A knock sensor signal rectified, filtered with a simple bandpass and amplified (basically what a knocklink does) is I find quite useful when you don't know how good an ECU's knock control is. I wouldn't dismiss these simple devices.

All you need to do to convert it into a useful scale of knock is to compare the value you get with a normal value at various engine speeds. Or you can differentiate the signal to get the spikes.

You can make it fancier by gating your sampling to only the time after each spark plug has fired when knock is expected. You can compensate signals with background noise, you can compare one knock sensor to another, or you can go full blown DSP, or better still ion sense.

 

I didn't know there was a local tuner, unless you was talkin bout Red from Bubbatoons.

OT, are using logworks Tom?

 

Nah, I am still using EVOScan. I line it for some reason, and never really found an advantage to go to Logworks. I know logworks does a bunch of stuff to make tuning easier, but for some reason I still like EVOScan..

 

Each engine has its own "harmonics" and distinct noise. Some things that effect this are stroke, bore, and rpm range. When the engine has knock at a certain RPM it will have a different frequency than another RPM. I am not totally against the HKS Knock Amp or the Knock Link. I just think that the stock ECU can better manage knock in our engines.
There are other things that will effect this though. Built engines with different internals and also removing the balance shafts. I am sure there are other things that will effect it as well.
If using the stock ECU to tune I would go by what the ECU says is knock. Most people cannot afford ion sense knock detector, the factory tuners are probably using ion sense and know exactly when and after thourough investigation why the engine is knocking.

 

I do believe he had a problem but I learned about 5 years ago that you fix the "knock" and then try to tune the motor. I've replaced knock sensors, ticking lash adjusters, loose intercooler pipes, chattering motor mounts, stiffer motor mounts, and the list goes on to about 10 more examples for specific cars where we had to fix false "knock" to start tuning the motor.

I always thought a stroker motor would be an issue. However I've successfully been working with a 35r stroker evo. He has some false knock and we work to correct it.

My personal DSM had HUGE knock issues. 30+ counts of knock when stock. I had to replace the lash adjusters and knock sensor to fix the issue. Even then part throttle knock was a huge issue and I had to alter fuel and timing maps to fix it (on a stock car).

My other friend as a seriously built 2g DSM with a 6 bolt motor that I was tuning sunday. 3" charge piping, 4" exhaust, T70 turbo, and DSMLink. We played nice with the stock knock sensor on his weisco piston motor at 27psi and pump gas. Yes he has knock "issues" but we played nice.

These are just data points. I'm not bashing you or your experience. I'm just saying, that since 2000 I've been logging, tuning, and playing nice with the OEM knock sensor. Its a ***** at times but play nice..........

 

It is good to hear it can be done with high clearance pistons, no balancer shafts, stiff mounts etc, but how on earth do you find the individual cause on the individual car and can you always find it?

 

Indeed.

The only evo I have not been able to tune via the stock ecu with a built or larger motor was a 2.3L without balance shafts. No matter what, 'knock' counts would go past 20 counts at 5500 rpm.

Could have been a bad build or even something else but every built motor with balance shafts intact have not been a issue.

The stock knock sensor can be a **** at times but it is there for a reason.

 

You should never build a motor without balance shafts for use with the stock ECU.

 

And about all I tune anymore are high end built motors without balance shafts so why is it an issue again?

 

so in summary to my topic from what i gather based on stock ecu tuning method:
1) Listen to the stock mitsu knock sensor via either Mitsulogger or Evoscan
2) Ignore the Dyno operator Knock gadget (can be HKS knocklink or The Knockbox)
3) Reason being stock ECU knock filter will pull timing if knocksum is too high til it causes the octane flag/level to drop

Correct me if I am wrong?

 

I tune for 2-3 knock sum with pretty conservative timing.

But my CEL is set to blink on knocksum of 4, Fuel is normally the main culprit...

I get the most knock directly after flashing because the ECU still needs to degrade the Octane number...

But think I need to run 80% Meth in my Alky inj as I have a 0.5mm Injector.

.

 

Someone correct me if I am wrong, but I don't think the ECU will pull timing untill the octane flag is reduced. I believe it will pull timing until the knock goes away, and if it is severe enough, then it will start to decrement the octane number.

Seems like it will only decrement the octane number if the knock is severe enough.

 

The ECU can definitely pull timing without the octane flag being decremented. The octane flag doesn't start getting decremented until a knock sum of 5 or 6 (IIRC) is reached.

 

yip you correct from 3 knock counts it will pull timing, after 6 drop to a different octane map
you are correct mrfred you can see it clearly in logs

 

Edit: Quote Removed

No he's right. The OEM knock sensor system with DSP integral to the ECU is so excellent that nothing in the aftermarket will surpass it on the original engine. The OEM knock system is so excellent that it has gone 9's in the quarter on DSMLink cars and possibly (but unconfirmed) 8's. I think buschurs old RWD talon wen 8's or 7's? On the stock ecu with TMO chip and a VPC. David can comment if he chooses to on the exact setup. I saw the car way back in the day (like 2001???) at Maple Grove but forget the exact specifics.