NVCS on HI CAM...Help..

[Sydneykid]

Hi guys, on a 500 bhp RB engine we only get between 3 and 6 rwkw from adjusting the inlet camshaft timing, most common is 2 degrees. On the other hand adjusting the exhaust camshaft around 4 degrees gives between 15 and 18 rwkw. I really don't see adjusting the inlet camshaft timing on a VVT road engine is worth it. The car will be slower accelerating anyway because you will loose a lot more than 3 rwkw in the mid range without the VVT.

Hope that adds to the discussion

[GTS-t VSPEC]

Sydneykid,

Isn't it possible to adjust the timing depending on rpm via an aftermarket ECU, won't this do the same thing as the VVT, or am I missing something?

See'ya:burnout:

[T0nyGTSt]

I thought it was established that replacing the exhaust cam gear was pretty much close enough... you retain the VVT but you still get a bit more power, bit fuller mid range.

The price of tuning will outstrip the mere cost of the gear itself though...

T.

[GTS-t VSPEC]

Most aftermarket cams don't support NVCS, so it would be good to know what is possible if we loose the NVCS.

See'ya:burnout:

[Sydneykid]

Hi guys, if I was doing another mid power upgrade on an RB25DET (mid power = max on standard internals) I would go for a set of cams designed for the hydraulic lifters and the VVT. The 2 that we have done worked out just so nice, it has to be worth the extra bucks.

For GTS-t VSPEC, yep we could use one of the outputs from the Motec to continuously adjust the VVT on the inlet camshaft. You could build a 3D map for it, based on RPM, throttle setting and boost level, it would be a bit of work, but you could do it. We would also statically adjust the exhaust camshaft timing with an adjustable pulley.

The M3 is much easier, as it has Vanos on both camshafts, so we can put them anywhere we like, independantly. The XR6 Turbo also has VVT on both camshafts, but the plurb says they move together, not independantly.

On the 2 GTT's that we have done, we used Power FC's and left the VVT staging untouched, in fact I don't remember it being accessable with the Commander. Can't wait for the datalogit guys to do one for the GTST's, open up some nice possibilities.

Hope that helps

[sidewaymambo]

Thanks guys all your input are valuable..thanks once again..

I think it makes sense now that leave the intake unchange to retain NVCS and replace adjustable came gear at exhaust side...

thanks..

[T0nyGTSt]

Philip,

It's a forgone conclusion... for most of us a single exhaust cam gear would be fine.

I doing a OS Giken or HKS exhaust cam gear when it comes to changing the timing belt. I don't care about what brand, just what is cheap.

T.

[GTS-t VSPEC]

I have the new Wolf so we will try changing the timing vs rpm, and I'll report back with my findings. Should have the cam gears next week.

See'ya:burnout:

[lukits01]

Sorry for digging up and old thread

was wondering if anyone has any opinion on running a 256 Ex Cam shaft with the standard RB25DET VVT inlet shaft?

Will this combination work? what kind of tuning is involved?

[51jay]

[. Can't wait for the datalogit guys to do one for the GTST's, open up some nice possibilities.

Hope that helps

Sidneykid.....I have the FC-Datalogit in my hot little hands right now. Software program is FC-EditRB25DET Ver 1.100. However it is a Beta version....didn't know that when I bought it

[Steve]

excuse my ignorance, but what is a Beta version?

cheers

(any chance of an evaluation copy of the software;))

[EnricoPalazzo]

beta means 2nd test version basically

alpha is first version.

[51jay]

means it's probably not fully sorted out yet, however they e-mail you any updates on a continuing basis

[Sydneykid]

Hi Jay, I ordered a Datalogit for the R32 GTST earlier this week. I wonder if it's a beta version as well.

Hi lukits01, you asked "was wondering if anyone has any opinion on running a 256 Ex Cam shaft with the standard RB25DET VVT inlet shaft?""Will this combination work?

Yes works great, not as good as a pair but still worth doing.

"what kind of tuning is involved?"

Lots, do you have a programable ECU? If not, then buy that first.

Hope that helps

[lukits01]

Thanks for info sydney kid

I only have a SAFCII

This idea was sorta result of impulse buying hehehe

My ex cam shaft shat itself somehow and I thought might as well get a mild upgrade

since I allready have HKS cam gear might as well finish it off

What about RB25DE inlet HKS 256 Exhaust

that would be a better combination wouldnt it?

[BOOSTD]

What sort of power increase is to be expected from the exhaust cam change only?

Also is there any cams that are better suited to a ported head?? I have more power up top now with porting but at the expense of more lag.

cheers matt

[Sydneykid]

Thanks for info sydney kid

I only have a SAFCII  

This idea was sorta result of impulse buying hehehe

My ex cam shaft shat itself somehow and I thought might as well get a mild upgrade

since I allready have HKS cam gear might as well finish it off

What about RB25DE inlet HKS 256 Exhaust

that would be a better combination wouldnt it?

No

[Sydneykid]

What sort of power increase is to be expected from the exhaust cam change only?

Also is there any cams that are better suited to a ported head?? I have more power up top now with porting but at the expense of more lag.

cheers matt

Hi Boosted, I have never experienced increased lag with a ported cylinder head, did you do anything else at the same time?