(digs out his turbo knowledge)
A number of you are on the money on some things. A number of you are not.
A single biggie turbocharger will have lots of topflow but lots of lag. Drag cars don't care so much about that, because they already spin off the line, so the lag is helpful. By the time they get traction, they are also getting boost. Now, the lag would be so bad that it would take longer than that, except for the fact that bigie turbos are often paired with biggie exhaust.
See, something that is very different with turbocharging from natural aspiration is that a naturally aspirated engine needs some backpressure in the exhaust piping. A turbocar does not. In fact, you want it as wide open as possible. Why? Well, the exhaust manifold sees the turbine housing as a major restriction, and creates more backpressure than you will ever need.... so having a wide open exhaust after it is ideal.
Using nitrous to spool a turbo is for the really crazy tube chassis drag setup or for the inexperienced. Running the proper exhaust pipe size is how you *should* be doing it.
Now, in the case of twins versus single, you have to be more specific about what turbos are being used in a twins setup. Sure, if you run twin T25's, a huge T66 will outflow them still. Of course the twin T25's will outspool it.
But what if you are running twin T3 turbos? This changes things dramatically, and now you have to consider that, while a T3 cannot flow as much as a T66, two T3's can.
Here is why: Consider a car with a T3 single vs. twin T2's. The T2 is only good for about 14 psi, after that it's overspun (meaning it has to spin so fast that it generates enough heat to cancel out the comression with heat expansion, meaning it makes no more boost). The T3, on the other hand, is good for about 18 psi properly tuned.
Bare minimum on most external wastegates is 7psi (that's what the spring is tensioned to). SO... imagine TWIN T2's. Running the minimum boost, they are each pushing 7psi, in parallel, into the same piping, for 14psi. At 7 psi they arent making much heat, so are well within their efficiency range. Yet have superior spool to the T3, and less crazy exhaust pipe requirements. As you push them to 10 psi, you are now still within their safe zone, but now pushing *20* total. Now you outflow the T3, still in efficiency range of the T2 flow maps, and still with superior spool. See?
Of course, it's not actually 7psi + 7psi = 14. You lose a pound or two. But still the strategy works better.
NOW, finally, there's the issue of compression. Look guys, these V8's aren't low compression like built turbo V8's, or even like factory four and six cyllinder turbocars. Typically those cars run anywhere from 7.5:1 to 8.5:1 and no higher. Some carefully prepped engines run 9:1 but they don't run alot of boost, only about 7-10psi, and generally are more torquey than big HP numbers. Big HP cars run lower compression, high boost, big exhaust. I don't see many of you ordering 8:1 pistons any time soon for a turbo project, I see many of you interested in bolting something on. IN that case, expect to run 7psi, not the biggie 20 psi of the OEM turbocars. Trust me, 7psi is alot! You have to consider that before you reach positive pressure, you first have to defeat the vacuum an engine generates. So 7psi is alot! 7psi on something like even a '94 Romeo will probably make it haul like no tomorrow. If anything it might even be the better choice of engines for it, since the smaller ports would act as velocity stacks durring turbo spool time.
If I had the time I would do it. Twins are easier on a V8 than running a crossover pipe for a single. Actually for the same reason, twins are probably going to be cheaper. Twin T2's. I can pick up a T2 for 50 bux a piece in perfect condition. They are small so they should find easy room under the side of the head. Together they have the potential, without intercoolers, of safely putting out 14psi (7 each), and WITH an intercooler (or twins, come cheapo DSM sidemounts, one for each), can put out 12-14psi each for a total of well more than I will ever need.
I think you'd see this undesirable '94 engine wake up and run good numbers.
Say, anyone have any pictures of a '94 exhaust manifold?