Cam timing with VVT/VCT
 

I have a st170 engine with throttle bodies and piper BP300 cams with timings of 38-66 60-32 and duration of 284in 272ex. Full lift is at 104deg after and before tdc.

I would like to keep the VVT to have more torque low down but I am not sure if this is possible. The ecu I intend to get is the Emerald K3 but that only has the VVT fully on or off, so that means the inlet cam will be either at 85deg atdc or 145deg atdc. That's a massive range so I phoned piper to ask their opinion or to see if they knew if they would be ok or whether there would be too much advance/retard of the cam and would make no power. But I got this

'They might work we don't know.'
so I asked if they knew the standard ford timings so I could compare
'Yes we do but we can't disclose that information to you.'
right, great help.

So....do any of you know if it will be ok? Or any opinions?

I just checked on the ford ETIS web to see what info it had on cam timing , it did not have the std timings , probably as the system is fully ecu controlled and it will constantly adjust from the info coming from the cmp ( camshaft position sensor ) and other sensors so the publishing of that type of data would just cause problems , the only sugestion I have is set cam up with dti gauge and see what figures you get with cam in fully advanced position and retarded position and compare with your piper one . My gut feeling is that you would be better off doing away with the vvt and setting timing up statically as this would give you the best control , and by using a adjustable cam pulley , small adjustments could be made to improve overall performance , giving you a balance between low down and high end power .

:)

We have similar guts then! Easier to map too

do the piper cams have the oil ways for the vvt?

I've got a turbo'd st170 engine which will hopefully be up and running in the next coupe of weeks. I intend to do a lot of testing with the VVT, so will have more info then. I suspect going from one range to the other may leave u a slight hole in the mid range, but give more power than fixing the timing. Don't forget, the std pulleys are adjstable. You can swing the VVT pulley too, just make sure there is no power to the solenoid, as this keeps it in the fully advanced position which is whatever you set it to, eg 109 degrees.

Rick.

AFAIK you time the cams up in the fully retarded position. Thats all I remember though so best to check

Fully advanced, which how they are at rest.

I agree with Rick that the standard pulley is adjustable , and you could make a new tool up to be able to adjust the timing using the slots in the back of the cam by making two levers that locate the cams and these are adjustable to allow slight variations in the slot position to horizontal , cheap and simple , what could be better :grin:

I gave DTA a call who recommended Rick Wood who has done a lot with the VVT. The S60 ecu allows full control of the solenoid and pulley so I can do it by degree if I wanted. Also the pulley moves 30 degrees as it goes by 60 degrees off the crank. So as you say, with the pulley being adjustable I could have the full 30 degrees of movement stopping at the point where it makes peak power

How does the S60 control VVT? I ask because what I have seen so far seems to vary duty cycle according to a map. The ford system works differently. It doesn't actually use oil pressure. THe pulley has 2 chambers, an advance and retard chamber. The volume of oil in the chamber dictates how much the pulley moves. The soilenoid plunger effectively has 3 positions. A "hold" position where it keeps the volume of oil in each chamber constant, so the pulley is locked. The other two positions are the advance and retard. In the retard, an oil way is opened to allow oil to fill the retard chamber and at the same time drain the advance chamber. As soon as the desired amount of retard is reached, the valve moves back to the hold position. The opposite happend if we want advance.

This requires a pretty robust method of control, which will have to be closed loop for certain.

Rick.

The Ford VVT is certainly closed loop, which is done by using a 4+1 trigger on the inlet camshaft in comparison to the CPS to measure cam timing position. The actuation system uses pressure to retard timing and a spring return to advance. The soleniod valve feeding oil is fed with a PWM signal by the Blackoak PCM, so in theory 50% duty would give around 30 degrees retard from fully advanced.

Even if your ECU has a spare PWM output and VR input you still need a control algorithm, usually developed or decompiled from a OEM PCM, by the ECU manufacturer.

If you want the OEM (Ford) cam timings then I found them on the Cat Cams website. On the turbo engine I've just finished I've disabled the VVT and gone back to old fashioned DTI and disk to time the inlet cam at full lift. Timing is taken from looking at quite a few fixed cam examples, and still leaves me with adjustment for optimisation with the 'vernier' pulley.

Martin

Martin,

When i examined the system, i assumed it was a spring pushing it back in position. This video describes the system as used in the SE/puma engine.

http://www.youtube.com/watch?v=Ba-oyIjGWGE

Ford's TIS manual describes the ST170 control method as identical to the Puma version. I'm not sure this is the case. If it isn't, and it doesn't use advance/retard chambers, but just a spring, then that would be far easier to control.

Lots of testing to come when mine finally fires up.

I don't want to be penickity, but that video describes the later Sigma engine (Duratec Ti-VCT)used from 2005. That's why its not the same mechanics as the 1.7 Puma & ST170.

However the principles of control are the same on them all, but I've not heard of anyone using anything other than a Ford PCM to control it. Honda VTEC is a little easier.

Martin

Martin, that's my point - ford TIS says they are all the same :S MS have some algorithms coming up, so i'll have a play with them.

Rick.

MS = MegaSquirt II ?

I'm running a Focus RS engine with MS I Extra. Its been a great way to convert from my experience of 20 years ago with carb & dizzy, but even as an ex C&I engineer I've not been able to tune things like boost control (still officially experimental !).

Martin

Update.

My engine is now running. Ignore my comments above about being advanced in it's rest position, it is of course retarded - think it had been a long week...

First thing is i got a shock when my compression test only gave me 5 bar... After a bit of thinking I realised the dynamic compression ratio would be very low, and after doing the maths it worked out about 6:1!

The engine will run like this (145 degree peak lift), but it doesn't like lean mixtures at idle, and feels very flat. I need to speak to Ken/James of Ms2extra code so that the MS can decode the 5 tooth cam wheel, which will at least enable logging of the cam timing.

For now, i adjusted the cam to 110 degrees. This is with pulley in most retarded position, with no power to the solenoid - no need for any other mods :) Cranking compression jumped up by 3.5 bar, and the car feels much more responsive low down. Time to get some miles on it now, more testing to come.

Rick.

any pics of you build pal?? what power and spec??

Paul

No pics, will get some sorted eventually. No idea on power, it's not even run in yet.

Rick.