Firing Order

OK, another one for you to think about.

Was there a particular reason manufacturers chose 1243 or 1342 for four cylinder engines? I am finding that there are 2 intake valves open at the same time on the engines that shared manifold passages with the 1432 order.

Make that 1342 order

(quoted from post at 17:34:19 12/30/13) Make that 1342 order

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tay away from the tables in Vegas.

ON a 4-stroke cycle engine, it takes TWO revolutions of the crankshaft to complete a combustion cycle. So a cylinder is firing every 180 degrees of crankshaft rotation. Let's look at what happens on an engine with a 1-3-4-2 firing order.

When #1 cylinder moves from TDC to BDC on the intake stroke, the intake valve is open. As the piston passed BDC and moves into the compression stroke, the #1 intake valve closes. At the same time, #3 cylinder has the intake valve opening on its intake stroke. When #1 fires and begins its travel to BDC on the power stroke, #3 is moving up to TDC on compression stroke...and #4 intake valve is opening on intake stroke. As #1 exhaust valve opens and #1 cylinder moves from BDC to TDC on the exhaust stroke, #3 is on its way down to BDC on the power stroke...while #4 is on its way to TDC on the compression stroke...and #2 is on its way to BDC on the intake stroke.

So tell me...at what point do two adjacent cylinders BOTH have their intake valves open?

Not trying to be a smarta**..just trying to understand what you're saying, as it relates to a 4-stroke engine. [On a 2-stroke engine, the intake valves on #1 and #4 would be open at the same time, and the intake valves on #3 and #2 would be open at the same time. But 2-stroke 4-cylinders are extremely uncommon here in the US...so the assumption is that you were talking about a much more common 4-stroke engine.]

I have been following your progress for the duration of your post. I was wondering how or when this would come up. I was expecting you to go direct to the combustion chamber like a diesel engine. You would just have to bore and thread the head for an injector. LOOKS to me like there will be tow intakes open regardless of the firing order. Why it makes for no problem on carburetor equipped engine is only one cylinder has suction enough to pull the air/fuel mix in. Just my thinking. Still want to buy the engine when you get thru playing.

I do not know if I will ever got done.

I built the plate tonight for mounting the coil pack, coil driver transistors and the oil filter. I put them all on one long plate, got it primed ready to paint tomorrow.

I got one of the two bungs built tonight, will finish the other one tomorrow, build an alignment jig and epoxy them in.

Hope to accurately map them cam this weekend.

The reason for the way the cylinders are paired is that it is easier to balance the engine if the center two and the end two cylinders move together.

I need to accurately map the cam, but it appears that the valves are open about 230 degrees cam timing, which is 115 degrees in crank time. I am seeing overlap on adjacent intake valves.

I will post once I have accurate results.