HOWTO: RB25DET High Boost mode with standard solenoid

[KayN]

just did mine just then, and it works great! can hear the turbo spooling up at 2,000RPM+ feels much better and very smooth.

took me max 2mins but 10mins finding a bolt and wire lol

[KayN]

just rechecked my boost, my boost gauge reads 10.15 psi = 0.7 Bar

is that ment to be right?

[gotRICE?]

If you have a turbo back exhaust and an FMIC then yeah its about right.

[stefan-w]

A few months ago I replied here that it didn't work with my car... I tried it again now I have an aftermarket boost gauge, and I discovered that it actually does work with my car;

- 7 or 8psi without the solenoid earthed,

- 10psi with the solenoid earthed, but...

- when linked to the original loom, I get 8psi till 4500rpm and 12-13psi above the 4500rpm line.

Anybody who knows what might be the case?

It's not boost creep, and I have an elbow-back aftermarket exhaust, stock smic, stock ecu, and a pod filter... so nothing fancy.

Edited December 5, 2009 by stefan-w

[koduRB25det]

I just did the thing for mt r33 gtst. my one is 93 S I. that was awesome. i hit 10 psi at 5000 rpm. that was awesome .

just ask from u. i got a ticking noice near my ecu. most likely relay ticking noice. from last 2 weeks. do you know any thing abt this...?

im using 10w-60 castrol edge oil for my car. it has done 87000 km on clock. what do u think...any thing better than this...? pls help

HOWTO: RB25DET High Boost mode with standard solenoid

Intended Audience: Stock RB25DET owners

Technical Level: Very Easy

Duration: 5 minutes

Effort: Easy

Result: Fairly Good

!!!Caution/Achtung/Attenzione!!!

Follow this guide at your own risk. You have been warned. We are not responsible for any actions you take. The instructions contained herein are only a guide and should be done with caution, If you doubt see your local mechanic. If you are unsure or are not confident don't do it.

Background:

As you all know the standard R33 RB25DET boost solenoid (value controller) is 5psi until rpm is greater than 4500rpm and then its 7-8psi. Continue reading if you wish to always be in high mode (7-8psi). If you have an aftermarket boost controller then you can stop reading now.

The standard solenoid has two wires running two it, one is constant power which is shared with the AAC value and some other components (see wiring diagram) the other is a ground signal. The ground signal (black wire) is run to the ECU. This wire is grounded when rpm is greater than 4500rpm by the factory ECU. Basically if you give the wire a constant ground instead of the ECU's above 4500rpm ground it will always be open, thus allowing it to be in high mode aka 7-8psi.

The mod:

Cut the black wire and run it to your own ground on the car body somewhere. Find a local bolt/nut or metal chassis component and attach a lead wire to it, then run this lead wire the black wire on the standard solenoid. For testing you could run this to the suspension tower, is has a huge bolt/thread on top of it. The other end of the two wires (black and white) should run to the factory harness plug (black odd looking plug), which can be simply taped up so it goes nowhere.

Be sure not to the modify the white one, as it's power for the solenoid.

See new-wiring.jpg for how it should look

Basically the black wire goes to your new ground, the white wire doesn't change. Make sure you tape up the loose end of the black wire out of the plug and don't leave it dangling around. Now to test

Test:

Start up your car, make sure you don't have any alarms or warning lights etc.. Safety is important!. Instead of your car going into 7-8psi above 4500rpm it will be in this mode all the time, this means when you take off in first youll be limited to 7psi instead of 5 and thus applies for all driving thereafter. Take it for a quick spin and see the difference. You'll notice first is whole different feeling to it and each gear thereafter seems to have more stick about it. Your top end power output will not be changed, ie if you made 140rwkw and you've done this mode it will still be 140rwkw it's just the curve will be sharper as you'll be on more boost quicker

Tips:

If you don't notice any different then you've either done the wrong wire or the ground is strong enough. Be sure to pick a strong ground and make sure its secured properly. You can get gold washer clips which will hold a wire and provide a good ground for use on a nut (see the yellow thing in new-wiring.jpg)

If in doubt you can simply unplug the black factory harness plug and your controller will be in closed mode which is 5psi all the time. With only a power signal the solenoid doesn't function and thus it will always be in "closed" mode which is 5psi

Questions?

How does the solenoid work?

The stock solenoid works like this, with power and ground it will be in "open" mode and let through a maximum of 7-8psi. With only power it will be in "closed" mode and will only allow through about 5psi. The ECU makes it go into "open" mode by giving the black wire ground signal which makes the circuit complete. All you are doing by "adjusting" the black wire is making the circuit complete all the time.

What will happen above 4500rpm now that I've done this mod?

The ECU will still ground the wire above 4500rpm but nothing will happen. As long as the black wire is taped up you will be fine. Of course if you are creative you could run this wire to something else and it will be turned on when rpm is greater than 4500rpm. Crap like turn on the water spray kit for the intercooler, flash a light, do some other crap

I've broken something, can I reverse what I have done?

Should you do some damage or have broken stuff you can get a stock boost solenoid from the for sale section of the forums for like $50 tops, as its fairly useless when you have an aftermarket boost controller. The standard wiring is fairly simple, one is ground one is power. You can't have a circuit without both. See wiring diagram if you are unsure or doubtful.

Have fun and enjoy

** Corrected wire colour mistake **

** Corrected 3 more wire colour mistakes lol Duncan **

[koduRB25det]

oooh yes. i got S I auto lots of fun. i hit 10 psi at 5000 rpm. stock car. no modi. just a pod filter.

Boost mod works well for auto.

[gotRICE?]

oooh yes. i got S I auto lots of fun. i hit 10 psi at 5000 rpm. stock car. no modi. just a pod filter.

You should be hitting 10psi before 3000rpm with the mod

[horrace]

did this on my series 1 stagea today was piss easy, i can believe how much of a difference it made, seems like a different car!

[stagman]

Could anybody re-up pictures? And judging from other's this is okay on the NEO engine so long as we ground the black wire? correct?

[gotRICE?]

Page 23

[HOWIROL]

A little confused about this... Been looking thru this thread and cant find my answer. With the earth wire, do you just splice into it? or cut it and earth one end?

[gotRICE?]

Did you read the 1st page? The 1st post?

Under "The Mod" on the 1st page it clearly says

"CUT the black wire, and tape up the other end"

[HOWIROL]

Of course I read it... I just didnt read it properly it seems!

[gotRICE?]

Haha all good. I sometimes skim read huge posts and miss stuff too. Gl with the mod . Makes the car feel like a new machine

[BstewyR33]

did this mod today along with a front mount install fun times ahead

so half way between 0 & +7 is about 7-9ish psi??

[RB25PWR]

Just did this today. My boost gauge now sits right in between the 0 & the +7 well before 4500RPM.

Edited February 26, 2010 by RB25PWR

[kb-r33]

did this on a friends car today and it worked great. nice response and power.

[Niz32det]

Hey guys,

I JUSt did this mod on my R33..

Im getting .3 bar 1st and 2nd gear.. but when im in 3rd it goes to .6 bar around 4000rpm.

I have a highflow turbo, fmic, stock exhaust, stock wastegate actuator, stock ecu.

Does this sound right?

Ive changed two grounding points and it seems to be the same.

Could the lack of boost be because of the lag on my turbo?

Im guessing i did it correctly because it does hit .6 bar (8 psi) before 4500 in 3rd.

[ShayR33]

I did mine on sunday and all I have to say is... best mod ever! Made the hugest difference in first and second makes the car drive even easier. I tried to resist putting one of these in but the temptation was to great

[Crackfox]

I did this mod a few weeks ago and can definately feel a difference, especially in 1st gear and 2nd. Full boost is now at 3000rpm maybe lower

My fuel economy has been horrible though - 16L/100km on this tank as opposed to the steady 10-11L/100km I have been getting for the 6 months before this. I dont drive any differently than I used to either, could this be related to my fuel economy? Instead of cutting the black wire I exposed it and ran a wire from ground to the point where the black wire is exposed. I might reverse the mod to see if it has anything to do with my fuel economy if I dont figure out the problem soon.