DIY Guide: The 'elephant hose CCV (catch-can) mod'

[Basil]

Yet another pikey performance mod

Disclaimer: this mod is strictly speaking only legal for commercial diesels in the US. Despite this, it’s a fairly common mod especially for Diesel Jeeps, to avoid problems with their Crankcase Ventilation systems. I know of one person who has been using this mod in the UK for quite some time with no problems.

Essential: a 1.5meter length of heater hose and suitable hose clamp (jubilee clip), hacksaw, masking tape and some epoxy glue. Legally required: a catch can that vents to atmosphere.

The OEM pollution control recirculates carbon from the exhaust plus oil vapour from the crankcase vent. Alone, neither one is a serious problem, but the mix results in gooed-up turbo’s and narrowed intake manifold passages.

Many people have by-passed the exhaust recirculation (EGR) by using an Allard racepipe and getting the CEL light mapped out. Result: no soot to clog up stuff, more "fresh air".

The CCV (crankcase vent) is attached by a short hose just after the MAF sensor at 90 degrees, so there is a venturi suction effect. It continously draws in hot air loaded with oil vapour, heating up the intake air! Suction would be highest when airflow is highest. This hot air is not measured by the MAF and could theoretically backflow to contaminate the sensor.

Also, the oil vapour coats the intercooler insides, reducing heat transfer and acting as a lubricant to help the IC pipes pop apart when running higher boost.

The lengths one goes to in order to get the coldest intake air into the engine makes this system a logical one to mod out of existence!

To do this mod: remove the OEM pipe. Hacksaw the upper air intake hose connector on the pipe you just removed and fill the end with epoxy. Place masking tape on and allow to cure standing up so that the end is closed off. Place masking tape on the intake open end to keep out dust while your “cap” cures. Alternatively rubber "end caps" are available from plumber supply shops.Plug off the open pipe so that no air gets in.

Attach heater hose to the other end and route down by the brake booster to just behind the console. Wire tie as needed. The lowest end is left open – hence the name elephant hose mod(as in elephant "trunk"). The system is positively pressurized so no risk of nasty stuff getting into the engine.The hot air and oil vapour (not liquid oil) are vented to atmosphere.

To be PC and do the right thing, the lower end should be connected to a catch-can that is vented to atmosphere. Typically this needs emptying only every 6-12 months. People have made them out of brillo-pad stuffed coke bottles, etc or gotten shiny ally cans to do the same thing.

This setup is legal.

If you live in an area that freezes, you need to make a slit at the lower end to prevent condensed water freezing and plugging the end.

Results: well, I notice that the car runs better at 43 deg C out here, more power by seat of the pants testing and far less smoke. Admittedly I did confound results by cleaning the airfilter at the same time so that may be just coincidental. The MAF now only measures the total amount of (clean cool) air from the filter without a varying amount and quality of stale hot crankcase air.....

Some reports claim a better mpg with this mod - that would need testing to verify.

Took only about 20 mins to do - a very simple pikey type mod.

The intake air that is coming in no longer has hot oily oxygen-poor air being continually injected into it, sucked in from the crankcase through a 22mm hose.

And that can’t be a bad thing.

Cheers, Bas

[devonutopia]

I know of one person who has been using this mod in the UK for quite some time with no problems.

:confused: Who?

Nice write-up.

[Basil]

Well, let's just say that he's the king of modding Fabias......

[Delcac]

Well, let's just say that he's the king of modding Fabias......

He sounds just run of the mill.

[skudmissile]

Another quality Mod there Bas.

Keep Up the good work mate

[Tech1e]

Nice write up Bas.

The 'better' way of doing it (if you dont mind Bas me inputting) is to not blank the intake off but to run the pipe through the catch tank. So you have camcover, heater hose, catch tank, heater hose, intake.

This way your not venting to atmostphere and the oil deposits being heavier than air collect in the bottom of the tank which can be emptiied periodically.

[Basil]

Thanks Ross - you're quite right of course - but I wanted to avoid any hot air at all coming into the intake.

[skudmissile]

Thanks Ross - you're quite right of course - but I wanted to avoid any hot air at all coming into the intake.

I can see where that would be useful in your climate.

Surely though if my brain is working correctly, is the engine loosing metered air through the vent :confused: I just can work out in my head at this moment in time.

[Tech1e]

The inlet is capped off so no air is being drawn in through there.

[skudmissile]

The inlet is capped off so no air is being drawn in through there.

Ar yes makes sense now. i pictured the engine pulling unmetered air through the hole in the turbo intake pipe. if thats capped then thats no problem

[Basil]

gonna clean out the FMIC this weekend just to make sure it's at 100% efficiency....

[Basil]

sorry - not really meant as a bump but:

1- car seems to be performing noticeably better (downright sweetly) at ambient temps of 43 deg C

2- found a complex scientific paper on oil vapor effect on heat transfer -

quote: " At high vapor qualities for all mass velocities, the oil has a very detrimental influence on local heat transfer, resulting in lowered heat transfer coefficients by up to 90%"

Turbo engine suck harder on the crankcase vent hose at high boost - with more oil vapor therefore less efficient heat transfer in the IC. Not good.

see chapter 16 http://www.wlv.com/products/databook/db3/data/db3ch16.pdf

I'm happy with this mod about a week on into it....

Bas

[ninja_alex]

Done this to mine and a mates vrs last week. Nice mod, but it does steam well under the car now, especially when the weather is cold an wet!

[skudmissile]

[PC mode on] should we really be venting oily resisdue onto the road? As a biker i wouldnt want to hit somoenes oil patch at high speed :eek: [pc mode off]

Nice mod but i recon it would be better with a can on the end to catch anything

[Basil]

The steam is apparently water vapour - legally you should have a catch-can (people have made them out of empty plastic coke bottles). You're venting vapour not liquid oil. Big trucks in the US do this mod all the time....

[skudmissile]

The steam is apparently water vapour - legally you should have a catch-can (people have made them out of empty plastic coke bottles). You're venting vapour not liquid oil. Big trucks in the US do this mod all the time....

I am fine with steam and vapour

I just had this image of oil pouring out onto the road for some daft reason, but if that was the case the sump would be dry in no time, I should really think before posting

[Basil]

In fact - in theory you should lose less engine oil than "usual" as the vapours are not being actively sucked out, just passively vented... The more you boot it, the harder they are removed apparently more so on a turbocharged engine (?!).

btw - anyone notice a difference in the UK after doing this mod? I know it made my car more responsive, but this climate is extremely hot.... I'd welcome any feedback, good or bad..

Cheers

Bas

[thirty3]

So venting straight onto the floor or venting straight onto the floor via a catch can where do you stand at MOT times surely its a fail.

[skudmissile]

In fact - in theory you should lose less engine oil than "usual" as the vapours are not being actively sucked out, just passively vented... The more you boot it, the harder they are removed apparently more so on a turbocharged engine (?!).

btw - anyone notice a difference in the UK after doing this mod? I know it made my car more responsive, but this climate is extremely hot.... I'd welcome any feedback, good or bad..

Cheers

Bas

Ill have some feedback shortly for you Bas

[ninja_alex]

Car deffo seems less smokey, not sure on performance as i did this and the dogmount at the same time. Car feels better though

[thirty3]

I have had this mod on a 06 golf pd since noveber. But catch the vapour in a can and re-route the air back to the air intake pipe.

I took is off today and got about a cup of water from it...I was gobsmacked by the amount in the small time frame.

[Lofty86]

Have done it to my Furby now, and run it for a tank.

Venting like an elephant turns out to be a top cheap mod.

Better mpg (in the uk, about 16-19c and dryish).

I havent got a catch tank, and have managed to get an almost oem look!

Will post pic tomorrow.

HTH, Dave.

[devonutopia]

Been running mine for quite a long time now. No obvious effects, but I'm :) that no re-circ is going on. Nice clean air going in all the time.

[thirty3]

Do you think this mod stops the egr clogging (because thats the sludge build up soot exhaust and water vapour from crankcase). Or do you think it just reduces the build up.

[Basil]

Having scraped the goo out of the intake manifold myself - it's really nasty thick sticky tar-like stuff being formed in there. It seems you need both components (carbon + oil) to clog things up.

Dry carbon soot shouldn't stick as badly and would burn off pretty easily I'd imagine.

HTH

Bas