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At what speed does the fan become ineffective? by Shonyman32
Started on: 06-28-2013 11:54 PM
Replies: 13 (685 views)
Last post by: jaredmurray88 on 06-30-2013 11:52 PM
Shonyman32
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Report this Post06-28-2013 11:54 PM Click Here to See the Profile for Shonyman32Send a Private Message to Shonyman32Edit/Delete MessageReply w/QuoteDirect Link to This Post
I am wondering at what speed does the fan become ineffective or at what speed does the fan pull air through the radiator? 1987 2.8 fastback auto. Although I'm sure its the same for all.
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theogre
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Report this Post06-29-2013 12:47 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Many aftermarket Standard Electric Fans ~2300 CFM and w/o a flaring. Some High Performance units ~3000 CFM w/o flare.
Most OEM are = to or less aftermarket Standard, w/ and w/o flaring.

I don't have math handy...

Fan CFM vs. car MPH is mostly useless

Running fan(s) or not depends on many things... a few ones:
Fiero Trim level, IE which nose.
Fiero uses body parts to duct air flow, that many owners has missing pieces.
Car has A/C or not
A/C on/off
A/C and/or radiator is clean
Cooling system and coolant is good

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trotterlg
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Report this Post06-29-2013 01:14 AM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
You would have to measure the airflow in front and behind to see, but I think it is likely better than 50 MPH I would say, it would be a fun science project to find out. Larry
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Purple86GT
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Report this Post06-29-2013 08:56 AM Click Here to See the Profile for Purple86GTClick Here to Email Purple86GTSend a Private Message to Purple86GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Pretty much and decent momentum (where you feel a considerable breeze when you stick your hand out the window).

You do not want to overcool the coolant in the radiator. It should only remain slightly cooler than the engine. If it's too cold, it will shock the engine when the thermostat opens. This affects fuel efficiency and engine longevity.

You can get a radiator probe for pretty cheap, it inserts between the radiator fins. You can then use a gauge to monitor coolant temps in the radiator while you are driving at different speeds and compare it to just the fan running.

Cheers!
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theogre
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Report this Post06-29-2013 12:55 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Do note... w/o flaring then only radiator cover w/ fan get air from fan, the rest get little to no air flow from the fan.
This means Flare can/will affect radiator cooling from the fan.

Older Fiero (86 and down) had fans w/o flaring mean ~1/3 of radiator gets little/no fan flow.


87&up has flare and a bigger fan.


Does have more differences... number, shape, pitch, size of blades and Motor RPM if different can/will affect CFM and often noise too. More confusing, 84 uses 2 speed fan setup.

 
quote
Originally posted by Purple86GT:
You do not want to overcool the coolant in the radiator. It should only remain slightly cooler than the engine. If it's too cold, it will shock the engine when the thermostat opens. This affects fuel efficiency and engine longevity.

Yes, This is why Stant makes SuperStat® Thermostat.
You can often see this effect on the dash gauge in Winter and stopped by traffic light etc. Causes drivers to think something is major wrong but just change to SuperStat often reduce/stops this. (And even New normal Stant Tstat does this in winter.)
See my Cave, Thermostat
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gtoformula
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Report this Post06-29-2013 01:03 PM Click Here to See the Profile for gtoformulaClick Here to Email gtoformulaSend a Private Message to gtoformulaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ogre,
Do you recommend replacing the old style fan with the later style fan/shroud assembly? Are they interchangeable? I've got a fan assembly that I pulled from an '88. Would that swap into my 1986 GT without modification? I honestly have never compared the two so I have no idea.
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theogre
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Report this Post06-30-2013 05:10 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you have one... Should take 15-30 minutes to switch.
I think they use same plug and mount screw holes. I only did quick check.

Is 87+ better? Not sure. My guess is yes... the shrouded fans affects radiator and A/C condenser when the fan is on.
Can't remember noise level... I think 87 is a bit quieter.

CFM being =?
86 may have more CFM but less area to cool down. Same thing using many aftermarket units.
So difference in CFM spec likely doesn't matter much.

87+ is only a little bit bigger. They moved the fan out/back to get more air flow from shrouded areas.
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Boostdreamer
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Report this Post06-30-2013 06:07 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
My 85 and 86, both with V6's have the second style of fan posted by Ogre. Both are original to the cars. Must be a 4-cylinder vs 6-cylinder thing.

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larry mimbs
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Report this Post06-30-2013 06:24 PM Click Here to See the Profile for larry mimbsClick Here to Email larry mimbsSend a Private Message to larry mimbsEdit/Delete MessageReply w/QuoteDirect Link to This Post
On most vehicles the fan disengages at about 35 mph. If you have a shroud, (almost necessary for good cooling) the fan should extend 1/3 into the shroud.
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dudewithoutfiero
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Report this Post06-30-2013 06:36 PM Click Here to See the Profile for dudewithoutfieroSend a Private Message to dudewithoutfieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
my early 86 se v6 has the later fan on it, and it is original to the car too. My old 85 sport had it also but it was a four banger
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Zack_White86gt
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Report this Post06-30-2013 08:40 PM Click Here to See the Profile for Zack_White86gtClick Here to Email Zack_White86gtSend a Private Message to Zack_White86gtEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by dudewithoutfiero:

my early 86 se v6 has the later fan on it, and it is original to the car too. My old 85 sport had it also but it was a four banger


Same here with my 86 GT. I'm pretty sure the 86 V6's also had it, not just 87 and 88.
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Report this Post06-30-2013 09:02 PM Click Here to See the Profile for TONY_CSend a Private Message to TONY_CEdit/Delete MessageReply w/QuoteDirect Link to This Post
My 84 has the fan with the full shroud, so did another 84 that I had. I don't ever recall seeing the shroudless one shown above. Maybe it's a non AC car?

[This message has been edited by TONY_C (edited 06-30-2013).]

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theogre
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Report this Post06-30-2013 11:03 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by TONY_C and others:
Maybe it's a non AC car?

Maybe... 86 has L4 but doesn't have a/c. 87 also L4 but w/ A/C.

 
quote
Originally posted by larry mimbs:
On most vehicles the fan disengages at about 35 mph.

Not in old GM cars... All C3 and maybe some P4 ECM have No control of any fans.
DIS L4 does control the fan (Temp on and off) But A/C/heater control can override ECM.

W/ coolant system working right, I've never seen Engine Temp reach On point (DIS L4 ECM is set on = 221°F) when moving... I mean ~20-25 mph. Need very slow traffic and hot weather for that.

Some old front inline engine w/ fan clutch, many had thermo setup that let fan to freewheel when not needed.
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jaredmurray88
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Report this Post06-30-2013 11:52 PM Click Here to See the Profile for jaredmurray88Click Here to Email jaredmurray88Send a Private Message to jaredmurray88Edit/Delete MessageReply w/QuoteDirect Link to This Post
My 86 four banger has the second fan but it has a/c. I have no idea if its stock or not though.
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