Curious Question about Engine Displacement

[Robie6]

ok, maybe we're talking about different things here but you say " you cannot have the window of the crank open while the piston is traveling back down the bore of the sleeve" but isn't 50 or 60 degrees of window timing ATDC when the piston is traveling back down the bore of the sleeve? when your talking induction timing ya should mention ABDC & ATDC & duration to those who might not understand. overlap comes in ATDC when the piston is pushed back down the sleeve by the igniting of the charge & the side intake & boost ports open before the exh. opens thus helping scavage the exh, although a good bit of the new charge is waisted through the exh. even though the reverse pressure wave in the exh. does push some of the charge back in (supercharging) :mex:

 

[HumboldtBlazer]

you guys sure know a lot about engines for sure. I deff just learned more, again great thread.

 

[Robie6]

I'm kinda limited on knowlage cause I dont have a flow bench which is easy to make & I started on 1 awhile back but I ended up making a bong outa it. Ya can't let your friends come over when your doing something serious:mex: :mex:

 

[HumboldtBlazer]

Originally posted by Robie6
I'm kinda limited on knowlage cause I dont have a flow bench which is easy to make & I started on 1 awhile back but I ended up making a bong outa it. Ya can't let your friends come over when your doing something serious:mex: :mex:

I award you 755 Punk Rock points for the last statement. Rock on wit yer bad self.

 

[scottm]

There is significant overlap with any performance engine, and induction timing will extend way past tdc in 2 and 4 s engines. This is because the designers are compromising the engine for high rpm, and because air has inertia. Once the column of air starts flowing into the engine, it will continue to flow, effectively ramming air in, after the piston has reversed.

Put a long extension on your vacuum and turn it on. Then separate the extension from the hose and feel the blast of air that continues to flow out the extension. This is the principal of the "tunnel ram" intake manifold of drag engines.

Designing an engine for higher rpm means longer timing intervals and counting on tuning tricks like headers and pipes, trading away low end torque for top end torque.

 

[Nitroaddict]

Originally posted by Robie6
I'm kinda limited on knowlage cause I dont have a flow bench which is easy to make & I started on 1 awhile back but I ended up making a bong outa it. Ya can't let your friends come over when your doing something serious:mex: :mex:

HA! That sh*t cracked me up.

Alot of interesting posts here. Learned more than I was trying for. So I guess the next question would be -

Since the extreme high end .21's put out as much or more power than the medium powered .26/27's - could someone make a top notch .26 or larger? Or would increasing the bore cause the crankcase to become too structurally weak to support those kind of pressures and rpm's?

 

[scottm]

Sure its possible, but until there is a sanctioned racing class, there is no point. The premium materials and construction needed would make the engine too expensive for bashers.

 

[Bill Hoskinson]

Originally posted by scottm
There is significant overlap with any performance engine, and induction timing will extend way past tdc in 2 and 4 s engines. This is because the designers are compromising the engine for high rpm, and because air has inertia. Once the column of air starts flowing into the engine, it will continue to flow, effectively ramming air in, after the piston has reversed.

Put a long extension on your vacuum and turn it on. Then separate the extension from the hose and feel the blast of air that continues to flow out the extension. This is the principal of the "tunnel ram" intake manifold of drag engines.

Designing an engine for higher rpm means longer timing intervals and counting on tuning tricks like headers and pipes, trading away low end torque for top end torque.

Dead on Scott....