Maximum R1900 RPM?

[Mike_11CTSV]

Do you happen to have any hard data on the maximum rpm of the R1900 supercharger. I could have sworn I read someplace that it was 23,000rpm. Now I'm seeing on the Caddy forums that a few people are running 10" lower pulleys with 2.5" uppers, which would spin it at 24,400rpms at 6100 on the motor??

Need to find out for sure, because I have a 9.55" lower, and a 2.38" upper waiting to go on, along with a raised rev limiter (6600) and shift points (6400). If I put on the 2.38 instead of a 2.55 with the 10 bolt hub, I'm looking at 25,680rpms at WOT shifts vs 23,968rpm.

What really happens at those elevated rpm? Does the blower just lose efficiency? If thats the only problem, then my larger heat exchanger should make up for it. But if its gonna get so hot that the bearings are gonna seize, then its another story.

I don't see it really being a problem since the motor almost never spends time up in the super high rpms, but it has the potential to be one.

[Mike_11CTSV]

No info? I have an e-mail into Eaton as well, but still no response.

[Jeff@Lingenfelter]

Hi Mike,

Its tough to get a definitive answer, as the OE is concerned with durability. We would not recommend going beyond 23000 rpm based on the design.

[Mike_11CTSV]

Alright, thanks Jeff. Guess I'll pick up a 2.5" pulley for the 10 bolt hub for now. I'll hang onto the 2.38 for when I do the cam, lid spacer and headers.

Any idea what size the stock idler is? It would be awesome if I could put on the 100mm idler along with the 2.5 and keep the same belt as I have now. :confused:

EDIT: Forget it, I just measured it myself. Looks like the stock upper idler is 88mm. Going to 100mm is 12mm larger. The 2.55 blower pulley is .45" smaller, which is 11.43mm. The same belt should work just fine. And beyond that, the 9.55" crank divided by 2.55" blower pulley is a 3.745:1 ratio, so at 6100rpms, the blower is only spinning at 22,845rpms. Perfect. I'll just lower my shift points back down to stock and it'll work great. Giving up about 15hp on the top end, but I never use them anyway, so its just bragging rights.