Has anyone yet built a complete replacement for the Jetronic?

[wmax351]

I only ever did fuel only. The stock system is kinda unique, I had discussed methods of dealing with it on the forums. In general, it is a method that is hard to implement with the microsquirt system.


I had been looking at making a toothed wheel and hall sender setup, I've got a solidworks file I had made for it, attached below.

[Arktasian]

That is generous of you, I can have a wheel cut through my Son who has access to CNC equipment ( my lathe and milling machine are analog)
However, had you researched the crank mount location (my favourite by the way) to know if that option is code supported? I ask as the current information suggests only one 3 cylinder engine format supported with code and that utilizes a 4/1 cam driven wheel and sensor arrangement.
Although this is not generally felt to be as uniform as crank derived signals, I suspect the K75 cam gear train is pretty solid and doesn't create a lot of slop for a uniform rotational reading.
Regardless, if that is the only code supported setting then that is what I will start testing.

[wmax351]

If you have all that available, it should be a cool project.


I had done research on the crank wheel support, and the problem is that the crank wheel on a k75 is actually essentially a 3-1 wheel, with 2 hall sensors allowing it to impute the missing tooth without having to wait. I think the stock bosch system uses the point where both sensors have a rising or falling edge (forgot which) at the same time to sync with (i think) cylinder 1. I considered using some logic circuits to convert it to an ersatz 3-0 and 1 tooth dual wheel setup. But I'm not sure you could code it to be accurate with the megasquirt methods, since the megasquirt really depends on counting the teeth to sync the spark.


One other option I considered is to make a timing cup that fits in the existing location with more teeth. One of the guys who did a K75 turbo did that, and used an optical sensor for what I think was a 12-1 wheel. I also considered modifying a stock K100 wheel as a starting point with the stock hall sensor, but those sensors aren't capable of using super small teeth, and the most I could have done was probably a 6-1.

[Arktasian]

Appreciate you taking the time to discuss these "esoteric" developments.
In the short time since I've started to research the K75 and how it might co-exist with an MS based control unit, I have determined that there does appear to be only one 3 cylinder engine type supported by existing code and tone wheel choice. That is the Daihatsu 3 cylinder with a 3+1 Cam trigger.
This I understand is a relatively thinly if at all tested format so I may be paving a pathway in more ways than one.
Because it is so difficult and deflating to test components on a running bike (or one that won't run properly or quits on the road), I will utilize the "JimStim" stimulator rigged on a test bench with ECU and lap top to prove sync, then I figure the best way to replicate a 3+1 tone wheel & VR sensor behaviour is to mount them to a dummy chain drive sprocket (introduce some jiggle) and see how she behaves at various rpm's.
More MS manual review in order, I'll be posting about things over on Project K Bikes

[wmax351]

I'd definitely stick with crank based signaling, rather than cam. If you want to do full sequential, you can use a hall sensor in the valve cover, and pick up one of the cam lobes for synchronization.

[Arktasian]

You won't hear anything but agreement from me on the wisdom of the crank location for a tone wheel plus utilizing higher numbers of teeth to improve resolution and accuracy.
However (& I'm currently raising these points for discussion and debate over on MSExtra forums) there is a significant lack of 3 cylinder tone wheel and code options for ignition control ( & more importantly, sequential ignition) so we'll see what facts present.

[wmax351]

One thing to keep in mind is that you can treat it as a 6 cylinder wasted spark setup as well. It's a little hacky, but opens up some options that otherwise aren't there.

[Arktasian]

I am no stranger to "hacky" contrivances - but have developed a safety net overview stance to redo anything that can be significantly improved, simplified, or take advantage of previously proven design.
Saying that, I've scored an earlier firmware version from a bloke in Norway that recognizes a 36 tooth crank wheel while doing wasted spark for three coils. I think once I'm back home I'll set up a lab and test that and a couple of other formats. I wish to nail the ignition component design befor I start focusing on other project aspects ( like turbo mount and manifold and plumbing items.)

[Arktasian]

 :oops:   This will prove to be easier than I had anticipated (misinterpreted tech advise over on the MS forums into believing there were limited tone wheel modes for 3 cylinder engines, nothing could be further from the truth and a bit of discussion over there has revealed top level options).
I will impliment sequential ignition and fuel injection control, with a single toothed cam sensor, and a 36/1 tone wheel and VR sensor on the crank shaft.
I'll be posting updates and detail on a post I have going on over at "Project K-Bikes" entitled "95 K75 on Mod Table".

[wmax351]

:oops:   This will prove to be easier than I had anticipated (misinterpreted tech advise over on the MS forums into believing there were limited tone wheel modes for 3 cylinder engines, nothing could be further from the truth and a bit of discussion over there has revealed top level options).
I will impliment sequential ignition and fuel injection control, with a single toothed cam sensor, and a 36/1 tone wheel and VR sensor on the crank shaft.
I'll be posting updates and detail on a post I have going on over at "Project K-Bikes" entitled "95 K75 on Mod Table".

Awesome! Are you going to be doing stock MS or MSextra?

[Arktasian]

I like MS Extra as it has lots of additional control for things like blow off valve & wastegate as well water meth injection. That means utilizing every spare circuit on the little MicroSquirt but has been working well on the R100RT. The last chapter I suppose would be a venture into Canbus control (also available)
So, basically enough to keep me entertained for some time 😎