Adding cam sync to VEMS plug-n-play

[four0four]

So, I've been puttering about wasting time adding cam sync to my VEMS install for some reason, figure I'll share some progress here


(I've also kept it somewhat documented here, but I don't pretend that wiki is otherwise active)

Two parts are pretty easy to adapt: VAG 058905161B and Bosch Motorsport 0232103037. I'm using the latter, but I did fit the former previously (didn't finish the rotor adaptation on that one). I'm pretty sure you could fit a sensor to the rear of the cam too, I've seen some 911s do this with a bolt added to be picked up. That does your adapter seal against oil though, so this is easier...


Anyway, VEMS requires a masking (or really, inverse mask - so allowing?) pulse generated by the cam sense circuitry for their "auditrigger" trigger architecture. If you check their schematic this is Q13. This means you can't have an arbitrary phase offset, the pulse needs to be squarely overlaid with the TDC pulse from the reference sensor. So, I stuck a bolt in the rotor, measured up the angle at TDC, and printed a bracket:

camhall_measurement.jpg (376.81 KiB) Viewed 906 times

camhall_firstry.jpg (209.16 KiB) Viewed 906 times

And, well:

shit.png (98.62 KiB) Viewed 906 times

Some help parsing that:

yellow: width of cam sensor pulse, 13.74ms
green: period of cam rotation, 113.67ms
magenta crank rotation 1, 57.87ms
orange: crank rotation 2, 55.91ms
purple: desired shift of cam pulse, 8.86m


Not sure why, but that didn't line up. Probably to do with precisely where along the face of the sensor it triggered, but even that doesn't account for 30 degrees! That's a lot!

Anyway, shifted it by 28 degrees to land the crank TDC smack in the middle of that cam pulse, reprinted (forgot to take a picture), and:

perfect.png (91.02 KiB) Viewed 906 times

Perfect

Just finished making the modifications to the ECU to support this - basically needed to swap some inputs around and solder in a single NPN transistor that masks the TDC signal unless the cam signal is also present. Will test it probably tomorrow, and hopefully document the VEMS configuration differences required (basically just doubling of teeth and rearrangement of the tooth trigger table for now - I don't have a harness in place for sequential inj/ign).

Of course I'll be sharing the models and some general directions once I know it works to...any standard.

[four0four]

OK, I know why it was off by 30 degrees - TDC mark comes way prior to TDC, obviously.

Hooked it all up tonight, seems to work great (VEMS sees 24 pulses per reference pulse). Puzzling over the trigger settings and really wishing VEMS was properly open source...The trigger system is really flexible, but also really....well, more evolved than designed :')

I think this is correct, but I'm going to need to rig up a remote hotwire and get out the timing gun to check some things first:

Screenshot 2024-01-09 143320.png (89.67 KiB) Viewed 839 times

Attached is the STL, since this seems to work. Probably going to iterate on it a little bit to add a removable cap at some point, but I don't feel bad putting this out since it seems to function

[Thom]

Good effort, nice work. I am sure you will experience a smoother engine with sequential injection.
What size injectors are you running?

[four0four]

I imagine so! I'll need to do the "make a whole engine harness" project to go fully sequential, but that's probably next anyway. If I could only identify the alternator/starter connector now...

The injectors are Siemens 110324 ("80 lb"). I had stock, and then briefly Bosch 0280155968 in previously, but quickly ran out of fuel.

[four0four]

So it's been... about a year longer than I thought since I messed with this

But I was playing around this weekend in the garage and decided to debug this a little more without checking my old notes, and it, uh, basically worked immediately.

Turns out all the difference was setting the reference tooth table to (in the 0..3..2..1 order in the UI) 0...18...12...6.

This makes more sense than what I posted earlier in this thread in retrospect, I'm glad I didn't find my notes on time

I also (...in 2024) added a mounting provision for the typical 2x2 Bosch coilpack. You probably need to make custom spark plug wires to use it (or combine 2 sets of whatever Golf set are commonly available on VEMS kits). I have yet to see how it lasts, I'm a little worried about the entire moment of the coil going thru the weakest axis of the print. Probably I'll revise it so that the thread inserts sit down at the point of concern and see how that survives before uploading it anywhere. Here's a picture of what I think is the design I settled on:

sensor_and_coil.jpg (2.43 MiB) Viewed 205 times

[cda951]

Thanks for sharing, and great job figuring out a DIY cam sync setup.

Did you add the cam sync to enable sequential fuel injection? If so, you need to alter the wiring for the fuel injectors (Peep's VEMS PnP harness accommodates the 944's original configuration of a pair of batch-fired DME grounds for injectors 1+2 and 3+4). You'll need to designate an individual driver for each injector to run sequential.

You might already know this, but wasted spark ignition does not require a cam synch, this is only necessary if using an individual coil for each cylinder. I run a similar wasted spark coil using the VEMS PnP setup. Check the attached pic of my coil pack mounting solution (which replaces the cruise control actuator). Bonus points if you recognize which commonly replaced part from another Porsche comprises the mounting bracket .

My original 951 harness was still working well last time I checked, but it is on borrowed time, and I put off doing anything about it due to the pipe dream of doing a 07K swap. Reality dictates that might not ever happen, so I have been considering this harness from the US distributor of VEMS, already wired for sequential injection and cam sync:

https://shop.vemstuning.com/products/po ... 71zbAkDqMw

[four0four]

I added it because I have strange compulsions

I actually wanted to tinker with fuel injection angle, so kinda? And I wanted knock gains to make sense rather than be 50% completely incorrect. IIRC the DME didn't even do batch fire, so this is still an upgrade! But now that I think of it, I believe it makes sense to swap 2/3 - that is, to fire instead of 1+2 and 2+3 1+3 and 4+2, which lets you time the injection events somewhat sensibly (doing this without cam sync makes no sense).

My wasted spark coil is in a very similar location (pending the spark plug wires being made)...Though I didn't use a horn surround? to do it!

I've actually chatted with that guy! I think they started offering it after I started seriously planning my own harness replacement. Even got most of the connectors, minus the alternator and the weird flat one that heads to the dash. Very tempting!

[AudiSport]

I used IGN-1A coils on a self made cam sync housing. Full sequential on my MaxxECU