PorKen

After climbing a steeeep learning curve (for an electronics noob like me), I made a simple circuit which interfaces with a Knocklite, and automatically applies the octane loop for a few seconds (adjustable), if knock is heard. It works!

The Knocklite has two output wires, knock, and rpm. There's scant info on these outputs, but I determined with measuring that the knock signal was a brief 5V low (0V). I read and read on the internets, and put together a simple 555 based timer circuit controlling a reed relay, with the Knocklite output wired directly to the chip's trigger, which waits for a negative edge input.

I have the WOT input to the EZ-F disabled, and a straight 5° advance over the stock EZ-F cruise map. The cams are advanced 3°. But, I have cold plugs, WR5DC, a cold thermostat, 75°C, radiator covers, and the rear hood seal removed, so it was difficult to get a knock to test it!

Today, I found a nice long steep hill, empty of traffic, and near redline, it finally showed a red knock light, which immediately went out. I looked over, the knock relay LED was on!

Next, I'm going to put in a double pole relay, and install a light in the unused <--> trailer turn signal in the pod, when the retard is active. Then I can hide the Knocklite in the glovebox.



The S4 knock sensor is mounted using a S4 block plug, at the front of the V.

IcemanG17

Ken
Where did you mount the knock sensors....did you use 2 or only 1?

PorKen

Brian,

Just one S4 sensor, at the front. Louie did some testing, and found one sensor could hear knock from around the whole engine.

IMHO, they used two sensors on the EZ-K to make it simpler to design the circuitry.

Glen McCartney

Ken, great stuff as usual...I see a new product coming!!!

PorKen

Glen,

I reckon John Speake or one of the other electronics guys could make a circuit board pretty easily.

dprantl

There are companies that will make you whatever circuit you want as long as you give them the specs.

Dan
'91 928GT S/C

IcemanG17

Hmm...so now you have an 86.5 with knock sensing.....so the only thing your really "missing" is the two stage intake...which probably is less efficient than the larger intake you already have....plus 1mm smaller valves...

John Speake

Good work Ken ! How long does the relay stay closed after a knock is detected ?

Mike Frye

Ken,

Very cool stuff! The perfessor is IN!

PorKen

I have it set to about 6 seconds. My circuit has a range of 1~11 seconds. If you change the Knocklite sensitivity settings 1-2-1 (1 = highest, of 10), it triggers the relay, so I can time it.

I keep the sensitivity at 2 while driving. At 1, it triggers on engine noises. Overall, the 928 engine must be pretty quiet. I've read about the Knocklite used on other engines having to be set at 7, to stop false triggering.

I could see using a counter to increase the retard time in steps, if it knocks again soon after the retard turns off. Using the SharkTuner, even the number of retard degrees could be increased in steps, using different resistance values for the air temp input to the EZ-F (5 cells).

With boosted engines, you could trigger a boost reducing valve instead, like SAAB's APC system.

John Speake

Sounds excellent - an idea worthy of adoption :-)

tomcat

Ken

What causes the engine to go into the octane loop without your new knock sensing circuit?

Also, is this circuit still live (i.e., able to go into the octane loop without knocks) after adding the knock sensor?

PorKen

John,

If I understand your question correctly, the normal way of enabling the octane loop is to plug two wires together at the EZ-F connector. This forces 3° retard at high load cruise or WOT. I could still do this.

I am tricking the EZ-F into 5° advance by adding a resistor to the coolant temp input (Temp II), and disconnecting the WOT input so the WOT map isn't used (always in the cruise map). Instead of the octane loop, I could have changed the resistance, so there'd be no advance. The stock EZ-F cruise map is quite conservative.

tomcat

Ken I think your development here is tremendous. Seems like you are optimizing the engine management system to get the additional performance out that the factory left in (i.e., wasn't able to get out without utilizing knock sensors).

My question is, with the factory set up what causes the engine to enter the octane loop mode? Is this the temp sensor mod that you worked around (i.e., was the higher temps causing the engine to default into the octane loop?)?

Thanks Ken.

PorKen

The only way for it to be in the 'octane loop mode' with the factory setup, is to manually plug the octane loop wires together.

My circuit automates this, turning on the 'octane loop mode' if there is even slight knocking (not audible in the car), then a few seconds later, turns it off.