no vacuum???

[mattysr20]

ok I'm at it again lol anyways I have searched but I can find anything at least not the same.

ok first thing is I've been having weird afr readings and I still haven't figured that out but maybe its all connected.

I have a s15 Sr20 and at idle the boost stays at 0 it is always at 0 never goes below just goes up. it seems to boost fine and it doesn't idle bad but to my understanding it should read -20 vacuum right? I dunno if it matters but my bov is on the cold side and my boost gauge goes right in the intake pipe it a turbo xs bov and a turbo xs mbc any help would be great thanx...


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[OrangeVirus1]

You have to have your boost gauge hooked up the your INTAKE MANIFOLD, AFTER the throttle body to see vacuum.

you are not going to see any vacuum on an intercooler pipe.

problem solved

[cotbu]

Your boost/vacuum gauge needs to be hooked up to a vacuum source after the throttle body, to read vacuum when the throttle is closed.

[jr_ss]

Yep, you need to move where you have it hooked up. Only after the throttle body is there vaccum. If you have it tapped on a port at the throttle plate or a charge pipe you'll only see boost.

[mattysr20]

it is on the cold pipe right above the bov


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[jhimes]

It goes behind the throttle body. you have it hooked up to your intercooler piping. It goes into the intake plenum.

[anti tyler]

like everyone else said, behind the throttle...

Car Engine Vacuum line basics | Repair | Leak leaks (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Vacuum%20Basics.html)

Automotive Vacuum Systems

http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Images/Vacuum%20Engine%203.jpg


yes i'm well aware this picture is not a 240. but it makes a better example of where to relocate your vacuum line.
How they work, and how to repair them

Contributed By: Enginebasics.com
Every car on the road since the invention of the combustion motor has used the motors vacuum to perform many functions, but just how does it work?
A motor can be looked at as a giant air pump. The bigger the pump, the more power it makes. Also, the more efficient the pump, the more power it makes. A motor is constantly moving air in and out of itself. The Vacuum that a motor produces comes from the intake stroke (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/4stroke%20Engine.html) of the motor where the crankshaft (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Crankshafts.html) draws down the piston (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Pistons.html) and air is pulled or “sucked” into the motor. In this situation, if the throttle butterfly (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Intake%20Manifold.html) is open, not much vacuum is produced since you are freely letting the air flow into the motor. Take that same situation when the throttle plate is closed and the motor will be generating a lot of vacuum as it struggles to suck as hard as it can to pull in air and feed itself passed the closed throttle plate.
One thing important to understand then, is that vacuum will only be present BEHIND that throttle butterfly. In front of the throttle plate there will be no vacuum present due to the fact that it is open to the air box and therefore atmospheric pressure. Also remember that the amount of vacuum a motor will have will be based on how good the piston rings (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Piston%20Rings.html) are, and also the cam (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Basic%20Camshaft%20Understanding.html) that the motor is running. Having a good seal from the piston rings most people understand, but when running a very large and aggressive cam, often there will be more overlap in the duration between intake and exhaust valves (http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Engine%20Valve%20Basics.html) that will cause a loss of vacuum at idle. This loss of vacuum causes the motor to struggle when idling at low RPM’s.

[mattysr20]

o ok that makes sense well should I fix it or is it ok ? it still reads boost just not vacuum but if need be ill just tap into a vacuum line


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[anti tyler]

there's no reason to ride around like that. do yourself & your car a favor and clean that line up. that way in the future if you ever run into any issues you wont have to try and figure out why the hell you have a vacuum line where you shouldn't.