Boost Guage Question

[performanceisland]

What is the best place to tap into for the most accurate reading for a boost guage for the downing atlanta supercharger system?

the downing atlanta intake manifold comes with an extra/unused vacum line hole, is this what you use, and if so how do you adapt it to the white plastic vacum line the guages come with.

thnaks in advance.

[xxxJohnBoyxxx]

Yes it needs to go to the port on the Downing intake manifold.

For adapting the small plastic hose from the gauge. Take a piece of vacuum hose and plug it into the DASC manifold then put the gauge plastic hose in the other side of the vacuum line and you should be able to zip-tie the vacuum line tight enough to make a good seal on the plactic line.

[performanceisland]

thanks i will give it a try.

[performanceisland]

ok so my boost guage works, the vac is at about 18 at idle, then when i drive and floor it the boost guage shows 6psi, then it jumps/spikes to about 8psi when i hit the rev limiter at which point the transmission light goes on, and i have to turn the car of and restart it to get rid of the light, although the light doesnt limit my trans to 3rd and 4th gears as it tipically does when it goes on.

why only 6 psi? im in illinois where it is no more then 30 degrees F outside.
why trans light?

thanks.

[Danny318]

tell us more about your car.


mine would max at 7.2 or so PSI so 6isnt that far off.

[performanceisland]

Originally Posted by Danny318

tell us more about your car.


mine would max at 7.2 or so PSI so 6isnt that far off.

mine is a 1999 318ti with 49K miles on it, runs like new. that is the only mod i did is the supercharger.

[Danny318]

How is your belt tensioner? Check to make sure the belt is not slipping.

Was the DASC kit specific for m44 or did you get it used? the m42 pully will make less boost on a m44 motor.

[performanceisland]

Originally Posted by Danny318

How is your belt tensioner? Check to make sure the belt is not slipping.

Was the DASC kit specific for m44 or did you get it used? the m42 pully will make less boost on a m44 motor.

the belt tentioner appears to be fine, i did my best to tention it the same amount as originally, my kit was specific for my car brand new form downing atlanta shipped to me this past thursday. i guess i can try to tention the belt more and see if that helps? my vaccum is ok at 18 at idle i take it then?

[Danny318]

yeah i think mine was about 20 for vac.

You should check to make sure everything is tight, and that you are not leaking boost on any of the places where it needs to seal.

oh check the bypass valve, make sure it closes all the way. I guess there is a screw for adjustment to make sure it closes tightly.

[performanceisland]

Originally Posted by Danny318

yeah i think mine was about 20 for vac.

You should check to make sure everything is tight, and that you are not leaking boost on any of the places where it needs to seal.

oh check the bypass valve, make sure it closes all the way. I guess there is a screw for adjustment to make sure it closes tightly.

how can i check to make sure that the bypass valve closes all the way?

[Danny318]

not sure, take it off and suck on the hose to simulate engine vac / boost?

does your car feel slow? How much boost do you think you should have?

[performanceisland]

Originally Posted by Danny318

not sure, take it off and suck on the hose to simulate engine vac / boost?

does your car feel slow? How much boost do you think you should have?

well considering the condition of my car i would think id have the 7.5 psi, not to mention its winter here with 25-30 degrees outside. ill try tommorrow to take a peak at the valve.

[xxxJohnBoyxxx]

Originally Posted by performanceisland

well considering the condition of my car i would think id have the 7.5 psi, not to mention its winter here with 25-30 degrees outside. ill try tommorrow to take a peak at the valve.

No it all depends on your pulley sizes. Most likely you have the 4" pulley on your SC. I posted on another thread of your how to measure the pulleys. Measure them, give me the sizes and I will tell you what boost you should be seeing. Also sometimes your gauge can be off unless it is verified with a second gauge.