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Discussion Starter · #1 · (Edited)
How to: Crankcase Vent Mod. *Updated* flow test pg.6

This Crankcase Vent Mod. will use the vacuum supplied by the exhaust through the reeds to create a negative pressure in the Crankcase.
This helps the internal parts do their “work” without the resistance of positive pressure.

The engine is more efficient with the pressure drop.

This mod. should help your engine rev. faster. HP gains? Depends on flow. I have not "yet" measured cfm on the 10.

How the Air Switching Valve works. I cut this out of the 08 service manual and inserted some text. May be useful to help understand what happens here.



1/2" T and 1/2" I.D. 5/8" O.D. hose replaces the stock components. Our vacuum supply.



This pic. is a screen shot of the crankcase vent line (highlighted in Green) from the service manual. This is the crankcase vent hose.



Here you can see an inside view of where the crankcase is vented to in the 08 airbox. Does the crankcase have positive pressure? Notice the small amount of oil circled in black.



Here you have your vent line disconnected from the airbox (circled) and the new line fits right inside. Reuse the same pinch clamp.



Airbox nipple gets a 1/2 - 5/8" I.D. cap and can be returned to the stock setup easily.



I routed the new vacuum line on the right side to avoid the already cramped fuel line on the left side.



Obviously, connect the vacuum line to the 1/2" T



When the mod. is complete it looks something like this.



I used about 3ft. of hose, one 1/2" Tee, two 5/8" caps (I think 1/2" caps would work) and 6 stainless hose clamps. Cost around $5.

Flowtest vid. on page 6
 

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Discussion Starter · #2 ·
I also used some insulated pipe wrap tape to make a heat shield while I had the airbox apart. I didn't take the bottom of the airbox off, but I was able to tape it up fairly good. No good pics of that.

Here is a pic of the Ram Air inlet part of the airbox that I insulated. I think this stuff was $3 or $4 a roll.



And a pic of the inlet set down onto the airbox. Fits great, no pressing or forceing it down.

 

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whats the point for this mod?i thought the reed valves could only work one way?so any crank pressure is going down into the exhaust port is that right?so you will still get popping ect on decel???:dontknow:
 

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There's only 1 small problem bro...that's not your crankcase breather ;) Those are reed valves and are for you air pump. Your crankcase breather is on the lower front side of the airbox that goes directly into your engine. There is actually no need for you mod at all, instead of cutting the pipe just vent the reed valves to each other and you're done. Check this out:
http://drainfade.com/tech_writeups/zx10r_valves.html

You can see what I did to block my reed valves to prevent backfiring on decel running my BMC/PCIII/Slipons.

P.S. Great effort though...and really nice pictures.
 

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He's not trying to do the "block off" mod to prevent the decel popping. Tenn is attempting to gain some Hp by creating a vacuum in the crankcase which in "theory" will allow the pistons to decend quicker on the power and intake strokes and therefore increase power.

I've heard the theory before and I think it's BS. The problem is that when 1 piston is coming down, another is going up. So really the air displaced in 1 cylinder as the piston comes down is actually pushed into the cylinder with the piston going up. If you create a reduced pressure in the case then it's going to hold back the ascending pistons so any gains you might see in Hp by "sucking down" the decending pistons is gone. This is all based on the fact that you could actually create enough vacuum in the case to make a difference.

I'd like to see some hard numbers on this to back up the statement that "the engine is more efficient with the pressure drop"
 

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He's not trying to do the "block off" mod to prevent the decel popping. Tenn is attempting to gain some Hp by creating a vacuum in the crankcase which in "theory" will allow the pistons to decend quicker on the power and intake strokes and therefore increase power.

I've heard the theory before and I think it's BS. The problem is that when 1 piston is coming down, another is going up. So really the air displaced in 1 cylinder as the piston comes down is actually pushed into the cylinder with the piston going up. If you create a reduced pressure in the case then it's going to hold back the ascending pistons so any gains you might see in Hp by "sucking down" the decending pistons is gone. This is all based on the fact that you could actually create enough vacuum in the case to make a difference.

I'd like to see some hard numbers on this to back up the statement that "the engine is more efficient with the pressure drop"
Its not just the displacing of the pistons air, it is any pressure in the crankcase including pressure that leaks passed the rings. On a car(8cyl race engine) running an air pump in reverse to keep a negative crankcase pressure hp increases of 20-30 hp are not unlikely even with the pump being belt driven so there is power to be had. the rings will seal better and you can get away with a lower tension ring set therefore freeing up more hp. This setup however I dont believe will create the amount of vacuum needed to make it effective.(I ran the crankcase on my car at 12" vacuum) On the motorcycle powered sprint cars the valve covers are modified to block off the runners to the exhaust and holes are drilled to allow crankcase pressure to escape the top port on the plate, we run breathers on each plate to keep dirt out. If there was a way to gain more power the circle track guys would have found it and all the engine builders are doing it by venting it with breathers.
 

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Discussion Starter · #8 ·
He's not trying to do the "block off" mod to prevent the decel popping. Tenn is attempting to gain some Hp by creating a vacuum in the crankcase which in "theory" will allow the pistons to decend quicker on the power and intake strokes and therefore increase power.

I've heard the theory before and I think it's BS. The problem is that when 1 piston is coming down, another is going up. So really the air displaced in 1 cylinder as the piston comes down is actually pushed into the cylinder with the piston going up. If you create a reduced pressure in the case then it's going to hold back the ascending pistons so any gains you might see in Hp by "sucking down" the decending pistons is gone. This is all based on the fact that you could actually create enough vacuum in the case to make a difference.

I'd like to see some hard numbers on this to back up the statement that "the engine is more efficient with the pressure drop"
I thought and argued the same thing for a long time several years back. I said the same exact thing when a friend and I started brainstorming this
idea for our ZX12's back in 01 I think. The best thing to do if you are curious is do a search on "crankcase vacuum pumps". There is a reason the make and sell these pumps.

The question (for me) is how much vacuum does my bike have? I have a vacuum gauge, but decided not to hook it up. Hg doesn't matter to me. I would like to see the cfm.

I beat my 12 to death on the dyno along with other board members. There are gains to be had. Just put this out there for those who might be interested.
 

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Discussion Starter · #9 ·
Its not just the displacing of the pistons air, it is any pressure in the crankcase including pressure that leaks passed the rings. On a car(8cyl race engine) running an air pump in reverse to keep a negative crankcase pressure hp increases of 20-30 hp are not unlikely even with the pump being belt driven so there is power to be had. the rings will seal better and you can get away with a lower tension ring set therefore freeing up more hp. This setup however I dont believe will create the amount of vacuum needed to make it effective.(I ran the crankcase on my car at 12" vacuum) On the motorcycle powered sprint cars the valve covers are modified to block off the runners to the exhaust and holes are drilled to allow crankcase pressure to escape the top port on the plate, we run breathers on each plate to keep dirt out. If there was a way to gain more power the circle track guys would have found it and all the engine builders are doing it by venting it with breathers.

Thanks for your input.

"Volume" is the key for big gains. I will be doing further research for the 10. Although the gains are not going to match those of the aftermarket vacuum pumps, the idea is to use what we already have in place to our advantage. Even if the HP gains are nothing, the reduced work/resistance in the case should net a faster revving engine at least. IMO
 

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the reed valves only open and suck in air on deceleration, to burn off extra unburnt fuel when you shut the throttle down, when you are cruising or at full throttle the system is shut down so exhaust wont go up threw the system, so by doing this mod you will be sealing your crankcase at cruising and full throttle runs, this is very bad for horsepower and will probable blow some oil seals quickly. examine how the reed valve works!!
 

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the reed valves only open and suck in air on deceleration, to burn off extra unburnt fuel when you shut the throttle down, when you are cruising or at full throttle the system is shut down so exhaust wont go up threw the system, so by doing this mod you will be sealing your crankcase at cruising and full throttle runs, this is very bad for horsepower and will probable blow some oil seals quickly. examine how the reed valve works!!
im no expert!but the reed valves were being opened by the ais servo pumping air trough fron air box down into exhaust ports? when the sensor detected closed trottle?so now the reeds air seing crankcase pressure at all times they will be constantly open???:dontknow:
 

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they work on vacuum, inside if your reed there is a one way valve that lets air in but not out. under that are holes that go directly to your exhaust ports. so at high throttle openings or cruising the reeds are pressurized by exhaust gas, closing the system. when you chop the throttle the exhaust pressure suddenly drop's. using the Venturi effect the exhaust port sucks in air threw the reed valve from the airbox. if you start the bike and remove this hose, you can here it sucking at idle, the noise suddenly stops when revved. the mild pressure of the crankcase will not overcome the extreme pressures of the exhaust at the port.
 

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Like Vince10R said; engines this size simply don't make enough vacuum to make any difference. This has been argued about ever since the '90s on pretty much every bike forum there is and no one can come up with any consistant, repeatable data that shows it really does anything.
 

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this is also why you find race teams with simple block off plates. i spoke to someone on attack kawasakis crew when i was at road Atlanta 2009. i was having an issue of oil pumping up into my airbox threw this breather tube due to my hi compression pistons and blow by. he told me that they remove the breather from the airbox. all it does is pump lots of extremely hot dirty air into your airbox at full throttle, this is not what your engine wants for good horse power, but it must be done this way for emissions. cant have oily blow by just leaking into the air. so he told me that they block the airbox hole and simply route this hose somewhere on the bike where they set up a catch pan for the oil that comes out. or they just simply use a crankcase filter on the top of the engine. that's what they do to there top level AMA bikes. if you go to maxton mile you will here of people roughing there breather into a catch also.
 

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Discussion Starter · #15 ·
they work on vacuum, inside if your reed there is a one way valve that lets air in but not out. under that are holes that go directly to your exhaust ports. so at high throttle openings or cruising the reeds are pressurized by exhaust gas, closing the system. when you chop the throttle the exhaust pressure suddenly drop's. using the Venturi effect the exhaust port sucks in air threw the reed valve from the airbox. if you start the bike and remove this hose, you can here it sucking at idle, the noise suddenly stops when revved. the mild pressure of the crankcase will not overcome the extreme pressures of the exhaust at the port.
Of course the exhaust pressure drops when you close the throttle. Not looking for gains at this point anyway.

I don't believe the system ever completely closes though. I am glad you bring this up. This is not something that I am 100% certain of so lets test it out. I will see if I can find something to measure the vacuum on with the throttle open and closed. If I can't come up with a cfm, I will at least test this using a vacuum gauge with a controlled leak for now.

I have been doing this mod. for over 8 years now. I've logged a ton of miles on different bikes with no negetive effects. Nor have I heard of any. I have heard of and seen small gains. I may make some back to back dyno runs one day, but I doubt any time soon. I've been there, done that honestly.

Just sharing info.
 

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Discussion Starter · #16 ·
this is also why you find race teams with simple block off plates. i spoke to someone on attack kawasakis crew when i was at road Atlanta 2009. i was having an issue of oil pumping up into my airbox threw this breather tube due to my hi compression pistons and blow by. he told me that they remove the breather from the airbox. all it does is pump lots of extremely hot dirty air into your airbox at full throttle, this is not what your engine wants for good horse power, but it must be done this way for emissions. cant have oily blow by just leaking into the air. so he told me that they block the airbox hole and simply route this hose somewhere on the bike where they set up a catch pan for the oil that comes out. or they just simply use a crankcase filter on the top of the engine. that's what they do to there top level AMA bikes. if you go to maxton mile you will here of people roughing there breather into a catch also.
When testing this before we ran this idea past an Attack crew member. Not gonna name drop, but this is not a "legal" mod. for racing.

Removing the Crankcase vent hose from the airbox is definately a good idea as long as you contain the oil of course.:+1:
 

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Discussion Starter · #17 ·
Like Vince10R said; engines this size simply don't make enough vacuum to make any difference. This has been argued about ever since the '90s on pretty much every bike forum there is and no one can come up with any consistant, repeatable data that shows it really does anything.
Very true. It's just a mod. that "I" do and I had time to document it so anyone interested could have a reference.

I'm not going argue the advantages or disadvantages of the mod. However, I am interested in intelligent info. that might lead me to learn something.:wink:

zxbrian10r makes a good point. If in fact the reeds do completely close, I wanna know. I don't "think" they do, but lets see.:eek:ccasion1
 

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to all the guys talking about when the reed valve open and close I would have to think if i was even going to try something like this I would run a one way check valve(something like used in a car for the vacuum hose going to the brake booster) between the crancase vent and the valve cover tee(this will allow vacuum to be pulled on the crankcase but not allow pressure to feed back into it). then i would take the reed valves and remove the reeds(keeping everything else in the reed assembly but not the reeds, you will need this as it is the gasket for sealing it) so it will alway pull whenever there is high exhaust flow. Just the exhaust flowing past the tube extending into the exhaust will create the vacuum your looking for. Just like the old style as someone else mentioned that got welded to the collectors but with less volume which inturn will create less vacuum(negative pressure) in the crankcase
 

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Discussion Starter · #19 ·
Actually we did once have something working back in the early 90's but not using the reed valves. We welded a one way check valve (made by NAPA) into the exhaust between the collector and muffler and as the exhaust gases rushed out the cannister the negative force pulled open the 1 way check valve which was connected to the crankcase breather placing a vacum draw onto the crankcase. It was good for 2-3 HP on every engine we did it. We did about 10 of those as I recall.

But that involved welding a steel part onto a steel pipe (most pipes were steel back then).


I don't see how this scheme using the reed valves would work. Seems like under hard acceleration the reed valves would be closed, only open under decell so I fail to see how that would improve anything.
However the concept of improving negative crankcase pressure is sound. All NASCAR engines use a pump to suck it out. They have done that for a long time.

I'm thinking this could be tested on my stands using RPM's as opposed to acceleration under a load?
 

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Discussion Starter · #20 ·
to all the guys talking about when the reed valve open and close I would have to think if i was even going to try something like this I would run a one way check valve(something like used in a car for the vacuum hose going to the brake booster) between the crancase vent and the valve cover tee(this will allow vacuum to be pulled on the crankcase but not allow pressure to feed back into it). then i would take the reed valves and remove the reeds(keeping everything else in the reed assembly but not the reeds, you will need this as it is the gasket for sealing it) so it will alway pull whenever there is high exhaust flow. Just the exhaust flowing past the tube extending into the exhaust will create the vacuum your looking for. Just like the old style as someone else mentioned that got welded to the collectors but with less volume which inturn will create less vacuum(negative pressure) in the crankcase
Good idea.

I was thinking along the same line of maybe removing the reeds if they actually close, but I need to get in there and understand more about how they work.

A check valve may be a good idea, but I would want some sort of very low pressure relief for this application.
 
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