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.

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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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

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

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!

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

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.

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.

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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Jonathan

'68-69 GTO Nose - The Project has Begun!
My '85 L67 Build Thread

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.

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

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.

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).]

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.

My 86 four banger has the second fan but it has a/c. I have no idea if its stock or not though.