Hacking Your Air Compressor for Fast Fill Up




My cheap air compressor was taking a long time to pump up. So I investigated and found some strange things that impede air flow. This Instructable will show you how to make your air compressor pump up faster. This particular air compressor was purchased from harbor freight.

Step 1: The Original Air Filter Is a Muffler?

So the original air filter has an indirect air path to the foam filter. This is to make it quieter. But its a loud air compressor. If you want more flow with out voiding your warranty just flip this cover over and air can come in from any direction.

Also in the third picture the highlighted area shows where the plastic was covering the air inlet. This was from super high quality Chinese manufacturing.

Step 2: The New Air Filter

I was looking at multiple solutions for a better air filter and I found this bad boy. Its total thickness is just a hair more than the original total setup.

Step 3: Tools Needed Step 1

A Dremil with a cut off wheel, or any rotary cutting tool, an Exacto knife, and sandpaper.

First cut off the bottom bowl.

Step 4: Step 2 Grinding and Cutting

now grind the rest of the material off until its flat. Sand the base flat as possible.

Also now you can use your exacto blade to remove the casting flaws that are blocking air flow. I highlighted the areas on mine that were clogged up with excess plastic.

Step 5: Asseble and Enjoy

1. Screw in the original base

2. Install the base plate from the kit with the washer underneath.

3. Oil the foam, and install the cover.

4. Enjoy your new fast filling air compressor.



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    15 Discussions


    1 year ago

    I have one comment on the TYPE of filter. I don't like the oiled foam filters when used on oil-free compressors (like my DeWalt 15 gallon, 200 PSI), because it will contaminate the air on that type. A dry "paper" (in reality it should be a Resin treated paper) filter is best, even when you need to replace the element from time to time, dpending on how dirty is the air in your shop. In oil lubricated compressors the oil added by the oil-foam filter is of no consequence, but it tends to be less eficient than pleated paper ones. Amclaussen.


    4 years ago on Introduction

    Interesting information, there are a few things you should be aware of though as you may be running your equipment outside of it's design parameters. Typically compressors are designed to use the maximum power provided by it's driver (motor, engine, etc.). This is determined by the operating pressure and flow rate. Making a compressor run beyond these parameters will generally cause the driver to operate overloaded and result in drastically reduced lifetime. My suggestion would be to check the amp draw of the motor and compare it against the data on the motor tag. If this is not available then a baseline drawn from running the compressor before modification might help. You can do an amp draw using a clamp meter. You will want to check the amp draw once the unit is near it's cut-out pressure.

    On the topic of noise, compressors like this are always noisy because of the speed at which the pump runs and also because reciprocating are inherently noisy. Reciprocating compressors consist of a piston, cylinder and pairs of check valves. In this unit it has reed valves which are little strips of spring steel that sit against a valve plate, as the piston moves up and down the reeds pop open and then snap shut, this is the origins of much of the noise. One way to reduce this is to relocate the inlet air filter. You will notice on your air filter assembly it looks to be standard 1/2" NPT pipe thread. If you plan to use your compressor without moving it you can move your inlet air filter assembly to the outside if this is practical. Simply run PVC pipe from the inlet to outside the nearest wall and thread your filter into that.

    Hope this helps some of you, I have worked on industrial air compressors for over a decade and this is how we help reduce noise in equipment.

    1 reply

    Reply 1 year ago

    A REPLY TO WayneEarl, jd-bugman and madpenguin8.-

    Friends: While your comments are based on some clear facts, your criticism is going a little too far, and you are NOT understanding the value of the modification made by the author, which I find perfecly advantageous, BTW.

    Let's analyze your comments in more detail:

    1) To WayneEarl's comment on a lack of a Baseline recharging time.-

    Here Wayne has a good point, as having a good comparison between both 'before' and 'after' is very valuable, so the comment is valid.

    BUT, from that comment on, Wayne goes astray, so astray that he suggests that this Instructable "needs additional research" and even saying: "Perhaps giving poor advice".

    Sorry, I disagree. Let me clarify: MOST commercial compressors are poorly designed and assembled, in fact. That is because the manufacturers seldom have the engineering knowledge to completely design all the subsystems for the equipment they sell. Most frequently, they just use whatever inlet filter thay can get from others at the lowest cost and the smallest size that still "works" (and "works" is an exaggeration, the proper wording would be: "BARELY WORKS").

    In my job (as a process design engineer, 39 years of experience in the petroleum industry) I've seen quite a bit of compressors, and most of the commercial ones are badly integrated, like the one the autor upgraded.

    2) To jd-bugman: How do you know that simply replacing the element would had solved the airflow restriction? Again, the advice given by the author directed to INCREASE the filter area is a good one, as it is practically impossible to install a "too-large" filter. 99% of them are way undersized.

    3) To madpenguin8, Please don't be so close minded... ("...running outside the design parameters...") Don't forget that any restriction in the inlet tract is going to reduce the air inlet flow, well. So the compressor will run with a slightly larger flow, OK. But you are worried about overloading the electric motor by placing a larger torque demand corresponding to the slightly larger airflow, but you forget the other damage mechanism: a longer compressor run also tends to produce more heat in the motor windings. By running it in shorter periods (with longer cooling pariods), an even LOWER resulting temperature would be entirely possible. You are right that the higher airflow COULD overload the motor, but the complete operating cycle of the compressor is now different, not necessarily harder on the motor, as the common service factor of 1.1 or 1.15 will easily absorb the larger flow, that is effective only for a short time, as as soon as the compressor raises the discharge pressure into the tank, the flow will go down correspondinlgy. In small household compressors, the WORST enemy is not the flow overload, but the need to re-start the compressor against an only partially discharged tank, which places the greatest starting current stress on the motor, but very few of the manufacturers install a discharge valve to avoid starting the motor against a large pressure whent he compressor re-starts.

    Installing what is called an "Unloader valve" that vents the compressor discharge during the re-starts avoids the huge starting current that the motor has to overcome when compressing against a partially filled tank. That will be the theme of my next Instructable, as I have seen lots of domestic compressors damaged by the lack of that valve, and the manufacturers seem that they do not want the compressors to last much more.

    Lastly, I find this Instructable a good one and feel your criticism can prevent some enthusiasts to take advantage of the benefit of an increased (or more properly said, RESTORED) airflow and corresponding shortened running times. Best Wishes. Amclaussen.


    1 year ago

    Hi bensmith, I did exactly the same thing to my DeWalt 15 gallon Oil-Free compressor bought at SAM's... The air inlet filter is housed in a too small container that had only six very small (I think it was 1/4") holes letting the air into the compressor head, probably for silencing purposes, but it appears to be a result from bad or mediocre design and lack of engineering; which gives us plenty of opportunities to try to upgrade the factory design.

    But the worst thing in the DeWalt, was that the electric motor-compressor housing had a round opening that let the Ozone-Ladden cooling air to be aspirated into the compressor, to be delivered to the tank, thus the compressed air had a strong ozone smell, which means that the compressed air is contaminated with the ozone produced by the electric motor brushes, and then the motor cooling fan blows that contaminated air and because the housing had a round opening that let the cooling ozone-ladden air to be blown downwards, to be readily aspirated by the inlet filter. As you may know, ozone is a very strong oxidant, that is legendary for its tremendous destructive power in regards to damage produced to Rubber and most elastomers... This is serious, as most household compressors are used for tire filling, no less!

    My solution was to seal the round opening of the motor-compressor housing with PVC foam ("foamy" sheets), and to lenghten the 1/2" pipe that connects the filter to the compressor head, so that the air filter now aspirates "clean" air and now that air is odor free, meaning that the ozone ladden cooling air is being blown away from the filter. The filter housing was kept, but the small hles were enlarged to almost 1/2" and additional holes were drilled. Now the filter housing breathes more easily and also make a little more noise, that is not objetionable as the rest of the compressor is quite noisy and masks the filter noise completely. Best Wishes and Congratulations. Amclaussen, Mexico City.


    9 years ago on Introduction

    wow i have one of these... and it works great. how much faster does it fill, and where did you get the b&s air filter kit?

    6 replies

    Reply 9 years ago on Introduction

    I bought the filter at home depot. It fills in about 5 minutes. It used to take what seemed like forever.


    Reply 5 years ago on Introduction

    so then, by "forever" are you saying you didn't take a baseline measurement? by definition, a functioning filter will always result in some air flow restriction due to it work as a filter - some mesh or other static material that will filter out things as a result of it's collision with moving air under pressure. this is partially why most air filter systems are supposed to be Very close to the drop where they will be used, and is also why it is good practice to have a pressure gage both before and after a filter - as the filter fills up and is used, it gradually increases pressure loss, and the manufacturer should tell you at what point the pressure loss means time for replacement. removing the filter will increase flow - until contaminants fly pass the filter less air intake and destroy your compressor motor, or you destroy painting targets or air tools with dirty air. I would suggest additional research on the topic - perhaps you have given poor advice here?


    Reply 1 year ago

    I agree. Usually when someone puts this effort into something they do it right, which doesn't seem to be the case here. How does he know it fills faster if he can't tell us how much faster? AND I'm guessing the original filter was a mess (he failed to show the foam insert) and by simply replacing that he wouldn't have had to go through all this.


    Reply 5 years ago on Introduction

    My advice is to remove the stock piece of crap air filter. Then replace it with a better filter with more surface area. The stock filter consisted of a cheezy 1" foam disc. It would possibly stop a bug from flying in but hardly stop dust. So the lawnmower filter is a massive upgrade is filtering technology. And as a bonus is fills up faster. This is due to the muffler less design. It is a bit louder, but its worth it.

    Lorraine Prather

    1 year ago

    Really we got interesting and important information from this.


    5 years ago on Introduction

    Another Harbor Freight Nut! They opened in my home town 3 years ago and I love the place. Hacking there equipment is mostly a must due to as you say the High quality Chinese manufacturing. The new filter has got to beat the original in every way accepting a slight noise increase. They couldn't get much noisier though. Great idea! My wife as a Customs broker imports containers full of High Quality Chinese manufactured products so I can't complain too loudly but I must add that as businessmen they're really butterheads!

    Geetha shree

    5 years ago on Step 2

    It helps to know how to hack an Air Compressor's easily by us. Inner parts are clearly shown as see the equipment really.