lost sync at 1700 rpm, MS3/MS3X

[MS2tester]

since you now completly excluded the ecu as the cause
would it not be best to look at the VR sensor and VR sensor wiring as the cause?
perhaps even the trigger wheel?

[benjaminearle]

Yes, we know the sensor and wheel are creating the problem - just trying now to mitigate it. Stock sensor in stock location, wheel is what it is but is making that little overshoot error (amplitude proportional to rpm, like the rest of the waveform). Just looking for a solution to the overshoot/back emf/whatever is happening during the missing tooth.

[MS2tester]

by that i mean maybe something is broken in your vr sensor
i can,t imagine other people having so much trubble with a VR sensor

[MS2tester]

you might just wanna try out a hall sensor
http://www.conrad.nl/ce/nl/product/5036 ... view1&rb=1
simply hook it up to your VR input

[benjaminearle]

The car owner doesn't want to use a Hall sensor (from experience - too delicate) plus the trigger wheel setup is based on the sensor's ability to distinguish between ferrous and aluminum materials (the "wheel" is a band of punched holes wrapped around an aluminum clutch adapter) - a hall might not have sufficient relief in the the wheel to adequately "see" the tooth edges.

[24c]

BTW, a Hall would easy see the ferrous material. The smart money would use a discriminating or gear tooth version, and a GM pattern part is around $10.00.

Anyway the Zeal board should clean things up, but personally I'd use a jbperf.com VR conditioner, they are rock solid, and have a better chip in them.
Have you measured the peak to peak voltage? How good are your punched holes? Not sure why you'd get "overshoot", but you know voltage is proportional & increases wrt rpm with a vr. You said in an earlier post you increased the resistance, and it moved the RPM limit higher, so did you go higher still with more resistance? Have you tried a variable resistor? Too high, and you won't get enough voltage to detect low speed cranking.

Good luck
Mike

[MS2tester]

can you post a picture of your current trigger wheel
in the test set up you made the missing gap looks like an egg shell shape but it,s hard to see
not saying this is the problem
but it would justify a second look
and maybe machine a more definit end to the teeth ?

[benjaminearle]

Actually the test setup is a completely different wheel for a front mount application. We came upon that missing tooth design after reverse engineering from the desired single, sharp zero-crossing sine wave that we're after. The wheel you see in the picture works immensely well - nice, sharp zero cross - no flat-ish spot, no need for a trigger level setting other than zero crossing.

Here's a picture of the stock Audi flywheel/sense ring.

A8_Flywheel.JPG

Now imagine that ring wrapped around a solid aluminum core (clutch carrier).

[MS2tester]

and you don,t have the room to put a ring version of the tooth wheel you designed on the aluminum clutch?
maybe the steel from the sides is messing with your VR pickup
the original system uses the VR sensor you are using with the hole ring you are using?

[benjaminearle]

1) Not really practical. The punched hole version was fabbed by water-jetting holes in a strip of steel, bending it into a circle and welding it into a hoop. That was somehow attached to the clutch mass (i wasn't there but it involved welding). Any different design will be placed on the crank pulley. Maybe soon.

2)Shouldn't, no more steel than in the stock setup

3)Yes, we're using the same VR sensor (tried 3, It's not the problem) in the same location on the same size and style steel ring. Only difference is that there's the aluminum clutch adapted in the middle - and we're using MS3/Zeal for conditioning the signal.

We're imagining that the Audi computer has a multi-stage circuit that has different trigger levels based on input frequency (sort of like what we thought the Zeal board did) and is well sorted out by people in lab coats getting paid. We tend to wear jeans with stains and it's late at night and we're doing this for free.

[MS2tester]

If you tried 3 sensors it safe to say that is not the problem ;)
You say it, s a strip of steel around a aluminium clutch wheel
How thick is this steel band and is the aluminium clutch wheel conductive?
The idea being that the vr sensor starts to work as a electro magnet creating magnetic fields on the surface
Of the aluminium inside the missing hole messing up the field and there for the signal inside the vr sensor
Other than that out of ideas

[jsmcortina]

Possibly eddy currents?
http://en.wikipedia.org/wiki/Eddy_current

James

[benjaminearle]

Well, we seem to have it running now - took the Zeal circuit out and added back the 23k resistor inline with the VR incoming signal. Not sure if we're getting all 7000rpm out of it but it's driveable from cranking to at least 5000 and we're starting to tune from there.

We started with the wizard values for AFR and VE using stock 335HP@5000rpm/320Ft-Lb@3500rpm. That seems to be working pretty well - ran open loop and watched the correction factors (all under 5% after letting Auto Tune run for 10 min or so and smoothing out the peaks and valleys).

Spark is another issue altogether. There's no wizard for starting spark table. Where do you start? I'm not sure where the current values came from and I know that teh surest way to nuke this thing is to spark it to death.

Suggestions? Come to the Mitty this weekend and you can look right at the laptop and see exactly what this awesome V8 got shoved in the middle of.

[benjaminearle]

Also, I think we're going to try and reverse engineer the drive by wire throttle body from the Audi. Anybody built a good circuit for that, including feedback from the TB?