Autometer boost gauge possibly faulty

[bill96]

hey guys/girls,

i recently installed an autometre mechanical boost gauge to my s15, and noticed when i give it a fair bit of throttle and build up a boost over 5 psi the needle isnt steady it oscilates too much, the needle actions not smooth and inst steady at all.On idle from cold start, until the cars warmed up, the needle is fine and smooth. however as soon as the cars warmed up, the needle vibrates again. On boost its almost impossible to get a boost reading. From vacum up until 5 psi the vibrating not that bad and its possible to read the gauge.


Does anyone know why this is happening? is it a faulty gauge?

your help would be much appreciated

cheers

 

[Auss15]

Could be a few things,are you running a boost controller?

You might have a boost leak in one of your lines(check all your clamps) or it could be the waste gate actuator is sticking.

 

[bill96]

hey, no im not running a boost controller, had a quick look throughout my engine bay and wasn't to happy to find that my wastegate has been tack welded shut, grrrrr. So could that be the reason why my gauge needle is ocillating heaps?

as for a boost leak i'll have to check it out?

 

[Auss15]

Yep, that will cause your boost to spike and be all over the place.You won't be able to hold steady boost through the rev range :no: Its a dodgy mod to hold boost

 

[bill96]

yeah i wish i picked it up when i bought the car but it hard to see, it happens i guess...if the wastegate is welded shut i would have thought it would eliminate boost spikes and that the boost would always be consistant, as i was under the impression boost spikes were from the actuator not opening at the right time, or not opening consistently at a set say 7 pounds?...either way why would that cause the needle to oscillate? if it were a boost spike shouldnt the needle still be smooth and would show the spike? my needle oscillates badly....

 

[mook]

Yikes and sh*tes!!!

A welded up wastegate would be engine suicide unless you have an external wastegate fitted. Welding up a wastegate would just mean boost rising and rising as revs increase with nothing bleeding off to keep it constant.

You must have an external wastegate if that's the case.

In terms of oscilating, this could be the external wastegate flickering as it's on the edge of it's operating window. Being a mechanical gauge it would be unlikely to be faulty in the way described, anacurate maybe, but not fluctuating like that, it suggests it's getting a pulsing reading which could be caused by by the wastegate as above.

 

[bill96]

i havent thoroughly checked the engine bay as such, but i service my car and do most of the work myself and dont think ive see3n any external waste gates unless its hidden well somewhere...so yeah im stil confused lol. On idle on a cold start the needle is smooth and working correctly, however once she warms up even on idle the needle ocsillates a bit, thus im thinking it could be a leak in the system somewhere??? vacumm leak????

 

[Auss15]

If you can't find it yourself take it to someone who does smoke down tests.
As has been said if the waste gate can't bleed off excessive boost it will put pressure on your turbo. Welding it shut is only practical if yourv'e got an external gate but in Auss under EPA rules they are illegal