reverse engineering the mpi
Turbo Mini Forums

jsut had a wee thought, was thinkign last night how to reverse-engineer a map. so i could see (for example) exactly what my rover ecu is doing. and came up with a disgustingly simple solution.

either do this onthe engine or make a "stimulator" a-la megasquirt to run the ecu.

then get a 2 channel oscilloscope hook one channel to somethign that stayes fixed WRT crank angle (for example, the VR sensor) and has a refference (missing tooth) . then simply hook the other channel to whatever you want to monitor, be it injector or the coil. and you can monitor dwell, injection time, spark angle, injection event "angle" against RPM . would be tedious to extrapolate a complete map from a running engine. but do-able. would give a good insight on how the rover setup works.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

I 'used' to have access to a 4-channel digital trace recorder that would have done it - but no-one in the manchester area wanted to lend me their MPi for a few hours to do some basic testing (back in the miniclassic days).

I might now have access to a trace-recorder again, but No MPi (once again).

It sucks.

What's a trace recorder.

I've currentlt got my hands on a 16 ch 80khz AIT recorder. Would deffo record the data, analysis could take awhile though.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

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digital trace recorder couldnt be used with a VR sensor though, only a hall effect crank sensor. and i believe the mpi's are VR sensor'd. if you loose that then you loose the invaluable reference to crank position. cam sensor on the mpi is also a VR sensor.

infact, you could use the soundcard ona computer for this. its accurate enough in the time domain (the important bit!) .. alas i dont have an MPi either

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

I've got an MPi crank sensor on my mini and have recorded data just fine!

fair play :) the Vr sensor outputs an analogue signal though, depends on teh signal conditioning in the recorder whether it'll take to it or produce alot of crap!

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

thats a project I have on the back burner....

Alex

AlexF

Ah, we'll have the answer before too long then. LOL

you've got a big cooker alex

You know me dave....

but good thing come to those who wait.

In my defense I did buy an SPi purly to do this too before moving on to MPi.

Alex

AlexF

Hi,
You may well already know this.... the MPi toothed wheel has 2 missing teeth, 180 degrees apart. I don't know if this would have any bearing on the ECU being able to calculate injection timing....
Also, does anyone know if the MPi cam has any overlap on the paired inlet valves?
Cheers,
Gavin :)

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MPi cam is actually quite a spritely cam. It has nothing special done on the overlap - noting at all...

Hi
Thanks Dave. I'll have to see what it's like with boost applied then!
Cheers,
Gavin :)

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Gavin,

For port injection, the minimum you need to have is a single trigger per rev so that you know when the outer cylinders are on the intake stroke. So without a cam input, you won't be able to time the injection with the MPi wheel because there is no way to know to which cylinder a missing tooth is related.

MS2 does not currently have a cam input and MS1/extra has one but cannot deal with the MPi type of wheel together with a cam trigger.

However, if you want to do the piggyback solution we talked about on the other thread, then you could use the MPi wheel because for throttle body injection you don't need more information than one trigger per cylinder per engine cycle. You may need to enter a configuration into MS to fool it into thinking that it's injecting fuel for a 2-cylinder engine with a 18-1 crank wheel but it should work.

One solution would be to somehow add a tooth on the wheel so that you have a 36-1 wheel but I don't know how you would do that. This would allow you to use the upcoming version of the siamese-port code. However, since I'm planning to add a cam input in a later version of the code, I'll make sure that the standard MPi wheel can be used for timing together with a cam trigger. I'm sure that it will be useful for a few people.

Jean

http://www.jbperf.com/

I suppose another way of doing it would be to leave the MPI trigger alone, and then machine the crank dmaper pulley to give the piggyback ecu its own 36-1 wheel to look at.

Hi,
Tom, you're right on my wavelength!
However, I'm also thinking further ahead.....
ATM I'm going to try the piggy pack on the standard MPi engine, with 10 psi, and a Turbo verto.
Next year I want 1380, 10psi. That'll mean pre verto, with no room for the Mpi trigger on the flywheel. I was thinking about 2 sets of teeth and sensors on the crank pulley, but Jean has just solved that one for me! :)
Also have you seen the MPi pulley, Tom? Will you be able to machine it?
Cheers,
Gavin :)

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I haven't seen one, can you do me a drawing of it with some dimensions on and then I can have a look at it properly?
Cheers.

MPi 36 -4, SPi 36 -2



http://www.msefi.com/viewtopic.php?p=103486#103486

The document telling you how to reposition the reluctor ring

http://www.minispares.com/Article.aspx?aid=79

Edited by Sprocket on 30th May, 2006.

Hi,
I'm sure there's only 2 missing teeth on my MPi one! That post on the MS forum is about K series engines?
I think there maybe just enough room to machine the MPi pulley, but I'll have to measure it up and see what Tom thinks.......
Cheers,
Gavin :)

Edited by Bat on 30th May, 2006.

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If you can give me some dimensions I'll draw it on CAD and then see what can be done. If there is a decent amount of balance weight on the outer edge of the pulley it should be possible.

Hi,
OK, I've been down the stores, to check....
There are indeed 4 missing teeth in two 'pairs' 180 dergrees from each other.
I looked at the crank pulley, and the area to machine isn't as wide as the end of a ford crank sensor. So it looks like another approach is needed..... KAD?
Cheers,
Gavin :)

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If you look at the end of the crank sensor, although it is 14mm O/D, it has the actual pickup encased in the centre, this is approx 5mm diameter.

I personally think it could work, assuming there is enough width on the pulley.

How many teeth does the MPi cam wheel have and what configuration do they have?

It seems to me to have some redundant information since a single cam trigger together with the crank wheel will let you know everything about where the engine is in the cycle. Of course it might take up to 2 revs to sync everything up so I assume that's what the cam sensor provides to allow faster starting.

By the way, the MPi wheel with the asymmetrical tooth pattern gives enough information for the upcoming MS2 code. Of course, there is a need to implement the decoding but that would give another option for an MS2 port injection setup.

Jean

http://www.jbperf.com/