M939 air filter mod

[army_nurse]

This may have been covered, so if this is a duplicate post mods please delete. I cut about 6 inches of the stock air filter housing out of the interior of the front (toward the engine) where it doesn't allow air to flow. So that increased the ability of the air filter to intake air without having to "add" any parts to the housing. There is about 2 inches of steel left inside the filter to allow the filter to stay in place. I will update on how it runs if there is any noticeable difference. I also plan to do the dual fuel mod soon as well. My goal is to get air and fuel to the engine simply and hopefully without the addition of any heat or any damage to it. This is a simple mod that if it proves to work any at all will have benefits. For just one rag (stuff in the intake) the cost of a 3 inch cutting wheel.

 

[army_nurse]

I went for a 20 mile shake down drive tonight. The truck runs totally differently. To start with it goes through the first 3 gears much much quicker. The engine sounds much different. It is smoother at idle and starts much easier even though it started well before the air cleaner mod. The real improvement was noted was in uphill pulling. There is a 12.5 % grade hill about 8 miles from my house. In the past I could only reach the top of that hill in second gear at approximately 20 miles per hour. Today I made to the top of the hill in 3rd gear at approximately 30 mph and the truck shifted into 4th just after the crest of the hill. I am very pleased with the results of this simple mod. Hope this helps someone else out

 

[gimpyrobb]

Just so you know, stock filters are washable. Might want to try and wash yours.

 

[MtnSnow]

What did you use to cut the housing down?

 

[Truckoholic]

I was looking at mine the other day. I have a plasma cutter that would be extremely easy to just stick in there and cut that part out of there. I should do it. My air filter is still super clean, but I can see a line there where it goes behind that part. Boggles my mind why they would have built it that way.

I also intend to do the dual fuel mod here soon. While I had the back head off the other day, I went ahead and took the plug out since I knew it would be far easier to do with the head off. It required heating a LOT with the torch, and one seriously bent up allen wrench, and one almost broken finger with the wrench I had on the end of the allen wrench slipped off and my finger got smashed between the tightly spring loaded allen wrench and the wrench I was using for added length. OUCH!!!! So I put the plug back in with some teflon tape on it, so when I am ready to get the parts and do it, the plug will be far easier to remove. ha ha

 

[army_nurse]

I used a small eletric 3 inch cut off saw. Cheap 19.99 harbor freight one. Easy peazy. If you have an air tool saw like that it's a perfect thing for the job as well. And yes I know the filters are washable. I washes mine. Flipped a 36 inch fan straight up and let it blow over night. That's what led to this mod. I got to looking at the filter housing. It looked to me that the 8 or so inches of metal to retain the filter in place was totally not needed. And as for that vortex thing how do you make a vortex pre filter not post? So....I left the 2 inches to retain the filter in location and then just put everything back like it was. I pot a big rag in the air intake while I was cutting and then cleaned everything out with wd-40 when I was done. Worked like a charm. Does anyone else see that this would be of benefit as far as air flow is concerned? If anyone else does this mod I would greatly appreciate your input and evaluation..

 

[lindsey97]

Maybe the engineers that designed the M939's did this as a air flow restrictor in order to detune the engine for durability.

ATV's and dirt bikes all have something done to the airbox that severely restricts the air flow into the carb. This is done in order to pass emissions and control noise output, especially with the newest four stroke bikes. They come very lean from the factory, and I have extensive experience with modding bikes and rejetting the carbs.

It wouldn't surprise me one bit if this was the case on our trucks. Please post pics of your airbox mods when you have time. I understand exactly what you did and the tool used, but would appreciate some pics.

 

[army_nurse]

I will take pics when I get home from work tomorrow and post them.

 

[army_nurse]

Here are the pics of the interior of the air filter housing. I included some measurements to show the increase of the area that air flows.

 

[Truckoholic]

After reading this post, last night it gave me the motivation to go out and pull my air cleaner out, and zip that section out with my plasma cutter. So now I have full air filter usage as well. I haven't driven my truck enough to really have anything to go off of to tell if it made a difference or not as far as performance or fuel mileage or anything. ha ha. But I know it has to help some giving access to that much more air filter surface.

 

[jpg]

One possible explanation for the original design is for fording. If water splashes up there, you don't want to suck it into the engine. If you drive into mildly deep water too fast, the bow wave can go quite high up into the engine compartment. With this mod, you might want to approach water more gently than before.

 

[hulabaloo]

lindsey97---with diesels, you restrict fuel flow, not air. Remember too much fuel with cause black smoke which also makes the temps skyrocket. Gasoline engines you restrict by cutting air.

 

[74M35A2]

lindsey97---with diesels, you restrict fuel flow, not air. Remember too much fuel with cause black smoke which also makes the temps skyrocket. Gasoline engines you restrict by cutting air.

With gasoline engines, you reduce fuel and air to reduce engine output. Spark timing can also be reduced with a gasoline engine to reduce engine torque, as is done during the up-shifting with automatic transmissions.

 

[therooster2001]

Subscribed!

opcorn:

 

[WillWagner]

Here is what I know. The extended tube at the end of a filter can is usually there as a stop. The excluder, the little rubber thing that looks like a set of lips...sometimes referred to in my part of the world as a dust pussy, located on the bottom of the filter housing facing down is there to drop large parts of debris out of the air stream being sucked into the filter and water also. Large pieces parts can lodge in between the pleats of the filter and as the air is sucked into the engine vibrate in the low parts of the pleats and eventually vibrate a hole in the filter media. Once this little hole starts, it only gets bigger. You, or your mechanic will not see the damage for a very long time, especially if the filter minder is used, it will nor register because the hole in the filter is letting unfiltered air into the engine...it is the path of least resistance. As for the water, the liquid will make the media wet, imagine that! The wet media will rip under the strain of the CFM the engine requires resulting in the same scenario as above.

That 5 extra inches of metal stops water and large parts from getting into the filter media. The velocity of the air spinning into the housing forces water and large debris into that area of the filter and into the dust pussy/excluder area so at the pre trip and post trip you as the driver can squeeze the pussy and let the debris out.

My advice is to NOT remove it. But your stuff ain't mine, so I guess you can do what you want with ur stuff. Just be aware of the consequences.

IF the filter mfgr didn't want it there for a reason, they would have left it out. it costs them money to put it in and if it wasn't there, the mfgr would be on the hook for engine damage.

But what do I know?

 

[Those Military Guys]

Hey guys if this help you save some time we sell these air cleaner kits to make your life easier it is a drop in kit no modes
http://www.steelsoldiers.com/showth...ITS-for-the-m939-trucks&p=1752815#post1752815

 

[shootist]

I put one of tmg's air filter kits in my 936a2 .....
the difference is night and day... I can no longer get out of truck and run around it going up. 3% grade....
the difference is immediately noticeable. I picked up 15 mph on grades it would literally stand still on...
shifts better runs better etc.
matter of fact I need to order another filter I run it so much. Where as before it was just to slow to go anywhere with.
then boosted the low end on pump...couldn't be happier minus the just yesterday bad transfer pto......
pall I can say is yep.....lowest bidder built.....
but try the filter mod from those guys, best thing I did to truck yet.

 

[Ford Mechanic]

Hey guys if this help you save some time we sell these air cleaner kits to make your life easier it is a drop in kit no modes
http://www.steelsoldiers.com/showth...ITS-for-the-m939-trucks&p=1752815#post1752815

Just ordered one from these guys!

 

[big block 88]

I cant get that link to work for the mod kit??

 

[WillWagner]

8 month old thread. Try contacting Those Military Guys, They probably have the kits.