[QUOTE=xviper,Sep 11 2006, 01:25 PM]Here's another point to rattle your brain:

The Vortech incorporates a "timing box".

 

I didn't say the Comptech was a safer route, just that the effective compression ratio was lower and that this would reduce the octane requirement. Vortech pulls the timing, which also lowers the octane requirement. Until I know more about how the ECU deals with knock, and any problems the blowers add to the equaiton, I don't know enough to say that one is safer than the other. Given a regular diet of quality fuel they're both extremely reliable, but given my current lack of understanding of the details of knock processing, I'd be very uncomfortable if I had to start using fuel that was three or four points lower in octane.

Before this thread I'd have put 87 octane unleaded in the car if nothing else was available, but now I'm not sure that's even possible.

 

I haven't any idea how the VT timing box works. I recall seeing "Slows2k" giving details on it some time ago.

 

So where's he hiding?

 

That's exactly where I'm at!

 

I wonder if there is any discussion of this in the factory shop manual? I don't recall seeing anything about the timing logic, but I need to take another look.

To me this is a pretty important issue, because I thought I knew how it worked, but now I'm uncomfortable with doubts. I'll browse thorugh the shop manual this evening and see if I can find any clues.

I don't really care how Vortech accomplishes their timing pull (though that would be nice to know); What I want to understand is how the stock ECU processes the knock sensor signals (not the filtering, but the logic that is used when a suspected knock is detected). I wish it weren't such a PITA to change the PLX wiring, because I think I might be able to figure out what's going on if I could collect some timing and knock sensor data.

Somebody here has already figured it out. We just need to get them to respond to the thread.

YO! ANYONE?

 

The shop manual doesn't say much; Just that the knock sensor is used to adjust the timing to the grade of fuel used. To me, that says that it has to periodically advance the timing until it detects knock, and then pull the timing until the knock stops and hold it there for some period of time. Of course it would also retard and hold for a while any time knock was detected.

I don't see any other way it could adjust the timing to match the fuel, so if nobody comes up with an alternate way that this could be acomplished it's the only thing that makes sense.

Further, if the supercharger causes false knock detection, Vortech would be advancing the timing to offset the false triggering of the knock sensor and resulting ECU timing pull, and I'm certain that's not what they're doing.

IOW, I can't be certain, but given the best information available I am pretty sure that your ECU will adjust the timing to prevent knock no matter what grade of fuel you put in the car. The manual DOES say that is the reason the knock sensor is there.

If I'm wrong about this I'm sure one of the resident experts will let us know.

 

The Vortech timing controller intercepts the CKP sensor signal, and uses an internal MAP sensor and RPM input to offset a timing retard or advance programmed into the controller.

The controller is made by Split Second, and loaded with a MAP from Vortech. The controller can be remapped with a PC and a serial cable using Split Second's R4 software.

My controller was remapped by me, to eliminate detonation on winter/oxygenated fuels in the 4-5K rpm range. The "stock" vortech timing retard starts around 4K RPM. The max timing retard on the map is 3 degrees.

I do have the ability to monitor ignition timing and knock sensor voltage to the stock PCM with my own pocket HDS scanner. ( www.teradyne-pocket-tester.com) What I don't have at the moment is the free time to run the tests and transfer the data to something everyone can read.