Why does the 4G63 fire 1/4 and 2/3 instead of an even stagger, like having 1 cylinder fire every 90 degrees of crank rotation?

PS I only have a basic idea of engine mechanics, go easy lol

 

It's called wasted spark.

4 strokes of the Otto cycle are...
Intake, compression, combustion, exhaust.
If you ignite the mixture (end of compression cycle prior to TDC) in cylinder 1, you'll be attempting to ignite an inert gas mixture on the exhaust stroke of cylinder 4 (doesn't do anything) This happens back and forth for 1&4 and 2&3 for wasted spark applications.

Interesting tid bit that I learned last week...
Evidently the stock evo ecu injects via batch fire(two cylinders at once) and sequential(one cylinder at a time) depending upon the conditions.

 

For balance the engine has two pistons going up and two going down. Of the various combinations possible, this works the best for a straight 4.

 

my bad I misunderstood the question.

 

its cheaper than COP ignition because only 2 coils are needed instead of 4

 

This makes sense, suppose it should have been obvious....

So I was reading and I think someone posted a relation to I4 cars and bov flutter being an issue. Is this caused by the way the cylinders fire? Instead of a nice steady boost in the IM at inboost/part throttle, there is an issue with there being some boost, then when 2 of the cylinders have an intake cycle the IM goes into vacuum, then back into boost in the IM before the other 2 cylinders start their cycle.

Am I on track with this? It makes sense when I visualize it.

 

No that's caused by an oscillation of the valve. Think PID control... too much Integrator. Just like that.

 

Can you explain further?

 

It has something to do with the pressure differences in the manifold where the vacuum line attaches to the DV/BOV and the pressure in the boost tubes themselves. This pressure difference causes the valve to partially open then close rapidly as the changes in pressure from the manifold cause the valve to crack open then shut again.

At least this is my understanding of it.

 

Your spring in your bov has feedback (boost/vacuum signal from IM). When the pressure differential is high enough from your blow off valve to your intake manifold (read vacuum) the blow off valve is lifted off it's seat allows the pressure in the charge pipe to be vented or lowered.

If this is done at the right amount it lowers the pressure differential low enough that the valve closes again...and then quickly builds the differential in pressure...venting...closing...building...venting. .. and it does this oscillation at a high enough frequency that we consider it flutter.

In electronics we would apply hysteresis to the valve/switch and make it toggle based on time decay or a threshold value. The threshold value method is what Dejon Tool does to their Gus Mahone modded 9 bov's with a Hobb switch and a 3 port solenoid.

 

Ok, that makes sense. What about a regulator that will only open once the vacuum level has reached a certain value, say 12"hg, such as one of these? http://www.poweraire.com/vacuum-vacu...FR8RagodTXZyuA

 

Bad idea as the compressor wheel would flutter when boosting since the DV/BOV would need to open during a pressure difference instead of actual vacuum.

 

Even at part throttle?

 

Interesting questions!! I like this kind of curiousity

 

There's only one cylinder on the intake stroke at a time. The other downward moving cylinder is on the power stroke. This is why waste spark ignition works: one upward moving cylinder is on the compression stroke and the other is on the exhaust stroke. The coil sparks the compression stroke and the exhaust stroke.