(X) or (H) PIPE

Would be interesting to see some dyno testing to see how much BSFC changes with the typical injection mode and then change to End-of-Injection mode.

A few scientific studies found that, with the engines that they tested (Zhai and Lai 1995 and Berkmuller 1997), that an open valve injection strategy provided an average of a 4.3% richer air-fuel mixture around the spark plug and then the study below took that a step further and tested a special variant of Open Valve Injection on a 4 valve engine in which they start injection only through one valve and then add the 2nd valve later and they managed to extend the maximum lean burn threshold of the engine from 14:1-17.5:1 @ 1,000 RPM and low throttle positions, and from 12:1 to 17.5:1 at 1,500 rpm and 1.5 bar cylinder pressure.

-No way a 23 deg 2 valve SBC matches that, but Bosch seems to pretty categorically state that OVI DOES extend the lean burn limit as a general rule, so I'm hopeful that SOME highway cruise improvement is possible by pushing lean burn to it's limits.

I have to think the more overlap the cam has, the bigger the BFSC gains you stand to make. A circle track engine with it's huge overlap and super fast headers would be close enough to an ideal candidate, IMHO, not that it could ever be used in a race...

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Id suggest you keep in mind that theres a good deal of data that proves headers and cam timing and port flow velocity/cylinder fill efficiency,
can all be designed to match and enhance the engines power output at a specific rpm level/rpm range,


example, from personal experience, using crower stack injection

and that with most engines using premium octane fuel, you'll find that about a 12.5-13.1 compression ratio, and MATCHED TO ABOUT A 12.4:1 AIR/FUEL RATIO, YOULL MAXIMIZE THE ENGINE TORQUE CURVE, now obviously you can select, modify or tune the components selected,(stack length, cam duration, LSA, port size) but at about 5500rpm-7000 rpm you can maximize peak horsepower in a big block chevy with a 4,5" bore and a 3.75" stroke (roughly 478 cubic inches) and with a properly designed long tube header power in the 1.7 plus hp per cubic inch can be achieved
700 ft lbs and 800 hp plus can be had with a decent engine combo
and yeah the headers used has a very noticeable effect on the torque and peak hp,
yes mileage is not the main concern ,but the sound and feel of a stack injecting car, is amazing!
just adding 4"-6" to the collectors made a difference in the seat of the pants feel of the car during testing.
and yes adding an Y pipe, with a common 4" /36" long curved merge collector, exiting just in front of the drivers rear tire with those open headers further increased and broadened the torque curve, or using an X pipe, with dual 3.5" exhausts when we used dual exhausts both helped broaden power, yes I love dual side exit exhaust exiting just in front of rear tires,
yeah you can use a 4". 4.25". 4.375" or 4.5" stroker crank & rod assembly to build larger displacement engines to increase potential power

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here's an interesting video, but keep in mind the engines tuned to work with the full exhaust, and benefits greatly from use of open headers,
but not with the exhaust cutouts, on the exhaust system, closed,
while Im sure the cut-outs cost power in that configuration, the result might be far different if the engine was tuned to work with the exhaust cut outs open, rather than with the exhaust system in place as the closed cutouts caused minor turbulence, while the open exhaust cutouts surely changes the fuel/air ratio needs, probably the ideal ignition advance curve, carb jetting, and cylinder scavenging, yes the open exhaust cutouts sure helped , almost duplicating open headers to some degree.
sometimes its not what a video shows as much as what factors it ignores thats critical.
the result might be far different if the engine was tuned to work with the exhaust cut outs open,
The difference was only 833 HP to 826 HP from headers only to exhaust system/cut-outs open. What were you expecting to happen??? Seems pretty close.

The cut-outs looked like they were attached to the end of the 18" collector extension, so the exhaust gases had to travel another ~6-8 inches.