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Got Over 400kw Atw?

T04GTR

By T04GTR,
in Engines & Forced Induction

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bigmikespec Veteran

bigmikespec

Posted
Posted

No, it's not closed loop. But that's a weird question

Why? How would you know exactly how far the cam has moved if all you have to go by it oil pressure? Cold day, thicker oil... and so on. If you can't check where the cam is you are just assuming it has moved going by the oil pressure you want via signal to the solenoid.

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colinhunt
colinhunt

Let's not turn yet another thread into a discussion about your car, please.

Lithium
Lithium
SiR_RB
SiR_RB

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SS8_Gohan Grand Master

SS8_Gohan

Posted
Posted

i was also under the impression the exhaust side was only really an emissions thing, not necessarily performance related - but if the rb25 VCT is up to say 5000rpm, you could then fiddle with the exhaust side from then onwards for a little more top end perhaps?

Rolls Grand Master

Rolls

Posted
Posted (edited)

BMW must have seen benefits to controlling both cams as they changed from single to dual vanos with the s54.

It is for emissions, that is mainly why they vary the exhaust.

i was also under the impression the exhaust side was only really an emissions thing, not necessarily performance related - but if the rb25 VCT is up to say 5000rpm, you could then fiddle with the exhaust side from then onwards for a little more top end perhaps?

You can change the VCT set points to whatever you want

Edited by Rolls
HYPED6 Collaborator

HYPED6

Posted
Posted

Why? How would you know exactly how far the cam has moved if all you have to go by it oil pressure? Cold day, thicker oil... and so on. If you can't check where the cam is you are just assuming it has moved going by the oil pressure you want via signal to the solenoid.

Umm, There is a stop point where the cam stops. Regardless of oil temp/flow/pressure.

Its not closed loop as there is no feedback needed.

Its on....... or off........ The computer all ready knows this.

If it was a full variable system where the cam was infinitely adjustable (by the degree) then yes most defiantly a closed loop system would be needed.

So the system is open loop.

Walk510 Enthusiast

Walk510

Posted
Posted

Umm, There is a stop point where the cam stops. Regardless of oil temp/flow/pressure.

Its not closed loop as there is no feedback needed.

Its on....... or off........ The computer all ready knows this.

If it was a full variable system where the cam was infinitely adjustable (by the degree) then yes most defiantly a closed loop system would be needed.

So the system is open loop.

big mike has vipec therefor it makes it a VCAM not just the normal nissan switched !

Rolls Grand Master

Rolls

Posted
Posted (edited)

big mike has vipec therefor it makes it a VCAM not just the normal nissan switched !

No it doesn't, it can still only be switched on or off.... unless you tried pulsing it on and off to get some degree inbetween, but I wouldn't like the chances of that working properly.

Edited by Rolls
The Dan Grand Master

The Dan

Posted
Posted

BMW must have seen benefits to controlling both cams as they changed from single to dual vanos with the s54.

The benefits are as stated above. The principle is to increase and decrease the overlap of the camshafts by changing the valve timing on one side. By doing both sides, you are still increasing or decreasing overlap, just in a different way. I'm not going to spend thousands making a system to do both sides as the benefit would be nil or minimal.

bigmikespec Veteran

bigmikespec

Posted
Posted

Umm, There is a stop point where the cam stops. Regardless of oil temp/flow/pressure.

Its not closed loop as there is no feedback needed.

Its on....... or off........ The computer all ready knows this.

If it was a full variable system where the cam was infinitely adjustable (by the degree) then yes most defiantly a closed loop system would be needed.

So the system is open loop.

Ok, misunderstood... on or off. That makes it a lot easier to control; they did not try very hard when Nissan developed it :)

I thought it was a fully variable, in that case the Vipec could control with PWM signal. At least Walks510 thinks its funny.

Walk510 Enthusiast

Walk510

Posted
Posted

Ok, misunderstood... on or off. That makes it a lot easier to control; they did not try very hard when Nissan developed it :)

I thought it was a fully variable, in that case the Vipec could control with PWM signal. At least Walks510 thinks its funny.

i believe the new series of nissan v8's run closed loop vvt the vk56vd engine

Rolls Grand Master

Rolls

Posted
Posted (edited)

and you probably couldn't run them with a vipec either.

If the vipec has PWM control that can be mapped to a rev table l I don't see why you couldn't. Eg revs vs PWM output, just be a simple 1 dimensional table.

Edited by Rolls
The Dan Grand Master

The Dan

Posted
Posted

You don't need any physical inputs, you just need the PWM output and use RPM as your input.

For it to be closed loop it will need a signal input from the camshaft position sensor that you will need to install. You can't just use RPM as an input for closed loop as it's unrelated to what you are adjusting

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