External Vct Controllers. What Have You Used?

[nigelswazi]

I have a R33 with a RB20DET ECU remapped and I cannot believe the power difference from having the VCT turned on at the stock points compared to switch permanently off. On the dyno naturally in top gears it doesn't make that much difference to a power run but in everyday driving it makes a huge difference to boost spooling etc in the lower gears its literally a pig to drive off until on boost.

Now down to business as the RB20DET ECU never had VCT it can't switch it off and on just like the RB26 Power FC on RB25. Now this lead me to thinking about other options and I recently bought a Buddy Club VTEC controller to try to wire in. Now the problem is this controller is designed to switch cam profiles at a set point in the RPM range. Now the problem is this will only switch on and then off once below that point which is perfect if it could act in reverse eg be always on till say 5000rpm then when the VTEC controller goes to make the switch at 5000RPM it could switch off the VCT but braking a switch instead of making it. How would you do this electronically so I can have it permanently on and have the VTEC controller turn it off once it hits the set RPM.

Otherwise can someone suggest a better device to basically turn it off and on at set points.

Any feedback would be much appreciated im sure there are a couple of people out there who have done this.

[Simon-S14]

I'm aboiut to use something that came from the states, its a simple Signal imput switching device with a 10% hystetis (sp) Cost around 40 bucks and you can set the RPM (or speed signal as it can be used for also) to whatever uyou want and it switches any device on or off.

[acsplit]

I believe Dr Drift has done a couple of these

[Simon-S14]

its nothing new, i run a 20 ECU on my RB25 in my 32... made 220 rwkw and not a lot of low down loss at all...

[acsplit]

And it was the buddy club vtec controller that was used. the vct on with stokc setup provides more mid range with slightly less top end

[Dr_Drift]

Buddy Club VCT Controller + Change Over Relay = VCT FTW!

[nigelswazi]

Buddy Club VCT Controller + Change Over Relay = VCT FTW!

So you have it turning on from 0rpm all the way to the BC VCT controller set rpm say 5000rpm. Is there any negative to have VCT on from 0rpm-1800rpm? Just that the stock ECU turns it on at around 1800rpm just wondering if they did this for a reason.

So did you just wire the Buddy Club VCT as follows:

Normal GND and 12V IGN + RPM to the usual spots and then the two wires which on the instructions go to the INPUT/OUTPUT of VTEC solenoid to normal R33 pin 113 wire and the other to GND but wire them through the relay?

Edited November 24, 2007 by nigelswazi

[Dr_Drift]

I'm aware of the Off @ Idle status of the factory ECU, I can only think that this may have been to prolong the life of the VCT solenoid by not having it switch on as much... I have not found any difference in drivability or idle.

We don't connect the VCT input of the BC (don't have a manual in front of me), simply use the output, through a changeover relay, to the VCT on the 33 loom... I can't remember as we now map the 33 ecu and haven't done this for a while...

If you hook the buddy club up to power, earth, and rpm, you can check the output (I think it provides a switched 12V output?) and use that through a changover relay to the required output (earth?) is on with ignition, and off at set rpm??

I can verify when I'm back in Melbourne next week and check my diagrams, just in Virgin Lounge at Melbourne airport on my way to Darwin to tune some cars.... mmm Hot Sweaty weather yay (not!)

Hope this helps...

Sam

[paulr33]

So you have it turning on from 0rpm all the way to the BC VCT controller set rpm say 5000rpm. Is there any negative to have VCT on from 0rpm-1800rpm? Just that the stock ECU turns it on at around 1800rpm just wondering if they did this for a reason.

from what i have seen the VCT turns on at any RPM below 4500rpm when

TPS > 0.33v && NTR switch is off

so it is actually active under 1800rpm it just wont turn on at idle (as TPS is 0.33v) and it wont come in netural gear

ive just setup a vafc II in my car to try and control the vct i dont think it will work but am trying something different

i can change the kick off rpm in the PFC anyway but wanted to try something different

[RB30-POWER]

VTC mapping code has some of the following functionality

minimum coolant temp for VTC actuation

maximum coolant temp for VTC actuation

minimum vehicle speed for VTC actuation

minimum TP for VTC actuation (only if RPM is UNDER ON point)

minimum RPM for VTC actuation

maximum RPM for VTC actuation

idle position on/off

in general however on RB25, it turns on when you come "off idle" and then turns off at around 4500rpm again.

the theory is simple, you want it turned off on idle to reduce overlap and get a dead smooth idle, off idle you want extra overlap for power and torque during the midrange and the only reason it turns off again is because somewhere along the line, you make more power with it off because of the excessive backpressure in the exhaust manifold which prevents cylinder filling efficieny. its easier to fill without the backpressure trying to go back into the chamber from the higher overlap.

[paulr33]

very helpful, thanks for the diag

[paulr33]

ive got the vafc installed so will try and play with the VCT soon if im brave enough

for those interested the vafc can pressure from an external map sensor

and display it in kgcm2, psi or kpa (you can choose) so thats very handy

it also gives you the choice of scale from the sensor so say 0 to 1.0kgcm2 or 0 to 30psi

[DECIM8]

Ive been talking to a Bel tuner and he recommended not to touch the vct as its to easy to screw up. I dont know how true or not that is but he also stated the power difference was not big enough to wreck the vct.

[Simon-S14]

Ive been talking to a Bel tuner and he recommended not to touch the vct as its to easy to screw up. I dont know how true or not that is but he also stated the power difference was not big enough to wreck the vct.

sounds like BS to me.

however there is little gains in power by having it on uop top, its designed to give more low down torquye