Sporattic boost gauge behaviour

[buzurk]

hey guys

installed a boost gauge, autometer mechanical one

I used rubber small fuel hose to get into the car, T piece in the BOV line n all that

once it gets to the gauge i had to use the plastic tube due to the conenctor supplied so i used a bit of that and pushed it inside the black line i ran, its real tigjt

weird thing is when its makin boost, the needle holds its pressure but really rapidly moves back n forth say .5 psi each way really quick

performance shop reckons its just the gate controlling boost

a small clip is below
http://s271.photobucket.com/albums/j...t=ac3f35e3.mp4

Any opinions?

[MattMPS3]

I have heard of this occuring before, although I never had any issues with my mechanical boost gauge when I was using it, did you use the Autometer t piece, or a generic one, I believe this has quite a bit to do with it, as the autometer one has a small brass pill in the outlet that goes off to the gauge, I think this helps regulate the pressure variations, resulting in cleaner readings.
I would also suggest using the autometer nylon tubing as well, you can buy longer hose kits if required.

[Toddy22587]

I had a similar issue when i installed a mechanical boost gauge exactly the same way you have. it would be fine but once i hit max boost it would start to jump around.

I fixed it by buying an electric gauge

[lup15]

I had a similar issue when i installed a mechanical boost gauge exactly the same way you have. it would be fine but once i hit max boost it would start to jump around.

I fixed it by buying an electric gauge

^ lol @ fix. I have a defi gauge and when it hits max boost it bounces off the max psi due to being limited in the first 3 gears. other gears its fine.

Just watched the video, mine does that but like i said only first 3 gears which I think its limited to 13psi or something? what gear was that video in?

[buzurk]

I might change where its tapped into
can anyone else recommend a spot other than the boost gauge line

[MattMPS3]

You can tap into the brake booster line (as per attached pic), this will give you a much more stable reading on your gauge, I believe the line is 3/8", I was running my gauge off here for a while, but you need to be mindful of heat though as its sitting around that whole exhaust / turbo area, there is a large grommet located in the firewall not far from this location that you can run the line through, it enters the cabin just behind the glove box.

Mazda3-MPS-engine.jpg

[lup15]

are there any saftey issues with that? I mean if you get a vacuum leak there, what will happen....

[MattMPS3]

Brake pedal gets hard to push in, but the engine will run like a dog due to the air leak before you notice the pedal issues, besides if you do the job properly with quality hose clamps etc there shouldn't be any issues.