This has been tested successfully on a false knocking car.

This code snippet reads the knocksum into r10 and then compares it with the value (decimal 36) that is stored on the JDM 7/8 at &H1782.

If the knocksum is higher than 36 then the knocksum is reset to zero.

To disable your knock control if you change the word value at &H1782 to 0000 it always forces the knock sum to zero.

ROM:0002059A mov.l @(h'10C,pc), r10 ; [000206A8] = Knocksum
ROM:0002059C mov.w @r10, r10
ROM:0002059E mov.l @(h'100,pc), r11 ; [000206A0] = word_1782
ROM:000205A0 mov.w @r11, r11
ROM:000205A2 cmp/hi r11, r10
ROM:000205A4 bf loc_205AC
ROM:000205A6 mov #0, r10
ROM:000205A8 mov.l @(h'FC,pc), r11 ; [000206A8] = Knocksum
ROM:000205AA mov.w r10, @r11

Usually you wouldn't want to do this and every effort should be made to find and eradicate the noise.

The alternative for this car was going to be a standalone that didn't have knock control anyway.

So here it is if you really want it. It would be better to change the calibration of the knock control, but this isn't well understood at present. I can't even find knock filters in JDM IXs.

 

If I ever did that I would probably be driving a van to work

 

JC, I am curious why you recoded. Is this preferable to directly altering the Knock tables in the ECU?

 

jscbanks, is there a tutorial you can write on how we can impliment this code on our ecu's for us layman's?

the work you guys are doing is amazing!

Thanks, Andy

 

Aaron, some ECUs don't have knock tables I can find, and even then the code to interpret them is a nightmare. So it was easier just to turn it off for this car.

Andy, a lot of these mods need bytes added to xml definition files, but the locations do vary from car to car. With other things to do at present, maybe it would be best to just show it is available as per this thread, and if someone wants it they can post their ROM and xml and I'll find the correct address to alter?

For this one it is usually the first occurrence of &H0024 in the ROM if you search from the beginning, but each one should be checked by disassembly.

For the new code snippets, that will really need full ROM images posted I think. Still in the testing phase for most of it, so I haven't done that yet.

If someone does want to write tutorials on these tricker topics I'll happily help with any info required.

 

jcsbanks,

Awesome find. This would actually be a great situation to use the live tuning in RAM and separate code.

DSMLink allowed us to disable the knock sensor based on conditions like RPM and TPS, for example. So, anything under 3000 RPM and 30% TPS, for example, disable the knock sensor. That allowed us to eliminate phantom knock from noisy lifters, etc.

If we could eventually add code like that to this routine, that would be great.

I will find this code in the 05 ROM later today and post the address.



Eric

 

The Evo's knock tables already do this sort of stuff.. the tables at very low RPM's are very insensitive to knock compared to over 3500rpm..

Its completely unwise to disable knock control unless the car is always monitored and the tune is very conservative

Truth is knock is unavoidable, and small amounts are inevitable, in this case there is a problem, whether its due to some noise in the engine, or something transmitting sound to the sensor, to a bad sensor, there is something wrong, and this is probably not the best solution. But as John said, its a workaround.

How did these pre-95 and carburetor guys every tune cars eh?? hehe..

 

I completely understand this, Jack. And by no means am I suggesting to turn off the knock sensor. Ever since I have been on these forums I have always stated that knock retard is THE most important thing to log and understand. And that is knock from the ECU, not just knock sensor voltage like some piggybacks.

The ECU does have filters as you mentioned, too, where knock will be less likely to be picked up at lower RPM and load areas, but true phantom knock, due to say, noisy lifters, will still trip the sensor.

I remember on my old Eclipse. It ran very nicely with DSMLink, but due to the mileage, the lifters were a bit noisy and I would always get phantom knock in ranges of very little throttle and load. I went though extensive testing to verify that this was phantom knock, which it was. I then used DSMLink to ignore the knock sensor under these conditions and the car ran even better. I had 117K on the odometer when I sold it and it was still running great, with 400+ whp all on the stock bottom end.

I don't really see situations like this being that common yet for the Evos, since there are fewer high mileage Evos than DSMs, but to have control over the knock sensor gives the person with the knowledge of what's going on a great tool. On the contrary, though, it gives someone the ability to do a lot of damage to their engine. That is why I was suggesting control over the sensor by other paramaters, rather than simply shutting it off.


Eric

 

In those rare cases, you can set the filters as high as they go inthe RPM range and it should basically ignore anything but an explosion.. hehe..

 

jcsbanks will have to verify whether this is the correct location or not, but here is the identical code from my ROM, which is the 05 ROM, identifier 96940011:

ROM:000273F6 mov.l @(h'D4,pc), r10 ; [000274CC] = h'FFFF8C40
ROM:000273F8 mov.w @r10, r10
ROM:000273FA mov.l @(h'C4,pc), r11 ; [000274C0] = loc_1382
ROM:000273FC mov.w @r11, r11
ROM:000273FE cmp/hi r11, r10
ROM:00027400 bf loc_27408
ROM:00027402 mov #0, r10
ROM:00027404 mov.l @(h'C4,pc), r11 ; [000274CC] = h'FFFF8C40
ROM:00027406 mov.w r10, @r11




Eric

 

If the value at 1382 is &H0024 then I'm certain this is correct. The offset of 400 on the address makes sense as some other values are offset by this much between ECUs.

I like knock control. This was for a car that simply wouldn't make power on the stock ECU so he tried an Autronic. Then when he tried this knock disable he could also make power on the stock ECU.

If your ears are well tuned you'll hear important knock even in the cabin, but most people's aren't. I've spent far too many hours listening to engines through det cans and watching knock sums, knock retards and knocklinks My main issue now is lifting off in time before severe damage is done, not hearing it...

I'm still very respectful of detonation as it did cost me a ring land and a headgasket on my Subaru even though I'd taken every precaution. The event was at very high speed and it hadn't detted there before. The PowerFC had no knock control. One single loud thunk did it. That was one of the early 2.5s and I was pushing it hard with a big Garrett though.

 

Yes, the value at 1382 is hex 00 24.


Eric

 

nice find!

 

Thought this would be a good thread to add this to. Bez has patched a ROM to flash the CEL at a configurable amount of knock counts. Also, he has found a way to eliminate the rear o2 cel.

I already found most of the tables in my 05 ROM and I think I know how to patch it, so hopefully I will test it out soon. I think these are two great features that I have been waiting for.


Eric

 

Is Bez going to share? Is there another thread on this? I hate my cel, but would like to put it to use on showing knock. Also, that rear o2 is the bane of my existance.