Knock sensors

Steve Arndt · Post by **Steve Arndt** » Wed Mar 28, 2001 10:22 am

Has anybody played with knock sensors on aircooled VW or Porsche engines? I would be interested in your findings.

The SDS website says that they don't work well for our application because of the noise our engines make. We have loose tolerances because of the heat cycles, and no thick water jackets or Iron to damp vibration/noise. Still I think that anything is better than nothing for better detonation detection.

On the Autospeed website they show how to build a small knock detection system. For $10 you take apart a small Belltone hearing amp and mount the sensor to the engine. You then listen to the engine with a set of headphones as you dial in your timing under load. It is supposed to be better than the naked ear.

Steven

Post by **Tom Notch** » Wed Mar 28, 2001 12:10 pm

I have "heard" but not tried it yet, that 911 (aircooled) knock sensor and auto retard can be adapted to the 4 cyl. VW motor.

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Tom Notch
Tom's Old VW Home

Chuck Schneider · Post by **Chuck Schneider** » Thu Mar 29, 2001 8:29 am

What about the whole ignition system on a Vanagon. The distributor drops right in and it has all the knock sensing you need. Tom you have any other info on that 911 knock sensor set up.
I heard a knock sensor won't work on a bug because of the noisy valvetrain on it. i can see it working on the 911 because it's overhead cammed, which are fairly quiet.
I am thinking if you want to have a motor that lasts some kind of knock sensing is needed. It would be nice to be able to run 87 octane on the street and not worry about detonation.

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12.70 @ 104

Steve Arndt · Post by **Steve Arndt** » Thu Mar 29, 2001 3:57 pm

You guys should read about the J&S SafeGuard. It is used by all the good aftermarket supercharger kit manufacturers (Energy Dynamics, Jackson Racing. . ). It does individual cylinder retardation as knock is detected. Amount of retard, sensitivity, etc. is all adjustable.

The knock sensors are supposed to be focused in a very narrow range to detect the sound of detonation. I think we can make them work. It should certainly work on the big block T4 which is aluminum and has quieter valve train the the T1. I know I am going to play with it.

Chuck, I was not aware that the Vanagon has a knock sensor. My dad has one on the engine stand now (new factory longblock, old one fried and R&Ring), and I don't see a knock sensor on it. It is a 1.9 so maybe they don't have them.

What we need is info on the 911 knock sensor. Maybe it is geared towards being able to not focus in on the clatter and clanking of our engines and hear the correct knock vs. a Honda ND sensor.

Steve

noincome · Post by **noincome** » Thu Mar 29, 2001 4:48 pm

Steve, isn't the J&S SafeGuard used by the Corvair guys? I think I read somewhere that was the hot ticket for them.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Steve Arndt:
<B>You guys should read about the J&S SafeGuard. It is used by all the good aftermarket supercharger kit manufacturers (Energy Dynamics, Jackson Racing. maybe they don't have them.
Steve</B><HR></BLOCKQUOTE>

noincome · Post by **noincome** » Thu Mar 29, 2001 8:58 pm

Early on in the planning stages of my project, I looked into trying to incorporate a knock sensing system. Since my current engine is turbocharged, my research led me to the Saab Automatic performance Control (APC system). This system was used in Saab?s turbo models starting in 1983, and is easily adapted to other turbo-equipped cars. The unit you want is the one from 1986 on. The APC allows you to run maximum boost without detonation (about 16 psi max with a Saab T03). The parts for this system can be purchased from a bone yard for as low as $25.00 depending on your location.
The main parts are the ECU; knock sensor, solenoid valve, and pressure transducer. In a nutshell the way the system works is, it listens for knocking and retards the boost in increments of 1.5 psi until the knock goes away, it then attempts to bring the boost back up again until it detects the detonation again. I think that it is a slick set-up. I have not installed this system yet; it is still sitting in a box in my garage since 98. Maybe I?ll get around to installing it this year.
Here is one of the links that still works.
http://www.teleport.com/~bertram/volvoapc/parts.html

turbo6bar · Post by **turbo6bar** » Fri Mar 30, 2001 7:52 am

noincome, how does the Volvo APC interface with the ignition setup? Does it have built it ignitors/ignition module, or does it have a trigger signal? Is it for single ignition coils or muiltiple coils? I looked at the website you referenced but saw nothing that told how it was used. Would you use this with carbs or aftermarket fuel injection?

Puzzled in TN,
jay

noincome · Post by **noincome** » Fri Mar 30, 2001 10:20 am

turbo6bar, the APC does not retard the timing, it retards/tapers the boost on a turbo equiped car when knock is detected.

SC912E · Post by **SC912E** » Tue Jun 05, 2001 12:40 pm

I believe the APC that noincome describes also has an adjustment for knock sensor sensitivity, as well as max boost. But it does only control boost.Does anyone know of a programable efi that will control ignition fuel/air and boost that incorporates knock sensing in closed loop?

Steve