Boost gauge question

[Luke600r]

I just finished installing a supercharger on my nytro I went with aem gauges. Boost and afr. Afr gauge seams to be working fine. But my question is the boost gauge at idle reads around neg. 8-10. Wich I'm assuming is vacuum. But once I give it gas shouldn't it go to boost levels ?? If I burp the throttle it will jump around. And go from -8 to about 0. And if I put it on the stand and do 1/4 to 1/2 throttle it's still not registering boost even if I hold it steady at 1/4 or half. I am new to boost. So not sure if this is common or a bad gauge or ???

 

[Agman 57]

Could be a bad gauge or installed in the wrong place.
Mine builds 1# at idle.
Mine is checking at the intercooler.

 

[Luke600r]

Mine is the yamaha/mpi supercharger. Currently no intercooler.

 

[Agman 57]

Where is your gauge checking boost?

 

[Luke600r]

My buddy that helped me with install of s/c did the gauges when I was at work. Lol. He said it's connected (the boost sensor). To a 5 way T that was included in kit. The Wich I believe is sensor to T. Then 3 to each throttle body. Then 1 to the blow off valve.

 

[Srxspec]

You're getting your boost signal from the vacuum ports on the throttle bodies. You're likely just not reading boost yet as the throttle blades aren't open enough and the motor is still seeing a vacuum or 0 signal.

 

[Luke600r]

Allen. Is it ok to have it this way. Or do u suggest a better way. Will I still read boost well trail riding. And at wide open throttle. So I would know not to over boost. And be able to watch for it. Thanks

 

[FLYBYU]

Take it for a rip around the yard. You'll see boost. Needs a load on the engine

 

[Srxspec]

You're fine with it that way. You're seeing a "true boost" reading. At wide open reading boost off the intercooler/plenum or off of the vacuum ports will be virtually the same. On the intercooler/plenum at part throttle you'll get a false reading where as your vacuum ports are measuring the actual boost the engine is seeing.

 

[Srxspec]

Take it for a rip around the yard. You'll see boost. Needs a load on the engine

On a supercharger you don't need to load the engine. Boost is directly related to engine RPM.

 

[Luke600r]

At my buddy shop. We did have a small area we were able to ride it. But not much. I think I did see it run maybe 3pounds or so. But then again I was pretty busy grinning ear to ear. And was also trying to watch the afr gauge. But wasn't much room to test either. Maybe 75-100 yards.

 

[FLYBYU]

Allen, we had to lay on it to get boost on the stand. I think blowoff spring was weak. Wasn't instant.

 

[FLYBYU]

At my buddy shop. We did have a small area we were able to ride it. But not much. I think I did see it run maybe 3pounds or so. But then again I was pretty busy grinning ear to ear. And was also trying to watch the afr gauge. But wasn't much room to test either. Maybe 75-100 yards.

It's nice when it comes. Just hopefully you did the setup for priming the supercharger correctly. You'll find out if you didn't on the trail. Allen has done many of these, If you have a slight hesitation if it wasn't done correctly stop and talk to Allen (srxspec). It'll save you a $1000 and a big headache with rotrex and mpi

 

[Luke600r]

I have read a lot on the priming situation b4 the install. And also stressed this to my budy during the build many times. He has done a s/c on his. And a turbo Install b4. So I'm hopeing it's right. Lol.

 

[Luke600r]

Allen, we had to lay on it to get boost on the stand. I think blowoff spring was weak. Wasn't instant.

Was this a s/c. Or a turbo