V1 Wondering about a mechanical boost gauge on LSJ

[Oldchevyguy]

Hi. I want to use a mechanical vacuum/boost gauge. Can I just tap into the line going to the brake booster, or is there a better place on the supercharger or manifold? Btw, how does the brake booster work on a supercharged engine?

 

[Ross]

It gets intake vacuum before the supercharger, so it wouldn't register boost if you hooked it up to a gauge.

 

[Oldchevyguy]

Ok. So where do I get the boost signal on the engine?

 

[Karter2026]

See the picture

 

[Oldchevyguy]

See the pictureView attachment 11862

Is this port normally not used?

 

[Ross]

According to AllDataDIY
"The powertrain control module (PCM) sends a PWM signal to the boost gage indicating the manifold air pressure."

I'm guessing the PCM reads the temperature manifold absolute pressure sensor to create the PWM signal.
Judging by their picture, it is in the upper right corner, with a bolt raised out of it's normal position, above the supercharger pulley.

1. Disconnect the temperature manifold absolute pressure (TMAP) sensor harness connector.
2. Remove the TMAP sensor from the intake manifold.

 

[Oldchevyguy]

I need to tap or tee into a hose that has boost. A small plastic tube goes to the gauge, similar to a mechanical oil pressure gauge.

 

[Parson Green]

I need to tap or tee into a hose that has boost. A small plastic tube goes to the gauge, similar to a mechanical oil pressure gauge.

There's a vacuum/boost line that runs between the circled nipple/port (see above pic posted by Karter2026) and this thing

https://i.ibb.co/qs000nm/Capture.jpg

Tee into said line and you should be golden.

BTW, here's some good, semi-related reading for all owners/operators of the LSJ engine:

ByPass Valve Actuator

Greetings The ByPass valve contains the entry point and exit point of air (pressure), Which one is going to where ? To test the sealing and correctness of the bypass valve, I connected the bottom line in a low pressure of 4psi (0.3 bar) And he opened the leg completely, How can I fix the...

z22se.co.uk