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Discussion Starter · #1 ·
I stumbled across this while doing some research for ways to drop the crankcase pressure (to reduce the engine's pumping losses):

- route the crankcase vents (in valve covers) into the PAIR air inlet ports
- the vacuum created by the exiting exhaust gases acts to draw air from the crankcase vents, thereby creating a partial vacuum in the sump, and reducing pumping losses.

The concept seems logical (and promising). Wondering if anyone here has tried it?

Thanks in advance
 

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Mikstr, Would you give more direction, or a diagram of how the hoses, need to be run?
Knowing you own a Superhawk also, And reading the threads on the topic... usually V-twin owners -either flip the reed valve over.. or block off the "PAIR" valve in the valve covers..
Does this procedure work on both Honda V-twin cycles?
And what are the power gains?
 

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Discussion Starter · #4 ·
Essentially, you would be routing the valve cover breather hoses into the fresh air inlet ports in the PAIR system. Doing so would require a 14-12mm adaptor and the necessary hoses to link everything up. With the rest of the PAIR hardware removed (the vacuum set-up), you esentially end up with a reed valve feedign directly to the exhaust system. This allows you to tap into the negative pressure in the exhaust (created from the exhaust gases leading) and using it to create a partial vacuum in teh sump, thereby reducing pumping losses.

I have read that virtually all roadrace teams use such a system (see attached pic; vented oil cap leads to PAIR inlet port) as it raises output due to reduced losses to pumping effect in the sump.
 

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this is what i use(and used.)
extremely long braided line,readily available at Nankai etc for many bikes

works well I reckon(engine oil can't go anywhere but back down),but I will be trying the NAG one shortly just to test
the line is about 80cm long or longer


 

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thread hijack

that exhaust pipe in the first pic you posted is pretty slick simon; are those welds buffed out or are they bends? looks like ti, if they are bends i've never seen any like that before
 

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thread hijack

that exhaust pipe in the first pic you posted is pretty slick simon; are those welds buffed out or are they bends? looks like ti, if they are bends i've never seen any like that before
one off exhaust by the Ladybird maker
lots of individual bits welded together then polished and burned
wasnt easy to make I hear



some bikes use the frame for a vent tank etc


 

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Discussion Starter · #13 ·
Still looking for info on the working of the NAG valve and found this:

http://zaidantj.hiho.jp/ron/19ron/ron_19_04.pdf

Have a look at figure 4 on page 2. This is pretty well how I imagined it to be (a one-way valve which works off the difference between the crankcase and airbox pressure). Simple and straightforward. In essence, the weight of the floating piston is what sets the vacuum setting in the crankcase (instead of a spring).
 

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Question is why are NAG's so expensive when they're such simple valves and why do they have so many of them? I'm guessing they each have different weight pistons to compensate for the differing engine types? Either way, they seem very expensive for what they are.
 

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Discussion Starter · #16 ·
Question is why are NAG's so expensive when they're such simple valves and why do they have so many of them? I'm guessing they each have different weight pistons to compensate for the differing engine types? Either way, they seem very expensive for what they are.
I have come to the same conclusion. I am considering trying to build my own using a standard pressure relief valve. I could then put a vented oil cap on, hook it up to a vacuum gauge and fine-tune it to get the desired vacuum level in the case.

Long winter..... lol
 

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I really wonder what kind of horsepower could be gained from something like this. Doesn't really seem like it would be much return for the time and money spent. I'd love to see before and after numbers.
 

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Discussion Starter · #20 ·
well, the benefits of creating a partial vacuum in the sump must be significant enough. The new 1199 uses a pump to achieve this, all MotoGP bikes use some means to vacuum creation, virtually all drag racing engines mechanical pumps for this purpose..... It all boils down to how much $$$$$ to get there.....
 
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