Jump to content
Sign in to follow this  
Superluminal

Air filters

Recommended Posts

Hello, im by no means a nitro expert - about this time last year I stripped down and completely rebuilt my kyosho mantis gp car. At the time I bought a brand new sponge kyosho air filter for it as the old one was 23 years old and had turned to mush.

Its not been run, simply sat in plastic box in a cupboard. Today I got it out to have a tinker as I would like to run it this year and the brand new sponge filter has also turned to a sticky gungy mush!!!!! The cars never been run - i simple stripped it, cleaned it, oiled it and rebuilt it.

Is this just one of thos things that happens to them? Or do they needs some sort of looking after rather than sitting in a box. I assumed they would be oil resistant as most nitro cars seem to be continually covered in a film of oil residue after use.

 

Resized_20200126_121603_6916.jpeg

  • Sad 1

Share this post


Link to post
Share on other sites

Do they come preOiled or dry?

Dunno haven't had any go to mush, mine rather go hard then disintegrate into powder when poked. 

Or when trying to wash out the dirty oil, the sponge reacts with the solvent and expands to thrice the size... and doesn't shrink back after drying. Whoops.

 

Wonder what can be used to DIY make new sponges :) 

  • Like 2

Share this post


Link to post
Share on other sites

I cant remember now! It might have been slightly oiled out of the packet - cant be sure 100%. I let all the parts soak in wd40 before reassembly and lubing with some 3in1 oil. It hasnt had any nitro fuel through it since rebuilding.

Is it possibly a reaction to the wd40 residue? I dried everything off before rebuilding.

I have some old dish sponges that I could cut up and reuse.

Share this post


Link to post
Share on other sites

Very likely that's it - kerosene in WD40 & 3-in-1 mineral oil ain't kind to rubber (so we've since learnt), likely not kind to foam rubber too.

I use 3-in-1 for Afterrun oil... must work, no rust after so many decades :) 

Btw when they say "oil your airfilter" they don't mean real liquid oil... it's more Dirt Bike foam air filter oil - it's a thickish (non greasy!) liquid that you soak in, wring out excess then let it air dry. The solvent in the oil evaporates leaving behind a real sticky (coloured!!) coating on the foam. Some swear by K&N Recharge kits (cleaner & fresh oil), I just buy Dirt Bike foam filter oil... think my last bottle is by Castrol, it's a white bottle. 

Otoh if you're wrenching on an old MG or many other BMC vehicles with an oil pan/bath Air Filter, they DO mean use fresh engine oil; the intake air bubbles thru a pan filled with liquid oil. Meh... upgrade to pancake filters or go up a better model :P mine came out from factory standard with twin SUs and Vokes filters. 

 

 

How how do you intend to cut your foam?

Its not just a plain solid lump cut to cylinder shape. You gotta carve out a cavity in the middle, size of an AA battery. Some have blind end of foam; some are just a foam tube capped at the top by the plastic body.

I don't think power tools would work on flimsy foam & carving with heat using a soldering iron might not end pretty.

  • Like 1

Share this post


Link to post
Share on other sites
17 minutes ago, Superluminal said:

Is it possibly a reaction to the wd40 residue?

Just like WillyChang said, my old air filters also crumbled.  I think it happens to every sponge after 5-6 years. I wonder if it had been pre-oiled for 5 years before you opened the packet?    

Sponges are cellulose. Carbohydrate like plant cell walls. Think of soaking spaghetti in oil, it's not going to maintain its shape for long.  I like to think of it as a one-time use item.  I don't soak it in oil until I'm about to hit the field.  Fortunately, you can get one from China for $1.   

Or you can get one of these for $15-$20.  I've got a K&N cloth filter in my Subaru. It's been in there for 16 years (or 144,000km) without any trouble.  With the money saved on paper filters, I bought 2 RC cars (so I tell my wife).  

GFXokWM.jpg

 

  • Like 1

Share this post


Link to post
Share on other sites

Those things commonly sold as "RC K&N" are really made for crankcase/gearcase breather filters :) I'm never convinced they're meant for unrestrictive air intake so I never trust them on an RC.

You don't want too much air restriction or your carb tuning would be too rich.

Other than the old OPS (disposable paper/plastic/aluminium element) or Delta (corcentina'd thick paper) I've stuck to oiled foam. The later RC foam filters were 2 or 3 stage of different foam densities, I only oiled the inner or middle stage. 

K&N reOilable filters are a coarse cotton weave, aren't they? The Vokes fitted by MG mentioned above are also a corcentina'd donut of coarse cotton... made in Britain, predates K&N by at least 30yrs...! :P 

 

Filter wash/reOil best fine days before use, not at the track so my pit box usually had a ziplock bag of extra oiled sponges... haven't seen that baggy for many years, wonder where that's disappeared to. Be curious to see how that foam has aged.

 

  • Like 1

Share this post


Link to post
Share on other sites

Thanks chaps - thats probably it, there probably left over oil in the bottom of the crank case thats soaked in / evaporated off over the last year and eaten away.

Carving out a new cylindrical piece with a bore down the middle is proving much more difficult than it looks (the deformed semi octagonal lumps my scissors are creating doesnt form a great dirt seal)

I will order a new one but not fit it until i intend to run it.

Share this post


Link to post
Share on other sites

There absolutely should be a filter on every Nitro engine

  • Like 2

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...