Rb25Det Vct

[ellle]

My apologies if this has been discussed already, I had a look and whilst I did find some info on vct I didn't find what I was looking for,

What are the options for running an RB25DET VCT without the cluster? Apparently the only way is with an aftermarket ecu?

Thanks

[iruvyouskyrine]

You mean the speedo cluster? It is not required for the operation of VCT.

Also 'plug-in' aftermarket ECU's will retain the VCT funciton, but if you use a NIStune ECU you need an RB20 or Z32 ECU and a window switch to control VCT.

[steve200b]

Z32 Nistune will control the vct or I use eboost street as a window switch and boost control

[GTSBoy]

You mean the speedo cluster? It is not required for the operation of VCT.

Not true. Nissan ECU requires functioning VSS in order to make VCT work. Therefore cluster is required, seeing as the cluster is the source of the VSS.

It has been done before by tucking a speedo head up behind the dash where a cluster is not otherwise desired in the car.

[iruvyouskyrine]

Neo with NIStune ECU, 25 box with navara mechanical speedo sender. My VCT worked and my cluster did not.

[Ben C34]

I'm sure nistune allows you to set the speed trigger for vct to zero, which would explain it working in that case.

Maybe on a stick ecu it wouldn't work. But who uses a stock ecu anyway?

[iruvyouskyrine]

It wasn't set on speed trigger zero, cannot remember exactly when it came on, but it wasn't constantly on.

Tuned by Trent for Chequered tuning if anyone knows how he usually sets these things up.

[GTSBoy]

I say it again - and even the Nistune docmentation says it - the std ECU requires functioning VSS to activate VCT. The threshold speed can be set to zero (in which case it possibly will work without functioning VSS). If Trent tuned it then it was almost certainly set to need zero speed to trigger. But there is another threshold which is minimum TP (load) which is about 48 on standard maps. That is why you only see VCT activate once you get to a certain speed/load. It's not road speed, it's not rpm, it's pure load. Then it turns off at the turn off rpm (5400 or whatever it is).

But here's the thing. I also have RB25 box with Navara sender in R32. The cable drive makes the speedo head turn. The speedo head generates the ECU's required speed signal. it is quite possible for the speedo head to be broken in a way that the needle won't work but the internals and the VSS are actualy working, so maybe that was the case.

I for one, have seen my VCT not work when my VSS wasn't.

[iruvyouskyrine]

I always assumed it worked via engine load not VSS, but obviously it uses a combination of that as you said. I did wonder if the speedo cable was able to drive a tacho generator and therefore the ECU was still receiving a VSS input, but i honestly wasn't sure.

[GTSBoy]

Having said so forcefully what I said....I see the std bin files for RB25 Neos all have the VCT minimum VSS speed se to zero anyway.