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| Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain. |
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09-07-2013, 03:51 PM
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#1 |
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vacuum at idle/decel
how much vacuum do your cars pull at idle and on decel? mine is pulling 21-22 on idle and 25 on decel. seems high to me, i can't even find a BOV spring stiff enough to keep it closed (turbosmart only offers combos up to 21inHg). just wondering if something is wrong or this is normal...
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09-07-2013, 04:01 PM
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#2 |
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You might have better luck trying this one in the forced induction section
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09-07-2013, 04:11 PM
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why? i'm asking how much vacuum any other 86 pulls. I don't care if the car has FI on it or not.
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09-07-2013, 04:17 PM
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Quote:
__________________
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09-07-2013, 04:31 PM
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#5 | |
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Quote:
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09-07-2013, 04:32 PM
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#6 |
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Ah yes, good call. How do I move it? Does a mod have to?
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09-07-2013, 07:46 PM
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At idle, the cams are parked into what's most likely an "underlap" position for combustion stability. This produces high vacuum. Also, a healthy engine with good compression may produce more vacuum than one with poor sealing. Now When you have overlap at idle, like a traditional cammed pushrod v8, you get less vacuum and less stable combustion.
On decel, the engine is free spinning against the restriction of a closed throttle. This also creates a high vacuum. It's pumping air through a very narrow opening. Basically, this is normal. Now any engine that uses aggressive dethrottling, like a BMW Valvetronic engine, will see very little vacuum at all under any normal conditions. This is because valve events control engine torque output rather than the throttle. |
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09-07-2013, 08:04 PM
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#8 |
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-20 to -21 at idle.
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