bouncing boost gauge
 

hi guys,

I have a 90 with the basic greddy kit, hi flo cat and tsudo catback. Car runs good so i installed a sunpro boost gauge ($25) and tee the vacuum line to where the the canister solenoid is hooked up to (red circle on pic). After connected I drove the car around and noticed my the gauge bouncing like CRAZY from 15 vacuum all the way to 5. But after passing the 5 vacuum reading mark it stays stable all the way through 4-5 psi of boost. My thoughts was that the connection was not tight and double checked, no visible signs of loose vacuum line or cracked T. Drove it around again same results. I then removed the Connection to the canister solenoid and hooked it up with the capped nipple ( blue circle on pic) and drove it around. No bouncing boost needle and pulled smoothly. Now I researched and found that the capped nipple vac. is usually used for the BOV and that is why i did not go that route first. Has anyone had the same problem and is it bad for the boost gauge to be hooked up the way I did.


Jun

Its the wastegate. The stock one that comes with the greddy kit is shit. Mine was completely illegible until I changed to another wastegate. I found a generic one that looked like it might fit and made it fit.

Connect the boost gauge at the back of the intake manifold near where the brake line is connected. BOV goes in the front where your current connection is at.

Tripple88 i just checked. There is another capped nipple but larger right below the brake booster vacuum is connected is this the one you are refering to?

Get a new wastegate.

I dont know the NA intake manifold however if the plug is in the intake manifold then yes that will be better for a boost gauge. I cannot comment on the greddy wastegate as i've never used it.

If the wastegate is junk though it makes no sense why it would bounce ever while driving nicely assuming your foot isnt moving too much, a bad wastegate would bounce only at wot or any time theres enough pressure at the turbo outlet.

the TB ports are not good for a boost gauge.

plugged the boost hose in the rear nipple that was capped. No bouncing and I did Psi reading was 1 psi more, but all in all im happy with it.

yup just switch to a port post throttle body and you should be good to go.

This was my thought. When accelerating it is constant, or under load (or when decelerating in gear) but when barely on the throttle it fluctuates.

Fail to see how a faulty wastegate would lead to a fluctuating gauge in the OP's scenario.

It's an incredibly shitty wastegate. Have you seen all the helper spring threads?

I had a blur of a boost gage, and changed only my wastegate. Rock steady boost. It happened. I was there.

Yes, but he stated he has steady boost readings. It is fluctuating when not in boost...if it was fluctuating in boost then yes, you would be correct, but in this instance it is not

I am using the AEM Boost gague that runs off a Map Sensor, But I am running it off the nipple that comes off the very back of the Manifold nearest the firewall, that is directly under the ground that are on the Manifold. It works really well.

Also when i installed my kit, i had the same issue as you with the bouncing when not even at WOT, it was the Wastegate are actually was adjust so LONG(or for least amoung of boost) that the gate actually had room to bounce between open and closed, if you read the directions they tell you how to adjust the gate during install. It is suppose to be set to keep that from happening. But SHORTEN the rod slowly cause it changes boost pretty quickly as it gets tight.

Oh, I never read the "not in boost" part.

No worries, reading is a lost art. The trend is to just jump in and express one's opinion with out any regard to the original request ;)

^ Thats rather.... American!!!

Well it's a good job I am English then!

I know far to many people that fit your "criteria"

You know all the MiataTurbo users?