Efficient Engine Design ???

[greasemonkee]

Originally Posted by bestclimb

What ideas do you have to get timing back to where you are getting peak pressure with the crank 90 past tdc?

This would produce a lot of light under the hood

[bestclimb]

Originally Posted by greasemonkee

This would produce a lot of light under the hood

Whatcha mean?

[gone-ot]

..."glowing" hot metal parts in the exhaust system.

[bestclimb]

Originally Posted by Old Tele man

..."glowing" hot metal parts in the exhaust system.

If he is that lean and not making much horse power loping down the road at 55 it would lack the heat necessary to make metal glow.

[greasemonkee]

Less heat yes, but CFM is the problem (would require a lot of throttle with that kind of timing to produce 20 hp). The same reason 1600*F egt at part throttle does no harm, but WOT at those temps are on the threshold of melting engine parts, especially in a forced induction app.

Geometrically there is little mechanical pressure/energy extraction taking place at that crank angle. 10-20* ATDC is a common window for peak cyl pressure.

If the pressure curve didn't resemble a sine wave that number would probably be different.

[bestclimb]

When I see operations with leaning WOT is very common. WOT rich to accelerate, then lean down to enough horse power to keep you moving at an acceptable speed. At the same time watch the EGTs plummet. At 20 hp he is down around 15% hp egt should be nowhere near the point of melting deposits on the exhaust valves or heating up the exhaust manifold. Unless it's is not running lean enough? Putting the timing into the point where the most mechanical energy is extracted seems like a good way to go.

Please note that I am not trying to argue a point here I am trying to reconcile my knowledge of leaning in aircraft with the possibility of doing so with an automotive system. With an engine with good mixture distribution the bottom threshold for lean is when cylinders start not firing due to a mixture too lean to support combustion and the thing starts missing. At that point the EGTs are up to several degrees lean of their hottest.

on an aircraft engine you are typically running at 50-60% of max rated in that configuration.

[pgfpro]

Whats with the "Other popular topics in this forum... " spam looking thing in this thread and others between post 31 and post 32??????????

[dcb]

LOL, not spam, just the admins experimenting I'm sure

[pgfpro]

Originally Posted by dcb

LOL, not spam, just the admins experimenting I'm sure

I Know,LOL I just had to raz them a little

[pgfpro]

This is what I built my engine design around.


This is what a normal standard engine would look like. Since I'm running a lean burn engine now I need to start the ignition earlier so I will still have max pressure to take place around 10-20* ATDC.