Calculating it is good enough, imo

there will be some belt slip and you're never going to hold it at max engine or max blower rpm for very long

you'll just kiss the max's before shifting

I'll be pushing the max impeller speed with my D1 build. So maybe Im just dumb 😂

 

I've seen where guys are pushing them to 28k at Bonneville so that's 2 miles of straight abuse. I wouldn't go that far but I'm with you on calculating it, if it is close enough, I'll send it...

 

it really comes down to the 'can' versus 'should' argument. another TVS build i followed was an LS7 intent on turning his TVS2300 at 22-24k rpm. he had a ridiculous custom 10rib front drive built and a 14rib OD rear (later swapped to 50mm cogs) to combat slip, internal nitrous bars to lower temps, the works...
still had high IATs & i'm thinking he trashed his rotor bearings at least once. this was also years before the 2650 was ever a thing.

just saying that if you're looking to overspin a blower when the same company makes a direct-swap larger unit, you're better off in the long run (cash, time, & headaches) to trade for the bigger rotor pack. best analogy i can think of is having a 4.8 truck & needing to pull a 10k lb trailer all the time with it - why get a huge stall, 4.88 gears, and a set of 29" tall wheels/tires when you could just swap in a 6.0?

that's also consistent with Magnuson & Whipple engineers' build advice over the years of "use the smallest blower tempered by the efficiency of the CFM needed for your goals". comparing the map above with the 2300 below using my car's specs (because i can reference them a little quicker), we can see that turning 6000rpm spins the blower to 15k & produces ~1.8 pressure ratio. that equates to roughly 2050m³/hr @ 63% efficiency. follow the chart in the opposite direction to see that moving equivalent air through a 1900 would be interpolated off the right edge of the map to a little over 18000rpm @ 58% efficiency. that just means more heat & belt slip to combat along with potentially accelerated bearing damage due to the higher belt tensions & impeller speeds.



...but on the other hand, you could slap come cogs on, turn 22k, and scream like a freaking banshee to impress all the lot lizards at the malls & truck stops

 

and i've never seen anybody use the rpm sensor - math works... verified by belt dust or shredded ribs indicating slip

 

there's also a difference in the valley-style units like the LSA/LS9, heartbeat, eForce, etc that have the intercooler(s) above the rotor pack when compared to the top-mount Magnuson, Roush, etc that have the intercooler in the valley. likewise, even the direct-drive units are different from the jackshaft setups with what's feasible on the belts.

the airflow path is much better on the valley rotor kits unless you shrink that margin with a plenum spacer on the top-mount - particularly once you start over-spinning the unit.

as for blower speed, the jackshaft is a better setup for spinning fast because you can overdrive the rear & use bigger pulleys up front - providing more surface area for the belt to grip without needing extra ribs as soon. my car's surprisingly still holding okay on the stock 6rib setup (save for the OD 8rib balancer): 8.125 crank -> 3.8 front -> 36:30 rear cogs. it's holding 13psi. to get similar results on a direct drive is looking at a 2.x" blower pulley and a 10-11rib accessory.

 

I'll sell the 1900 and get the 2650 before I go nuts on a drive system beyond what I already have. I won't go down that hole just skip over it if it's in my path...

 

Keep me in mind if you decide to unload that 1900 😉

 

Wisest choice. Don't think you'll regret it.

 

if you're just being facetious... you might actually consider it.

so after taking a play from OnStar's book & digging through your truck's personal data, it looks like you've got the direct drive TVS1900 (top-mount, non-jackshaft unit with the intercooler brick under the rotor pack) being spun by a 10% OD balancer & a 2.8" pulley.

i went through & plotted the blower speeds in relation to each 1000 engine rpm (red circles) on a street pull, and here's what the math says your blower'd be doing if you simply transferred it as-is to a 408 (7.5psi falling to 7psi):



now if you were to put those same pulleys on a TVS2300 with that 408, here's what you'd get (12psi falling to 11psi):



and finally, a TVS2650 runs 16psi down to 15.5psi



and now the apples:apples visualization of my original statement - if you run a 3.6 snout pulley on the 2650 to achieve the same-ish pressure ratio as what the 1900 made on the 2.8, you get this (and it rises from 7psi to 10psi by the end of the pull):


**disclaimer: the maps of each unit design are slightly different - even when using the same rotor groups - and i ain't got no clue which specific design each of these maps correspond to... however, they'll be close enough to make an informed guess. also, this assumes you've mitigated any belt slip.

 

and since i never thunk to actually plot this out before, here's what my car's doing right now: