The Machine
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We all should know this in order to make intelligent decisions regarding upgrade radiator fans. Right?
Anyone know the cfm & amp draw of OEM fan?
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The Machine
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Anyone?
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my answer
not enough cfm and not well placed against the radiator to be effective
on draw due to age maybe too much
the if you have no cooling issues than your fine , otherwise valeo duals are great ($89 form gbodyparts.com ) along with a 160 thermostat and a modern chip that will turn fans on at appox 168,
to solve the draw issue on old stock harness i recommend the hotwire for the dual fans from brian or racetronix
if you're missing the sides and lower mat like air baffles your loosing cooling due to air moving under car and around sides and not through the radiator , brian at gbody sells these too
this should net temps of no more than 178 regardless of weather or if a/c is running , i see 170 at line and 176 at traps , never been over 178 even with a/c and using old original radiator
if it doesnt run cool after fan upgrades than maybe the radiator needs looking into
if stock appearing isnt highest on your list the fbody rad is a cheap ($117)and very effective alternative , but youll want to add an external trans cooler (should run one anyway) and you may want to run an external oil cooler since the fbody doesnt have one
otherwise AZ gn sells a new (stock end tank) radiator that should solve an radiator related cooling issues.
not enough cfm and not well placed against the radiator to be effective
on draw due to age maybe too much
the if you have no cooling issues than your fine , otherwise valeo duals are great ($89 form gbodyparts.com ) along with a 160 thermostat and a modern chip that will turn fans on at appox 168,
to solve the draw issue on old stock harness i recommend the hotwire for the dual fans from brian or racetronix
if you're missing the sides and lower mat like air baffles your loosing cooling due to air moving under car and around sides and not through the radiator , brian at gbody sells these too
this should net temps of no more than 178 regardless of weather or if a/c is running , i see 170 at line and 176 at traps , never been over 178 even with a/c and using old original radiator
if it doesnt run cool after fan upgrades than maybe the radiator needs looking into
if stock appearing isnt highest on your list the fbody rad is a cheap ($117)and very effective alternative , but youll want to add an external trans cooler (should run one anyway) and you may want to run an external oil cooler since the fbody doesnt have one
otherwise AZ gn sells a new (stock end tank) radiator that should solve an radiator related cooling issues.
The Machine
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Yea, but what are the specs of the OEM fan?
And the shroud is too short end to end.
But what I'd like to know how much air the stock fan pulls (the cfm rating).
and
I'd like to know how much current the stock fans draws (amps).
In order to make an intelligent descion or selection of upgrade fans, someone should know these two facts first.
Not just so someone can be sure to get a higher flowing fan, but also know how much current draw should be their jumping off point. It would be nice to know how much current draw / engine drag is being saved by the newer more efficient fan designs.
I'm surprised this doesn't seem to be documented somewhere thus far.
All of your other advice is in line with whats been said by others, and I'm with'ya 100%.
Thnx!
And the shroud is too short end to end.
But what I'd like to know how much air the stock fan pulls (the cfm rating).
and
I'd like to know how much current the stock fans draws (amps).
In order to make an intelligent descion or selection of upgrade fans, someone should know these two facts first.
Not just so someone can be sure to get a higher flowing fan, but also know how much current draw should be their jumping off point. It would be nice to know how much current draw / engine drag is being saved by the newer more efficient fan designs.
I'm surprised this doesn't seem to be documented somewhere thus far.
All of your other advice is in line with whats been said by others, and I'm with'ya 100%.
Thnx!
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fans dont run at WOT , so no parasitic loss or drag
The Machine
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Thanks, do you know the current draw & cfm rating of the OEM fan?
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using search came up with this
http://turbobuick.com/forums/showthread.php?t=98008&highlight=fan+current
http://turbobuick.com/forums/showthread.php?t=98008&highlight=fan+current
The Machine said:
If I had to guess, I would say the stock CFM rating is around 1000 - 1400 cfm and operating amp draw might be 10-15 amps. The spike that everyone sees is normal or technically measured as LRA(Locked Rotor Amperage) which is usually 2-5 times the operatng amperage. I have a clamp-on Amp multimeter so one day I will check it out. I run the stock fan on high and we have seen a few days over 95 degrees and my car has never gone past 190 degrees with the A/C on. I also have a FMIC and recored radiator.
The Machine
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Thanks Guys!
I think that helps a bit.
If stock draws a constant estimated 18 amps and flows an estimated 1800 cfm, then I know from the Derale specs that the 16" Tornado would increase the flow 300cfm & draw aprox the same current. Therefore an upgrade, and not a mistake in the wrong direction.
Thanks to Marc87GN & the other thread mentioned above, I now have another logical question. If the LRA current spike is and estimated 35, and we know this to be the low speed fan licking on at around 170 degrees (aftermarket chip), is the LRA the same if we skip low speed & go directly to high speed?
The way the factory designed it was low speed kicks on first, then if that doesn't do the trick, high speed kicks on at the higher temps (maybe 215). If this is the case, it would seem the LRA takes place at low speed on, then there would be another "slight" spike when high speed kicks on. Is the LRA still within acceptable limits if you go directly to high speed? Possibly this is why some larger fans burn up their connectors?
At any rate, it would still be helpful if someone were to send their factory fan in to somplace like Derale to have the specs verified.
Just a thought.
I think that helps a bit.
If stock draws a constant estimated 18 amps and flows an estimated 1800 cfm, then I know from the Derale specs that the 16" Tornado would increase the flow 300cfm & draw aprox the same current. Therefore an upgrade, and not a mistake in the wrong direction.
Thanks to Marc87GN & the other thread mentioned above, I now have another logical question. If the LRA current spike is and estimated 35, and we know this to be the low speed fan licking on at around 170 degrees (aftermarket chip), is the LRA the same if we skip low speed & go directly to high speed?
The way the factory designed it was low speed kicks on first, then if that doesn't do the trick, high speed kicks on at the higher temps (maybe 215). If this is the case, it would seem the LRA takes place at low speed on, then there would be another "slight" spike when high speed kicks on. Is the LRA still within acceptable limits if you go directly to high speed? Possibly this is why some larger fans burn up their connectors?
At any rate, it would still be helpful if someone were to send their factory fan in to somplace like Derale to have the specs verified.
Just a thought.
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all this worrying is easily avoided by going to the racetronix dual fan hotwire kit or the caspers dual fan hotwire
then the oe harness is only used to turn on relays and the draw comes direct off the battery which can support large load spikes
then the oe harness is only used to turn on relays and the draw comes direct off the battery which can support large load spikes
The Machine
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That's helpful information about the hotwire kit for the fans. I thought I was up to date hotwire wise, guess not.
The original question was one of pure common sense. If you know what you've got, then you know what is better.
Me I had 5 Derale 16" Tornado fans sitting around, so I wanted to know how to compare them to my OEM GN fan. It appears the specs are better. So after taking all the measurements, I had an aluminum fan shroud made, and mounted it up. Looks great, fits great, seats a lot closer to the radiator, & should be alot more efficient since it covers the entire backside of the radiator. At this point I think need to bypass the fan resistor & I'll be good.
I thought about having several extras made to sell, but I like to avoid the potential for complaints. :wink: At least I shouldn't have the "bad motor" problems I've read about with some of the less expensive dual fan setups out there, and I don't think Derale is going anywhere anytime soon.
Thanks again guys!
The original question was one of pure common sense. If you know what you've got, then you know what is better.
Me I had 5 Derale 16" Tornado fans sitting around, so I wanted to know how to compare them to my OEM GN fan. It appears the specs are better. So after taking all the measurements, I had an aluminum fan shroud made, and mounted it up. Looks great, fits great, seats a lot closer to the radiator, & should be alot more efficient since it covers the entire backside of the radiator. At this point I think need to bypass the fan resistor & I'll be good.
I thought about having several extras made to sell, but I like to avoid the potential for complaints. :wink: At least I shouldn't have the "bad motor" problems I've read about with some of the less expensive dual fan setups out there, and I don't think Derale is going anywhere anytime soon.
Thanks again guys!
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as for hotwire kits , there are hotwire kits for injectors , coilpack , fuel pump , dual fans, headlights and powerwindows .
i run hotwires for both fuel pumps , injectors, dual fans and i even have my lt1 maf hotwired
i have msd dis 4 so i didnt do the coil pack
i run hotwires for both fuel pumps , injectors, dual fans and i even have my lt1 maf hotwired
i have msd dis 4 so i didnt do the coil pack
Missing Info
You need to know a little more to compare fans. The fan manufacturers use different pressure values with their cfm ratings. Some use 1" of H20, others use different pressures. Ideally, you would like to have a fan "curve", comparable to a pump curve, but lacking that, you at least need to know the pressure that goes with the cfm rating.
You need to know a little more to compare fans. The fan manufacturers use different pressure values with their cfm ratings. Some use 1" of H20, others use different pressures. Ideally, you would like to have a fan "curve", comparable to a pump curve, but lacking that, you at least need to know the pressure that goes with the cfm rating.
The Machine
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Sounds like someone could write a book about fans.
Derale rates theirs at 0 pressure.
There's also been improvements made to blades & motors making both more efficient than a few years back. I read somewhere on here that there is a general rule of 1 amp per 100cfm, I think they've surpased that these days.
Seems like after 20 years somebody would know the actual specs of the OEM fan on the 86/87 GN.
At least there are people who can say what works for their car tho.
Derale rates theirs at 0 pressure.
There's also been improvements made to blades & motors making both more efficient than a few years back. I read somewhere on here that there is a general rule of 1 amp per 100cfm, I think they've surpased that these days.
Seems like after 20 years somebody would know the actual specs of the OEM fan on the 86/87 GN.
At least there are people who can say what works for their car tho.
The stock fan pulls about 16 amps @13.8 volts, no rad in front of it, so it could go higher. It is fed from the fusbile link at the starter and then goes through the relays. A good 5 feet of wiring with either #12 or #10 awg wiring, it looks like #12 to me, which gives you a voltage drop of about 1 volt to the fans. Also the factory alternator wire is only #10 awg to feed the whole car, which if you feel it under full load, will get hot, i almost melted it with the 200 amp. I now run a #4 awg from the alt, and i get great voltage ouput in the whole car. Gm cut corners to save money it looks like. No matter what fan you get, dont use the factory wiring, run new wires and fuses #10 awg min!!
The die electric grease that has turned into a black tar inside the fan relay pins and relay connectors will cause a big voltage drop. My high speed fan was probably spinning at 250-300rpm. barely turning at all. After cleaning all that crap out and making everything like new, the fans work properly. The fan resistor is rated 50 watts I think. I just ran a different, lower ohm, (.01 ohms I think) 50 watt resistor across and jumped it there, so that low speed fan will cause the fan to spin alot faster than normal , but not quite as fast as high speed. Works great. I dont like the idea of just jumping it with a wire.
I have an idea for the gap between the stock fan and the radiator although I don't think it's that far. I ordered some weather stripping from JC Whitney and plan to go around the edges and than re-install it after cleaning the motor like mentioned above. That should thoroughly take care of the gap without damaging the cooling fins and hopfully make a 5-10 degree difference. I bought a new GM fan motor off of ebay for $38 a year ago, but don't want to use it until this one craps put.
The Machine
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Maybe you meant to say you were gonna clean the relays. I need to do the same thing. But I wouldn't try to clean the motor.
I think the OEM shroud can be repositioned at the top to go behind the tabs that hold it in place, bringing it alot closer to the radiator, but when you take a close look at the length, you may agree that it was made too short from the factory.
That's when I decided to have a shroud made that extends the entire length of the radiator core, and add a fan that outperforms the OEM fan.
Good luck!
I think the OEM shroud can be repositioned at the top to go behind the tabs that hold it in place, bringing it alot closer to the radiator, but when you take a close look at the length, you may agree that it was made too short from the factory.
That's when I decided to have a shroud made that extends the entire length of the radiator core, and add a fan that outperforms the OEM fan.
Good luck!
