Rb25det - Nvcs Concept

[QRI05E]

Hey guys, I been reading up and apparently the series II RB25det's have NVCS which is like VVT/VVL.. and also apparently it is controlled by a solenoid somewhere on the engine... at the moment, untill I hit 4500RPM, the tourqe is nothing special.. but from 4500 to redline you get a huge rush of power!! its even noticable on my dyno graph...

Heres my question... is it possible to to have the solenoid always 'on' so that you have the advanced timming on bottom end too?? or to even connect a switch to it similar to the "high boost mode" idea???

Anyone got a pic of this solenoid??

Regards,

Sarkis

[Craved]

the VCT solenoid is the hexagonal thing coming out of the side of the head near the end of the fuel rail and the water outlet...

its a simple on/off solenoid which allows oil to flow into the unit on the end of the cam shaft, and change the advance/retard on the cam.

i actually believe that its "on" from about 1500 to 4500 and OFF before and after that.. so you actually sound like you want it off.

you can do a run with the solenoid unplugged and see if it helps your results, but i dont think it will..

[paulr33]

im doing a kick off point rpm test at our next dyno day for the NVCS on the rb25. you do a dyno run with stock setup (kicks off at 4500) then plot power w/rpm. then turn nvcs off (make it kick off at say 1200rpm) then dyno run again. plot it on the same chart and the point where the two intersect is the ideal rpm kick off point. im not sure how useful it will be (if anything at all). but still something fun to try.

powerfc users can alter the kick off point via datalogit

[N I B]

I do this on every car i tune to find the best changeover points.

Usually on at about 1400 and of again at about 5500.

The car in the first post would be the boost stepping up.This detail should be on the dyno graph.Ask if the can see you what your boost was doing.

[paulr33]

right so it does vary a bit on each engine, sweet as.

in the powerfc i can only change the rpm point.

so it comes on always at about 1400 and then off again at 4500.

so you found the ideal kick off point is near 5500 once tuned ?

[N I B]

5500 has been the lowest point with some as high as 6100.

Im not talking small gains either,its real worth while.

[QRI05E]

So is there anyway to advance the timming via the solenoid with the factory ECU? or would i have to get a pair of adjustable cam gears fitted??

Cheers

P.S Happy Easter Everyone!

[N I B]

Need an ECU.

[paulr33]

very interesting, thanks for the tip. will be keen to give it a shot.

how does it feel on the street once its been done?

[N I B]

More linear power curve. If the cam changes to soon you can loose power and torque,if you can changes at 4500 and it needs to be at 5500 for example then you are giving up max power for 1000rpm right in the guts of your curve. Do a power run with the vvt off then do one with it on from start to rev limit and its easy to see where to switch at.

[Craved]

nice ..

might check this out on tune time i think too..

[Links]

QRI05E - what your having happen is possibly the duel boost solenoid switching from 5 to 7/8psi hence the increase in torque as it's running higher boost.. Cutover point is 4,500rpm..

Is your car pretty modified much?

[QRI05E]

LINKS - Im currently running the Hi-Boost mode on my factory solenoid therefore constant 7psi... my car is fairly stock except for the split dump and 3" hi flow CAT and exhaust + K&N Pannel filter (165rw/kw) and at 4500 - 5000RPM i get a slight pop (at times) from the exhaust and a rush of power to redline! Its not a misfire for sure cause theres no hesitation and the coils + NGK plugs are only 6 months old.. Im definate its the NVCS kicking in via ECU and CAM gears... all i was hoping to do is get it kicking sooner to get more bottom end... i guess ill need an aftermarket ECU...

Do you guys think resetting my factory ECU would help after getting the exhaust or any other mod fitted?? any benifits?

Cheers