Rs4-s Owners - What Have You Done To Overcome The Boost Solenoid To Run 7+psi Or Is My Understanding Wrong?

[BCCairns]

From what I'm reading in various SAU threads the boost solenoid on a RS4S bleeds of boost that is higher the ~7.5psi, and this is controlled by the ECU.

My understanding is you can

A) Get ECU management and tune it out

b) Install some type of boost control

c) Earth the solenoid out but run the risk of infinite boost, (but u can remove the risk by installing boost control?)

I have a TurboSmart duel stage boost control, and when I try to adjust the high boost with 1 or 2 clicks up from 7-8psi, I get a hesitation and it doesn't boost past 7psi (which I now think is a boost bleed off, not coils) As I have duel stage boost control is it safe for me to earth out the solenoid?? I really would like to run 10psi maybe even 11psi..

I would really appreciate if Rs4s owners could let me know if you experienced this problem with boost past 7psi and how you manage it. Or even if your RS4S had this issue

Thanks heaps and for all those that have helped out with my recent posts... You rule =)

Mods

FMIC, 3 inch from manifold, duel stage turbo timer.

[Duncan]

most likely its not really boost bleeding off.

when it runs over 7psi does it keep accelerating smoothly or just subtly lose power?

A lot of people have found that the factory tune is very intolerant of running extra boost, and it starts running very rich and retarding the timing- which in turn means it makes less boost and drops of quickly. In my car it was very voilent, felt like a bad missfire, but mine had an uncommon ecu.

BTW your standard solenoid should not be connected if you are using a turbosmart or any other boost controller. So earthing the solenoid should make no difference

[BCCairns]

Ahh cheers Duncan didn't know the solenoid was removed from the circuit when a boost control was installed (to point out the obvious ' its my first turbo car' =)

As far as description it's like 2 v.quick subtle loses of power between 4500 and 6500 seems to power through after the power loss... Boost gauge seem to flutter around 7 to 8 pound mark. So far my testing has been limited to 30 mins of driving, tying to up the boost one click at a time until the above described prob happens. I think ill seal my coil packs on the weekend(as i think this could also be an issue). If it still happens ill try below, who knows just mite help.

http://www.skylinesaustralia.com/forums/By...mp;hl=boost+mod

[lilcrash]

I have got a turbosmart boost t in mine running at a peak of 10-11 psi. As you might hve noticed the turbo can't keep the boost up when the revs get higher, I'm thinking that's why Nissan put the vct in to try to add power when the turbo ran out. My car has a massive hole you could drive a bus through between when the boost drops to 5 psi and the cams coming on at 5000 rpm. But honestly just buy some aftermarket coil packs if u suspect a problem as sealing them is only a temp fix in my opinion. Feel free to pm me any questions if u want to compare things in my car (1999 rs4s)

[Race__24]

Mate, there shouldn't be any issues with "boost bleeding off"

Possible causes-

- exhaust wheel on turbo in poor shape

- blockage in either the exhaust system or intake

- ignition problem - coil packs/spark plugs

- some sort of weird computer issue

- dodgy gauge reading low

Basically a stock RB25 should be capable of boosting over 11psi, I'm not saying it's safe, or that you should do it, just that the turbo should be able to supply that much pressure easily before running out of flow anywhere in the system.

I don't think you really get how the stock solenoid works, all it does is bleeds of pressure to the wastegate actuator above a pre-determined RPM, making the actuator actuate at a higher manifold pressure. It is either on or off. The switching point MAY be adjustable in theory but the boost levels are not. Whatever the setup, the boost solenoid does not limit boost when a boost controller is added (if done properly) or even if a hose comes off.

Edited May 20, 2010 by Race__24

[BCCairns]

I don't think you really get how the stock solenoid works, all it does is bleeds of pressure to the wastegate actuator above a pre-determined RPM, making the actuator actuate at a higher manifold pressure. It is either on or off. The switching point MAY be adjustable in theory but the boost levels are not. Whatever the setup, the boost solenoid does not limit boost when a boost controller is added (if done properly) or even if a hose comes off.

Ahh cheers Aaron im slowly piecing this together.

[pipster11]

think its all been summed up so far, i'll back it all up tho

i've grounded out my stock solenoid through a switch which means i can use the low stock boost setting all the time or the high boost all the time

by grounding out the solenoid you are actually allowing air to escape the wategate vac/pressure line back into the intake and effectively lowering the pressure the wastegate sees = more boost

most rb25's see a dip in power at around 5000rpm for some reason with a stock tune, i think its just nissan protecting the motors with the tune

new coilpacks and a nisstune will see you with more power, more torque and better fuel economy for not much over $1k all up

but putting some URETHANE SEAL COAT on the coilpacks will give you an indication of their condition too (check the plugs while you have the coils out too)

[KiwiRS4T]

I prefer to bypass the stock boost solenoid rather than earth it. You can adjust boost by altering the diameter of a restrictor in the bleed line or with an aftermarket boost controller. Power dip at 5000 rev/min seems to be a feature of the rb25det ecu and shows up on lots of dyno charts. You can tune it out with aftermarket ecu or nistune etc.

[32TAXI]

Im With Duncan - Rich and retard!!!

Have personally been affected by this with my RS4S and fitted PowerFC inc secret squirrel mod and now running 11psi all day with no black tailgate.

Edited May 21, 2010 by RED513

[66yostagea]

I really dont know but, just tested my Stag after fitting plenum and FMIC and its pushing 13psi then dies. I know its not a crook gauge because it goes like f***k and scared the leftovers out of me before she saved herself from selfdestruction.

Engine is stock as.

[32TAXI]

I really dont know but, just tested my Stag after fitting plenum and FMIC and its pushing 13psi then dies. I know its not a crook gauge because it goes like f***k and scared the leftovers out of me before she saved herself from selfdestruction.

Engine is stock as.

Did you fit that restrictor to actuator line? I'd remove it as T-piece should have restrictor internally.

[pipster11]

^^^ x2 to this

there are restrictors int he vac lines of the stock setup and MUST be removed if you have an aftermarket controller or it will f**k up

also check for boost leaks causing excessively rich running, things like carbon canister, bov hose clamps, idle thingos (most of it is behind the j pipe, just before the throttle body)

[66yostagea]

Did you fit that restrictor to actuator line? I'd remove it as T-piece should have restrictor internally.

Itis the stock tee piece and restrictor. I just measured the leg of the tee and it is less than 2mm dia where it goes into the arms. I dont know the size of the restrictor bush but it definately there. The setup is the same as when I only got 8/9 psi. The FFP, pod and FMIC should not make that much difference. And I can now hear the turbo spooling.This is odd.

[lachlanw]

this thread really does prove the rule that 50% of people are below average

[lachlanw]

i have an rs four s

it has a catback exhaust , gutted cat , HDI fmi . standard air box .defi boost gauge

when i fitted the fmi it would run an unstable .8 bar on standard boost controll and was not happy . surgey . hit boost cut a couple of times

i bypassed the stock solenoid and and swapped the waste gate actuator for a r32 one plumbed straight off the compressor housing , rock soild .8 bar car not happy . started pulling timing between 4500 and 6000 rpm

i now have standard waste gate actuator back on and old school avc-r boost controller . .7 bar and car is happy . goes hard . standard coils .standard ecu. what ever plugs came in it . 126000 kays . no hint of a stain above the exhaust 0-100 in 6.2 seconds

[lachlanw]

ps earthing the solenoid on a rs four "S" does nothing . they are on high boost all the time

[66yostagea]

this thread really does prove the rule that 50% of people are below average

X2 you see them when you look in the mirror

[66yostagea]

ps earthing the solenoid on a rs four "S" does nothing . they are on high boost all the time

I used to have a two stage switch for this. Switch off stock boost all the time, switch on high boost all the time. Only used it when coming up the mountain. But then mine is an RS4

[pipster11]

ps earthing the solenoid on a rs four "S" does nothing . they are on high boost all the time

I used to have a two stage switch for this. Switch off stock boost all the time, switch on high boost all the time. Only used it when coming up the mountain. But then mine is an RS4

i did what he did ^^^ so i can run low boost if i want to = saving fuel and prevent the mrs from getting speeding tickets in my name

[lachlanw]

X2 you see them when you look in the mirror

so is your post twice as useless as mine ??

and how many people do you see when you look in the mirror??