After topswap vacuum problem

[hockeybawler]

So after putting in my topswap I am seeing -7in/hgs of vacuum on my boost gauge and -9.5 on my aeroforce. How should I check for vacuum leaks?

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[Turbocharged400sbc]

id the aeroforce reading in psi? boost gauge vac readings are all over the place sometimes

whats the idle in kpa

 

[hockeybawler]

Yea it is reading in psi and I am not sure, how would I check?

 

[Turbocharged400sbc]

-9psi would be about right if it is

i dont know if the aeroforce has a inHg pid but i know you can pull up manifold air pressure in kilo-pascals (kpa)

 

[hockeybawler]

alright if that seems right then I guess that is why when I was spraying starter fluid the engine didnt rev up. Thanks for the help

 

[1quick]

how is -9 psi vacuum about right?

 

[hockeybawler]

I just used a calculator for it online and -9.5(which is what my current readings are based on my aeroforce) is about -19.3 inhg which is about where I should be on vacuum. Just had to calculate it out using the different units of measurement to get the info I needed

 

[1quick]

oh yeah yeah i was thinking 9 in vac like your boost gauge was showing -9

 

[Turbocharged400sbc]

how is -9 psi vacuum about right?

your doubt me?


*ahem*

 

[1quick]

I thought maybe you had too much spinach today Popeye lol, didn't realize you were talking about a different measurement

 

[Turbocharged400sbc]

yeah different scales/gradients

 

[hockeybawler]

How much boost do you think is safe to run on a 04 gp that is top swapped, headers, HAI, and 3.5" pulley with a zzp 1.0 tune? Right now I am running 4 pounds of boost and seeing no KR so how much do you think would be safe?

 

[1quick]

If you have a gen v and a 3.5 pulley your boost gauge is broke or you have a big vacuum leak you should be around or over 10lbs of boost on that setup

 

[hockeybawler]

Well I had it installed at my grandpas friends house and he took off one of the sensors or something like that so the computer doesnt control the boost and I have to manually control the boost by adjusting this blackish cylinder looking thing(if I remember the shape correctly) on the SC

 

[Turbocharged400sbc]

the computer doesnt control the boost except to dump boost by opening the bbv during traction control events.

all that can be tuned out via the pcm.

removing the bbv solenoid (either physically or just removing the vac line to the manifold and bbv) results in a bbv system that only opens with manifold vacum (steady cruise/decel/idle

tell grandpa's friend to leave your bbv alone, it should be adjusted to be closed engine off and be able to open 90* with vac applied for it to be working properly.

you should probably be close to 8ish psi with the airflow mods.
if ya have stock catback and the oem maf sensor it'd probably be lower.

dont get hung up on boost, its a measurement of restriction and doesnt correlate with peak power

Al's 04 dropped 3psi of boost getting rid of the factory restrictive catback, and it sure didnt lose power lol

 

[hockeybawler]

Alright, I was just wondering to see what I can bring it up to. Should I have him put the bbv back on?

 

[Turbocharged400sbc]

The bbv is the black vac actuator and the butterfly valve in the blower...the bbv solenoid is what he deleted
you do not need it but with it in place the PCM can limit power during traction control and torque management

I also wanted to make sure that he left the lower vacuum port open on the actuator where theboost bypass valve solenoid connects to the actuator.

if it is capped off then as it heats up a can force it to open and dump boost
so to be clear about this the top port goes to the vacuum tee on the top of the blower...the lower port is open or connected to the solenoid

 

[02BlueGT]

The bbv is the black vac actuator and the butterfly valve in the blower...the bbv solenoid is what he deleted
you do not need it but with it in place the PCM can limit power during traction control and torque management

I also wanted to make sure that he left the lower vacuum port open on the actuator where theboost bypass valve solenoid connects to the actuator.

if it is capped off then as it heats up a can force it to open and dump boost
so to be clear about this the top port goes to the vacuum tee on the top of the blower...the lower port is open or connected to the solenoid

I've ran w/o the solenoid and just the lower port open for years w/o issue.... Because James told me to do this many years ago

 

[hockeybawler]

Let me go check and see if it is plugged or not and I will get back to you guys asap

 

[hockeybawler]

Sorry I have been busy today changing a alternator and belt on my car to stop a damn squealing noise, I think it is the pcv valve after some research. The bottom of the bbv has a hose hooked up to it that goes right under the snout of the supercharger and connects to maybe the LIM? It is not connected to the blower itself but right underneath it. Also my boost gauge is hooked up inline with this hose

 

[Turbocharged400sbc]

Yer bbv got hooked up wrong
Unplug the lower hose from bbv actuator and plug it with a bolt/golf tee and leave the lower bbv fitting open
Hopefully he didn't touch the other upper hose
After you do this you'll build boost
As its plumbed right now...when you build boost your opwning the bbv and dumping it....no wonder you only see 4psi

 

[hockeybawler]

Where do I hook up my boost Guage then? And do I plug under the snout of the supercharger also? Like where he had the other side of the house going to?

 

[Turbocharged400sbc]

That hose went to the bbv....leave it plugged with the boost gauge hooked to it
Or reinstall the bbv sol

 

[hockeybawler]

Alright sounds good. Do i plug up where ever the hose ends under the snout?

 

[02BlueGT]

Alright sounds good. Do i plug up where ever the hose ends under the snout?

Hose under the snout should go to the MAP and the FPR. If either of those is hooked to a different vacuum source it is good that you were seeing low boost. The GTP FPR will actually lower fuel pressure under boost if it is hooked to a pre S/C rotor vacuum source. (If you have an 97-03 of course)

Maybe this pic will help:

*not my drawing