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Fmic = Decrease In Boost?


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i fitted a miami gt FMIC (cheers paul) last week and have only just had time to drive the car properly, but have noticed i'm running lower boost.

the 1st peaks at 0.7 bar and the 2nd max just over 1 bar, i thought fitting one of these front mounts was meant to increase power!!!!

any ideas?

 

oh and ive tried it with the stock air filter on and with the apexi air filter on but no change!

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The drop in max boost only happens on supercharged engines (tightly coupled to the engine)

 

Turbos are forced to spin harder until they reach the point where their actuator is set. If you haven't meddled with the turbo's boost pickup point (right after the compressor) then you shouldn't be seeing less boost - not appreciably anyway. Check for leaks.

 

Boost and Power don't always go together by the way - colder air would show less static pressure (boost), yet it would make the same (or more) power.

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All things being equal, if your wastegate flows the same amount of exhaust gas that means your turbos will flow the same amount of air, but the more efficient intercooler cools it more. So you have the same mass of air but it's colder and therefore denser, so it's lower pressure = lower reading on your boost gauge for the same pressure. What this means is you can tweak your boost controller settings to get the pressure back up and *that's* where you get the extra power from the intercooler. More mass of air for the same boost pressure. it's also why bigger turbos generate more power at the same boost.

 

I ducted my intercooler back when I had hybrids on and saw a 0.05bar drop in pressure on average because of this effect :thumbs:

 

-Ian

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I hate to ever disagree with JohnA but you will see a drop in boost if your last intercooler was not leeking and you new FMIC is large simply due to volume, it however should not be that noticable. It points more to a boost leak.

 

Mmm when the system is fully pressurised the volume of the intercooler is irrelevant. You may experience more lag if it's a big change in volume, as it gets pressurised, but no overall pressure drop. The physics don't allow it.

 

-Ian

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I hate to ever disagree with JohnA but you will see a drop in boost if your last intercooler was not leeking and you new FMIC is large simply due to volume, it however should not be that noticable. It points more to a boost leak.

the volume of the i/c affects pressure after it in no way.

It does affect pressure inside the core, yes.

A mild static pressure drop will be due to the air being slightly cooler, because the turbo 'sensing' signal is still taken before the i/c.

 

But we're talking here a fraction of a psi, it's not that the engine was non-intercooled before!

 

Time to check for boost leaks indeed.

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