Vaccum Line Blocked Off To Bypass Butterfly Valve In Inlet?

[kyle345]

So i was at TAFE today and we discovered something with my car.

As you can see below (from what i described) the vacuum line from the air box was broken off and was blocked off with a cap and taped up.

Now blocking the vacuum line off caused the butterfly valve in the inlet manifold to stop working (open and close/ open under throttle) Im not exactly sure what the valve does.

Now that i have connected the vacuum line back to the air box as seen in picture one, i have noticed its more torquey and got a slight improvement in power.

I dont understand why the previous owner blocked that line off? Is there something going around on the internet telling people that you will benefit by blocking it off or something?
The hose broke off, i could see that was evident from the condition of the hose, so maybe it accidentally got ripped off when taking the air box out and the person didnt know where it came from so they just taped it up and blocked it off??


Any ideas?

[Reedo]

i have a 34 neo n/a in my neo so ill cap off that line tomorrow and take it for a drive and see if i notice anything at all. from following the lines i figured that it was a pressure release point and just into the airbox for pollution crap. because i have a 33 airbox my line just dangles underneath the airbox. but anyways ill post again tomorrow after a test run.

[kyle345]

ok cheers mate will be interesting what you seem to think the difference is

[iseekool]

It's for the variable length intake manifold. Helps with providing more torque at low RPM. Once you are at high revs though, it makes no difference.

Only reason why it would be blocked off is if the previous owner was trying to troubleshoot vacum leaks (osolate problems) or thought they are smarter than the Nissan engineers, thinking that blocking it off will give more power

http://en.wikipedia.org/wiki/Variable-length_intake_manifold

[kyle345]

It's for the variable length intake manifold. Helps with providing more torque at low RPM. Once you are at high revs though, it makes no difference. Only reason why it would be blocked off is if the previous owner was trying to troubleshoot vacum leaks (osolate problems) or thought they are smarter than the Nissan engineers, thinking that blocking it off will give more power http://en.wikipedia.org/wiki/Variable-length_intake_manifold

Ahhk that makes heaps of sense now.. i saw the valve opened under high rpm to let more air in was my assumption, but i couldnt understand why they didnt just have it open all the time.

Thanks for your help