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Twice now I have watched Pat Goss on Motorweek (PBS) state that a dirty air filter does not hinder fuel mileage because the fuel air ratio is monitored and adjusted after the filter. In my opinion a dirty filter requires more engine power to draw the air & therefore has to require more fuel.

Your opinions?
 

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plain and simple, air=hp. More air, needs more fuel for propper combustion. I would never have a dirty air filter.
 

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Both are correct. More air = HP with more fuel.
But for better MPG you need minimum fuel. Therefore if the required air can go thru the dirty filter, then you get as much HP as you need. And the MPG is the same. Right?

Only with carburetors or fuel injection that does not compensate for airflow will the air fuel ratio get messed up with dirty air filters. If the air fuel ratio is correct and you get sufficient air then why would the MPGs go down?

The only caveat might be if you are pulling a trailer in hilly terrain. Or if you want to get to the next light in 6 sec instead of 10 sec. Then you might not get sufficient air flowing thru the air filter (a poor design) to develop enough HP. In that case the air is the limiting factor for HP but the computer will still compensate and burn only the right amount of fuel. This assumes an engine with low losses. I.E. the right kind of oil and not 50 weight racing oil. Everything working properly.

I try to never have a dirty air filter either. Old school thinking I suppose. An old gear head at heart...

What Pat Goss is getting at I think is a really dirty filter only up to the extent it is blocking the air flow necessary will not decrease HP or MPG. The HP might go down with insufficient air only but not the MPG. The work required to get the air thru the filter is insignificant compared to the work produced. It is like a drop in a bucket. If you double the work now it is two drops. EH! So it might be insignificant.

So basically the HP will be limited but the MPG will remain the same due to the PCM's compensation.

Yes I know a lot of you are going into denial. That Damed Radar is full of sh*t. :) *&^%!

Opposing positions welcome with science behind it or some rational.
But not hand waving...it is so because it is so type of reasoning will not make it so.

-Rg
 

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I can find no flaw in this logic. I do suppose, however, that if you never changed your air filter, it could get so dirty that at some point, the air would be blocked completely, therefore causing the engine to stall at idle. In which case your mpg will be impacted because you can't go anywhere.:D
 

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I can find no flaw in this logic. I do suppose, however, that if you never changed your air filter, it could get so dirty that at some point, the air would be blocked completely, therefore causing the engine to stall at idle. In which case your mpg will be impacted because you can't go anywhere.:D
Right! Your MPG takes a step function. 0 miles/0gal = infinity???
I forgot my theory but anything divided by zero approaches infinity.
Or is zero/zero a special case? :D
Are we getting enough off topic yet?

-Rg
 

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0/0

Interesting, never considered it. One could argue the answer to be zero, one, or infinity depending on what rule you would like to use.

It seems the answer is zero, which makes sense. Googling "What is zero divided by zero" has 88,000 hits which is amazing.



 

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plain and simple, air=hp. More air, needs more fuel for propper combustion. I would never have a dirty air filter.
He's right. It's Air, Fuel, Spark - Add more of any of the three it's more HP, but... Maybe not so much for spark.



 

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Improvements only occur with balanced air/fuel mixture.

He's right. It's Air, Fuel, Spark - Add more of any of the three it's more HP, but... Maybe not so much for spark.
EHHH! BZZZ! No, you really meant add more of the first two in the right ratio and you have more work = more HP!

If you add more air only the mixture gets too lean and will eventually not ignite. Too much fuel = too rich! It will run like crap and pollute. Just to be clear for those that might be inclined to butcher their air intake thinking huge gains in HP will be made.

That is why all the mods in the world to the air intake can only help so far. No improvement after the limiting factor; how much air you can get naturally aspirated into the combustion chamber is reached. And exhausted after combustion. Any further mods will not help unless a balanced improvement to the whole system is made.

-RG
 

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I know this seems of subject, but is there any kind of alternate intake you can use that can not cause hydrolisis or any kind of wet engine damage?

Also, yeah, you're right, I forgot to input all the fuel air ratio stuff. I will now take "Dirty filters" for $500 radar.



 

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to answer your question, a short ram should be fine, but in flooding, could still get wet, ie driving through streams,ect.

on the fuel air issue, having a dirty filter is like the difference between having a stock intake filter, or aftermarket performance filter. Why would anyone want to starve their engine of air/power?
 

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You guys need to read more carefully.

I am saying that you can increase the performance of the air intake. It might help to reduce the restriction over the stock setup. But it will only help as much as the weakest link. If the exhaust or valves etc will not let any more air thru into the combustion chamber naturally aspirated, any further improvements to the intake are a wasted effort.

Surje, it is hydrolock, not "hydrolisis".
Hydrolysis is a chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions (cut and pasted from Wikipedia).

Since you guys never believe me or disagree, check this out.
Read half way down to the comments by CRXguy. That is a funny one:
http://forums.beyond.ca/showthread/t-853.html

or

http://www.elantraxd.com/forums/showthread.php?t=10030

My cousin spent over $6.000 to fix his hydrolocked stock Nissan “Z”. Literally bent a connecting rod he told me.

Nuff said? Go ahead and modify the built in water trap/resonator/air cleaner several engineers making $100k plus salary worked on for months to design. If you guys were building a race car that would be a different story. But not for a DD. Please, it makes no sense what so ever! To me.

I went thru the modify stage many years ago. Heck I still do as a necessity so I can do thing I can not otherwise. I'm working on disk brakes for my new TiLite (titanium) wheelchair. My current one has them. Manufacturers do not make them that way. Living in a hilly area with disks I can hotdog down hills. I do know where you guys are comming from!

But not to re-engineer an air intake that works perfectly well. Increasing the chances of hydrolock in the process for a few HP? No way unless I lived in a dessert where it never rains would I ever even consider it. What am I missing without the mod and how important is it? Ask yourself that question before making the mod.

To be fair maybe the issue is that the ’08 has more HP so I see no need. Maybe if I had a Gen 1 or Gen 2 I would think differently. :rolleyes:

-Rg
 

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They have short ram by K&N. Is that any good? I know it's cheap. There's no real danger of flood or high waters here. The most I've ever had to drive through was about 6 inches of water. Is there still splash possibility from that much water? What about rain or carwashes?

That, and to Radar. Woops: "hydrolock." You're right. I do also know what hydrolysis is, I just had a stupid moment and combined my thoughts. Extra power would be nice on the 2nd gen, mine's the first year the second gen came out, not very many upgrades or improvements. The car has enough power, but the hills... it complains and cries and tells me it doesn't want to go up the hills. I live in a town that's made of just hills. Plus, I like to modify everything. I don't really need it, that's why I ask if there's a SAFE alternative. I don't want to do anything that could cause damage, no matter how cool it is. And I didn't say I didn't believe you or disagree. You're absolutely right, there's a lot of engineering that went into eve nthe stupid pins that hold the bumpers on, so yeah. But I'm not said "master" of air control on a vehicle, that's why I ask.



 

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Serje,
Only an old fart like me can have stupid brain farts. Or moments.
I am guessing that you are under 30 so stupid moments are not allowed! :D

-Rg
 

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Original opinion

In response to the original topic of a dirty air filter not hindering fuel mileage, I believe that it does have an impact. Actually, most people here will tell you it does.

Try breathing through a nice thick towel. That's a clogged air filter into your lungs. Sure my body will regulate what air I get so that I continue to live, but eventually it won't run so well... In the other logic, if a dirty air filter was the same as a clean air filter, then why do we change them?

If you have a stock crv, it shouldn't be too hard to change and the air filters (even from the stealers/dealers) don't cost that much. You can probably go longer without changing the cabin air filter, but even that gets nasty. Happy Breathing!
 

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Air filter change criteria

In response to the original topic of a dirty air filter not hindering fuel mileage, I believe that it does have an impact...
No one is debating that it does not at the extreme. No air, no work, no HP. It cannot breathe if 100% completely blocked. This is true!

The original jest was Pat Goss’ statement that a dirty air filter does not reduce MPG. I did not see the program but from the ones I have seen, Pat Goss (or his staff) knows their stuff and seems to enjoy busting myths. Playing the Devil’s advocate I can see the argument going something like this; there is a gray area between completely blocked and brand new that is acceptable and it will not change your MPG! On new injection systems that compensate for reduced air flow from dirty air filters by reducing the fuel injected using the PCM, in that case the air fuel ratio remains the same. Therefore so does the MPG. After all for max MPG you do not tromp on the gas to get max HP; you take it easy! :rolleyes:

I cannot disagree with that logic. There has to be some safety margin in the filter size design. Otherwise the first speck of dust would render the filter unserviceable without any safety margin. That and the fuel compensation issue should be sufficient of a myth buster for those still following advice from the pre compensation era. As in it always has been done that way therefore it must be the right way type of thinking. For those using a K&N I have read about a certain amount of dirt on the filter enhancing filtration. By a helping with grabbing dirt particles as opposed to a freshly cleaned filter. I did not say I believe it either; I am just the messenger. In this case it might have actually been a suggestion by K&N so that the filters are not cleaned too often, or more often than necessary. I forgot. :confused:

On the other hand since I cannot tell the point at which just enough air will reduce HP by reduced air flow, I will continue to use the criteria I learned (and possibly wrong) many years ago: if you cannot see the light from a trouble light bulb easily thru the filter (a 75-100W bulb) then the filter is getting pretty dirty and no point in trying to squeeze any more miles out of it. Having no test fixture to test for restriction that is the best and only thing I can do??? :confused:

Now if the filter is cheap enough, them even if it passes the light test, I might just go ahead and change it anyway. :) Since I bought it!

Most of us do that; we just go ahead and change it under the possible false understanding that it will affect our MPG. Now your max HP might change but the MPG will not (if I write enough times it must be true???).

Yes, I know, there are mechanics turning over in their graves all over the world! :eek:

All of this issue to delay changing filters only applies to DIYers. If you have a shop do the maintenance and follow the scheduled maintenance recommendations or MM, then unless you drive on dirt road often you will be all set. A little dirt on the surface does not necessarily mean it is time to change it when there is just a slight film of dirt.

Two engines, one with a new filter and the other with a layer of dirt visible on the filter will both get the same MPG since the fuel ratio is the same and the extra work required to breathe is negligible in the overall picture. Yes the work to breathe is insignificant compared to the output of over 100 HP. See my post #3 with the drops in the bucket analogy.

The two engines might not have the same peak HP. Who really uses 200 HP most of the time unless you are driving in the autobahn at 100-120 MPH into the wind? Or are pulling a load in very hilly terrain. Don’t these two criteria exclude most commuters? Most of us drive in fairly flat highways under 70MPH. Well maybe under 80 MPH!

That I believe was the jest of what started this post; yes most of us agree anyhow. "Oh no! That is not right! That is not what I do! That can't be right! I did a tune-up and MPG went up (but that is not the only thing you did or changed)!”...all denial type statements without even considering the logic and science behind the initial premise.

I have not seen anyone present any hard evidence otherwise.
Evidence guys, evidence to the contrary!
At least sound reasoning. PLZ!
I want ya'll to convince me otherwise.

-Rg
 

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I know this seems of subject, but is there any kind of alternate intake you can use that can not cause hydrolisis or any kind of wet engine damage?
Like illegal said a shord ram should be okay There are also covers to go over the air filter similer to the one for the K&N typhoon.

But If you don't feel like spending the dough on an air intake you could eliminate the stock airbox and hose (or jus the airbox) and attach a K&N air filter to the end of the throttle boddy (or hose). allthough I have never heard of anyone doing this in a CRV.

Radar it is difficult to convince you otherwise :D
 

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I think it really depends on the car and its condition if a DIYer wants to change the filter. I used to own a truck that when the air filter was clogged enough, it cut the air off and the truck wouldn't start, and I would have to shake the air box to get it to work. Replaced the air filter and it didn't happen again, then again, this truck was falling apart and there was probably a lot more to it than that. That's the truck I learned how to fix everything on. When I switched to Japanese cars though, I had to re-learn where everything was. Went from a Chevy and a GM to a Honda.

I can't say wether an air filter causes any damage to HP or MPG until it's extremely bad or not. I did however look up all those fuel saving ideas a while ago that were tested on a Ford Pickup. Some people have some funny ideas.

Link to article on useless fuel saving ideas.

Almost all of the ideas have something to do with the airbox, and it doesn't seem like anything affects it much, except to reduce horsepower, so with that, it looks like some kind of minimal blockage from dirt may make a difference. In one of the experiments in the aricle, the shove a weird tin thing in the intake hose near the sensor, and it actually reduced the HP, even though it was paper thin.

Which actually goes back to your original point, Radar, that no matter how much you (try) to increase air flow, the intake is still only going to work as well as its weakest component. I'll have to agree with you.



 

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Radar it is difficult to convince you otherwise :D
This is true. Evidence, man evidence! :D

I just do not see any point in Typhoon anything. Or those conical shaped K&N filters that look cool.

I just do not see much point otherwise. I do not need to look cool! I cannot afford to be cool! What in the overall scheme of things will it accomplish.

I'm into functionality improvements without sacrificing anything.

I am not willing to take the chance that just the right puddle or just going over water on the road might destroy my engine!

-Rg
 

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This is true. Evidence, man evidence! :D

I just do not see any point in Typhoon anything. Or those conical shaped K&N filters that look cool.

I just do not see much point otherwise. I do not need to look cool! I cannot afford to be cool! What in the overall scheme of things will it accomplish.

I'm into functionality improvements without sacrificing anything.

I am not willing to take the chance that just the right puddle or just going over water on the road might destroy my engine!

-Rg
thats why we said not to get a CAI. Most of the mods i do are to make the car perform better, or be faster, thats the way I've always been, the looking good mads, are because I want to. :)
 
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