tomcat

Centrifugal systems can run more boost because their position on the front or side of the engine allows the use of a larger intercooler than can be used with a roots or screw compressor. This higher boost will not be available until higher RPM, which is theoretically easier on the drive, but your Bravo XR still isn't going to like it.

Whipple Charged

Ha ha, not sure, what is scrap aluminum going for these days? LOL

Best to throw them on the OSO classified. Watcha got in that Scarab?

Whipple Charged

The bigger the centrifugal, the larger the lag time, as boost curves get bigger (from low rpm to high rpm), the harder it is to prop the boat for maximum drive-ability. Some big boats, even with vent systems on their drives, still require full throttle, full boost at low rpms. Those boats simply would never get on plane with centrifugal equipped motors. Small boats, single engine would not suffer as much as the bigger, go fast boats and thus could be good canidates for centrifugal systems. RPM becomes very key to making centrifugals work, because you need smaller pitches on the prop then rpm to get the MPH, but then the centrifugal keeps building boost, which can be a limitation.

Both systems have their purpose and best markets, both make great top end hp, but torque curves are extremely different.

articfriends

iTrader: (1)

Why would a BIGGER centrifugal have a longer lag time,its going to pump more air earlier at a lower rpm,its not like its a turbo waiting to spool up? I could see the smaller centrifugals not making boost until the rpm's come up. I have seen 4-6 psi of boost around 3000 rpm's if I go to wot taking off. I have had people tell me now for years about how centrifugals don't make any torque on the bottom end but my 8-1 540 made 775 ft lbs at 3000,858 by 3400,896 by 3600 and it continues upward from there peaking over 1000 ft lbs and carying 900 to 6000 rpm's. If I had built my motor at 9-1 instead of 8-1 (I built it at 8-1 to run more boost on top end) it would have even more tq down low but I couldn't use any more low end any ways,Smitty

kennyo

Smitty, You figured out my problem Yet? I'm thinking warped exhaust valves. Doing a leak down tomorrow. I guess i'll throw another two grand at it.

articfriends

iTrader: (1)

Ken,I see the lightnings are for sale,were they reverting and getting water on your valves? Call me,Smitty

Whipple Charged

Actually, larger centrifugals have larger boost curves, they leak more at low speeds and are not as efficient at low rpms. Check a few blower maps, you'll see, plot your blower speed through the curves. When the SC comes into it's higher VE range, the boost starts to increase steadily. When using a smaller centrifugal, they are typically spun at higher rpms and go through their ideal range earlier, giving more boost down low, more torque and then don't build up as much on top.

Screws, roots, etc. all do the same thing, just not as dramatic.

Whipple Charged

Well I bet that bad boy runs pretty darn good!

Blow-N-Thunder

Then why do I not show any boost when coming on plane and running below 4000 RPMS. It is not until I get over 4000 rpms that I start creating measurable boost.

Which I like because it helps with the gas miles.

I have GEN V 502 w/ inconnel valves and whipples on a 43 black thunder flat deck.

Turbojack

The amount of boost that you show at diffferent rpm is based on the load on the engine at that RPM when running part throttle. If you were to put a larger prop prop on then you would start showing boost at a lower rpm. Smaller pitch prop then you would have more rpms before you would start showing boost. This is all at part throttle. On a centrifical charger If you go WOT off idle your boost will increase as the rpm's increase, with max boost at max rpm. With a whipple then when you go wot from idle you would see aprox. max boost all the way to max rpm.

My boat does not show running boost until around 3800 rpms. I have a friend that is in boost at around 2800 rpm.