K series Caterham VVC intake cam phasing control

[Scott_]

I am doing a Duratec swap towards the end of this year on my '99 Caterham 7 K series VVC.  I have been collecting parts, have a block coming from Esslinger, and recently bought a Haltech R3 ecu for the swap.  (I have prior experience with a Haltech ecu in a Miata race car I once owned and think the R3 would be perfect for the Duratec.)    

 

I have been entertaining the idea of installing the Haltech R3 ecu  in my running VVC-engined car this spring.  This would allow me to sort the wiring under the dash and harnesses in advance of the Duratec swap and I will know I have a fully functioning and tested system for the new engine to be hooked up to with only an updated engine harness.

 

I have worked through all the sensors and developed a wiring diagram for the Haltech/Rover engine on paper and the only hang up I have is the intake cam control strategy.  There are multiple options available in the Haltech and I feel certain one could be made to work with the unique Rover setup.  For example, I could easily switch from vvc- solenoid to vvc+ solenoid at a set RPM and above a set oil temperature, but I'm thinking the stock control might be more sophisticated than that.

 

Has anyone scoped a MEMS2 or 3 VVC to get a handle on the control of the two solenoids or does anyone have an understanding of the control strategy that they would be willing to share?  

 

I know the Emerald ECU does it so there must be a cam control setup screen but I have no access to a base map for the VVC engine to look at in the Emerald software.

 

Thanks,

 

Scott

 

 

 

 

Edited April 2 by Scott_

[slowdude]

I've got a base map for an emerald vvc, i'll message it to you.

 

Revilla on the blatchat forums should be able to answer your mems question. he reverse engineered the mems system.

 

andrewrevill.co.uk/EU2EngineLoom.htm

 

 

Edited April 3 by slowdude

[Scott_]

33 minutes ago, slowdude said:

I've got a base map for an emerald vvc, i'll message it to you.

 

Revilla on the blatchat forums should be able to answer your mems question. he reverse engineered the mems system.

 

andrewrevill.co.uk/EU2EngineLoom.htm

 

 

that is awesome, and thank you for the map and links no to Andrew.    I’ll download the emerald software and take a look.  
 

Scott 

[Scott_]

Looking at the Emerald file answered my questions.  Thanks @slowdude 

 

I don't know if it precisely mimics the MEMS control strategy but what the Emerald appers to do is make it RPM dependent and it starts increasing the duration of the intake valve opening at 3000 rpm, decrases it slightly from 4000 to 5000 rpm and then starts towards maximum duration at 7500 rpm.

 

Scott

[slowdude]

 Happy to help another K series owner. I've learned a lot so more than happy to help share some knowledge in the US.  

[redursidae]

On 4/2/2026 at 2:28 PM, Scott_ said:

I have worked through all the sensors and developed a wiring diagram for the Haltech/Rover engine on paper and the only hang up I have is the intake cam control strategy.  There are multiple options available in the Haltech and I feel certain one could be made to work with the unique Rover setup.  For example, I could easily switch from vvc- solenoid to vvc+ solenoid at a set RPM and above a set oil temperature, but I'm thinking the stock control might be more sophisticated than that.

 

 

 

 

I'm curious what is unique about the K series VVC system? In the engines I've worked on this is normally a 2 pin solenoid, 12v on one, low side ECU control on the other, and PWM operated. How does the K series work?

Edited yesterday at 04:26 PM by redursidae

[Scott_]

I thought it should be straightforward as well but what sent me down this rabbit hole is that the K series VVC features two solenoids, VVC- and VVC+, that facilitate oil flow to a valve. This valve activates eccentrics that, instead of advancing the timing, alters the speed of the cam rotation throughout the cycle. So unlike simply advancing or retarding the entire camshaft, it modifies the cam period and the duration of the inlet valve opening by employing this eccentric drive arrangement. 

 

When fully off, the K VVC has the shortest duration. As you want duration to increase, the rotation is slowed down when the opening begins until it closes, allowing for more overlap at the opening and delayed valve closing.

 

I was uncertain whether the stock ECU simply switched on and off the solenoids at a specific RPM or if it employed a push/pull to provide intermediate speed settings across RPM or loads.   I think it’s the former, at least that’s how I’m going to approach it with a 3000 rpm switchover.     
 

I’m open to any ideas.   
 

Scott

Edited yesterday at 07:00 PM by Scott_

[redursidae]

Wow, now that's a very cool system I had not heard about before. Thanks. I haven't worked with these, but it is supposed to be a fully variable system, not a switched one, where one solenoid advances the period, and the other retards the period which is closer in control to a BMW S54 VANOS.

From https://www.mgfcar.de/library/ENGINE_MANAGEMENT_SYSTEM_ MPi_VVC_MEMS_3.htm:
 

Quote

VVC Mechanism Control (Where Applicable)
Hydraulic Control Solenoid
The ECM controls two solenoids in order to control the VVC mechanism. Only one solenoid will be energised at a time to either drive the VVC mechanism towards minimum cam period, or towards maximum cam period. The desired cam period is calculated by the ECM using engine speed and manifold pressure (engine load). The current cam period is measured by the ECM using the camshaft position sensor. The ECM then energises the correct solenoid in order to move the mechanism towards the desired position.

 

That and other documents I read indicate it is variable, based on RPM and Load (either MAP or TPS).

In Haltech you can select 2 solenoids for the Cam Control function, and wire them accordingly, but the part I'm not sure about is that usually these are cam phasing targets, but this VVC system is "cam period" targets? I don't know how Haltech would deal with that so you may be best asking their support line. 

 

Could you share a screenshot of the targets in the Emerald ECU?