vacuum issue has me stumped - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Tom25666 · 12-08-2009, 08:13 PM

first of all: the car is an s13 with a redtop sr, stock smic/bov, t25 @ 7psi. jeg's mechanical vacuum/boost gauge.

problem: my vac/boost gauge never reads vacuum. reads boost fine, just never shows vac (gauge never goes below zero). gauge is tee'd off the line between intercooler piping and wg actuator. everything seems to be working fine, seems like it wouldn't make 7psi if there was a vacuum leak, i don't hear anything either.

back story: up until about 2 months ago, my t25 was not making any boost at all. i don't know wtf the problem was, but one day i'm driving to work and i can actually hear the turbo and i have fuck tons more power. i had hooked the boost gauge up while the turbo wasn't working and it didn't read vacuum or boost. just sat at zero and actually read some vacuum under hard acceleration.

the gauge is not broken, the engine is making vacuum, and it doesn't appear to be leaking anywhere. sorry for the novel here, but i'm ready to figure this shit out

jspaeth · 12-08-2009, 08:19 PM

Quote:

Originally Posted by Tom25666

seems like it wouldn't make 7psi if there was a vacuum leak, i don't hear anything either.

Well if the leak is very small, it actually still will reach 7 psi, the turbo will just have to work a little harder!

But if it's reading boost but not vacuum, doesn't that mean it HAS to be the gauge is busted?

cotbu · 12-08-2009, 09:20 PM

unless the throttle body is cracked open at idle, your not gonna see vacuum the way you have it hooked up. hook your gauge up to something after the throttle body. AKA either one of the top ports on the stock throttle body. I don't now your setup so just see if it works.

jspaeth · 12-08-2009, 09:28 PM

Quote:

Originally Posted by cotbu

unless the throttle body is cracked open at idle, your not gonna see vacuum the way you have it hooked up. hook your gauge up to something after the throttle body. AKA either one of the top ports on the stock throttle body. I don't now your setup so just see if it works.

Oh god how did i miss that! Cotbu is right, your boost gauge needs to be connected to a manifold source.

warauto · 12-08-2009, 09:57 PM

Their is a couple vacuum lines that come from the manifold.

Three on top and i thin 2 on the bottom of the Throttle body. T the one that you use to open you blow-off/bypass-valve and connect it to the boost guage.

One goes to the carbon canister, another goes to the blow-off and one goes to the fpr.

Tom25666 · 12-08-2009, 10:20 PM

there are 2 on top and 1 on bottom. top left fpr, top right bov, bottom blocked after charcoal canister was removed. i always heard not to fuck with the fpr or bov lines. ??? does the cold pipe --> wg actuator line not see vacuum?

importdude · 12-08-2009, 10:20 PM

like posted above you need to connect to a vaccum source not a boost source

warauto · 12-08-2009, 10:23 PM

The wastegate actuator is connected directly to the hotpipe take that off and you go into full boost. T your BOV valve line and connect it there man. As long as the lines are messed you your going to be fine.

SoSideways · 12-09-2009, 11:48 AM

Quote:

Originally Posted by warauto

The wastegate actuator is connected directly to the hotpipe take that off and you go into full boost. T your BOV valve line and connect it there man. As long as the lines are messed you your going to be fine.

No.

You never hook it up to the BOV line.

Tee off the fucking FPR line like EVERY-FUCKING-BODY-ELSE, and everything will be kosher.

Tom25666 · 12-09-2009, 02:26 PM

Quote:

Originally Posted by SoSideways

Tee off the fucking FPR line like EVERY-FUCKING-BODY-ELSE, and everything will be kosher.

and kosher it is. thank you everyone.

12-08-2009, 09:20 PM	#3
cotbu Post Whore! Join Date: Sep 2005 Location: SWFL Age: 50 Posts: 3,318 Trader Rating: (3) Feedback Score: 3 reviews	unless the throttle body is cracked open at idle, your not gonna see vacuum the way you have it hooked up. hook your gauge up to something after the throttle body. AKA either one of the top ports on the stock throttle body. I don't now your setup so just see if it works. __________________ LoverTechnologies "Half Broken Things!"

12-08-2009, 10:20 PM	#7
importdude Zilvia FREAK! Join Date: Nov 2006 Location: san j0 Posts: 1,391 Trader Rating: (19) Feedback Score: 19 reviews	like posted above you need to connect to a vaccum source not a boost source __________________ built ka-t

12-08-2009, 09:57 PM	#5
warauto Zilvia Addict Join Date: Oct 2007 Location: GA Posts: 633 Trader Rating: (3) Feedback Score: 3 reviews	Their is a couple vacuum lines that come from the manifold. Three on top and i thin 2 on the bottom of the Throttle body. T the one that you use to open you blow-off/bypass-valve and connect it to the boost guage. One goes to the carbon canister, another goes to the blow-off and one goes to the fpr.

12-08-2009, 10:23 PM	#8
warauto Zilvia Addict Join Date: Oct 2007 Location: GA Posts: 633 Trader Rating: (3) Feedback Score: 3 reviews	The wastegate actuator is connected directly to the hotpipe take that off and you go into full boost. T your BOV valve line and connect it there man. As long as the lines are messed you your going to be fine.