Like Tree0Likes

Blower on top or charger on the side?

Reply
Old 07-24-2008, 04:14 PM
  #21
Registered
 
tomcat's Avatar
 
Join Date: Feb 2001
Posts: 1,484
Default

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.
tomcat is offline  
Reply With Quote
Old 07-24-2008, 10:28 PM
  #22
Registered
 
Whipple Charged's Avatar
 
Join Date: Oct 2000
Location: Fresno, CA, 93722, USA
My Boats: Engine, speed, powerboats, Outerlimits SV43 with Whipple 1375SCI's
Posts: 1,436
Default

Quote:
Originally Posted by Jeff P31 View Post
I have a pair pro chargers I would love to trade for a fresh set of whipples . They work good but I know the whipples work better. Maybe Dustin would like me to test a set for him ?
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 is offline  
Reply With Quote
Old 07-24-2008, 10:34 PM
  #23
Registered
 
Whipple Charged's Avatar
 
Join Date: Oct 2000
Location: Fresno, CA, 93722, USA
My Boats: Engine, speed, powerboats, Outerlimits SV43 with Whipple 1375SCI's
Posts: 1,436
Default

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.
Whipple Charged is offline  
Reply With Quote
Old 07-25-2008, 01:06 AM
  #24
Platinum Member
Platinum Member
Trade Score: (1)
 
articfriends's Avatar
 
Join Date: Jun 2004
Location: Frankenmuth
My Boats: EX 99 MPH 272 Baja owner, 1999 Scarab 33 AVS NOW
Posts: 6,072
Default

Quote:
Originally Posted by Whipple Charged View Post
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.
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
articfriends is offline  
Reply With Quote
Old 07-25-2008, 02:50 PM
  #25
Registered
 
Join Date: Feb 2004
Location: MT. JULIET, TN.
My Boats: '99 33 Outlaw HP 500's,
Posts: 3,698
Unhappy

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.
kennyo is offline  
Reply With Quote
Old 07-25-2008, 02:55 PM
  #26
Platinum Member
Platinum Member
Trade Score: (1)
 
articfriends's Avatar
 
Join Date: Jun 2004
Location: Frankenmuth
My Boats: EX 99 MPH 272 Baja owner, 1999 Scarab 33 AVS NOW
Posts: 6,072
Default

Quote:
Originally Posted by kennyo View Post
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.
Ken,I see the lightnings are for sale,were they reverting and getting water on your valves? Call me,Smitty
articfriends is offline  
Reply With Quote
Old 07-25-2008, 03:03 PM
  #27
Registered
 
Whipple Charged's Avatar
 
Join Date: Oct 2000
Location: Fresno, CA, 93722, USA
My Boats: Engine, speed, powerboats, Outerlimits SV43 with Whipple 1375SCI's
Posts: 1,436
Default

Quote:
Originally Posted by articfriends View Post
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
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 is offline  
Reply With Quote
Old 07-29-2008, 01:18 PM
  #28
Registered
 
Whipple Charged's Avatar
 
Join Date: Oct 2000
Location: Fresno, CA, 93722, USA
My Boats: Engine, speed, powerboats, Outerlimits SV43 with Whipple 1375SCI's
Posts: 1,436
Default

Quote:
Originally Posted by Jeff P31 View Post
Running hp500's with pro chargers threw the carbs and harden exhaust with xr uppers & 2'' shorty imco's .
Well I bet that bad boy runs pretty darn good!
Whipple Charged is offline  
Reply With Quote
Old 07-29-2008, 01:48 PM
  #29
Registered
 
Join Date: Jun 2005
Location: O'Fallon, Mo
My Boats: 43 Black Thunder Flat Deck
Posts: 118
Default

Quote:
Originally Posted by Whipple Charged View Post
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.
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.
Blow-N-Thunder is offline  
Reply With Quote
Old 07-29-2008, 03:44 PM
  #30
Registered
 
Turbojack's Avatar
 
Join Date: Sep 2001
Location: Houston, TX, USA
My Boats: 2003 Eliminator 30' Daytona
Posts: 2,285
Default

Quote:
Originally Posted by Blow-N-Thunder View Post
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.
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.
Turbojack is offline  
Reply With Quote
Reply

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
JLS
General Q & A
2
02-16-2005 09:00 PM
Steve Snider
Cigarette
10
01-28-2005 01:30 AM
38flatdeck
Cigarette
5
09-06-2004 05:23 PM
electrical1
General Q & A
1
07-19-2004 11:08 AM



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 01:38 AM.


Copyright 2011 OffShoreOnly. All rights reserved.