Megasquirt Support Forum (MSEXTRA)

Did my Toyota 2jz vvti is supported in this code? I'm trying to start the engine in dual wheel mode with no luck.
Thanks

MOD EDIT: Split this topic off from the general VVT one.

Have you posted information about that VVT pattern before? I don't remember it and certainly haven't added it.

James

I have a 2jz-gte vvti installed on a Cherokee jeep, my pattern is 36-2 crank and 3 evenly spaced point on the cam. I'm using none semi sequential just main bord injection. Wasted spark. I try the code as is but no work.
Any help will be appreciated James. Have a run on the weekend.

Please take a composite log using "log crank and cam" and attach it to a post here.

James

I have the composite log but I can't upload I'm on my iPhone can I have your email and I will send it.
Thanks I appreciate your help.

Here we go. I think managed to upload the file. (Fingers crossed) If I did this is my 2JZJTE VVTI composite log from the engine. Just take a look and let me know what you think. I appreciate your help.

The cam wheel is slightly irregular - is that correct? I'm seeing 240 degree, 260 degrees, 220 degrees between teeth. Very odd and annoying.

James

I been looking for some info and it's looks like my log is not correct I will try to do some different ones. This what people say about my setup:
The engine idle is about 1300 RPM (this slows to ~700 RPM after the engine is warm).  Analysis reveals that the crank signal arrives for every 10 degrees of engine rotation and is generated 34 times in 360 degrees (there is no crank signal for 20 degrees of the revolution).  The cam signal arrives every 240 degrees of rotation so that there are 3 signals for each 720 degrees of rotation (each complete Otto cycle).  It seems that the stock ECU would identify the beginning of the engine cycle when the falling-edge of the cam signal and the 20 degree gap in the crank signal align.

Some other info that I found:
The VVT-i uses a 36 minus 2 teeth trigger wheel on the crank. The trigger has its teeth positioned every 10 deg with two teeth missing after the number one cylinder’s TDC mark. This gives the ECM signal of revolutions every 10 deg instead of the 30 degs (better control and orchestration). You still need a trigger at the cam to determine proper cam phasing. The cam uses 3 teeth on the intake cam positioned 120 deg around. The timing sequence for the supra starts when the cam trigger sends a pulse. The timing sequence for the VVT-i begins when the cam triggers simultaneously with the two missing teeth on the crank trigger. Since the other two teeth on the cam are positioned 120 deg apart they never pass when the missing teeth on the crank are lined up. Only that one tooth of the three on the cam will pass with the missing teeth on the crank. Once started the ECM always receives signals from the cam and crank. It controls the phasing of the intake cam gear based on a preset map and table in the ECM that the factory engineering has programmed into it.

How much movement is there in the cam through VVT operation? From the tooth log it looks unclear on how to decode that wheel as the cam tooth does not actually align with the crank missing tooth region, but is close enough to be a problem.

James

It have 60 degrees of movement, -30 and +30, when you start the engine it is spring loading valve that hold cam in the most retarded position -30 that is 0 duty, 50 will be 0 degree and 100 will be +60 but all this I assume will be oil temp and pressure dependent.

Sorry I mean 100 duty will be +30

Is that crank or cam degrees ?

James

It is cam degrees

It's looks like the engine compression and the timing belt slag is affecting the initial reading, I been doing some other logs and the results are very similar to the one here. I scope the signal with the engine on and looks like a steady 3 spike count. It is any posibility to log crank and cam at the same time with the engine on?

I found some people who say tha Apparently the solenoid is energised during cranking of engine to allow more breathing for start up, once the engine fires upo it is turned off and than re-energised at approx 4000rpm but I can confirm this yet. I will keep investigating, I have also some runing scopes of other people I will post them later.

What else I can do? How can I help?

porelmundo wrote:What else I can do? How can I help?

I wrote a first draft of code the other day. Hopefully I'll test it next week.

James

Thank you James.
I was wrong with the valve solenoid operation, the 50% duty is not 0 degrees it is the valve hold position and we don't know if is exactly 50%, it is a 3 position, 4 port valve, 1 oil press supply (from the engine) 1 oil return(back to engine) 2 bi directional supply to cam vanes. 3 positions where a spring hold it at retard position (0 duty), hold (probably 50% duty) and advance (100% duty or around that).

Thank you

Some more on solenoid operation:

The solenoid valve on many (or all?) implementations of VVTi is in full retard position at rest, constantly applying oil pressure in the "retard" direction. That would actively pump the cam back to full retard even if it's not already there. A spring ensures it will return to full retard as well if there's no oil pressure, to provide zero overlap when starting. This spring seems to have no function with the engine on.

The timing control solenoid requires a certain duty cycle to even move to "hold" position. In this position, all ports to the cam gear are blocked, causing it to remain in whatever position it is. A bit of leakage would probably still occur though, causing a slow walk, probably in the retard direction.

Apply more power to the solenoid than needed for "hold" mode and it will go to "advance" mode, pumping oil to the other side of the piston, moving it in the "advance" direction.

In either "advance" or "retard" mode, the piston port that does not get oil pressure, is opened to drain. With some imagination this is similar 'switching' to what happens in a power steering system. Pressure to one side, drain the other, and vice versa for steering in the other direction.

So, it is not that you're controlling oil pressure directly, and working against a spring so a certain oil pressure amounts to a certain advance angle. Instead, you're operating a valve that can actively steer the timing piston in either direction, and optionally also hold it at whatever the current position is.