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New project 8 years after first Vems project:

V12 ITB'S Turbo charged.

The goal is to control a V12 with sequentional ignition and injection.

This is a brief overview of the process with the problems I ran into. Also the solutions are given.

Engine setup:

V12 with itb's and turbo

6 teeth on crank

1 teeth on cam

coils: replaced by VAG COP coils

injectors: high-Z

Ordered a Vems with no options.

This was not good as the info to build up for my setup was not easy to find and some were confusing.

Ordered a 2nd Vems with options:

VR for crank and cam




As Vems got only 8 outputs I wired the injectors in six pairs (6x2). Controlled sequentionally.

Ignition in wasted spark; two coils firing at the same time.

The goal was to control the V12 with one Vems.

This was no go due to the 2stroke mode be obsolete now.

Solution: use of a 2nd Vems.

Needed to place a 2nd cam sensor in order to do so.

By doing this we split the V12 in two 6 cylinder engines.

Build of Vems:

Soldered the LM1815 on the 2nd Vems for the 2nd cam sensor.

Ran a wire from the output of the LM1815 (for the crank) of the first Vems to the crank input of the 2 nd Vems.

The crank signal is for both Vems boards the same.

In order to mount the 2nd cam sensor we fabricated a new cover to hold the original cam sensor and the new one.

The V12 fires each 60 degrees. So the new cam sensor should come 30 degrees after the original one.

This was unfortunately not possible due to the mounting stud being exactly on that spot. So mounted the 2nd cam sensor 90degrees after the original one.

Igntion output stages were also rebuild for use with the VAG cop coils. These need a positive 5V signal to charge/ignite.

Used a small PNP transistor (BC640) to do the job.


When testing the ignition outputs of the first Vems I got this problem:

output 6 (05) retriggers itself after 25msec.

All other ouputs were good.

The same happened with the 2nd Vems: also output 6 (05) retriggered itself.

The solution was a 10nF cap on the +5V line towards the BC640's.

The igntion output needs to be 'inverted' in VemsTune.

When testing the outputs I ran into this problem:

When powering up Vems board the igntion coils are energised for about 4 seconds.

This is way to long to charge a coil so the fuse blew.

Why does it take 4 seconds to invert the output when powering up Vemsboard?? => can this be looked after by the designer of Vems??

My solution for now was building a power on delay relay into the +12V power feed to the ignition coils.

Maybe I can solve this also by adding another NPN transistor in my output stage and choose back 'normal' for igntion output.

Will be tested/tried later.

Software setup of engine in VemsTune:

12 teeth for full engine cycle


TDC reference: 50 degrees (which was not correct, as found out later)

Used for startup a mapping of a Ford Sierra Cosworth.

Live test of Vems boards on the engine:

This was not as hoped although the engine ran.


- Lots of misfires

- No response on the throttle

- Right bank stayed rather cold on exhaust


The first had 2 causes and solved the 2nd problem also.

The 3rd was caused by me (made a mistake).

The first: this was due to bad spark plugs.

After replacing these there were less misfires.

After resetting TDC reference to 30 degrees: no more misfires.

Also the engine responded now on the throttle.

So 2nd problem also solved.

The 3rd was somewhat more hidden.

The exhaust gasses of the right bank where not as hot as the left bank.

We put the cam sensor 90 degrees after the original cam sensor. This implies that the right bank starts at the 2nd cylinder.

I started at the 3rd cylinder...

The ignition occured in the correct sequence only 60 degrees to late. This gave a low temperature of the exhaust gasses of the right bank.

After shifting the igntion sequence it was good.

2 hours later of tuning the engine ran good and revved good.

Also idle was stable.

Now time to go to the rollers for the rest of the mapping.

Questions still remain:

How to setup the Y axis of the VE table for my setup?

From 0 to 100% or from 0 to 250kpa??

I have itb's so for the NA part it's Alpha-N and speed density when boost comes up.

The VE table is 16x14; the igntion table is 12x12.

How to change the ignition table to 16x14??

Boost table is 8x8.

Can this be enlarged to i.e. 12x12?

Problem that remains:

The idle motor is something special.

It is controlled by reversing polarity.

Can this be controlled by Vems?

If yes, how?