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Hi Everyone! ;) The top pulley on my blower is a 30 & the bottom one is a 28, what difference in boost will it make if I switch the top & bottom pulley? It's a 392 Hemi w/ an 8:71. I thought I'd seen a chart somewhere but I can't seem to find it..... Bill
well, what is good enough fo you? you are barely underdrive now. what is your pressure?
Kitz
It's about 7% underdriven now, swap 'em and get about 7% over. 14% increase should make a noticeable difference.
You'll go from 10 lbs to 16 lbs according to BDS charts.
.....WOW! I think I'd better leave the pulley's right where they were! {30 top/28 bottom}. Thanks Kitz! actually I haven't even driven or fired the motor yet! I just figured it's never enough so might as well switch the pulley's now! And no boost gauge, should I get one?..... Thanks R Pope! ok, now I see how the math is done! 30 divided by 28 & then 28 divided by 30.... Thanks Tech! I went to the BDS charts & wow! I'm already {with 10 pounds of boost} at the edge of not pinging! NO way 16 pounds will not ping on pump gas!!! Since I'm in the middle of getting the bottom pulley to fit I figured I'd just swap 'em now, but no, I'll go with the 28 on the bottom. Plus it fits better cuz it's smaller! ;) Thanks again Bill
10 lb to 16 lb will boost your effective CR about 1/4. (Atmospheric pressure, 15#, plus 10#=25...AP + 16#=31. 31/25=1 6/25, which is about 1 1/4 times cylinder pressure. A lot of variables enter the picture making this inexact, but you get the idea.
Just up the nitro 5 percent
We could never do that because we were running the can anyway. And around 30% overdrive at 28* lead