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Old 09-30-2011, 05:09 AM   #1
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Default MAF and atmospheric BOVs

Does the Miata have any issues loading up with fuel when using a BOV if you still have the MAF? I may have a solution for you guys but I need more information. First if there's a problem or not. Does the Miata have decel fuel cut? Second is the MAF voltage proportionate to airflow? More air = more voltage? Or visa-versa?

I thought about a solution while driving around today. Although my Turbo Miata has been sold for awhile now, I never ran the MAF so I'm not sure if there's a problem.
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Old 09-30-2011, 09:26 AM   #2
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(Posting from my phone.)

The problem is really dealing with idle with a valve that leaks at idle
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Old 09-30-2011, 06:06 PM   #3
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I drove my car for years with an older FM2 setup that had a 2-stage BOV and a MAF. With just vacuum it would recirculate, add boost on the other side of the piston and it would move further and vent to atmosphere. No fueling issues.

As Braineack says, the problem is a BOV that leaks, because now you're getting unmetered air. Dumping already metered air when you lift off the thottle is fine -- the computer's shutting the injectors down at that point anyway.

--Ian
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Old 09-30-2011, 06:18 PM   #4
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Quote:
Originally Posted by Braineack View Post
The problem is really dealing with idle with a valve that leaks at idle
^ This.

A bypass valve which is ideally adjusted for best performance will be open at idle, permitting air to flow through it backwards (from the "outlet" into the intake tract.)

With an airflow-based system (be it MAF or VAF) and a bypass valve which is open to the atmosphere this will result in a lean condition and stalling at idle.
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Old 09-30-2011, 07:15 PM   #5
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I understand the un-metered air with a leaking BOV. I could electronically cure that too but this has to do with fuel loading. I came up with is a simple solution that works like a decel fuel cut by clamping the MAF voltage under closed throttle only. If Miatas don't have issues with a BOV then it must have a good decel cut circuit from the factory and wouldn't need it. Mitsubishi on the other hand has issues with it.

I thought I'd ask here first since you guys are generally open to new mods.

Scott are you still selling complete COP harnesses?
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Old 09-30-2011, 07:19 PM   #6
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The forge VTA should solve your leaky at idle issues.

The miata does cut fuel on decel however it does so in closed loop, until it hits that temp, you'll be running open loop and dumping tons of fuel.
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