Varible cam system

[Kclank]

i am building a custom car using a Datsun 240z chassis, updated suspension, a fiberglass Ferrari clone look alike body and most importantly to this forum a RB250DET series 2 engine from a skyline. i am looking for a piece of technical info on this engine. specifically "is the N-VCS a proportional or on-off system"? i ask this because of the requirements of the after market computer management system i am trying to use (SDS, EM4-f) only works "on-off". any info would be appreciated. if i am in the wrong place for this question just let me know.

[mtnickel]

i am building a custom car using a Datsun 240z chassis, updated suspension, a fiberglass Ferrari clone look alike body and most importantly to this forum a RB250DET series 2 engine from a skyline. i am looking for a piece of technical info on this engine. specifically "is the N-VCS a proportional or on-off system"? i ask this because of the requirements of the after market computer management system i am trying to use (SDS, EM4-f) only works "on-off". any info would be appreciated. if i am in the wrong place for this question just let me know.

 

Here is from my RB notes. I basically had to learn every system as I was going to use Megasquirt. For my system it would have required a few logical statements to program properly.

I have since scrapped Megasquirt. I have a 24/1 wheel if you need one for Ignition, though surely Edis system will be easier/cheap/foolproof. I've heard mixed reviews on getting the 2 slot optical sensor working properly if it's not receiving the 360* signal.

 

NCVS Notes:

 

 

Light Load

At light loads and below 6100 rpm, NVCS is OFF with the intake valves retarded. This helps to promote a smooth idle and engine stability.

 

Medium to Heavy Load, 1050 < 4500 rpm

At higher loads but lower RPM's, it is possible for air that has flowed into the cylinder to bounce back out again. This decreases volumetric efficiency and therefore an earlier valve closure is desired. So under these conditions NVCS is ON and the intake valves are advanced by 20 degrees. Doing this can increase engine torque in this range by close to 20 lb-ft.

 

Medium to Heavy Loads, > 4500 rpm

Now at higher RPM's, whereas before the problem was that air was bouncing back out through the intake port, now the problem is that not enough air has had a chance to flow in yet. In order to take advantage of inertia effects, a later valve opening is preferred, even if it is the same duration. So at high revs, NVCS is now switched OFF and the intake valves are retarded back 20 degrees to their original position. This can help with top-end torque by as much as 10 lb-ft.

 

Your logical rule will likely be:

If MAP > 500mbar/-15in vac AND RPM is between 1050-4500rpm then NCVS is on.

 

Megasquirt couldn't do 3 conditions (map> 500 AND RPM>1050 AND RPM<4500, so for me I would have had to set it up:

Dummy RPM output = RPM>1050 AND RPM<4500.

NCVS output = if MAP> 500mbar AND Dummy RPM = on.

 

I'm not sure of the limitations of your system though.

 

I also have Voltage curves and other info on the stock coolant sensor, air sensor, etc. So you can calibrate the system to use those instead of what most do (get GM sensors).

 

 

I've abandoned Megasquirt due to hour many hours and hours it will take me to wire and test. Let alone try to get it running. I've instead decided to first run stock ECU and see how I like the power. Perhaps mild boost controller.

After that, best RB tuning solution is to use Z32 ECU chipped to run nistune.

 

Good luck!

Edited September 7, 2012 by mtnickel

[Kclank]

good detailed info. i have lot's to learn about my SDS system but i shall keep the info you sent plus you answered my basic question so i guess you are not a politician (lol), thanks again