VVT observations - current vs. advance
04-12-2010, 03:58 PM
#123
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1) the VVT cam sensor output resembles the NB1's.
2) The software thus far has been written to read off of the NB crank sensor
It's not too hard to fit an NB crank trigger wheel and sensor onto an NA. j_man's done it.
2) The software thus far has been written to read off of the NB crank sensor
It's not too hard to fit an NB crank trigger wheel and sensor onto an NA. j_man's done it.
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04-12-2010, 04:32 PM
#124
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1) why would that matter?
2) that's fair enough
And I have a 2001 motor fitted, I have the sensors, but little inclination to build the circuits to use them.
If it ain't broke
2) that's fair enough
And I have a 2001 motor fitted, I have the sensors, but little inclination to build the circuits to use them.
If it ain't broke
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04-13-2010, 10:29 AM
#126
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The VVT control is closed loop. It uses the difference in timing between a sensor reading a wheel attached to the cam and a sensor attached to the crank to determine where the cam advance currently is. The NA CAS is only attached to the cam... there goes your ability to compare separate readings.
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04-13-2010, 11:14 AM
#127
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The VVT control is closed loop. It uses the difference in timing between a sensor reading a wheel attached to the cam and a sensor attached to the crank to determine where the cam advance currently is. The NA CAS is only attached to the cam... there goes your ability to compare separate readings.
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04-13-2010, 11:40 AM
#128
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The biggest problem is you can't compare the CAS to itself. If you had one sensor on a fixed cam and the other on a moving cam, it may be possible to write code for it. But it sounds like it would be less trouble to just wire up the stock sensors.
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04-13-2010, 01:51 PM
#130
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The NA CKP signal does resemble the NB CKP. The rising edges IIRC are in the same place, but the NB pulse widths are very short. A rising edge detector aka hipass filter with possibly an inverter, will make the NA CAS output be NB computer friendly. However I would recommend a real NB crank sensor for more accurate timing.
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04-21-2010, 11:27 PM
#131
Wow, yeah, asking questions like that (about using a CAS signal) means you probably don't care enough about performance to even need something this advanced. GAWD. Run the crank triggers or go home.
You mean two high impedance inputs won't bother each other? Up to pull ups, perhaps....
Yeah - as long as it's fixed, as long as it gets the highest priority interrupt, fine - but add 50 microseconds of variability and that DIRECTLY translates to 2.5 degrees of additional retard I'd HAVE to run to keep the motor together.
I'm not sure on the relations between gains in cam timing and degrees of timing, but the first trick to engine tuning as I understand it is running as much advance as possible.
Meaning the tuning software will be awesome? :-) Windoze, linux, ???
You mean two high impedance inputs won't bother each other? Up to pull ups, perhaps....
The output timing signals are essentially passed through during the interrupt that was triggered by the input timing signals within the MCU. Essentially, the output signal that is generated occurs within a few microseconds of the input trigger -- basically enough time for a few instructions to be executed at 8MHz. I won't go into the nuances of execution time per MCU instruction, but you get the idea. There is no buffering of the signal.
I'm not sure on the relations between gains in cam timing and degrees of timing, but the first trick to engine tuning as I understand it is running as much advance as possible.
I've been running the box for quite some time now, but have otherwise been cleaning up the rough edges. 
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04-23-2010, 10:58 PM
#136
Ok, a bit of a tease - but it is true as well... Going away from the CAS is a really, really good thing. Rock stable timing, and as I was implying above, you're giving up advance when you give up stability, and giving up advance is giving up horsepower. Why would you do that to yourself when the sensors are already there? Buy a $200 CAS when you can use a $0.15 op amp?
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04-24-2010, 05:50 AM
#138
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Ok, a bit of a tease - but it is true as well... Going away from the CAS is a really, really good thing. Rock stable timing, and as I was implying above, you're giving up advance when you give up stability, and giving up advance is giving up horsepower. Why would you do that to yourself when the sensors are already there? Buy a $200 CAS when you can use a $0.15 op amp?
I have all the 2001 sensors and my MSII I built 2 opamp circuits for the CAS inputs. it works great, and I'm wont to 'fix' something that isn't broken, BTDT...
I've not researched into the mods required for the MK2 inputs, but I've read of people having lots of issues, true? Or will my two opamps suffice?!
P.S. My CAS was free it came off my old engine :P
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