Author Topic: PCV valve (Read 8399 times)

KD5ITM · **on:** March 15, 2018, 08:13:29 pm

Who has installed a PCV valve on the crankcase where the crankcase breather hose goes into the air box? A long time ago somebody to talk about that on here but I can't find the post. What's the exact purpose of doing that? Is it just to keep oil fumes from getting into the air box causing a slight oily residue on the air filter?

KD5ITM · **Reply #1 on:** March 15, 2018, 08:13:51 pm

Pictures in the part number would be appreciated.

Arizoni · **Reply #2 on:** March 15, 2018, 09:43:11 pm

I think Ace did that to his with the idea that it would lower the pressure in the crankcase.

Lowering the pressure in the old Iron Barrels crankcase which housed just the crankshaft/flywheels, piston and connecting rod was/is important to improving performance and reducing the amount of oily mist that is blown out.
The stock Iron Barrels blow a LOT of oil out of the crankcase breather.

With the relatively huge volume of the UCE engines crankcase, IMO, it is no longer important.
The stock UCE engines blow little to no oil out of the crankcase when they are running.

KD5ITM · **Reply #3 on:** March 15, 2018, 10:44:43 pm

Well I just pulled out my K&N air filter and the rubber on the back of side opposite of the opening had a very thin film of oil on it. I wiped out the airbox and there was some oily residue in spots.

hpwaco · **Reply #4 on:** March 16, 2018, 12:04:17 am

Amen to the iron barrels blowing out lots of oil! My 02 es would regularly fill/overflow the "catch bottle". Finally ran a hose back to the rear fender/license plate (like triumph did on my 500 scrambler) and put a duckbill on it. Problem solved. I periodically check my GTs airbox but its always clean/dry.

KD5ITM · **Reply #5 on:** March 17, 2018, 09:42:27 pm

Remove my air filter at the other day for the first time since installing it at around 6000 miles ago. Filter looks brand new. But there was a very thin film of oil on the back of the filter opposite the opening on the bottom side. And the airbox had a few spots with oil. Nothing one sheet of paper towel couldn't fix.

Jellyroll · **Reply #6 on:** March 18, 2018, 11:29:33 pm

I haven't seen that problem yet, but oil blows right past the nylon washer on the big bolt on the right side cover. I'm considering cork, treated paper, copper, or my own made from Permatex Ultra Black. Otherwise the engine looks like used flypaper. Or a 'proper British motorcycle'.

KD5ITM · **Reply #7 on:** March 26, 2018, 01:40:52 am

There's a video on the Royal Enfield of Fort Worth Facebook page for November 22nd that shows a Continental GT with some racing stripes and modified exhaust. They eliminated the crankcase breather hose and installed a crankcase breather filter. Much like the crankcase breather filters that you see on valve covers that people put on their hot rods.

KD5ITM · **Reply #8 on:** March 26, 2018, 01:49:43 am

Crankcase breather filter

Richard230 · **Reply #9 on:** March 26, 2018, 02:10:28 am

Quote from: KD5ITM on March 26, 2018, 01:49:43 am

Crankcase breather filter

That modification is good for a $10,000 fine in California.

KD5ITM · **Reply #10 on:** March 28, 2018, 09:29:55 pm

Just living in California is a good fine for something

Guaire · **Reply #11 on:** March 28, 2018, 09:43:20 pm

I put in the PCV valve with a hose that ends above the chain.

hpwaco · **Reply #12 on:** March 28, 2018, 10:55:38 pm

Is that a paper or gauze filter? What happ ens if/when it gets wet?

ace.cafe · **Reply #13 on:** March 28, 2018, 11:23:01 pm

A "breather filter" also good for a loss of performance. Air is never supposed to be sucked in thru an engine breather. Only pushed out.

Chuck D · **Reply #14 on:** March 28, 2018, 11:29:21 pm

Quote from: ace.cafe on March 28, 2018, 11:23:01 pm

A "breather filter" also good for a loss of performance. Air is never supposed to be sucked in thru an engine breather. Only pushed out.

If you've only taught us one thing...

KD5ITM · **Reply #15 on:** March 31, 2018, 06:48:47 am

That's funny, the crankcase breather hoes on my Olds 350 goes right up to the air cleaner

Guaire · **Reply #16 on:** March 31, 2018, 01:40:18 pm

Quote from: KD5ITM on March 31, 2018, 06:48:47 am

That's funny, the crankcase breather hoes on my Olds 350 goes right up to the air cleaner

So did the old hose on my GT. We know better.

ace.cafe · **Reply #17 on:** March 31, 2018, 02:36:03 pm

There is engine vacuum in the air filter housing. Air is pulled out of the crankcase by that engine vacuum, via that PCV hose. The PCV valve in the hose closes if there is any condition that could permit air to go back down that hose into the crankcase.

PCV means Positive Crankcase Ventilation. This means it vents out.

I realize that misconceptions abound about this subject, but I assure you that I have researched it very thoroughly in scholarly texts and in real world testing. If anyone doubts, truth is clearly found out by doing your own research. I am 100% certain that your independent research will concur with my statements.

KD5ITM · **Reply #18 on:** April 01, 2018, 12:48:54 am

How much crankcase pressure does the 535 build up?

ace.cafe · **Reply #19 on:** April 01, 2018, 02:43:48 am

Quote from: KD5ITM on April 01, 2018, 12:48:54 am

How much crankcase pressure does the 535 build up?

535cc volume change with every stroke.
ThiS is not the only issue however. There is something called pumping losses which occur as the engine tries to pump 535cc of air in and out of that little 10mm hole 1000-5500 times per minute. This is extra work as it acts as an air compressor which uses up horsepower that could have been used to drive the wheel.

If you think it's negligible, have a look at the vacuum pumps that are standard equipment on virtually every drag race car on the planet. If they are concerned enough about crankcase evacuation on a 1400hp Super Stock car that they install vacuum pumps to reduce crankcase pressure and pumping loss, maybe we might want to think about it on our 20hp RE. We can't afford to lose much, because we don't have much.

Bilgemaster · **Reply #20 on:** April 01, 2018, 02:07:44 pm

Quote from: KD5ITM on March 15, 2018, 08:13:29 pm

Who has installed a PCV valve on the crankcase where the crankcase breather hose goes into the air box? A long time ago somebody to talk about that on here but I can't find the post. What's the exact purpose of doing that? Is it just to keep oil fumes from getting into the air box causing a slight oily residue on the air filter?

I recently had pretty much the same common breather issues on my old 2005 iron barrel, only a bit more dire (i.e., occasional near-total oil loss). It and the easy fix for "The Heavy Breather Sploodges" are described in this thread, with links to all the necessaries that quickly sorted it out well enough for the leisurely likes of me, along with info on "Ace.Cafe's" far more performance-friendly but difficult mods if you're wanting to wrangle every last pony out of that engine.

ace.cafe · **Reply #21 on:** April 02, 2018, 12:29:23 am

The airbox has a vacuum present during running, which draws air from the crankcase most of the time. The PCV prevents air from going back into the crankcase if the vacuum condition isn't present.

The problem with that is that oil has no octane component, and can cause detonation when it is in the combustion chamber. And oil could be burped into the airbox under certain circumstances, and oil-soak the filter. So my preference is to avoid venting to the airbox for those reasons.

Bilgemaster · **Reply #22 on:** April 02, 2018, 03:03:13 pm

Quote from: ace.cafe on April 02, 2018, 12:29:23 am

The airbox has a vacuum present during running, which draws air from the crankcase most of the time. The PCV prevents air from going back into the crankcase if the vacuum condition isn't present.

The problem with that is that oil has no octane component, and can cause detonation when it is in the combustion chamber. And oil could be burped into the airbox under certain circumstances, and oil-soak the filter. So my preference is to avoid venting to the airbox for those reasons.

Not to threadjack here, but I cannot help wondering if that airbox inlet hose for the breather catchcan gizmo, once disconnected and plugged as it is with mine, might not be used as a water injection inlet of some sort. For those unfamiliar with water injection, a fine mist of water is introduced into the fuel-air mixture, which, if done right, increases the octane and power a bit, also cools down the engine, and as a side benefit leaves your combustion chamber squeaky clean. Google is your friend for further details. Suffice it to say that water injection is why your engine will often just seem to run sweeter on a lightly misty morning.

ace.cafe · **Reply #23 on:** April 02, 2018, 06:07:07 pm

Quote from: Bilgemaster on April 02, 2018, 03:03:13 pm

Not to threadjack here, but I cannot help wondering if that airbox inlet hose for the breather catchcan gizmo, once disconnected and plugged as it is with mine, might not be used as a water injection inlet of some sort. For those unfamiliar with water injection, a fine mist of water is introduced into the fuel-air mixture, which, if done right, increases the octane and power a bit, also cools down the engine, and as a side benefit leaves your combustion chamber squeaky clean. Google is your friend for further details. Suffice it to say that water injection is why your engine will often just seem to run sweeter on a lightly misty morning.

The airbox is not a good location for that, but the water injection on the throttle body could work. Probably the best way to do it is set it up like a carburetor jet with an outboard float levelocity for the water supply.