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Old 11-15-2015, 10:31 PM   #1
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Default Boost is unstable at peak when wastegate opens

Hey guys.

I have a 1992 miata with a FM2 kit on it.

Same old garret 2560r. Im running a megasquirt ms3 build by rev. Im also using a manual turbosmart boost controller.

My problem is, the car pulls and drives really well until you hit the wastegate pressure. Then the car bounces around almost like its hitting a fuel cut rev limiter.

I can see in the graphs that the boost is really unstable when the wastegate is opening.

This can happen at a variety of rpm's and if I dont hit peak boost to open the wastegate everything is smooth and fine. My boost controller is set to 12psi.

Any ideas? Ive attached a log in which this happens often and here are some photos of the issue aswell.

Thanks!






Attached Thumbnails
Boost is unstable at peak when wastegate opens-80-boostdrop1_a7dc26bc8269637ebaebbd75ab2aba0e39a3074a.png   Boost is unstable at peak when wastegate opens-80-boostdrop2_a76df328fd7e86428af79ee38379a57437d6fb05.png   Boost is unstable at peak when wastegate opens-80-boostdrop3_e262d9e9d1df9f1b65ef34403601bf6c91163fa7.png  
Attached Files
File Type: msl 2015-11-13_21.37.26_drive.msl (2.08 MB, 60 views)
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Old 11-19-2015, 01:50 PM   #2
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Figured out it was spark blowout (was unfamiliar with this).

Needed to gap the plugs down a bit more.
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Old 11-19-2015, 02:04 PM   #3
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Thanks for following up with the solution, I hate searching and pulling up old unresolved threads.

Sometimes new plugs will help if yours have been in there a while. If you keep having issues the Toyota COP thread is great for walking you through building a relatively inexpensive coil on plug conversion.
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Old 11-19-2015, 03:01 PM   #4
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Ya, me too, thats why I came back and posted what I found.
Obligatory XKCD https://xkcd.com/979/

I got some nice new plugs and wires, gaped em down, and have no issues now.

COP's are on my list of things to eventually do to the car.

Thanks!

Last edited by Fatvod; 11-19-2015 at 07:04 PM.
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