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Rb25de Vct Performance Modifications

Brentmcd12

By Brentmcd12,
in Engines & Forced Induction

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Eug Grand Master

Eug

Posted
Posted
cant the time VCT enables/disables be altered without an aftermarket computer (other than afc4) if so how? cheers

never heard of the AFC4 (apexi item?).

you can enable it and disable it, by unplugging the solenoid. that's how you determine the most optimal rpm point for it to engage, by doing two dyno runs one with and one without.

i'm pretty sure you will need an aftermarket something to control when the vct/vvt/nvcs (whatever you want to call it) is activated/deactivated, whether it be a full replacement ecu or a little piggyback controller.

stock; the vct turns on just above idle rpm and turns off around ~5000rpm'ish. don't quote me exactly on that though.

the power fc guys require the fc datalogit (laptop program) to be able to access the function.

i know that doesn't exactly answer your questions, but hopefully it'll provide a little grounds for discussion.

SKiT_R31 Experienced

SKiT_R31

Posted
Posted (edited)
never heard of the AFC4 (apexi item?).

you can enable it and disable it, by unplugging the solenoid. that's how you determine the most optimal rpm point for it to engage, by doing two dyno runs one with and one without.

i'm pretty sure you will need an aftermarket something to control when the vct/vvt/nvcs (whatever you want to call it) is activated/deactivated, whether it be a full replacement ecu or a little piggyback controller.

stock; the vct turns on just above idle rpm and turns off around ~5000rpm'ish. don't quote me exactly on that though.

the power fc guys require the fc datalogit (laptop program) to be able to access the function.

i know that doesn't exactly answer your questions, but hopefully it'll provide a little grounds for discussion.

Cheers, Yeah meant the AFC Neo, Apexi Air Flow Convertor 'neo', it calls itself number 4 (upgraded from a SAFC2 because i thaught it had VCT altering functions)

Yeah i understand what your saying about how to decide when to activate the VCT, i just now need to figure out how to make it automatically engage at that point.

Ill properly talk to my tuner about it when i get the car ready, just waiting on damn extractors, and loom

Edited by SKiT_R31
Brentmcd12 Enthusiast

Brentmcd12

Posted
  • Author
Posted

is 6200 the rev limiter for the 25de ??? coz thats when mine bounces back.. i thought it was 7500 ??

the engine needs wayy more torque is crap at speeds goin from 5th to 4th just to speed up and usuing 3rd to hold power... anything under 3000rpm is terrible

Eug Grand Master

Eug

Posted
Posted

mine sees 7000 regularly at QR, it tends to taper off around 6800ish anyway

4500-6500 is usually about the thick of it for me, very thick and chunky through there.

i agree, could do with abit of torque, but at the end of the day it's a 2500cc motor. you'll need cubes for torque.

the rb is a fairly revvy motor, and i personally think that's what makes it fun.

with regards to 'under 3000rpm is terrible'

- the high gearing and ratios have something to do with it, especially when you are just cruising around

- i have no dramas getting a decent progressive punch 1st and 2nd on the motorkhana and skidpan.

Brentmcd12 Enthusiast

Brentmcd12

Posted
  • Author
Posted

ah k well maybey because mine is in a R31 the tacho reading might be wrong.. yeah true with the gearing but similar stuff at 100kays... 5th to 3rd.. again..

im doin RB30DE very soon...

wat i was going to ask is...

what series head do i have its a 93 RB25DE the afm has 4 wires if that helps is that S1 or S2 ? yes it has VCT...

i want to buy camshafts of Nengun i belive its cheaper than just jap... which ones are good for midrange power ? keeping in mind it will be for RB30DE..

SKiT_R31 Experienced

SKiT_R31

Posted
Posted (edited)

My limiter with a stock 25DE ecu, was at exactly 6800rpm, now have a Mines ECU with no limiter... - goign to get somthing like a jaycar and set it at ~ 7000-7200rpm (or whever power drops off, dont want to take it much further than that though, it is a 30 block after all)

are you goign to fully balence it, maybe get a new harmonic balencer? dont forget 30e's have bad harmonic issues in mid 7k rev range

being 93 i would have said S1, but 4 AFM wires!?

Edited by SKiT_R31

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