knock sensor

[forwheeler]

Originally Posted by John at J&S

forwheeler:

You have the same set up as sjf911?

According to the drawing posted, you would need two three channel Vampires.

No. I was refering to the 2 knock sensors. I have CIS and the stock ignition.

I wondered if you have a controller to accomodate 2 sensors or if I could parallel 2 sensors on 1 input. I doubt that it would work since the other sensor would prevent the controller from seeing the voltage rise from the sensor which is sensing knock.

[John at J&S]

forwheeler:

The version for distributor ignition has a "magnetic pickup" output centered around ground, so it will trigger the Bosch CDI.

We used to sell to a Porsche tuner in the Daytona Beach area. He used only one sensor with good results. One of his customers describes the mountng location:
http://forums.pelicanparts.com/1923608-post13.html

Louie Ott is using two sensors wired in parallel on his 928. He measured the output on a scope using a spring loaded center punch on the block to produce a uniform knock signal. He found the second sensor reduces the signal by about 30%, but there is enough range on the sensitivity knob to make up for it.

He (Louie928) describes results in this thread on the efi101 forum:
EFI University Electronic Fuel Injection Tuning :: View topic - Det hearing system

[John at J&S]

sjf911:

I thought of a way to do it with one unit, but you will need two three channel igniters, but only one EDIS module.

Use an EDIS to provide three ignition channels to an Interceptor that has been set up as an inverter.

The Inverting Interceptor would then drive two three channel igniters, or one six channel igniter. 300zx used a six channel igniter.

******** Parts Catalog

[sjf911]

Originally Posted by John at J&S

sjf911:

I thought of a way to do it with one unit, but you will need two three channel igniters, but only one EDIS module.

Use an EDIS to provide three ignition channels to an Interceptor that has been set up as an inverter.

The Inverting Interceptor would then drive two three channel igniters, or one six channel igniter. 300zx used a six channel igniter.

******** Parts Catalog

I thought of switching to direct coil control with the MS using 2 Bosch or Haltech 3 channel ignitors in parallel although the 300ZX 6 channel ignitor would be half the price. Can the Interceptor control 2 coil outputs for each ignition cycle simultaneously?

[John at J&S]

sjf911:

Do you mean full sequential six channel ignition, with six dual coils?

I would have to study it, but I think you would use six channels of the (inverting) Interceptor instead of three.

[sjf911]

The 2 coil packs run in parallel so 2 coils are always charging and firing at the same time for the same cylinders. I would have to run 12 coils to run sequential such as LS-1/LS-2 CNP or COP. This means the interceptor would have to interrupt/control 2 coils simultaneously for each ignition event as a wasted spark.

[John at J&S]

Your drawing shows six dual coils already. Enough to do full sequential and dual plug.

Does the MS have capability for six cylinder full sequential ignition?

I'll draw something up and post it.

[sjf911]

Originally Posted by John at J&S

Your drawing shows six dual coils already. Enough to do full sequential and dual plug.

Does the MS have capability for six cylinder full sequential ignition?

I'll draw something up and post it.

For the twin plug you can't drive both sparkplugs in the same cylinder with the same coil effectively so unless you go with 12 coils, you can't do sequential. I don't know if the MS-II can run 6 coils without major firmware changes. MS-III can but is not quite available yet and I don't think it will fire 2 coils simultaneously so the coil signal will have to be split to control 2 3-channel ignitors in parallel for wasted spark or 12 CNP/COP running from 6 output channels for true sequential.. My plan is to upgrade to MS-III and run sequential injection when available. At that point I may switch over to direct coil control although I don't know if the output signal is strong enough to be split to parallel ignitor/coils.

[John at J&S]

Is the firing order 123456?

[sjf911]

Standard distributor firing is 1-6-2-4-3-5. IIRC, wasted spark is A/A-C/C-B/B-A/A-C/C-B/B firing (1+4/4+1)-(6+3/3+6)-(2+5/5+2)-(1+4/4+1)-(6+3/3+6)-(2+5/5+2).

[JohnJL]

Correct, you get around firing order issues by adjusting the connections to the pins of the EDIS or Accel coil packs. I use Accel units from Summit.

[John at J&S]

VW Passat six cylinder waste spark coil packs have internal drivers, available from ********.com for about $180. Two required.

Connect J&S Interceptor between coil packs and the EDIS.

[sjf911]

The EDIS units directly control dwell and timing of dumb coils, so, you are saying the the interceptor can take a direct coil control output and convert it to a low voltage signal for a smart coil?

[John at J&S]

The coil driver signal has to be inverted, so you would need to order an inverting interceptor.

[John at J&S]

The Interceptor has an analog output to drive our bargraph display, but the signal can also be data logged.

Link to video showing the interceptor working on the bench. I'm playing an old knock tape into it:

Picasa Web Albums - John - J&S Vampire I...

Bob Boyer of Random EMS supplied Nize with his equipment. Bob programmed a Vipec ECU to reduce boost when the J&S is retarding from knock. He sent this data log showing the results. The orange trace at the bottom is the bargraph signal, the black trace is boost. I think the time scale is 0.1 seconds per division.

[John at J&S]

Here's a pic of the pre-production interceptor unit. It can handle up to eight ignition channels.



The production units have another knob, for nitrous retard, and the discrete LED's have been replaced with an LED module. Note the headphone jack in case you want to listen for knock.

[nize]

Originally Posted by John at J&S

Bob Boyer of Random EMS supplied Nize with his equipment. Bob programmed a Vipec ECU to reduce boost when the J&S is retarding from knock. He sent this data log showing the results. The orange trace at the bottom is the bargraph signal, the black trace is boost. I think the time scale is 0.1 seconds per division.

i should mention that the brand-new vipec EMS system designed by Random EMS is only one of two aftermarket systems i am aware of that has a 2-stage knock protection which;
1) retards timing, and if knock is still present
2) cuts boost

aside from the porsche factory system for the 951, the only other system i know of that has this two-stage timing retard+boost-cut knock protection failsafe is the Wolf EMS. both are available from here;
Random Engine Management Systems

[beepbeep]

Originally Posted by nize

aside from the porsche factory system for the 951, the only other system i know of that has this two-stage timing retard+boost-cut knock protection failsafe is the Wolf EMS.

I believe I mentioned SAAB Trionic before. They invented the thing. It senses the knock with ionization-current and pulls down ignition per cylinder. If outside the margins, it pulls down the boost. Been around for 15 years.
It runs sequential ignition and injection without the cam sensor by triggering ignition twice when cranking and detectin firing phase with ion current. Very trick. It has CDI ignition, 32 bit CPU, ion-current knock detection (that doesn't go deaf at hi revs), boost control, no cam sensor...and this is from 1994. There is still no ECU that can match it.

Doing knock detection by microphones compared to ion current is like navigating with sextant compared to GPS. There is a group that plans to develop ion-current sensing for DIY but it's still in development.

http://en.wikipedia.org/wiki/Trionic_T5.5

[John at J&S]

Goran: Saab introduced the APC in 1980. Boost reduction by knock detection, using acoustic knock sensor.

It was an analog system. It worked well, but if we follow your logic, it was junk, and they should have just waited until '94 when they had ion sensing.

You can sit around and wait for the DIY group to give you ion sensing, meanwhile you tune by ear or experience, the navigational equivalent of dead reckoning.

Without individual cylinder knock control you are in second place, if that. You either leave power on the table or did not finish.

You generalize and say knock sensors don't work very well. Obviously, you haven't tried my system.

[beepbeep]

Oh, I played with APC a lot. I even have two of them, one partially disassembled. It's a pinnacle of 70's analog technology and quite advanced for it's day.
I definitely don't consider APC junk. It's good for it's day but it had inherent drawbacks that were recognized by factory and subsequently removed by Trionic:

1. It was "programmed" to taper boost above 4000 RPM as knock sensors went deaf from chain noise in engine.
2. It couldn't control ignition. Only lower the boost. Winding back boost is very slow and engine risks damage under period turbo is spinning due to inertia if pinging. You would prefer to keep motor on edge of detonation on each cylinder instead of collectively (and slowly) lowering boost.
3. It was tuned for looking for knock overtones in iron B202 block (which many didn't quite understand and retrofitted it to another engines, most notably Volvo iron engines). It didn't always work.

Back to present day: Delphi is about to release their own mass-production ion-sensing ignition cartridges in 2012. 15 years late but I sincerely hope that mass production of ion-sensing ignition will give DIY:ers power to adopt it to MegaSquirt just like they adopted EDIS. This will be nirvana of DIY EFI. It will be Linux in IBM and Windows world of aftermarket EFI.

A DIY MSIII + Delphi ion current coils will be a terrific package.

Delphi Ionization Current Sensing Ignition Subsystems

Right now, I'm aware of only handful of manufacturers besides SAAB that utilize it:

Harley Davidson
Bugatti Veyron
BMW (in their new cars).

Regarding my comments on microphone knock detection:

It works (and has been working since early 90's) but is still something that needs to be tuned per engine type to be really effective. Ion-current implementations don't care about block resonant frequency...it will detect knock after each combustion in any engine, thus very fitting for universal ECU.