At what restriction should I change the filter

[mitsuman47]

I've had my wix restriction gauge for a few years now. I changed one air filter at 80k miles because the gauge never budged, and I thought that my restriction gauge may not read a low enough amount of pressure for my little 1.7L, low power engine to register on it. I've seen a recommendation for gasoline engines to change at about 20 inches of h2o, but figured that the reference engine is considerably larger than mine. So, what do you guys think is a good amount of restriction for me to change the filter in my 1.7L honda?

 

[Mr Nice]

Just change the filter every 40K mikes.

I don't see why a restriction gauge is necessary.

 

[NHGUY]

I'm surprised a little engine even has enough sucking power to move the needle.Usually you see those things on diesels or Z71 V8 GM trucks.

 

[The motor guy]

Got one on my truck. The filter will probably rot a hole in it before that gauge moves. I just replace the every 40,000 miles or so on my truck. It's not even 20 bucks for the filter.

 

[DBMaster]

With all the discussions on this forum stating that replacing the air filter TOO often is bad for your engine, folks have become paranoid. The end result of those discussions for me has been that I will not open up the housing to "check" the filter and I will just replace it at the intervals specified in the owner's manual. Done and done.

 

[johnachak]

Originally Posted By: DBMaster
With all the discussions on this forum stating that replacing the air filter TOO often is bad for your engine, folks have become paranoid. The end result of those discussions for me has been that I will not open up the housing to "check" the filter and I will just replace it at the intervals specified in the owner's manual. Done and done.


+1

 

[rrounds]

I have one on all my cars but the one I use the most is on my S2000. I can get 80 to 100k miles on my filter before the gauge tells me to change the filter. On the S2000 the air filter is a cone filter that sits inside of the airbox so you can open up the airbox and not disturb the air filter.

Even if you(I do) had a .75L engine(motorcycle) it would move the gauge if you didn't have any air leaks in the system and the air filter was restrictive.

If you think your engine doesn't have the umph to make a vacuum, just take the intake hose off and put your hand over the T/B and see how hard it can suck and make a vacuum. Even at an idle it would make pounds of vacuum not the little 15" of H2O vacuum you should have before you change out the filter. You check the restriction of your air filter by going WOT up to redline and then you check what the gauge reads.

ROD

 

[circuitsmith]

The size of the engine has nothing to do with how much pressure drop is produced across the filter, if the filter is properly sized of course.
A larger engine does not have "more sucking power".
A 3 cylinder in a Chevy Metro will draw the same 20" Hg manifold vacuum at idle as a big block V8, given comparable cams etc.
A larger engine will draw a larger VOLUME of air of course, but no more pressure/vacuum.

 

[Jim Allen]

Originally Posted By: LT4 Vette
Just change the filter every 40K mikes.

I don't see why a restriction gauge is necessary.



Obviously, you have no understanding of how and why a restriction gauge is used. If you want to know, we'll explain it.

 

[Jim Allen]

Originally Posted By: circuitsmith
The size of the engine has nothing to do with how much pressure drop is produced across the filter, if the filter is properly sized of course.
A larger engine does not have "more sucking power".
A 3 cylinder in a Chevy Metro will draw the same 20" Hg manifold vacuum at idle as a big block V8, given comparable cams etc.
A larger engine will draw a larger VOLUME of air of course, but no more pressure/vacuum.


Exactly right.

Sometimes an OEM manufacturer will specify a maximum restriction and you see this often with commercial diesels that usually come equipped with a restriction gauge. Otherwise use the maximum restriction of 15 or 20 inches of vacuum for a gas engine and engine size does not matter much, except for sizing the gauge to the engine and most often, that's just differences in the scale of the indicator (some indicate 5 inches to 15 and others 10 to 30... obviously you want one that indicates in the range your engine needs).

Bear in mind the gauge records the maximum restriction it has seen. If you are putt-putting around town and never see WOT, it could take an eternity to reach 20 inches of restriction but along the way it may be restricted enough to cut back on available WOT power. That's why you set the clean filter baseline with a good full-throttle run. You then do that periodically and observe the readings. When it reaches 20 inches at WOT, or whatever maximum restriction is specified or desired, THAT's the time to replace the element. Doing it that way assures that you will always have your rated power output.

 

[mitsuman47]

Thanks a lot, Jim! Exactly the type of answer I was looking for.

I did a wot run with my new filter and my gauge didnt budge. I guess the 8-24 inches that my gauge reads is a little high for my engine. But, as I understand, I can keep an eye on it by testing it every few thousand miles, then change it when one of those tests shows about 15 inches of restriction.

And, as far as putting around goes, I drive about 140 miles per day, all highway. So, my car sees just about the easiest usage possible.

 

[Jim Allen]

Originally Posted By: mitsuman47
Thanks a lot, Jim! Exactly the type of answer I was looking for.

I did a wot run with my new filter and my gauge didnt budge. I guess the 8-24 inches that my gauge reads is a little high for my engine. But, as I understand, I can keep an eye on it by testing it every few thousand miles, then change it when one of those tests shows about 15 inches of restriction.

And, as far as putting around goes, I drive about 140 miles per day, all highway. So, my car sees just about the easiest usage possible.


Yeah, 8-24 is a little high but only if you care about reading the numbers as they go up. The main thing is that the unit will read your required restriction, which it does. At some point, you'll see the "8" indicated and then you'll know you are "on the gauge."

One thing I neglected to mention... every time you plan on doing a WOT test, reset the gauge. That assures you the unit is working. Under normal circumstances, a WOT test after a long period of normal driving would show the increase (if there is any) but resetting and rechecking services as a basic functional check of the unit. They do occasionally fail.

 

[rrounds]

One more thing, on all of my engines that have a filter gauge. When the filter starts to show a restriction from the air filter, the time it takes to get from 6" to 15" takes a lot less time and miles than it took to get from 0" to 6". Once it starts to read a restriction I check the gauge more often.

 

[Smokescreen]

Has anyone found that the restriction gauge losing its ability to read over time? Does the mechanism get sticky after oh lets say 15 years?

 

[Jim Allen]

Originally Posted By: Smokescreen
Has anyone found that the restriction gauge losing its ability to read over time? Does the mechanism get sticky after oh lets say 15 years?


I think it's a possibility... anything mechanical can fail. That's why you do an occasional functional check, e.g. reset at WOT test it. Also, you can pull it off and do a "suck test" on it. I would presume some units are better quality than others and so some might last longer than others.

Interestingly, I recently bought a 1974 John Deere combine and it has a restriction gauge on it. The original one AFAICT (original type as shown in manual at least) and it still works perfectly. It eve suck tested well. I will replace it with a Donaldson informer just because the Donaldson has a scale where the OE just has green/yellow/red.

 

[ARB1977]

30K on the CRV and call it good. The Tacoma gets cleaned every 30K, AFE Pro Dry.

 

[FZ1]

Originally Posted By: DBMaster
With all the discussions on this forum stating that replacing the air filter TOO often is bad for your engine, folks have become paranoid. The end result of those discussions for me has been that I will not open up the housing to "check" the filter and I will just replace it at the intervals specified in the owner's manual. Done and done.
+1. Every 2 -2.5 years.

 

[Colt45ws]

Originally Posted By: rrounds
One more thing, on all of my engines that have a filter gauge. When the filter starts to show a restriction from the air filter, the time it takes to get from 6" to 15" takes a lot less time and miles than it took to get from 0" to 6". Once it starts to read a restriction I check the gauge more often.

Interesting. I was wondering if something like that would happen. I already have 6" with 8k miles on my Amsoil filter. If I dont even get 16k out of it before it needs cleaning, then I wouldve had a power loss if I did it by mileage since Amsoil calls for it to be cleaned after 25k.

 

[Jim Allen]

Originally Posted By: Colt45ws
[
Interesting. I was wondering if something like that would happen. I already have 6" with 8k miles on my Amsoil filter. If I dont even get 16k out of it before it needs cleaning, then I wouldve had a power loss if I did it by mileage since Amsoil calls for it to be cleaned after 25k.


I have one truck (turbo diesel) that indicates more than 6" with a perfectly clean (K&N no less) filter. Go figure.

But that's the benefit of a restriction gauge. It tells you when it's time to change... whether that's a short interval or a long one. Colton, did that filter start at zero or did it have some initial restriction? Amsoil advertises their filters are more efficient than the others (smaller particle capture) which would tend to make them load up faster unless you increased the media area to compensate. Which you couldn't do if you bought a replacement element to fit the OE airbox.

Or do you live in a dusty area or encountered some? Is Mt. St. Helens quiet?

 

[Colt45ws]

Started at zero. Though its completely possible it started with some restriction initially that was somewhere between 0 and 6 inches.

Fairly dusty, I would say. The wind likes to whip through here pretty often and keep the dust stirred up.

We shall see what she does. Will probably be about a year before I know. An interesting test would be to take it to the track one weekend with a new Motorcraft filter and the plugged Amsoil. Run as back-to-back as possible 2 or 3 runs of each and see what 20" of restriction means for WOT power.
1" of H20 = .036PSI. So at 20" you are losing .72PSI across the filter.