3900 Info

[bszopi]

I'll see if I can find the default. I also want to see if I can get a listing of all of the parameters that are used in determining the phasing...

Not sure if this will be of any help, but here is a response I got from one of the GM engineers...

In that case can it be assumed that the cam will run straight up in the event of a phasing system failure in an effort to maintain flawless driveability minus some horsepower and torque as well as in the event someone drops the engine in a non VVT car?

Since it's basically pulse operated like an injector if I understood it correctly, a basic stamp computer should be easily programmable for rudimenary function of just varying pulses to advance or retard based on rpm and throttle position. I have programmed one to pulse a fuel injector and that was pretty easy.

[bszopi]

Not sure if this will be of any help, but here is a response I got from one of the GM engineers...

My experience is in the VVT system and not the variable intake valve.
Like fuel injectors, the VVT system works with Pulse Width Modulated
(PWM) electrical signals. Older PCMs would not have the built-in drivers
to generate this signal. Your member is correct in the description of the
close-loop feedback control system that is used to monitor measured cam
position relative to the crank position and constantly correct by it
changes in duty cycle to reach a desired set point. The are many inputs
into the determining the desired set point and a lot of calibration
settings on how fast to get there. Boxes can be and have been built.

[AutoTech]

Any updates?

[CNCguy]

I'll see if I can't dig up any info, either via some GM contacts or other means...

Sounds good Brad... hopefully you will have better luck that I've had.

[bszopi]

I'll see if I can't dig up any info, either via some GM contacts or other means...

7.5 mm is a good bit, my guess would be that the baseline is set at maximum low end torque efficiency and then advanced from there with rpm increase. I no longer have my trigonometry book to help calculate the number of degrees that would translate into but I wouldn't doubt it's close to a 1:1 ratio. My curiousity now would be if there is any serious advantage to be gained if the cam were reground to higher performing specs in addition to the VVT function.

Given the knowledge of the potential for interferance with the valve train I imagine you would need to know the clearance between the piston and the valve at full retard and advance before making such a move on a $400 cam.

[CNCguy]

Two wires suggest it's a function of variable voltage, perhaps a potentiometer linked to the throttle to advance the cam in the appropriate RPM range would be even better considering at a minimum the cam would have to be installed straight up to get at least the normal range of power.

I assumed variable voltage also but do not know if there is a direct relationship between voltage input and cam timing or if cam timing is constantly calculated by the PCM using feedback from cam/crank sensors and voltage is varied to make required timing changes. If there is a direct relationship, a small controller could be built that would control the actuator using RPM & MAP inputs. Perhaps the same controller could handle the variable intake also.

Between work and some other new products, I haven't had much time to spend on this issue. I was hoping that someone would jump in with some accurate info on how the VVT & variable intake control systems operate.

In case you're interested, the electrical actuator for VVT has around 7.5mm of travel.

Two wires suggest it's a function of variable voltage, perhaps a potentiometer linked to the throttle to advance the cam in the appropriate RPM range would be even better considering at a minimum the cam would have to be installed straight up to get at least the normal range of power.

[CNCguy]

How does the VVT appear to function, I get the impression it has a hydraulic component?

The VVT is operated by hydraulics but controlled with an electric actuator. The actuator pushes a valve in the center of the hydraulic unit. I am still trying to find what kind of signal is used to operate it. It only has two wires, so I am assuming it operates on a DC voltage.

I am planning to make either a gear or an adapter to eliminate the VVT feature for those who want to install in cars with limited space.

How does the VVT appear to function, I get the impression it has a hydraulic component?

Is the front of the block tapped for the plate used to prevent the cam from walking? and does it appear to be possible to retrofit the non VVT valve train components for use by increasing the length of the timing chain a notch to make up for the change in cam location?

Never mind I recall there being a difference in cam bearing size

Close but an 07 just to be on the safe side with the 6 spd automatic attached to it. The Rendezvous is all wheel drive I believe and the bell housing on that engine might be different from the 07 now released for the G6 and a couple other FWD cars. The 07 also has higher horsepower and rpm ranges than the 06. I'd be interested to see if it takes up as much room as the 3.4 DOHC, from other pictures I've seen it looked like GM trimmed the heads down some.

[onefastV6]

What I would like even better is to get the 3.6 DOHC. Who knows, I was fortunate enough to get the 05 3500 for a great price, maybe I should keep my eyes open a little wider.

You mean, like this?

http://cgi.ebay.com/ebaymotors/Buick-Lacrosse-3-6L-Engine-Rendezvous-7-Mi-Motor_W0QQitemZ230030935685QQihZ013QQcategoryZ33615QQrdZ1QQcmdZViewItem

As mentioned by Colin awhile back (when he first got his hands on a 3500), it wouldn't be that difficult to plumb the existing oil squirter to 2 additional oil squirters so that all cylinders are covered.

That's to much work for a 3500, I want the extra .4 litres minus the added risk of making a plumbing mistake and having 3 squirters with plumbing riding around in a circle on the crank should it come loose. I suspect there is also the issue of having the right spring pressure in the pump for the additional free flowing tips also, that would be a disaster waiting to happen were it not corrected before adding two turbos for a further pressure drop.

I originally planned on using the 3500 but I have a few 3900s near by getting closer to my price range. I was planning to use two .60 compressor .48 turbine housing T3s and look at what I found for $25 at a core shop, complete and brand spanking new, I took the wastegate actuator and tail end off to find out why it was seized, turned out there was a piece of cleaning brush lodged against the turbine wheel so someone thought it was no good, my blessing, now all I have to do is refresh the one I already had. This ones .60 cold .63 hot, very popular for the early ford and chrysler cars