KPierson

iTrader: (1)

I have heard people mention Variable Valve Timing as being standard on the VQ35s but I couldn't find any reference to it in the ESM. Does anyone have any information about this?

Armitage

iTrader: (15)

The VQ35 has what is called CVVT or Contiously Variable Valve Timing. According to Nissan's site:

Continuously Variable Valve Timing

Acceleration begins with calculated gulps of air. Off the line, a massive high-flow manifold coupled with a highly intelligent ECU manages the tremendous air consumption for enormous amounts of low-end torque. As velocity is quickly found, the ECU and manifold alter the flow path for optimum consumption, while continuously varying the valve timing all to make the most of the zero-to-sixty experience.


Basically what it does is alter the timing of the cams depending on a bunch of different factors, including air intake, fuel, and throttle. It will advance or retard the timing of the cams which controls the valves into the cylinders, allowing for a better, stronger powerband. (Someone correct me if I'm wrong, I'm just talking of what little I know).

The normal 287 hp engine has this feature on only the Intake cams. The new 300 hp engine has it on both the Intake and Exhaust cams.

KPierson

iTrader: (1)

I guess thats why you can't see it on a dyno sheet, it appears if the changes are gradual, unlike Hondas VTEC system which is on or off. I'll look up CVVT in the ESM and see if I can find anything on that!

Thanks,

King Tut

iTrader: (1)

VTEC is not continuously variable. It just has 2 sets of lobes on the cams which is how it varys the valves and is why you can feel the cam lobe change.

THX723

iTrader: (3)

newer generation of the VTEC-i also has the addition of the 'infinitely variable' cam timing capability on top of the dual cam profiles (w. seperate valve timing, lift and duration) ... making it the most versital system around.

KPierson,
There are portions of the ESM that discuss the variable valve timing. I don't recall off the top of my head. Was there anything in particular you need answered? May be I can help.

Armitage

iTrader: (15)

Yes but the VQ is one of the few engines that does it on both the Intake and Exhaust cams. AFAIK, the iVtec engines only do it on the Intake cams.

THX723

iTrader: (3)

Only the newer '05 '300hp-spec' VQ has CVVT for intake and exhaust. All '287-spec' '05s, '04 and prior only has intake CVVT.

Many other manufactures already have similar systems for sometimes now. BMW, Toyota, Mitsubishi and Porsche ... just to name a few.

Sharif@Forged

iTrader: (92)

There are not two sets of lobes on the VQ cam. CVVT is nothing like VTEC. VTEC's actually increase valve lift and duration, once the Vtec kicks in.

With the VQ..all we have is adjustable and continuously variable cam "phasing". Essentially, its like an automatic and very sophisticated set of adjustable cam gears. Our system adjusts cam phase, but does absolutely nothing in terms of lift and duration. That's why you don't see any spikes or dips, as you would with VTEC as the longer duration lobes kick in.

Hope that clarifies it.

Armitage

iTrader: (15)

See my 1st post, 2nd post in this thread.

KPierson

iTrader: (1)

The reason I asked is because I'm working with a local Honda owner to develop a programmable VTEC controller and I was looking to see if I could benefit from it on the G. Looking at my dynos I didn't think I would be able to, but without knowing exactly how the system works I wasn't sure.

To alter the timing of the cams I would imagine they cams can actually move on a radial axis to advance and retard the timing. The VTEC system is a lot easier, as its just a simple on/off and with bolt ons you can benefit from the system kicking in at a lower RPM.

THX723

iTrader: (3)

Yes ... it's relatively straight forward for the legacy VTEC system. APEXi's V-AFC series module is widely adopted by the Honda crowd to control fuel trim and VTEC switch point. The newer generation VTEC-i motors w. added infinitely variable cam timing (as well as the dual cam switch over) will need to the additional tweak similarily to our CVVT system. It employs a pulse modulated hydaulic system that alters the cam sprocket offset (deg. of advance or retaard).

Our ECU, as well as the Honda ECU has a map that's dedicated to how the cam phasing ought to be with respect to rpm and load.

KPierson

iTrader: (1)

with a system as intelligant as this I'm not sure there is any room for improvement.

The Apexi unit is basically what we are creating, but we are starting one step at a time. The local guy just swapped a VTEC motor in a non VTEC car with a non VTEC ECU. He has a pushbutton switch on his shifter (ghetto) to engage VTEC. We are starting with an RPM switch manufactured by KPtechnologies and then will most likely venture in to the fuel injector duty cycles and then hopefully timing.

THX723

iTrader: (3)

I see ... cool.

Do keep in mind even or the non-'i' VTEC systems, the VTEC switch over point is not fixed. It varies with engine load and/or other conditions such as engine oil pressure, oil temp, etc. In the case of low oil pressure or excessive heat ... VTEC solenoid is prevented from firing as the same oil source is used to push the VTEC pin into position.

Good luck w. your project. Keep me posted

KPierson

iTrader: (1)

Yeah, if I remember right there are three sensors that will keep VTEC from engagine, two of them were temps (oil and water) and the last was oil pressure if I remember right. All of those should be easy enough to tap in to. I wasn't aware that it kicked it at different RPMs though, I was under the impression that it was a constant RPM level.

Armitage

iTrader: (15)

IIRC, throttle also has to be at more than 35%, but I'm not positive.

KPierson

iTrader: (1)

Eh, throttle is over rated.....