Compression Ratio and Boost Query

I don’t wholly disagree. But, I do think a properly setup blow-through carburetor can deliver fuel just as efficiently/safely in a drag/wot situation. I do agree that the injection, in cooperation with the ECM and the sensor compliment working in unison gives a huge safety margin. Just not FI alone.

I got to thinking the main reason may be low speed cylinder pressure.

I agree in part. I don’t think its the injection alone though. Its the injection and timing being controlled by the compliment of sensors via the ECM.

I got to thinking about it last night, and I think the primary difference between a 4G63T and an LA handling boost is low-speed cylinder pressure.

The eclipse made 14psi from about 6000-7200 rpm. I don’t think it made boost at all until at least 3800 from a cruising WOT pull.

My point is. That 318 will be lucky to reach 6500 N/A with those heads and springs. To have useable boost, it will need to come on lower in the rpm range. That means more pressure during less rpm = more dwell time = more heat soak. I suspect that is the primary limitation/advantage here. There isn’t much dwell @7200rpm compared to 5800rpm.

If you are building a 225, this is going to be something to consider. I don’t think the one I had would exceed 4200 rpm. (But it was a little sick)
A cam with a very late intake closing might help. But.. it might cause other issues with boost?
While all that may be true, a carburetor can never manage fuel and ignition like a computer.