knock sensing ignition retard?
 

Can this be used on the 911? or is it just "TOO" loud for it to work?


Specifically i have a J&S knock sensing ignition retartard sitting on my shelf begging to be used.


J&S

This is exactly what hot rod 911s need as integrated or add-on to their electronic ignition systems – single and twin plug.

What is missing in most 911 hot rods is closing the loop. Most EFI does that. The manufacturing cost of the electronics is almost insignificant. If someone can more that recoup the development and other costs, there are all sorts of possibilities to make money and supply us needed systems.

Best,
Grady

I asked a similar question and here's what Goran had to say:


quote:
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2: During some surfing I found that tuners are using the APC knock sensing system off the Saab turbo. They are fitting them in aftermarket turbo installations to engines with no knock sensing capability. Has anyone considered using this in a 911 turbo project?
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I wouldn't use it. I've been fiddling with APC a lot, and it's electro-acoustic system that listen's for knock with piezo-microphone.

I believe that (i cannot say "our" anymore as i sold my 930) aircooled 911 engines are too noisy for this kind of setup, generating lot's of false-alarms. Of course, it's not dangerous to try :-)

it just seems like such a nice concept...

One of my friends has a Acura Integra with 20lbs of boost and when his girlfriend borrowed it she put 87octain in it.:eek:
the J&S heard the knocking and retarded his ignition so much that the car was able to make it 30miles till it was back and his hands. (the look on his face when the knock retard indicator was going crazy was priceless!)


Grady, i dont see why it wouldent work except for the ammount of backround noise..... why wont it work?
wont this product help in "closing the loop."


Using a single knock sensor, the system detects the onset of detonation and retards the timing on a per cylinder basis. A mode switch lets you select a maximum of either ten degrees or twenty degrees of knock retard. In the ten degree range, the unit retards one, two, or three degrees per ping. Double that for the twenty degree range. The system is always trying to re-advance to stock timing. In the ten degree mode, it re-advances at the rate of one degree every twenty revolutions.

The system does not need a cam or crankshaft reference to determine which cylinder to retard. The unit is programmed to "know" that the knocking cylinder is the one that just fired, and that it won't fire again for two more revolutions. When the knocking cylinder comes around to fire again, software dials in the retard amount for that cylinder. It does this as each cylinder goes by, building up a different retard amount for each cylinder.

The unit has a high energy ignition with constant energy dwell controller. The system monitors the coil current, and adjusts the dwell time to achieve seven amps of coil current. Compared to a GM HEI, this is a 62% increase in energy stored in the coil. The system can also be used to trigger an MSD

The J&S SafeGuard harnesses the power of the microprocessor to allow your modified high output engine to run normal ignition advance for optimum responsiveness. Since the SafeGuard is a closed-loop control system using modern knock sensors as a feedback mechanism you no longer have to turn dash mounted knobs, twist distributors, or even second guess the future with a PC programmable device. Hundreds of times per second your J&S Safeguard will both monitor and adjust your engine's ignition timing on a cylinder by cylinder basis.

i guess i will have to try it out. If it dosent work... then no loss.


I mean i have the thing siting in a box right next to me!

just cant think of a nice solid place to mount it:(

According to several manufacturers, a valid method of testing a knock sensor is to place a metallic object (e.g. long drift punch) against the engine block, then smack it with a ball peen hammer while monitoring the crank pulley marks with a timing light.

Not sure whether this would be valid for an air-cooled engine, but piezo knock sensors are usually tuned to the frequency of engine knock rather than other engine noises (timing chain tensioners, loose piston clearance, worn conn rod/main bearings, etc. :-)).

Let us know how this works out; it would be a valuable addition to engine longevity.

Sherwood

I don't quite understand why some of the doubts about the effectiveness of acoustical knock sensors on 911 engines ... aren't you guys aware of the knock sensor on the 964 DME engines???

I'd get one in a heartbeat to trigger a Light if there was a nice one available. I've seen units in Summit, or somewhere.

The last time I read about knock sensors around here there was No definative answer on mfg, etc.

this one has a light... tells you witch Cylinder it has to retard even!

"oh crap... number 3 is acting up again":p


and it will retard JUST #3 if you set it to.. or all of them...
http://www.jandssafeguard.com/images/dualmonitor.jpg

I am working on an ITB EFI conversion using a distributorless ignition (DIS). The spark software will allow the user to use a knock sensor. If a knock is detected, above or below a user defined RPM and above a user defined MAP, the ignition will retard by the by a user defined first knock amount. Any more knocks are ignored untill the defined Wait Time has passed. If it receives another knock it will add a retard by the user defined Subsequent Value and wait till the timer (Wait Time) has passed. If no knocks are found it will advance by the user defined Advance amount and wait till the timer runs out before adding some more advance. If it receives any knocks during the advancing stage it will immediately retard and restart the timer. There is a max Retard Allowed setting so it can be pegged. There is also a built in limit of 30Deg Retard allowed, I can't see that being a problem.

Warren mentioned the 964 knock sensor, I may investigate the use of one of these sensors in the package if it works with the software.

We are in the development phase, and I will post more definitive data as it is collected.

I would speculate (WAG) that the factory knock sensors are supplied by Bosch and the sensor Porsche uses is a Bosch generic piece (or at least compare Bosch part numbers to verify).

If so, one could visit the nearest pik-a-part or equivalent and snatch a used knock sensor from a similarly-equipped vehicle (Saab, Volvo, MB, etc.) for a few bucks, install in a suitable mounting location and wire it into your electronic control unit.

Sherwood

My wife put regular gas into my turbocharged Buick Grand National once, just once. Typically, turbo motors have relatively low compression, that is until the turbo is called upon via pedal to the metal. I temporarily disconnected the waste gate until that tankful was empty. Without forced induction, the motor ran fine, albeit weak on climbing any hills. ;)

If I had mashed the gas I could have easily lifted a head and rearranged head gaskets. It has a factory knock sensor and I have aftermarket visual and audible alarms inside, but even those precautions don't prevent motors from detonating and possible motor damage under extreme circumstances.

You may be able to save some time by posting this question to Todd at Protomotive's forum. If anyone has done it successfully it's him.

Just wondering. For us non-ECU guys, is there a more reasonable alternative to knock detection and ign. retard? I'm looking for the right box to control a Crane ignition box (if there is such a thing).

I'm estimating the J&S solution is going to run almost $700. Is that right?

Sherwood

Sherwood,

The ecu I am working on could be used to just control spark/ignition retard. The ECU will work with the ignition module which in turn will fire the coil. All based on a crank trigger. It is accurate to 9k. It's set up will be very similar to the Electromotive system and have a lower price point.

Sherwood asks. "Just wondering. For us non-ECU guys, is there a more reasonable alternative to knock detection and ign. retard? "

Yes, we old timers call it "setting the timing right in the first place";)

Eddited to add the smiley face i forgot

Here's a couple data points, this is not gospel, just what I've heard:

- I thought that knock detection was "tuned" to a motor and it may well be however, when I asked a guy I know (Jerry Peligrino, owner of EPE) if changing the displacement from 3.6 to 3.8L changed the frequency enough to confuse the knock detection he told me that the Porsche knock sensing doesn't work that way. It works by listening for a "change" as opposed to a specific sound. I'm paraphrasing so something may have been lost in the translation.

- I remember (and we all know how bad my memory is) reading that Stepan Kasper (Imagine Auto) mounted the knock sensor for 930's on the big bolt that the throttle crank platform sits on.

-Chris

Well, from memory ... the pics in BA's <i><b>Handbook</b></i> show the sensor bolted to a 'bridging piece' that connects all three cylinders on one side of the 964 engine, and most engines of the water-cooled variety have the sensor bolted to block or intake manifold!

"Yes, we old timers call it "setting the timing right in the first place"."

Sammy,
I didn't see the :) following your comment.

Ignition timing requirements vary depending on many factors (air density, A/F mixture, engine and air temp., charge temp., humidity, rpm, compression ratio, fuel octane, engine load, etc.). The advance curve in a mechanical distributors is but a compromise between optimum power and no detonation at any given rpm, and there's a wide spread in most cars. Change things and engine power is compromised more than before.

The ideal system, and one promised by the knock sensor-ign. advance/retard systems, is to maximize the spark lead for best power and torque regardless of the above variables.

Sherwood

Yes, 964's have a threaded boss on the side of the cylinder for the bridge to bolt to. I looked into this a few years ago and concluded that there wasn't an easy way to retrofit this to earlier cylinders.
-Chris