Heh heh heh. Actually, the crossovers don't add turbulence. In a way, you can think of them as adding scavenging, or suction, to help pull exhaust gasses out.
But hey, if you can't work it out, then don't worry about it. You're probably only talking 5 or 10 horsepower anyway.
I actually DON'T have a crossover on my Corvette, because like you, my exhaust spreads apart and goes into sidepipes right away. The only way I could manage a crossover is with a long pipe connecting the sidepipes, and then, I doubt if it would do any good, except maybe to help mellow the exhaust note a little.
Think of a crossover like this, the exhaust pulses are like waves of high pressure gas in the exhaust pipe. Following each pulse, or wave, is a null, which is low pressure. The high pressure pulse that comes along next is sucked into the void, helping to scavenge the cylinder that came out of. Pumping out more exhaust gas.
Now what if the ideal "second" pulse was coming from the opposite bank of cylinders. It's timed just right, if only there was a connection between the left and right exhaust pipe. The X-pipe creates a brief merging between the two. The energy of each pulse is a lot stronger going through there than there would be if it was an H-pipe.
Sorry if that's confusing. But basically, you've got it.
HR Lincoln, I thought about your other point you made, that the exhaust has to be tuned for a certain rpm. It's not that peaky, but yes, the headers are tuned to a RANGE of rpms. The shorter headers do better up high, and the longer headers do better at lower rpms. But even with that, there are variables. The pipe size for one. The bigger the pipes, the freer they flow at high rpms, but they also slow down the exhaust, hurting torque. So you can offset longer pipes by increasing size to get back some high rpm performance.
Just when you thought you had it all figured out, along comes the "merge" collector. This works through Bernouli's law. Gas flows faster through a decreased area. This is tuned so that scavenging increases at a certain rpm range, increasing torque. Get that range nailed just right and you boost horsepower too. Too bad they are selling for stupid money, because it's a good idea.
Look...street cars don't need to get into such high tech for their exhaust. They can benefit from headers, but you'll be just fine without a crossover, merge collector, etc. Just get those smaller headers you were looking at, and it'll run fine.
Good luck with your "Exhaust PHD"...there WILL be an exam.
