Re: intake manifolds
Your pressure drop is because your are taking more air from the SC which means it output pressure falls. Think of a leak, lower pressure because your bleeding off more air.
Your bleeding off the pressure because the pair of manifolds flow more air into the cylinder as they share the air flow - less restriction from the SC to the intake valve. More air better volumetric efficiency and thus more power. It took me a while to figure this out when I first made them, I thought there was a problem. I even plugged up the crossover to see that the pressure went back up to previous readings.
When my experiments on the use of a second intake ((DCAI)) were going on, the bottom end power gain was wild, like 25 hp on the dyno charts. THat was simple as the intake to the TB on the SC was breathing rarefied - thinner air due to the friction losses in the intake and filter. I actually did some blasts to measure the pressure loss with the single cold air intake and it WAS 1 PSIG!!!! Thats enormous because we carbon based units are breathing 14.7 PSIG air and a single PSIG loss is like 7% !!!!!!!
The buttometer showed good gains from the DCAI and the crossover manifolds that robs making are allow you to have the best intake that can be imagined. Unless you add the bigger down pipes, there is almost nothing left to improve. Were not getting a different SC or engine, but with the response and power these add ons provide, there is no need to go crazy looking for more power. THis engine breathes very well now!
Enjoy, Woody