Overboosting!

[SHAGwagn]

Popped off the intercooler and installed some new ITV22 plugs this weekend. After the install took it for a spin and everything was nice just as it was before the install of the plugs. Yesterday started noticing hesitation and knock in the upper gears (4,5,6) when trying to get on it throughout my highway drive home. This morning i noticed, in those same gears, that at WOT the boost will spike past 20psi at first(i only have a 20psi gauge) settle to 17ish then somewhere midway through the powerband itll spike back up to 20psi again...after which i immediately let off. Tried this a couple times and it happened every time. This does not happen in gears 1,2,3 so im really puzzled about what it could be. Any help or suggestions would be great. Thanks!

 

[matsuda]

Popped off the intercooler and installed some new ITV22 plugs this weekend. After the install took it for a spin and everything was nice just as it was before the install of the plugs. Yesterday started noticing hesitation and knock in the upper gears (4,5,6) when trying to get on it throughout my highway drive home. This morning i noticed, in those same gears, that at WOT the boost will spike past 20psi at first(i only have a 20psi gauge) settle to 17ish then somewhere midway through the powerband itll spike back up to 20psi again...after which i immediately let off. Tried this a couple times and it happened every time. This does not happen in gears 1,2,3 so im really puzzled about what it could be. Any help or suggestions would be great. Thanks!

2 things to check:

1) Carefully check the 2 "vacuum lines" connected to the wastegate actuator for any cracks or other problems. One goes to the turbo compressor outlet and the other goes to the wastegate solenoid valve.

2) For a test, disconnect the electrical connector (2 wire connector) that goes to the wastegate solenoid valve. This should limit the boost to ~10 PSI on a stock MS3 (it will be higher if you have exhaust mods).

 

[SHAGwagn]

2 things to check:

1) Carefully check the 2 "vacuum lines" connected to the wastegate actuator for any cracks or other problems. One goes to the turbo compressor outlet and the other goes to the wastegate solenoid valve.

2) For a test, disconnect the electrical connector (2 wire connector) that goes to the wastegate solenoid valve. This should limit the boost to ~10 PSI on a stock MS3 (it will be higher if you have exhaust mods).

thanks, what does this test prove?

 

[eatsleeprace]

Your are getting Fuel Cut from the ECU, its has a limit if you go over your fuel will cut is a safety thing so you wont blow your engine. I had the same problem. I had to figure something because i did'nt wanted to buy a fuel cut because i need a Boost Controller. So i had my Forge Bypass Valve it help becouse it hold the boost. And then i got my Cobb AP it help. (I love my Cobb AP)
But first what are you mods?
You can try this.
1. If you have Forge Bypass valve you can put the two shims and the red spring.

2. Buy a fuel cut defender and boost controller.

3. Get it tuned or buy Cobb AP.

Get a guage with higher PSI, or if you get the AP you don't need a guage. I hope this helps.

 

[Darth Vader]

Whoa, two shims under the red spring? That's a touch dangerous on this motor. The car, and all other turbo cars, require a little flutter to safely operate under lean conditions or transitional load conditions. Your are pretty much suggesting locking the valve shut under all but WOT shifting operation with that much spring tension, in my view.

I run the red alone, feeling it's pretty similar to the blue + 2 lots of people run on otherwise stock engines and it boosts the torque and driveability down low.

 

[eatsleeprace]

I was Running for a year with 2 shims my car runs perfect, but now I have the Cobb AP and i had to buy the HKS SQV because of my APT FMIC.

 

[Saskatchewan17]

I noticed no difference other than sound in running 1 shim + blue and no shims - red.

 

[matsuda]

thanks, what does this test prove?

It proves that the wastegate (and the associated "plumbing") are OK.

 

[mazdaspeed32007]

i thought via my boost gauge i was running a 21 or so boost spike and holding 17 too, but when i read the boost though my accessport i was hitting 20 psi and holding 19 till about 5500 then it ran down to 17. you may be alright....maybe if all else checks out ok