EFI w/ Knock Control on old mag case motor

[John at J&S]

Walt:

For twin plug with two HPV-1's, you will need the "dual three channel" Vampire version.

The negative terminal of each coil connects to a Vampire "control wire".



For access to the negative terminals of the coils, you will also need coil interface modules from MSD. These are "break out" boxes that fit between the HPV-1 and the coils. They were designed to allow MSD to inject high voltage to the coils, but we use them to connect the Vampire to the negative terminal of the coil.




I did one for Robert Poirier a few years ago. I don't know if he is on the forum, but he did reply by email at the time that it was working well.

I created the above drawings for his installation.

During the install, he found the Electromotive designer reversed the terminals on "Coil A", probably to simplify the PCB layout, so you must verify which terminal is Coil Negative for each coil.

[John at J&S]

The newer XDI DFU's do not require the MSD coil interface adapters.

Connect the Vampire control wires to wires A, B, and C of the four pin cables connecting each DFU to the XDI ECU's.

Again, the dual three channel Vampire is required.

[burgermeister]

Just another interesting datapoint - the J&S seems to have detected early failure of the mechanical AFM on my car.

Recently my J&S became rather active, especially at part throttle. Shortly after, *really* active, as in active anytime the car was not at steady cruise. The car ran fine, sounded fine, RPM blipped fine, no change in power - no sign of anything amiss whatsoever. I first replaced the knock sensor, thinking it somehow went south for the winter, and then checked all of the wiring to the J&S, but got the same knock activity level.

After more diagnosis, turns out the flapper AFM had worn away enough of its potentiometer track to muck up the engine management. Voltage was jumpy with flap travel. Apparently not enough to be noticeable to me as a driver, but definitely noticeable to the J&S. I did the "shift the contact points" trick mentioned elsewhere on this forum, and the knock activity is back where it used to be (very little).
Of course, different weather, different results - but driving season is over in MI, so further testing will need to wait for next year.

In retrospect, there was some other early warning before the knock issue. The engine (per J&S AFR readout) seemed to run lean. It was a very gradual change, and was mostly at WOT - I was under the assumption the AFM is ignored at WOT in favor of RPM, is this incorrect? Anyhow, I figured maybe the O2 sensor, installed for at least 5 track seasons and 30+K miles, was past its prime. Replacing it did produce 'richer' readings, so I thought 'problem solved' - apparently not!

So, thanks for the early warning John!

[John at J&S]

Thanks for the attaboy.

I'm flapper-gasted.

[Speedy Squirrel]

I think I have stated this before at some point: the 964 style bridge is used to control knock in each INDIVIDUAL cylinder. It is not required if you are controlling all of the cylinders the same as a batch.
It is also generally true that OEM’s do not advance the timing beyond MBT, only retard away from MBT when knock is detected.
OEM systems have an adaptive behavior that continually learns the propensity for knock in each cylinder.
There is quite a bit of effort that goes into filtering and windowing the signal from the knock sensor. The sensor is essentially an accelerometer that measure vibration amplitude and frequency. Modern knock sensors actually have this active filtering built into the sensor.
The worst knock in our engines is pre-ignition, not combustion, and is not easily predicted from the knock sensor.

[John at J&S]

The knock bridge is not required for individual cylinder knock control, given an intelligently designed knock controller.

Knock detection actually occurs in the electronics connected to the sensor.

The knock frequency is proportional to the cylinder bore diameter.

All modern knock sensors are non-resonant, flat response, out to 20kHz. Bosch has been producing them since the mid '80's. These are the so called "donut style" two wire sensors. They produce a low level output signal and require a shielded cable.

Resonant knock sensors are an earlier technology. These are mechanically tuned to a certain frequency. They are larger diameter, stud mounted, most commonly with a single wire, unshielded output cable.

The earliest are called "spike tuned", and have the highest response over a very narrow frequency band. This would seem to be ideal, but the knock frequency shifts with combustion temperature and could go out of band, losing the knock signal.

"Broadband resonant" knock sensors produce an output over a wider bandwidth, allowing one sensor to fit a wider range of engines, and allowing for the frequency shift with combustion temperature. In the '80's and '90's, GM produced broadband resonant sensors in three frequency bands, to cover all cylinder bore diameters.

Given modern electronics with intelligent knock control, non resonant sensors are now preferred, as one sensor can fit all engines.

[reclino]

How does one adjust your system the bore diameter. I would love to use the Universal unit on my 930 with 97mm bore size.
Thanks
David

[John at J&S]

There is no adjustment for bore diameter. The system uses adaptive signal processing to ignore engine noise while maintaining high sensitivity. It's been demonstrated to work on many engine types.

For example, I was searching just last night and ran across this old thread on a Ford Mustang forum, about our Vampire version. It uses the same detection strategy as the Universal version:
https://www.moddedmustangs.com/threads/whoa-975-hp-from-a-terminator-and-2-9-whipple.578170/page-2

[spyerx]

This is where we ended up
7r case
Custom 2.8 nickies with 993 style knock boss cp custom pistons
Heads got the full and complete xtreme treatment

Here’s a head with provision for cht

Long block is done.

Induction and electronics assembly next week.

Controls is motec m130