Curious Idea No Clue If It Would Work

[unarmed_skyline]

As you all know on the rb25det's the exhaust cam gear is electronically adjustable and both of the cam gears are idenitcal, so i was wondering if it were possible to use a second adjustable cam gear set up from the exhaust cam and use it to control the intake cam and then hook it up to i think apexi do a cam controler computer or something for like $200.

If this were possible would it give you any advantage or and more power?? i guess using it you could set a small cam on idle so it was smooth at idle then later in the rev range open it up more

what are your ideas im not thinking about doing it just got into my head the otherday and i was wondering if it were possible

[mattymagoo22]

The intake cam is the only cam that is variable on the RB25 and it has an oil control solenoid that operates the advance/retard if you look at your motor you can see it at the front of the motor on the head with a black and brown plug, this is what swithces the control solenoid at <4500 rpm. the other half of this system is in the actual pully itself. and the inlet and exhaust pulleys are different for that reason.

I think your looking at the Cam Angle Sensor.

Cheers Matt.

Edited February 20, 2007 by mattymagoo22

[Simon-S14]

on another note. how does one go locking the vct in one place and disabiling the system?

[Adriano]

To disable the vct, simply unplug the soleniod. I believe that it would most certainly be possible to do a dual vct setup, all it needs is two inlet cams with camwheels, a soleniod to switch the oil pressure(with a bleed orifice to relieve the pressure) and an iol port drilled into the head at the appropriate spot. Would probably want to run biggish cams to make the most of it though. Also need a jaycar controller, and a lot of dyno time.

[unarmed_skyline]

opes i got the cams around the wrong way i knew what i was thinking in my head but not on the car, so it would be possible, would it give many gains thou or would it be just another thing that could go wrong, the out lay doesnt seem that expencive could be done for possibly around $1500 if some of the work was done by yourself, do you know of anyone whos done it before? the car would be able to change the power-ban to a lot higher and pull harder without loosing your idle, it must not be that good an idea if no-one out there is doing it, love to hear from someone whos tried

[Adriano]

HKS do a kit, but its around $8000. You could probably do it for $1500 if you have the head off already, already have an aftermarket ecu and know someone with a dyno, although to make it worthwhile, i would only think there would be a real benefit if you are making over 300rwkw, and are planning on fitting some 272's. Remember you dont only have to set the switch on pionts, but also adjust them (i dont know if all the vct gears are adjustable)Icould see a whole day of stuffing around on the dyno to gete the most benefit. Does anyone know how much the vct adjusts the cam timing by? Remember you will also need to sort out somethig for the cas.

[mattymagoo22]

in theory its a great idea big cams with good drivabilty down low and high power potential up high but you'd be asking for trouble as adriano mention the exhaust cam controls the CAS to time your motor so could cause problems

I know subaru 2.5 turbo motor has variable cam timing on all 4 cams and has the control on the insde of the cam gear it uses cam and crank sensors with the mgnetic pick up on the actual outside of the pulley so that the cam can advance or retard without affecting the sensors......

Not sure what the advance is but would be good to know, anybody know how much the cams advance on the rb25??????????????

[BHDave]

I suppose anything is doable with enough know how and money.

What you are proposing re big and small cam isn't how the nissan system works though, all it does is advance and retard the inlet cam there by reducing/increasing the overlap.

You would have the added complication of having to run the cas off something other than the normal drive on the end of the exhaust cam as 1) it will be blocked by a vct gear now, and 2) you cant drive it off the cam anymore anyway as that is moving around, you'd need to drive it of the outside of the gear which would stay constant in relation to the crank.

Second consideration; by the time you do all this and spend the money, the guy who put in cams for $1k will still make more power pretty much everywhere with very little effect on idle quality, fuel economy....well that's a different story if your system is set up right.

So by the time you remove and machine the head to accept a second solenoid and give oil a way to get into the cam gear, get an oil feed up to it, get a second inlet cam to replace your stock exhaust cam as well as the new vct gear, then a couple of controllers, head gasket, etc i figure you will be up over 1k already not including any labour, a couple of weeks of down time for the car, yadda yadda, vs the drop in cam option, drive in drive out in under a day for less money ex labour (which will be significantly less too) and then the tune for each.

Not worth it for me.

Edited February 21, 2007 by BHDave

[T04GTR]

HAHAHAHAHAHAHHAHHAHAHHA lol

@ varable exaust cam

[T04GTR]

anyway.. yes there would be gains in having a twin vct system. having a system like the toyota beams 3s would be sweet

[psi]

its not a new idea. toyota is a local company who do it well. Honda have done it for quite some time and then you have one of the masters of doing it.. BMW.

the humble RB just wasn't designed to do it.. and for the pain and headache of getting it all up and running.. y would anybody bother. cam upgrades are a cheaper and easyer optioon. sure if you had a maxium effort engine that was already stretched to its limit and you were desperatly tring to get a less peaky engine, that had a wider torque curve, then i would go for it!

but good luck with that one.. there is always somedody thinkin outside the square. Go for it and be famous for the first bugga to do it. make sure u take heaps of photo's so we all can copy u!

any other thoughts