the air that the engine requires because most driving conditions (cruising on the flats in overdrive) don't draw on much of the power or torque capabilities of the engine.  Marginally under-powered tow vehicles on the other hand occasionally seek to draw on the full capabilities of the engine when climbing grades and accelerating to the speed of traffic.  This is largely because the engines in marginal towing vehicles often need to access the full torque capability of the engine on hills which means by definition that they need to operate at higher engine revolutions per minute (RPM).  As engine RPM increases, the volume of air that must pass through the air filter increases linearly.  For example, an engine that requires airflow of 50 cubic feet per minute (cfm) at 1500 RPM will require airflow of 100 cfm at 3,000 rpm, or twice as much airflow.  in this case, if the air filter is restricting airflow to a little less than 100 cfm, the engine will be starved of oxygen  at its factory designed compression ratio and it will have less power.  This is not really a problem on flat roads at sea level, but can impair power on hills, especially at higher altitude and ambient temperatures which further reduce oxygen due to less dense air to start with. 

Last summer I spent time up in the North Cascades of Washington and got ready to pull my LE II over the North Cascades highway from east to west.  Thinking that I was way overdue to wash my K&N filter, I stopped at a NAPA store in Winthrop, WA and bought a brand new OEM style pleated filter.  In fact, I upgraded from standard NAPA filter to their "Gold" filter that claimed better engine protection (probably with greater restriction in air flow).  I then started up the pass and it was like I was driving a different vehicle.  I didn't notice a difference until I had to slow down for 30 mph curves on a 4%-5% grade and found if was more difficult to accelerate on the grades from the lower speed.  I was baffled that the engine wasn't performing as well as expected, considering the ambient temperature was only in the upper 50's and altitude was under 5,000 feet.

When I got home, I installed a new K&N filter and my performance was restored on my next trip towing the Ollie.  Was this all in my imagination.  Possibly but I don't think so.  Might other marginal tow vehicles benefit from using a high performance (high flow) air filter?  I don't know.  The air filter in my vehicle is pretty small to start with.  I am convinced though that my vehicle's performance suffers under full load when using a stock media air filter.

Those Ollie owners that have more than adequate tow vehicles are unlikely to notice any real difference from a high flow air filter, but those Ollie owners out there with under-powered tow vehicles might want to try out a high performance air filter, especially if you are heading to the mountains.  At best, it will help.  At worst, you will save some money over time by not having to replace your air filter again in the future (just wash it).

If I have got something wrong here, please chime in.  If anyone has also switched from an OEM pleated air filter to a high flow air filter in the past, or does so in the future, I would be interested in learning of their experience.

 

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Steve and Lornie

LE II Standard  Hull #657  2004 4Runner 4.7 L V8

Oregon

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Oiled filters do NOT provide nearly as much protection as a quality pleated paper one. This has been proven with oil analysis tests. I use OEM Toyota paper engine air filters only, and change them often.

I can’t comment on your performance claims, but I can state that with some vehicles a properly calibrated cold air intake (with ECU tuning) or a snorkel will noticeably improve power. My LC200 has a snorkel, I do not see any improvements at all and it is noisy and whips road spray onto the passenger side glass at highway speeds. My 1996 Series 80 had a snorkel, and it really woke up that engine, probably because there was an up to 40 degree drop in intake temperature (recorded with an OBD2 monitor). One great thing about a snorkel, it makes it really easy to find your white SUV in a sea of white vehicles at the box store…. 

Do you intend to keep towing with your 4.7 Toyota? That is a very marginal power plant for a 6000 pound Ollie.. It is a tough little truck but IMHO that is definitely abusing it.

John Davies

Spokane WA

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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags, Safari snorkel.

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43 minutes ago, Chukarhunter said:

I had to slow down for 30 mph curves on a 4%-5% grade and found if was more difficult to accelerate on the grades from the lower speed.  I was baffled that the engine wasn't performing as well as expected, considering the ambient temperature was only in the upper 50's and altitude was under 5,000 feet.

I am with John Davies; I prefer quality pleated paper air filers.

But, your anecdotal report piqued my interest.  It is my understanding that today's engines have many sensors and onboard computers which adjust engine performance in response to changing conditions.  Could your experience last year over the [spectacular] North Cascades Highway have resulted from your 4 Runner engine's response to the different air flow characteristics of the paper filter?  

Hull #?

Central Idaho

2019 Tundra Double Cab 4x4, 5.7L with tow package

 

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Rivernerd, An 18 year old Toyota engine isn’t that sophisticated. It has pretty basic electronic sensors and controls. I believe that year did not even have VVT-i (variable valve timing). Though strangely that was in my recently sold 1998 Lexus SC400 4.0 engine.

John Davies

Spokane WA

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags, Safari snorkel.

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There is no doubt John that pleated paper filters do a better job filtering the air than the oiled filters like the K&N.  I will admit that often when I have gone hunting  or off-highway driving in dusty conditions I would switch in an OEM paper filter for the trip.  I really can't remember why I decided to go with the oiled filter 20 years ago  for everyday driving but I think it was based mostly on cost saving of not having to replace the filter every few months.  Maybe I have just lucked out as my engine has not appeared to suffer any issues that could be attributed to dirty combustion air.  I wouldn't recommend anyone switch to an oiled filter though.  But if someone is like me pulling an Ollie with an older marginal tow vehicle like the Tacoma, etc., they may want to try a high flow air filter out.

Rivernerd, I don't know if changing the filter caused the engine sensors to modify the engine combustion parameters.  Your thought though triggered my memory that before heading up the pass, I also filled the engine with non-ethanol premium which I rarely use.  It is certainly possible that the change in fuel affected engine performance.  One would speculate that non-ethanol fuel would increase the performance, but maybe not the case at all.  Others may have insights on the differential effect of non-ethanol versus E10 fuel in older vehicles like my 4Runner under heavy engine loading.  I just don't know.

And no, I do not intend to keep towing with my 4Runner too much longer.  I truly wish I could have switched it out by now but live in the heart of Portland, OR and I cannot fit a full sized pickup in my "less than normal height garage".  I originally bought the V8 4Runner because it was the beefiest tow vehicle I could fit in my garage.  I rebuilt the garage 8 years ago and was able to squeeze a few more inches of height out of the door in the process, but still not enough for a full size pickup.  Based upon preliminary specs of the 2003 Sequoia, it appears that even the new Sequoia may be an inch or two too tall as well.  The Rivian SUV will fit nicely in my garage but the long range version is well beyond a year in the future by which time I hope there are more options for me.  To the extent that I am abusing the 4Runner, it is probably the transmission that is suffering the most abuse although when towing, I almost never let the automatic transmission pick the gears or downshift on its own, and often shift gears manually.  I never use the top (overdrive) gear when towing the Ollie.  And I try to keep my GTW under 5,500 lbs even with full water tank and full propane tanks.  Living on borrowed time I know.

 

 

 

 

 

Steve and Lornie

LE II Standard  Hull #657  2004 4Runner 4.7 L V8

Oregon

COIDKSMOORTNUTWYmed.jpg

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20 minutes ago, Chukarhunter said:

, I also filled the engine with non-ethanol premium which I rarely use.  It is certainly possible that the change in fuel affected engine performance.  One would speculate that non-ethanol fuel would increase the performance, but maybe not the case at all.  Others may have insights on the differential effect of non-ethanol versus E10 fuel in older vehicles like my 4Runner under heavy engine loading.  I just don't know.

There is your answer, putting in non-ethanol gas will wake up most engines, it has a higher energy density.  I really notice a difference with my LC200 when towing. If I could reliably find it in long trips, I would run it all the time, in spite of the extra cost, but there isn’t much point in doing a few partial fillups here and there with it. Most Maverik stations out west have it at each island. I use it exclusively in my small engines.. When the stabilized fuel is old, say 8 months at most, I put it into the truck.

John Davies

Spokane WA

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags, Safari snorkel.

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K&N does publish actual dyno run data for their products that shows a performance increase.  I was actually surprised to see the significant increase in torque for the test on an F-250 6.2 liter gas engine, especially in the lower part of the RPM range.  But the dyno runs always seem to be in a single gear (3rd gear run in this case).   So I’m sure K&N is cherry picking their data a bit to show the best results, and this test is for a complete K&N cold air intake, not just the filter.    

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2019 Oliver Legacy Elite II - Hull #461

Tow Vehicles:

Primary - 2019 Ford F-250

Backup - 2019 Nissan Armada 

 

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