sr20det nvvt

[ex-ctr]

can the vems be used to trigger the solenoid for the vvt

[rob@vems.co.uk]

Yes, perhaps not exactly as the OEM system as I think some of it is speed related.
The solenoid can be driven from one of the spare Injection channels.  On the Nissan you'll use one to drive the IACV, one for the boost controller, which means you have two others to play with.

Triggering will be controlled using the Misc Output feature, which can be setup with the window found at: Extras->MiscOutput Settings
Where you can choose the triggering factors: Minimum & Maximum RPM, Min & Max TPS, Min & Max Manifold pressure.
So you should be able to mix and match the switching variables to swing the VVT stuff around.

[dnb]

Does the solenoid require PWM to get a varying duty cycle or is it simple on/off?

If it's duty cycle then you can probably use the boost controller output (set up very carefully!!) to drive it.

[rob@vems.co.uk]

Looking at the S14 workshop manual.
The ECU uses the following values:
Amount of intake air.
Engine speed.
Engine coolant temp.
Throttle opening angle.
Neutral position.

Valve control solenoid is on when:
Vehicle is running (not in neutral)
Engine coolant is 50degC or more
Engine speed is between 1050rpm and 5700rpm
Or
Engine Load is high (Use MAP input)
Engine speed is 1050rpm or less

All other times the solenoid is off.

We can't trigger based on Neutral or coolant temp, so it will have to be speed and/or MAP

[ex-ctr]

i was thinking a straight on/off at 1050/5700  i think the 1050 on is for oil presure to be high

[dnb]

You could use TPS instead of neutral.  It wouldn't be quite the same, but I'm sure with a bit of boolean algebra the whole thing could be worked out nicely...

On if ((MAP=high) | (RPM<5700) | (TPS>10%)) ought to do it. 

Shame there isn't a temperature dependance on the misc outs!!  (Hint to developers )

[ex-ctr]

the vvt is to add off boost /low  to medium rpm torque, i think its time to load the software onto my laptop and have a look

[Ben]

On the S15 it works slightly differently:

Below 1050rpm, B/Fuel Schdl above 1.3m/s, Neutral Switch Off = VTC ON
1050rpm - 5700rpm, Neutral Switch Off = VTC ON

Any other time VTC = OFF

Obviously this isn't really going to work when you start messing around with the fuel injector sizes... Personally I think it would be better to have it configurable on the map, i.e. just select the cells where you want VTC to be on.

[cliffb75]

Just switch it on speed and load (MAP) and don't worry about neutral and temp compensations. The neutral hold out will be so it doesn't switch during a throttle blip or gearchange and cause a stumble, but if you use a load input then you can hold it out anyway, and the coolant temp will be to stop it switching before the car can take the different timing (poor combustion stability) on an emissions test and for driveability, but then again with an appropriate load threshold you wouldn't have a problem as you wouldn't thrash your car until warm would you ?  You may want a time after start hold out though to stop it trying to switch during the start and flare.

[damo_S13]

did anyone get the vvt working? as im now in need of doing this too

thanks

[rob@vems.co.uk]

The key part is getting the resistance of the VVT solenoid, controlling it is easy.  Getting it right might take a little longer.

From what I've been lead to believe, the VVT is done to allow cam timing at top end that would cause emissions issues at low to mid range. The issue of not kicking the VVT off when the car is in neutral might have something to do with raised RPM static emissions, I'm guessing this a grown-up may be along later to tell us properly.

Of course if this is an issue it would be simple enough to use the neutral switch externally.

Rob

[damo_S13]

ok cool. im hoping to have the engine in all tho will have no exhuast system end of next month so will have to have a play then

[s14nismo]

The sr20det variable cam timing is notoriously unreliable and usually makes an annoying rattle just off idle
 Nearly all big power sr20's junk the system alltogether and use a vernier pulley to fix the timing.
It made a vast improvement on my engine, it ran quieter and totally smoothed out the power delivery from the mid range onwards
So i'd recomend it to anyone! the results on the dyno sheet also see a smoother torque curve and no detectable loss of Hp.
 And its one thing less to worry about when tuning!

[damo_S13]

ah i see, i was thinking of keeping it as im build a track car to run in timeatack this year. payed the entry fee now

think i will start a thread on sxoc about it

thanks
damo