belt driven fan HP loss??
11-26-2010, 04:20 PM
#1
Race Director
Thread Starter
belt driven fan HP loss??
Since I need to de-tune the 928 Estate to make less HP-torque to make my target power-weight for NASA GTS2...I could install the belt driven fan? The Estate runs a bit hotter than I would like anyway..so why do install the fan to drop my power a bit....so how much is the loss? 10hp or so? That would be PERFECT!
11-26-2010, 04:52 PM
#2
Not the sharpest tool in the shed
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Add weight rather than mess with a good cooling system to offset the power/weight ration needed.
11-26-2010, 05:46 PM
#3
Chronic Tool Dropper
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You could just put in a K&N...
11-26-2010, 06:06 PM
#4
Nordschleife Master
Figure on 1 or 2 HP.
Picture the energy a 5HP lawn mower displays and the radiator fan ain't hitting any rocks.
The fan gets a bad rap. The reason automakers went away from it was, first off, transverse engines and that at highway speeds the natural convection is enough. It only takes 30 or 40 BHP to cruise at 60 MPH so cutting out 1 or 2 is a nice MPG boost. Electric fans are a more compact package, too. It's actually more efficient to run the fan mechanically than to generate electricity and run a motor from that. The difference is that it's easy to turn an electric fan fully off.
Picture the energy a 5HP lawn mower displays and the radiator fan ain't hitting any rocks.
The fan gets a bad rap. The reason automakers went away from it was, first off, transverse engines and that at highway speeds the natural convection is enough. It only takes 30 or 40 BHP to cruise at 60 MPH so cutting out 1 or 2 is a nice MPG boost. Electric fans are a more compact package, too. It's actually more efficient to run the fan mechanically than to generate electricity and run a motor from that. The difference is that it's easy to turn an electric fan fully off.
11-26-2010, 06:23 PM
#5
Three Wheelin'
I used to run no fan at all. It never was a problem.
The car was bare minimum and the stock 4.5 motor put it into GTS3 where there's alot of competition, at least in the SE.
The race weight with driver and fuel was 2780. For most tracks low weight is an advantage but throw in some long straights and a heavier car with more power could be the ticket.
Do you have a big GTS2 field? Here there's no 2 but 3 is the biggest GTS group.
The car was bare minimum and the stock 4.5 motor put it into GTS3 where there's alot of competition, at least in the SE.
The race weight with driver and fuel was 2780. For most tracks low weight is an advantage but throw in some long straights and a heavier car with more power could be the ticket.
Do you have a big GTS2 field? Here there's no 2 but 3 is the biggest GTS group.
11-26-2010, 09:38 PM
#6
Race Director
Thread Starter
I used to run no fan at all. It never was a problem.
The car was bare minimum and the stock 4.5 motor put it into GTS3 where there's alot of competition, at least in the SE.
The race weight with driver and fuel was 2780. For most tracks low weight is an advantage but throw in some long straights and a heavier car with more power could be the ticket.
Do you have a big GTS2 field? Here there's no 2 but 3 is the biggest GTS group.
The car was bare minimum and the stock 4.5 motor put it into GTS3 where there's alot of competition, at least in the SE.
The race weight with driver and fuel was 2780. For most tracks low weight is an advantage but throw in some long straights and a heavier car with more power could be the ticket.
Do you have a big GTS2 field? Here there's no 2 but 3 is the biggest GTS group.
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11-27-2010, 12:00 PM
#11
Chronic Tool Dropper
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Problem adding M is that additional M affects handling and braking too, in a negative sort of weigh... Better to reduce F slightly
11-27-2010, 01:52 PM
#13
Inventor
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The power draw of the fan would depend on the temperature at the fan (and if the fan clutch works).
I cut the belt on back-to-back dyno runs and saw a ~7 hp increase on a '86.5. That was a one time test, not sure what an average would be.
Adding the fan, and/or setting the ignition advance to stock (4.7L=20°@3000) or less should net at least minus 10?
I cut the belt on back-to-back dyno runs and saw a ~7 hp increase on a '86.5. That was a one time test, not sure what an average would be.
Adding the fan, and/or setting the ignition advance to stock (4.7L=20°@3000) or less should net at least minus 10?
11-27-2010, 08:25 PM
#14
Race Director
Thread Starter
The power draw of the fan would depend on the temperature at the fan (and if the fan clutch works).
I cut the belt on back-to-back dyno runs and saw a ~7 hp increase on a '86.5. That was a one time test, not sure what an average would be.
Adding the fan, and/or setting the ignition advance to stock (4.7L=20°@3000) or less should net at least minus 10?
I cut the belt on back-to-back dyno runs and saw a ~7 hp increase on a '86.5. That was a one time test, not sure what an average would be.
Adding the fan, and/or setting the ignition advance to stock (4.7L=20°@3000) or less should net at least minus 10?
Right now I am still running the seriously old stock radiator minus trans cooling with the stock pusher fan and a 14" 1800CFM puller electric fan....it works fine up to about 95F then starts to fall behind....
Of course a new radiator and with dual electric pullers is ideal...but I am still trying to keep my budget reasonable....
If the fan cost 7whp that would be about perfect...since it would drop my numbers to 196whp and lets say 235torque which is 3124lbs...or about zero ballast!!!
11-27-2010, 09:09 PM
#15
Captain Obvious
Super User
Super User
Your probelm is not the fan, your cooling system is failing. The only time a fan does anyt good is in a stop and go traffic. As soon as you are above 30mph, the fan is uselss. Maybe you need to look at sealing up the air around the radiator.