Pulley size vs. rpm
Pulley size vs. rpm What would be better, run a small pulley and shift sooner or a slightly larger pulley and shift later, assuming both setups would be near max impeller speed?
On my 355/f1a combo I run a 7.65 crank pulley and a 3.40 drive pulley. Max impeller speed is reached at roughly 6200 rpm and I see about 18psi when shifting at 6100 rpm.
Would it be beneficial, for instance, to run a 3.70 drive pulley and shift around 6600 while max impeller speed is roughly 6750 rpm?
Would this maybe give me a longer powerband?
On a side note, how bad is it to overspin a centrifugal?
On my 355/f1a combo I run a 7.65 crank pulley and a 3.40 drive pulley. Max impeller speed is reached at roughly 6200 rpm and I see about 18psi when shifting at 6100 rpm.
Would it be beneficial, for instance, to run a 3.70 drive pulley and shift around 6600 while max impeller speed is roughly 6750 rpm?
Would this maybe give me a longer powerband?
On a side note, how bad is it to overspin a centrifugal?
Depends more on your cam at that point. What are you running?
Talking with Vortech they would tell me (only unofficially of course) that occasional over-revs to 10-15% over max would not do anything to the unit. At some point you will start making too much heat as the impeller gets out of its efficiency band, and you could fail a bearing. Extreme case you might explode the impeller but I have never heard of that happening for over-rev only, it's always been a foreign object that got into the unit.
You car looks sweet, btw...
Jim
Talking with Vortech they would tell me (only unofficially of course) that occasional over-revs to 10-15% over max would not do anything to the unit. At some point you will start making too much heat as the impeller gets out of its efficiency band, and you could fail a bearing. Extreme case you might explode the impeller but I have never heard of that happening for over-rev only, it's always been a foreign object that got into the unit.
You car looks sweet, btw...
Jim
I bet you'll run faster with the smaller pulley and shifting sooner, although a lot of variables come into play. I would be curious to see what your inlet air temps would compare with the two combinations. Bob
With that cam, I agree with Bob. Any belt slip problems? And what did the dyno numbers look like? Post a chart?
If you were doing road racing courses I would probably go with a bigger cam, and bigger blower pulley and rev it more, and you would end up with a wider powerband. Maybe something in the 224/232 range on 113-115lsa. It wouldn't necessarily be any quicker on the street/strip though. What heads and exhaust setup?
Jim
If you were doing road racing courses I would probably go with a bigger cam, and bigger blower pulley and rev it more, and you would end up with a wider powerband. Maybe something in the 224/232 range on 113-115lsa. It wouldn't necessarily be any quicker on the street/strip though. What heads and exhaust setup?
Jim
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I'll dig up the dyno chart. It made 754/747 but was leaning out so we didnt make a full pull. No belt slip problems. Heads are ported factory lt4's, Pacesetter lt's, ory, Corsa catback..
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