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redmist

V6 VVT cam sync issues.

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Having problem with VVT inlet cam activation. On a V6 engine both cams are in sync for a good percentage of the time however on the outskirts of the VVT table where interpolation is biggest they become wildly out of sync by up to 22 degrees. PID setup is default. Cam control mode is VQ35. I've included a snapshot of the issue (my logs are over 10mb each).

post-1272-143621563029_thumb.jpg

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Hi Daniel,

I've had a look at your screenshot. Do you have any error counters incrementing? One thing I would suggest doing is checking the condition of the VVT solenoids, it looks to me like there is something mechanically wrong. Failing this, try adding a little more P and I gain, this will increase the level of aggression that the ECU is using to control the cam positions.

Regards,

Phil

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Unfortunately the onboard logging doesn't log VVT error counters. (or at least I haven't found them). Both VVT solenoids have been replaced. We've always experienced some form of VVT inbalance between banks however it's more observable given on board data logging (it tends to be worse in low RPM low throttle situations that weren't tested on the dyno). It's also more critical given the huge investment in the new Cosworth/Nissan engine. I'm no VVT expert. But I would think that given VVT's simplistic nature that if it traced both ramp up and down correctly in other advance requests (as it often does) then it should function in a consistent manerism for all advance/retard requests. I would guess that my next step is to log runs to a solid state device via PC Link to get error counters?

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what are the duty cycle clamps set to?

 what does the vvt solenoid duty cycles do when this happens?

what cams are fitted?  have they been reground?

what is the oil pressure like at the solenoids?

what else has been done to the engine as you state cosworth/nissan engine in the post above

Regards

Dave

info@dtechmotorsport.com

 

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I've garnered these logs from the onboard logging during last weekends race. Unfortunately we didn't pick up on these issues as it only appears at low throttle utilisation and non steady state. The onboard logging doesnt log and VVT parameters other than cam actuals. Cams are Cosworth ZK2 270 degree ramp to ramp, 10.65mm lift. Ground from billet. Haven't checked the pressure to the solinoids. However ramp rates both up and down can match, but intermittently don't even try. If this were to be a hardware issue it would appear that they sometimes ramp perfectly and other times have the ability to ramp (you can see the jagged lines as the solinoid duty cycle is increased then decreased again) but for some reason don't. The heads, pistons, rings, rods, cams, bearings, oil pump, hardware are all Cosworth. Block and crank are modified Nissan 350z.

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I would suggest you have a mechanical issue

I say this as a general statement not a you have a broken commponent but more

that cam control is electrical and mechanical

issues with electrics are solenoids not working or cam sensors faulty/ getting errors and this can quite often be due to 'poorly made setup cam triggers' especially on aftermarket cams   this is my experience here.

Mechanical is the oil system it  takes flow and pressure to move the cam   and this changes with temp and revs,  the cam then has to move against valve spring pressures  and then if the tensioner is a bit soft as common on those engines then the target will move accordingly, then you have the actual cam pulley it self  this can have leaky seals or even air in it  as examples.

 so its not as easy as it first seams   and then when you have two seperate cams the issues get harder as one cam sometimes needs more duty to hit the target quick enough and this falls under a mechanical issue as it is a oil supply difference from one side to the other

These are some of the issues that i have observed and found

Regards

Dave

info@dtechmotorsport.com

 

 

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hello guys,

i will be running a nissan 350Z TT engine on a g4 extreme ecu, i am interested in what was the issue and how did you fix it?

and also if someone can provide me with a base map for this engine.

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Hi Nabs,

Unfortunately I don't have a 350Z base-map, but hopefully someone else will have one for you. Out of interest, does your VQ35 have only intake cam control, or exhaust also?

Cheers,

Scott

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