V8 3.6 litre Ignition - Electromotive

[rude tim]

Al,
any idea how much Vacuum an omc pulls when the butterflies are closed at RPM?

[fastcat1]

So it’s idle to 1K rpm at about 4 degrees BTDC with a max of 18 degrees BTDC somewhere after 3500 rpm. So in a stock motor there is no load base, temp or altitude adjustment? If there is no timing adjustment could they benefit from it? The reason I am asking is I have a stock 4.0 that I would like to install a lightweight flywheel and this would be a good time to update the ignition.

[rude tim]

I would say that you would want 18 degrees much sooner than 3500 rpm. The thing with 18 degrees is keeping the engine from melting down at rpm. A programmable ignition would be a good investment. You could ramp up the timing into the low to mid 20s degrees in the lower rpm ranges and retard it to 16- 18 degrees as it reaches the top rpm. If you ever start porting the engine and want to get more rpm the programable ignition would be even better. Lots of dyno time or on track testing will be key.

[fastcat1]

Thanks rude tim. I like the Electromotive ignition module solution, but would like it even better if they made a module that can handle 8 cyls. Seems that having a two system solution is adding complexity and cost. I am not interested in converting the engine to FI so a complete engine management system would be overkill. Dose anybody make something similar to the XDi, but that it can handle an 8cyl 2 stroke engine? Has anybody done this?

[powerabout]

I think these guys will do you a v8 in one box.
http://www.emeraldm3d.com/

[fastcat1]

Thanks powerabout. Its my understanding that the V8 is two 4cyl put together. If so, can the ignition system be wired to run as a wasted spark? Being that it’s a 2-stroke will there be enough time for the coil and driver to recover? Keeping the max RPM below 7000.

[BarryStrawn]

Thanks powerabout. Its my understanding that the V8 is two 4cyl put together. If so, can the ignition system be wired to run as a wasted spark? Being that it’s a 2-stroke will there be enough time for the coil and driver to recover? Keeping the max RPM below 7000.

No on wasted spark. That requires two cylinders to be at at top dead center at same time. On a two stroke that means firing them at same time.

[powerabout]

Thanks powerabout. Its my understanding that the V8 is two 4cyl put together. If so, can the ignition system be wired to run as a wasted spark? Being that it’s a 2-stroke will there be enough time for the coil and driver to recover? Keeping the max RPM below 7000.

Its still an even fire engine and yes the short dwell time and halved crank angle is why very few systems can hack it.

[fastcat1]

Thanks BarryStrawn. OK, I understand.

[fastcat1]

What would be the consequence of running a wasted spark set-up with two cylinders that are 180 degrees of crank separation? Would this effect the intake charge? I know that the Yamaha Banshee (2 cylinder – 2 stroke) has a wasted spark set–up. Does, the V8 have a crankshaft set-up where the cylinder are at 180 degrees separation?

[BarryStrawn]

I suppose it might work but just seems a bad idea to fire the plug at 72 degrees ATDC into the intake charge. With no compression it might never light up.

On the Evinrude/Johnson two stroke V8, I think it would work with four coil outputs like a four stroke V8 "wasted spark" but the spark wouldn't be wasted. Assuming a high energy ignition that can provide enough to fire both. Or maybe I've been working out in the sun all morning:-)

[fastcat1]

No on wasted spark. That requires two cylinders to be at at top dead center at same time. On a two stroke that means firing them at same time.

On a two stroke the cylinders have to be 180 degrees of crank separation not both cylinders on TDC.

[powerabout]

if you run wasted spark ( assuming it will work) you are creating an ignition event twice as often, so dwell time cut in half again