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Discussion Starter #1
Hey guys. I am thinking about putting a K&N air filter in my 02 Prius to see if that will give it any better gas mileage...not expecting much but if it will give me 2 or 3 mpg, hey why not? Plus the fact that you never have to buy another air filter again...it practically pays for itself. So just wondering if anyone has put one in their Prius? Did you get better gas mileage?

It is K&N part number 33-2186.
 

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K&N

I was just reading about their filters. From one of your other posts it looks like you have put one in. Did it help the mpg?
 

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I ordered one but I haven't received it yet. It should be in today actually. I will let you know if I see an increase in mpg. I am not expecting anything huge but it is proven that K&N's cotten filters flow like 100x better than the paper filters which should equal better gas mileage and maybe a few horse power...not much though.

My other car is a heavily modded 2000 Mustang GT and I might have picked up 2-3 hp by switching to a K&N air filter and I might have picked up a few mpg but I don't watch it's gas mileage as closely as I do the prius.

Every little bit helps, right? Plus the K&N filter is reusable...just clean it out, reoil it and it is ready to go. Never have to buy another air filter again.
 

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Gitty Up,
Please report back after you've put your filter in. Please take particular note of snugness of fit compared to the OEM. Also, if you can look at the intake at the time of change and after a few thousand miles with the K&N. I'm not sure power/fuel efficiency are worth commenting on as these are so variable this early, but if you have a subjective opinion that will be helpful too.
--evan
 

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Discussion Starter #5
Yes, I will be sure to report back. I will even post some pictues of the filter and the fitment in the airbox for you guys.
 

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Ok, here are some pics of the newly installed K&N air filter. I can definately see an improvement in gas mileage with it. The tank before the K&N, I averaged 42.3 mpg and with the K&N I averaged 47.8 mpg. I am going to monitor is some more to make sure it wasn't a change in my driving style or whatever.

I will tell you that the filter fits in the airbox like a glove (as you can see by the pics). I am very happy with this purchase.
 

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Discussion Starter #8
Oh yeah, I thought I would mention that the tank with the K&N that I averaged 47.8 mpg was a road trip from VA to NC. I got 519 miles before I had to fill up (with 1 bar left) so I think I could have gone another 50 miles before completely empty. I think this is impressive...about 570 miles to the tank! WOW!!!!!!!!!!!!!!!!
 

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Thanks for the excellent follow up. Only problem is I can't figure out how to view the pictures.
--evan
 

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Gitty UP - What year?

Gitty Up,
You didn't mention what year? Are they all the same filter. I'm getting my 04 in a couple of weeks.
 

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Ah, he specified 2002 in the first post, and lists his car as a 2002 Prius in each subsequent posts. I'm going to guess it was a 2002 Prius?
--evan
 

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K&N in 2004 Prius

Took a look inside the air box of my Prius and I don't think the K&N filter would be of any use. There are 2 filters involved. The primary filter is in the lower half, left side of the box. It is a normal pleated type filter. However, there is also a finer meshed fabric type filter in the top half of the box. This secondary filter appears designed to trap even finer particles of dust than the pleated filter. Because the physical size of both filters is the same, replacing the pleated filter alone with the K&N would not improve air flow at all unless the top filter was also replaced with a less restrictive filter or eliminated altogether. I think Toyota engineered a little filter over-kill here in the interest of engine longevity. Everything about the design of the car is starting to look like they want this to last a VERY long time, probably to reinforce the durability of the hybrid system. I think it best not to modify anything involved with the HSD system...Toyota engineers have done an excellent job already. Wash the car, wax it, change the oil and filter, drive it, and LOVE IT!
 

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Discussion Starter #13
efusco...have you figured out how to view the pictures yet? On my computer they are small pictures in the thread, then you click on them and enlarge them. If you still can't open them, let me know and I will email them to you.

dengraham...yes, it is a 2002 Prius and I don't know if it will be the same filter for the 2004. Might want to check K&N's website.

JerryP...I didn't see the "other" filter you are referring to. However I will tell you the K&N spends alot of time and money testing their products and they are built to outflow and filter better than any stock filter....period.
 

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It appears that the air filter box was redesigned for the higher hp 2004 1NZ-FXE engine. I checked out the pics you posted and the new one is quite different. I ran a K&N in my Echo and it did increase mpg by a bit, but really helped throttle response. Maybe K&N will make a 2 filter set for the 2004......I would really consider that if it was available.
 

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Discussion Starter #15
JerryP...oh, I didn't know you had a 2004. I haven't seen the filter set up on those yet. I bet K&N will come out with a 2 filter kit for it then (if they find it necessary). That is interesting it has 2 filters. Can you take any pics for us? We would appreciate it.
 

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gitty up said:
efusco...have you figured out how to view the pictures yet? On my computer they are small pictures in the thread, then you click on them and enlarge them. If you still can't open them, let me know and I will email them to you.
I can't veiw them at all...of course if the 2004 is different it might not make a difference. Still, if you can e-mail to [email protected] that would be great.
--evan
 

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Ok, the problem with these oily filters is that the oil has a tendency to end up fouling your MAF sensor (Mass Air Flow) which screws up fuel delivery precision.

Something else to consider - a less restrictive filter lets more crap into your engine. In my opinion - these aren't worth it.
 

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Well stated! Let's give Toyota engineers credit here for equipping the Prius with a perfectly adequate, nay maybe even optimum, engine air filter. This is one feature I have no inclination to "improve" upon.
 

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K&N filters

I've often wondered about these. Motorheads (and the shops that cater to them) seem to think they'll "straighten" airflow, allow more air to pass with less contaminates, keep terrorists out of the country, etc (OK I made the last one up).

Seems to me if they let more air through that means they are more porous, which means they will also let more particulates through.

I would also expect the limiting factor in airflow to be the design of the airbox and its intake, not the filter element composition (the size of the element which is tiny in the Prius of course also plays a part).

What I know for sure is that K&Ns are considerably more expensive than traditional filters, and are not what the car was designed for. YMMV.

Steve
Portland, OR
2002 Brilliant Blue
34999 miles
 

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I wish I knew how to make a picture to describe why the concept of increased air flow does not, necessarily, mean that the filter is more porous.

I guess the best way to think about it is this....
If you take a 6" x 6" piece of paper and make 1" circles on it there will still be a lot of paper left. If you take the same size paper and make honeycomb shaped holes in it with just thin walls in between but of the same 1" diameter you will increase flow of all particles less than 1" diameter, but still stop anything greater than 1" diameter just like the circular holes would do.

Does that make sense?

Now, I'm NOT saying that that is exactly how the K&N filters work, but conceptually that is the logic of how you could increase air flow without increasing the size of particles allowed to pass through.
--evan
 
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