Audi 5-cylinder engines with triple trigger

[mickeymarrows]

That's the crank signal James, I ran it through the MS circuit just as an experiment, I didn't really expect it to work. I'd run it through an LM1815 if I could find my divider board, but it is evading me at the moment

That said, if its not possible for Jean to reprogramme the divider chip its pointless me proceeding further

[mickeymarrows]

I've built the OR gate using a 4001 NOR chip as Eric suggested. I've taken the signal out of the crank 1815 and combined it with the cam signal, then into another NOR gate to invert the output (effectively an OR gate), then through the relocated R12 and into Jeans chip...

[mickeymarrows]

This is the output from the rpm lm1815 and the output from my OR gate. Its difficult to count, but it does appear to be 270:1

How does it look to everyone? Does that look right?

[mickeymarrows]

Anyone?

[timmy2.3cabriolet]

how did this set-up pan out on the 10v 2.3 5 pot audi engine ?? info is so hard to find on tuning of these engines . help me please , i really dont want to buy a £500 7 psi electric motor .lol

[elaw]

Anyone?

Doh! I was out of town when you posted this, I'm not sure if I didn't get a notification of the topic reply or I just forgot...sorry!

I see in your other thread that you modded the cam signal to make this work. I'm glad to hear you got it working, but just for future reference I can think of a few alternatives.

There's one thing that confuses me about Jean's divider code. I can easily understand the difficulty in suppressing an output "tooth" when input tooth #270 is reached, as the code presumably uses an 8-bit counter and an 8-bit counter can only count to 255. But it seems to me a simple fix to that would be instead of counting input teeth, count *output* teeth. Once such a counter is set up, you write code such that if the counter value is 0 or 45 the output tooth signal is suppressed. Unless I'm missing something, that would do what's needed.

There's also another approach that could work, although it has a couple of drawbacks. It's actually what I did when I first started this adventure, and I can attest that it works.

Basically what Jean's divider does is simulate a missing-tooth crank wheel, with the timing position of the (synthesized) missing tooth being based on the signal from the pin VR sensor.

But Megasquirt does not necessarily require a missing-tooth crank signal. It can work with a crank wheel that has no missing teeth, as long as you have a cam sensor. In that mode, the MS determines the crank position based on when it receives a trigger edge from the cam signal. For more info on that mode, go to http://www.msextra.com/doc/ms3/trigger-wheel.html and look under the section titled "Non-missing tooth crank wheel with one cam tooth".

On the Audi, the above is not as simple as it seems. You still have the issue of the flywheel having too many teeth for the MS to handle, so you need some sort of divider circuit to reduce the number of "teeth" the MS sees. And here's the best part: the divider circuit needs to be synchronized with the pin signal, otherwise your timing could be off. It's a little hard to explain, but suppose you build a divide-by-3 circuit to simulate a 45-tooth wheel from the 135 teeth on the flywheel. The problem is, each time you start the car the flywheel will be in a different position. The divider will always start counting at 0, but there's no way to know which flywheel tooth that represents. So every time you start the engine, the timing will either be correct, off by one (flywheel) tooth, or off by two teeth. The solution to that is at power-up, hold the counter at zero until the pin VR signal fires. Then it will always start counting at the first tooth after the pin.

If anyone's interested, I actually designed and built a circuit that does the above. It's nowhere near as elegant as Jean's... it uses nine 14/16-pin chips, but it works.

And there are a couple of drawbacks to the non-missing-tooth crank wheel setup. First, the Megasquirt cannot achieve "sync" (knowing the engine position) until it sees an edge of the cam signal. So the engine can potentially take 2 revolutions or longer to start.

The other potential issue is that if the cam signal edge is near one of the "crank wheel" signal edges, slop in the cam drive may cause the two to overlap which is a huge problem.

[elaw]

how did this set-up pan out on the 10v 2.3 5 pot audi engine ?? info is so hard to find on tuning of these engines . help me please , i really dont want to buy a £500 7 psi electric motor .lol

Um... it works just fine? For me, and several other people running 5-cylinder engines (10v and 20v, from the perspective of the trigger setup it doesn't really matter). I've got a thread here: http://www.msextra.com/forums/viewtopic ... 04&t=40690 with some details, and links to build threads for my two cars on Motorgeek.com.

That's with "Jean's divider board" - a special board made by Jean Belanger of jbperf.com (racingmini_mtl here) that processes the Audi VR signals so the Megasquirt can work with them. MS3 also has a "tri-tach" mode built in that I've had some luck with, but there were a few hiccups so I went back to using Jean's board.

The above is not meant to say it's just "plug it in and it works"... it can be a somewhat finicky setup, and sometimes some tweaking of component values is needed to get it working. But I've been driving my Audis with that setup almost every day for a couple of years now, with very few problems.

[elaw]

Still on my TODO is to allow Eric's existing wiring with the triple-trigger code to make it easier to debug.

James

Hey... has there by any chance been any progress on this?

I've actually switched from VR to Hall sensors in my setup and would be interested in seeing what results I can get with the tri-tach code.

[jsmcortina]

Nothing yet. I might have to do a special one-off for that. Allowing the tach-in interrupts to be swapped around is a bit tricky as some are handled by the XGATE co-processor and some by the main CPU.

James

[savagerocco]

I have been putting this off for way too long, but I have a stable test setup on my car. I still have all the stock crank sensors on my car ran over to passenger compartment, I am planning on hooking up a few adaptor boards and tweak circuits till I get a good pattern while the engine is still running on the other ms3 and the 60-2. I got frustrated trying to get a good signal while only cranking the motor over.

[mickeymarrows]

I should point out that I now have Jean's board working on the V6.

The build is pretty much exactly as Erics BOM/Schematic. The changes needed are as below:

The camshaft position sensor has had a second window added so that it produces a signal every 360 degrees of crankshaft rotation.

The signal from the Hall circuit is fed, via a SOIC-23 logic inverter, into a SOIC-23 AND gate.

The output from the VR2 LM1815 is also fed into the SOIC-23 AND gate @ R12.

The output from the SOIC-23 AND gate is then fed to the CPU. This gives a TDC signal every 360 degrees/135 teeth as per the flywheel pin on a 5 cyclinder.

The injectors are then rewired at the ECU to be bank fire (factory wired as sequential).

I'd like to thanks Jean, Eric and James for all thier help in getting me to this point. With Tunerstudio set to toothed wheel, 45-1, I get perfect sync every time.