HKS Vcam Step Pro Issues

[The Mafia]

Hi Everyone. 

So we've installed a HKS Step Pro VCam kit to my RB26 2.8L engine. (Dry sumped etc)

Head has had a full overhaul in the past - 1mm oversize valves, Shimless Buckets, 150psi aftermarket springs etc. 

So the issue i have is the VCam system can't advance unless the RPM is at 3500rpm or more. I have eliminated all electrical Issues / ECU control issues. 

The oil pressure feed line has been moved somewhere where there is plenty of oil (engine has a dry sump with heaps of pressure), and the VCam itself has been disassembled and checked thoroughly.

Could there be a chance the valve springs are too heavy for the VCam system to open the valves at lower RPM and oil pressure?

Anyone have any ideas? 

Thanks

[GTSBoy]

On 5/16/2022 at 9:06 AM, The Mafia said:

Could there be a chance the valve springs are too heavy for the VCam system to open the valves at lower RPM and oil pressure?

I can't see how that could be the case. All it has to do is rotate the camshaft, which the camshaft is already doing and already popping the valves open upon demand. The real counteracting force against the oil pressure is the return spring in the positioner itself, no? So, whilst it is difficult to blame the valve springs, your theory might, could, just possibly have something in it.

I suggest fitting a pressure gauge to the supply line close to the actuator and see what's what. Maybe the pressure there is disappointingly low until 3.5k.

[The Mafia]

We installed a pressure gauge right on the side of the cam cover, 40psi at idle couldn't move the cam. Had to increase the rpm to 3500rpm (100psi) and it started to move. 

I've asked so any people - No one is sure. 

[Piggaz]

150 psi springs? Why? 

[Dose Pipe Sutututu]

On 16/05/2022 at 11:20 AM, Piggaz said:

150 psi springs? Why? 

I suspect it will be revs to 5 digits.

[r32-25t]

When you opened the the cam gear did you tighten the back up with the cam installed in it and made sure the backing plate isn’t touch the cam at all?

[The Mafia]

Sorry Guys - Edit - The Springs are 125psi. We had the choice out of 90psi and 125psi and 125psi was optioned. 

[The Mafia]

On 16/05/2022 at 12:23 PM, r32-25t said:

When you opened the the cam gear did you tighten the back up with the cam installed in it and made sure the backing plate isn’t touch the cam at all?

I'll find out mate

[Butters]

Currently installing a V-Cam also. So following thread with interest.

In the instructions it does recommend an upgraded oil pump due to the pressure required by the vcam.

40 psi at idle is pretty stout though, can't imagine that being an issue if the flow is good.

 

For my own interest, how are you confirming that it is or is not opening the vcam ?

What are you using to control the vcam ?  Assume an ecu over the HKS control box ?

 

My only suggestion to help and I am sure you have looked at this is go through the o-rings(Cam cover ones especially).

If one is pinched, 40 psi at cam cover is going to result in a lot less to cam gear if you have a leak.

 

I agree with others above, the valve springs should have nothing to do with this.

 

[The Mafia]

On 16/05/2022 at 1:02 PM, Butters said:

Currently installing a V-Cam also. So following thread with interest.

In the instructions it does recommend an upgraded oil pump due to the pressure required by the vcam.

40 psi at idle is pretty stout though, can't imagine that being an issue if the flow is good.

 

For my own interest, how are you confirming that it is or is not opening the vcam ?

What are you using to control the vcam ?  Assume an ecu over the HKS control box ?

 

My only suggestion to help and I am sure you have looked at this is go through the o-rings(Cam cover ones especially).

If one is pinched, 40 psi at cam cover is going to result in a lot less to cam gear if you have a leak.

 

I agree with others above, the valve springs should have nothing to do with this.

 

Hey mate, we double checked the o-rings. One was pinched and we replaced it and it had the same behavior. 

Cam is being controlled with an Emtron KV8. To bypass all of the ECU side of things we connected the solenoid directly to 12v and ground and had the same result. Cam wouldn't move until 3500rpm on the trace in the ECU. 

Something is not right. It's frustrating that's for sure. 

[The Mafia]

On 16/05/2022 at 12:23 PM, r32-25t said:

When you opened the the cam gear did you tighten the back up with the cam installed in it and made sure the backing plate isn’t touch the cam at all?

Can confirm all of this went back together correctly 

[Butters]

On 5/16/2022 at 11:28 AM, The Mafia said:

Hey mate, we double checked the o-rings. One was pinched and we replaced it and it had the same behavior. 

Cam is being controlled with an Emtron KV8. To bypass all of the ECU side of things we connected the solenoid directly to 12v and ground and had the same result. Cam wouldn't move until 3500rpm on the trace in the ECU. 

Something is not right. It's frustrating that's for sure. 

 

So to be very specific . The KV8 is sending PWM to the negative side of the solenoid at a specific RPM say 2000 ?

Then you are reading the reluctor sensor on the side of the cam cover to see the advance ?

And not seeing a change in the cam until 3500rpm ?

 

[The Mafia]

Yep, that's it. ECU was reporting the cam angle.

A quick test to rule out solenoid control was to get a tail, plug it into the solenoid, and give it 12v and ground directly. It wouldn't move until 3500rpm and 100psi on the little gauge we had inbetween the line and the cam cover. Exact same behaviour as when the ECU was trying to control it. 

[Komdotkom]

I was doing some data stuff on my car which is also dry sumped and we didn't want the engine running, so used a Subaru cam belt (15km long) and a dry sump mandrel on a power drill. This allowed us to spin the pump independently of the engine and log some data, and the drill can be located in a convenient location without some poor bastard on his back under the car.

Perhaps you could do this and see if there's any other weird shit going on? Overall oil pressure isn't your problem, so it's leaking out or you have a faulty solenoid. Alternatively there's something mechanical dragging on the gear, as above it's got nothing to do with valve springs.

[The Mafia]

On 16/05/2022 at 4:48 PM, Komdotkom said:

I was doing some data stuff on my car which is also dry sumped and we didn't want the engine running, so used a Subaru cam belt (15km long) and a dry sump mandrel on a power drill. This allowed us to spin the pump independently of the engine and log some data, and the drill can be located in a convenient location without some poor bastard on his back under the car.

Perhaps you could do this and see if there's any other weird shit going on? Overall oil pressure isn't your problem, so it's leaking out or you have a faulty solenoid. Alternatively there's something mechanical dragging on the gear, as above it's got nothing to do with valve springs.

Hi Mate, I have two VCam kits, we swapped the solenoid and that didn't help either.

We've ruled out quite a few things that's for sure. 

[Butters]

My money is still on an oil pressure drop post cam cover.

 

The other thing you have to question here is the data sampling and again I am sure you have done this but given we are running out of ideas

 

I am wondering if it is actually activating before 3500rpm and your only seeing the change in the data at the point.  Simple things like only log  after 3500 for all parameters

Are you holding the engine steady at 3000rpm for a period of time and activating the solenoid and seeing no change in the KV8 data ? 

[The Mafia]

On 17/05/2022 at 10:33 AM, Butters said:

My money is still on an oil pressure drop post cam cover.

 

The other thing you have to question here is the data sampling and again I am sure you have done this but given we are running out of ideas

 

I am wondering if it is actually activating before 3500rpm and your only seeing the change in the data at the point.  Simple things like only log  after 3500 for all parameters

Are you holding the engine steady at 3000rpm for a period of time and activating the solenoid and seeing no change in the KV8 data ? 

The sampling data was live mate. from idle to 3500. It's like the VCam couldn't move under 3500rpm (Oil pressure I'm thinking) because at 3500rpm the pressure at the guage was going over 100psi. Under that it couldn't control the position properly. 

When the oil was cold it was a little under 3500rpm which makes me think it's a pressure / flow / resistance (springs) issue. 

New springs are going in and I will report back. 

[joshuaho96]

On 5/16/2022 at 9:59 PM, The Mafia said:

The sampling data was live mate. from idle to 3500. It's like the VCam couldn't move under 3500rpm (Oil pressure I'm thinking) because at 3500rpm the pressure at the guage was going over 100psi. Under that it couldn't control the position properly. 

When the oil was cold it was a little under 3500rpm which makes me think it's a pressure / flow / resistance (springs) issue. 

New springs are going in and I will report back. 

There is some kind of locking pin on the VVT cam gear that holds it in place during cold start and other conditions where the VVT is not going to work properly. So you're going to have to trace the path from the gauge to this pin and verify there's no weird behavior like leaks, etc.

[The Mafia]

Okay, so changed the valve springs and the VCT works as it should now (nice and responsive at idle). 

125psi springs were just too heavy for it. 

I have heard that when people have put heavier springs in the Barra those have stopped working too. 

Currently running HKS springs. 

I recommend lighter springs 90psi would be pushing it. 75psi or below will be my safe estimation.

(Please bear in mind your RPM targets, cam selections, etc). It's a careful balancing act. 

Edited May 18, 2022 by The Mafia

[GTSBoy]

Eeek.