Fmic Piping Size Queries For Gt3076r Turbo?

[anthonymcgrath]

hey all,

I'm fitting a gt3076r to my rb25det at the moment. Engine side is all sorted (forged, bored etc..)

However my fmic piping is a little shoddy with worn clamps n clips, so I'm looking to size up my fmic piping a little to accomodate the extra power.

here's what I have/had at the moment:

-arc fmic. Inlet/outlet diameter is 67mm

-the pipe coming off the fmic to the throttle body was 57mm

-the oem crossover pipe (which I used on the other side) was 63mm. This led down to another 57mm ID pipe.

I'm now fitting the turbo & greddy gtr style plenum:

-greddy plenum ID is 80mm.

-Q45 90mm throttle body to go on.

so my question is what size fmic piping shall I run? Looking at what I have then I'm coming off the turbo and into the fmic which will be 67mm. the air then exits that fmic 67mm and has to go into the 90mm throttle body.

My own deductions are to run somewhere between 67 - 76mm (3") piping all round but I'm curious on ppl's thoughts. I dont want to fit too small and restrict the pressure but I also dont want to fit too big and cause excess lag altho I wonder how much diffference that would make. I am happy to be corrected, advised and educated so if anyone has any thoughts for a learner in the uk then that would be cool! pics also ultra helpful too!

ta

ant

[W0rp3D]

How much power are you looking for and how much boost are you going to run?

The dimensions you mentioned seem ok for a 3076 just replace clamps and joiners if there worn, use the standard tb on the plenum (you can get adaptors on here somewhere) and i would also change the afm for a Z32, unless your going to over 350rwkw then the Q45 is just over kill.

[RBceffy25]

I would also like some info on this.

What are the pro's and cons of bigger cooler piping? i.e less restriction? more lag? etc

And I really want to know what are pro's and con's of bigger throttle body?

Sorry if these are dumb questions. I havnt experimented with this yet so i'm quite interested in some info/opinions about it.

Cheers all!

[anthonymcgrath]

@ worp3d

I'm aiming for 500bhp with the gt3076 - I dont know what psi of boost that is but possibly 1.4 to 1.6 bar (20 to 23 psi)

I already have a Z32 afm on. I've heard that they're fine for 500. I also have a Q45 afm sat about the house but thats overkill. RSP over here also said that they are a bitch to map the car with - never seem to give as smooth a signal as a Z32 afm.

I want to run the car tho with the bigger Q45 90mm throttle body so not putting the original one on even tho I have an adaptor for my plenum for it.

well I figured I wont go any bigger than the in/out diameter on the fmic which is 67mm. I think this is a good size to upgrade to.

@rbceffy25

basic rule of thumb is too small and the pipes become a restriction themselves especially as you run more power/boost. Conversely too big and lag occurs. I'm going up from 57mm to 67mm which for the extra 150bhp the car is making with this turbo I think will certainly help. the bigger throttle body will allow more air to enter the plenum faster I'm told. I cant see it making a massive difference tbh but its more a curiosity thing and if it just requires a longer cable and some slight rewiring to get it to work I may as well try