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Fmic Increases Psi ?

Cyprus

By Cyprus,
in Engines & Forced Induction

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Cyprus Enthusiast

Cyprus

Posted
Posted

i recently read a post on this forum where a member was stating that his PSI level had rose from 7psi to 9psi just by installing a FMIC ..

how exactly does this occur when the stock ECU still has a boost soleniod setting of 5psi low and 7psi high

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https://www.sau.com.au/forums/topic/166768-fmic-increases-psi/
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Al Grand Master

Al

Posted
Posted

The factory smic is restrictive, thus if you where to measure the boost b4 the smic it will be higher than the boost after the smic. Installing a better flowing cooler will have less restictions, therefor the boost b4 and after the cooler will almost be the same.

The factory solenoid is similar to a bleed valve, as is calculated/manufactured to allow the turbo to boost up to 9psi. This is with the restictive smic, replace with a fmic will reduce restriction, therefor flow more air.

STATUS Grand Master

STATUS

Posted
Posted

based on my experience with silvias the factory cores have on average a pressure drop of about 2-3psi an aftermarket one has on average less than that and the average differrence in pressure drop is realised as a boost increased.

paulr33 Grand Master

paulr33

Posted
Posted

this also depends on where the actuator gets it signal from

on the r32 it comes off the compressor cover so it wouldnt be an issue on the 32

but the r33 gets it post intercooler so its after intercooler core drop

rob82 Mentor

rob82

Posted
Posted
based on my experience with silvias the factory cores have on average a pressure drop of about 2-3psi an aftermarket one has on average less than that and the average differrence in pressure drop is realised as a boost increased.

Pressure differentials across intercooler cores is based on airflow more so than boost pressure. Its just that higher boost pressure usually means more airflow. So your figures are a little ambiguous.

mad082 Grand Master

mad082

Posted
Posted
Pressure differentials across intercooler cores is based on airflow more so than boost pressure. Its just that higher boost pressure usually means more airflow. So your figures are a little ambiguous.

if an intercooler is a restriction then the pressure will be higher before the cooler than after. the more of a restriction the higher the difference.

foznice Veteran

foznice

Posted
Posted

it's interesting, because we all not that standard boost for an RB20 is 10psi, and standard boost for an RB25 is 5/7psi... but they're measure from different locations...

but if we were to measure them from the same place we might get similar figures. Just thinking out loud.

Cubes Grand Master

Cubes

Posted
Posted
it's interesting, because we all not that standard boost for an RB20 is 10psi, and standard boost for an RB25 is 5/7psi... but they're measure from different locations...

but if we were to measure them from the same place we might get similar figures. Just thinking out loud.

You won't as the r32 actuator is rated to open at a higher pressure.

Grab an r33 actuator and r32 actuator; the r32 actuator is considerably stiffer.

MBS206 Grand Master

MBS206

Posted
Posted

You shouldn't really get a pressure increase at all!

The same pressure is hitting the solenoid, at 7PSi before or after the intercooler change.

Alot of people actually notice a pressure DROP (If pressyre taken before intercooler) due to a more affective cooling intercooler (Pressure is dependant on temperature too!)

And if the actuator gets it's pressure from AFTER the intercooler, there should be ZERO change in pressure.

If the actuator is set to open at 7PSI with x amount of air bled off, then it will open at 7PSi after some air is bled off.

foznice Veteran

foznice

Posted
Posted
You won't as the r32 actuator is rated to open at a higher pressure.

Grab an r33 actuator and r32 actuator; the r32 actuator is considerably stiffer.

I was just wondering to myself, if Nissan would have compensated the pressure drop into the adjustment of their actuators, but then I wondered where WE are measuring boost from, so that probably comes into play. But hey like you said the r32 actuator is stiffer anyway so there you go... (still thinking out loud)

Roy Grand Master

Roy

Posted
Posted
this also depends on where the actuator gets it signal from

on the r32 it comes off the compressor cover so it wouldnt be an issue on the 32

but the r33 gets it post intercooler so its after intercooler core drop

LOL...ah, now you agree with me. I remember you thinking i was on drugs when i was commenting why R32s make more boost at the inlet after a fmixc install :(

gts-4 dreamer Mentor

gts-4 dreamer

Posted
Posted

hmmm....fmic = MUST more driveable car with more consistent results. cold nights also make a BIGG differnece where as before was always crap by comparison. split front / dump 4psi increase with stock controller..... *yeS*

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