This car is a MB SL 500 with AMG 5.5liter supercharged engine conversion. V8, with dual-sparkplug per cylinder ignition and 3-valve heads.

In stock trim delivers over 500hp.


We tuned the engine and got 401 kW (546hp) and 790 Nm @ 0.7 bar of boost. We are going to make one little session more to try better exaust and check that all of the maximum load sites are tuned for either maximum torque or to prevent detonation (near max torque area, 3500 rpm).

OLD: Yesterday we got the new connecting shaft between engine and dyno installed and did some tuning and tested the strength of the shaft. It's a steady state dyno and we opened the throttle but not letting the engine rev above 2000 rpm, dyno was holding it back. Held up good.

Soo, some mixture tuning and we showed somerpm and boost to the beast. Got it revved up to 4500 rpm @ just mere 0.4 bar of boost (138 kPa absolute) and engine shut down. It was dyno safety switch that will shut it down when coolant reaches 100 degrees. We knew it was faulty because independent temperature gauge showed just 92and so did VEMS's display (calibrated).

Car started at first try on engine dyno last Monday but apparently was too powerful: it snapped the connecting driveshaft between flywheel and dyno after 20 minutes.

It ran very good and smooth.

Here it is on a dyno:


Primary trigger 60-2 configuration (VR).

Camsync: not needed

Ignition - for the 2 * 8 sparkplugs

One 2x2 coilpack and 2 3x2 coilpacks (if you have the 4 pin connector for the 3x2) would be more economical, less weight, and less work to mount. But the owner already purchased 4 2x2 coil-packs - good anyway.

Real wasted spark

Since there are two sparkplugs per cylinder, we could go "full sequential", but that is not a good idea after all => remember that wasted spark automagically uses 90% of the coil energy in the cylinder (full of unburnt air) to be fired. The other cyl, containing exhaust gases (and ions) has much lower resistance so only wastes appr 10% of the energy (in the "series connection" wasted spark circuit).

So if you try to "improve" and drive a given cylinder's 2 sparkplugs by (the 2 outputs of) one coil, you only get considerable reduced energy, 5/9 of what you would get with wasted spark ! Avoid this ! With wasted spark, you get better spark energy.

Wasted spark arrangement also improves reliability through redundancy (if one coil, coilpack powerline, driver, or connection or fuse breaks), than both cylinders serviced by the given (failing) coil are still ignited through the other sparkplug. For the best redundancy, make sure that for any given cylinder, the 2 sparkplugs are serviced from coils from different coilpacks.

Timeline table (firing order 1,5,4,2, 6,3,7,8):

Note that the first 4 and second 4 is exactly the same ignch and coilpack, only the cylx differs:

With the above, enable ign_dualout and use h[2] ign_sequnce like:

Note that logically there is only 4 output-pulses to control (the other 4 is timed the same way). Eg, the 4 stepper outputs would be a good choice to drive (2 each) a total 8 active wasted spark coils (if active coils were chosen... the Bosch motorsport coils are passive).

With passive coils, it is strongly counterrecommended to drive 2 coils from 1 IGBT (to prevent overloading of the) power ign. output, so the ign_dualout option must be configured to drive 2 outputs simultaneously. This has to be considered during mapping... the above example was made with this in mind.

Drive by Wire Throttle

Engine features also drive-by-wire throttle that has separate little motor and could be controlled independently (TPS for VEMS anyway) but owner decided to got mechanical throttle. We'll see, maybe we'll experiment with the MB DBV setup also since it don't need any outside assistance.

The throttle valve for supercharger boost control operates from 12V, and uses high current (max 10A). We'd like to control it from VEMS. Since all ignition and injector putputs are in use, a separate hi-power FET output (with flyback diode inside ECU) is needed => request +1 10A FET-output with flyback in the order note (done).


Engine has gearbox overload protection which means that before every gearshift the gearbox sends a signal to ECU to reduce timing to 5degrees BTDC for 400mS in order to save gearbox from stress. This is called "shiftcut", a standard feature, and implemented through an analog mcp3208 input channel (you have free analog input => fine). Normally shiftcut is configured for cutting ignition (can also be fuelcut).

[engine, gearbox and supercharger system .doc]


Supercharger throttle control schematic .doc]