Controlling VCT on RB25DET

[BOOSTD]

Probably a question for Sydneykid...

My 33 came across to the Aussie side with an aftermarket Chipped ECU. The car was labled a freak cause it constantly made 10-15kw more than any other car with the same mods.

A strange thing occured to me, the VCT with the "chipped ECU" wasn't being activated untill 5000-5500rpm. Also was running massive timing advance. I am wondering if there is any advantage from doing this???.....I can't see how there could be unless it has a different inlet cam. Anyway felt really cool, sort of had three power bands.

[AeroGrace]

Originally posted by BOOSTD

Also was running massive timing advance.

Just wondering are you running on pump fuel?(98 Octane?)

[BOOSTD]

Currently BP Ultimate,but, with Wynns Race Formula Octane Booster.

With the stock turbo as above just Normal 98

[BOOSTD]

bump

[TomR33]

Interesting question, hope someone can answer.

[BOOSTD]

me2.....

[51jay]

I thought the vct on thr RB25 was activated on startup and acted to improve low to midrange torque cutting out at some point in the higher rev range. My EMS computer is supposed to optimise performance by setting the optimum point to cut out the VCT to give the best output for both low and high revs

[whistla]

VCT on teh RB25 is activated in the lower/mid range

~2000rpm

Im running a Wolf v4, and while we were initially tunning it we had some time to fool around with the VCT on the dyno

We did a comparo by changing its activation point and basically the conclusion we came with is its best left where its designed for

We had it active "ala honda vtec style" higher up in the rev range and it wasnt as efficient in making power as it was lower down inthe lower to mid range

hope this helped

[SATO GTS]

as whistla said it works best where its designed for.

i dont think the nissan engineer's put in that operating range because they can , they have spend a hellofa lot more R&D then any of us ever could..

if you want to help the VCT work more effectively try a adjustable exhaust cam wheel .

[BOOSTD]

That's what I thought, only would make sense if the cam was aftermarket.

SATO GTS I have an adj exhaust wheel. How would that help the VCT on the inlet side of things??

[51jay]

retarded 3 degrees it boosts low and midrange torque makes the car infinitely more driveable

[51jay]

retarded 3 degrees it boosts low and midrange torque makes the car infinitely more driveable

[Steve]

I was waiting to find this: http://www.tomei-p.co.jp/_2003web-catalogu...haft-specs.html or something similar until I posted:)

NVCS comes in just over 1000 rpm and cuts out at 4500rpm on RB25DET.

the best way I have heard of optimising NVCS is by doing two runs on a dyno, one with the NVCS switched on, one with the NVCS unplugged. Where the lines cross it the best point to switch off.

easy:D

[Steve]

Another interesting thing to note is that the RB25DE is supposed to run VCT until 5700rpm, so perhaps someone put the wrong NVCS chips in at the factory by accident and created these 'freak powered' R33s....hehehehe

[BOOSTD]

I noticed that!, R34 cam looks good 2,

[Duncan]

If there are two easily mapped power curves, why wouldn't Nissan have put the change over at the optimal point :confused:

[51jay]

It probably is at the optimal point for a stock standard Skyline

[BlockHead]

They most likely as he said optimised it for the engine they built. As soon as you start modding an engine it no longer is the engine they built. So by changing it you could squeeze out some more horsepower.

[Al]

Originally posted by Steve

the best way I have heard of optimising NVCS is by doing two runs on a dyno, one with the NVCS switched on, one with the NVCS unplugged.  Where the lines cross it the best point to switch off.

easy:D

This is exactly what i told my mechanic to do when programming/tunning the Wolf 3D. I believe that unless you change internals the optimum point is at the factory setting. This proved true, when tunning my car.