Knock Sensor

[boostedmini]

Hi all,

this might be a silly Q but can you wire in a knock sensor to the MJL system?
as some of tou will know it is hard to hear pinking/knock on a a series at 15psi and 3000rpm upwards.

Grant

i now have all components just have to make some brackets to mount the VR, coul pack, ign module and make the harness.......

[brentp]

Hi Grant,

Knock sensing is a sophisticated problem to solve, as evidenced by companies that offer comprehensive knock sensing solutions like <a href="http://www.jandssafeguard.com/">J&S SafeGuard</a>.

There is some good information on the Megasquirt website discussing knock sensing using components sourced from General Motors:
<a href="http://www.megamanual.com/ms2/knock.htm ... ock.htm</a>

So the short answer is that the current version of the MJLJ firmware does not support knock control. However, the firmware could be modified to accept an input from a module like the GM unit described above, and then act upon it, typically by retarding the timing in some fashion.

If you read the Megasquirt documentation you will see that the GM module and sensor is tuned a specific way, likely optimized to work well on the GM engines it was designed to fit on.

The question is, does your boosted A-Series knock signature sound like the GM's V8? Is it close, or way off? Is it similar enough to realize *some* benefit? Obviously the same goes for all engines. I'm running a turbocharged Toyota 4AG that would certainly benefit from knock control; you bet I'm interested in such a thing.

So after that long answer- There will be knock control of some sort for either this version of MJLJ or an upcoming version.

(Adding to the FAQ)

Thanks,

[4600cc]

I cant wait for MJ to support knock sensing.

On the right, in top 5 most recent files, there is knock.zip, which describes how to make a knock indicator. It suppose to buzz and light up when knock is present. It was taken from a website which is known for a lot of very accurate information about fuel injection, so it should work..

One might even go as far as integrating that unit into megajolt, in a sense, it is similar to GM's knock sensing module.

You can assemble this unit on a piece of cardboard, and connect everything using wires.

[boostedmini]

Thanks Guy's.

I am also pretty new to this stuff, so i have a lot to learn, i have not even downloaded the ECU running program and see what is in their.

i will have a lot more Q's to ask soon enough.
can you tell me the RPM increments you can adjust the timing and is it easy to work out and say at 5psi @ 2500 rpm i want22 degrees etc or is it just in psi increments.

i guess i need to open the program and see for my self

i am just a little confused thats all

Grant

[brentp]

Hi Grant,

It should be pretty easy to get started. the Ignition map that is included with the default firmware has a fairly 'safe' map that works for boosted as well as NA applications.

The controller allows for 100 RPM increments for the RPM axis- and 0 - 255 KPa (for MAP sensor) or 0- 100% (for TPS) on the load Axis. It's just like a spreadsheet table. You can download the software and it will let you edit a an Ignition map without being attached to a controller.

Hope this helps,

[Ivan]

When you want to go to the limit you need knock sensing no?
I'm running a safe map that works well, but I'm sure there is more
to gain here!!!
The only thing holding me back is that I'm not ritch and can't afford to
blow a engine.
Ok I'm racing and there is always the the risk of blowing up the engine.
Normally when you have knock sensing to change the ignition you must be safe
to explore for the limit.

So hurry up the saison starts in 2 months

[MartinM]

If you can detect knock outside of the MJLJ with a sensor that has a suitable output characteristics (I'll leave that to the techies to work out) then why can't you connect it to the Option input on V3.1.0 software use it to switch the maps:
- sensor says "no knock" = map 0 = normal map
- sensor says "knock" = map 1 = knock map, which is normal map - (say) 3 degrees on every bin.

Crude, but might work...

[brentp]

Brilliant!

However it does take some CPU time to switch back and forth between the maps, and the MJLJ won't respond to the EDIS module for a few ignition cycles. It doesn't seem to be enough to make the EDIS module go into limp home mode, however.

So when you're racing aren't you *expecting* your engine to blow? If you can't afford it you better run some pretty conservative settings! Of course that doesn't account for driver-error, like mechanical over-rev- ask me how I know about that.

[Ivan]

Sorry to hear that you already blown some parts!!!

Anyway if this changing maps could work I don't think it bad for the engine
when it takes some time to proces, it probebly saves your plant !!!
When racing it takes two or three seconds to have alot of work to rebuild.

I know that this is the way to go for everybody to fine tune the thing.
Not everybody has a powerbench and testtrack.
My problem is that i can't drive the car on the road, being a race car.

I hope this changing maps works for the older type mainboard.

See yah