I removed the driver side fan from my LT4. (saving a little weight and hp) Is the passenger side fan the primary? What temperature should it turn on? The remaining fan does not turn on. Is there some interlock with the other fan?

 

The main fan comes on at 228 F and the second fan comes on at 238 F. I recommend you put the fan back in, 3 Lbs saving of weight in a 3300 Lb car is miniscule and not worth the risk in an overheated engine.

 

Saving weight? 3 to 4 lbs at most. And how are you saving HP?

You will sacrifice HP running higher temps anyway due to the lack of one fan.

 

Not sure about your year, but for the 90' removing the fan will not save any HP, except at low vehicle speeds.

I think that removing one fan hurts you more than it helps you. Taking advantage of the fact that you can optimize fan settings is a better way to go.

One of the PROM parameters is fan cutoff speed in vehicle MPH. There are two MPH parameters, one for each fan. My understanding is that the fans cuts off at vehicle speeds above this MPH setting. Accordingly the fans are no longer drawing current and adding load from the alternator.

To significantly increase power:

1. Change your thermostat with one that opens at a lower temp
2. Reduce the cut on and cut off temps for both of your fans
3. Bump up the WOT timing to take advantage of the lower engine temps and lower susceptability to pinging.

Carl

 

The fan weighs 6 pounds. 0.2% weight reduction isn't much, but this offsets the weight of the ZR1 oil cooler and 3" Davis radiator added, which offset the removal of the AC.
The fan isn't coming on because the car runs under 238 while stuck in traffic in 90 deg. weather.
I'll route the primary wires to the secondary fan for the lower switch on point. (reprogramming later....)
Pulling the fan also allows for better air flow

 

Man, no offence but thats crazy. I'm pretty sure you can trim 6lbs. in a more practicle manner. How about trimming some hood underside fiberglass. Heck, I'd do that before eliminating a fan. Or how bout eliminating the wiper wash bottle, water is like 7 lbs. per gallon.

 

The driver's side is the primary fan. When mine went out on my '92, the car quickly heated up to over 255 degrees before I realized something was seriously wrong and shut it off. I was very lucky I didn't warp a head or do even worse damage to the engine.

Since the fan is an electic motor, it doesn't take any extra horsepower to opperate. The engine has to turn the alternator anyway. In fact, this "mod" will probably cost you power since your engine will run hotter, and a hotter engine produces less power. Yeah, you can save yourself a couple pounds, but there's a good chance you'll ruin your engine too.

Next time, post the idea here before you do any more "mods."

 

Partial quote:
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Since the fan is an electic motor, it doesn't take any extra horsepower to opperate. The engine has to turn the alternator anyway
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You do not get something for nothing!!!! When the fan is on, the alternator supplies the current and the engine supplies the alternator with HP to make the electricity. Any current being used while the engine is running takes HP away from the engine and is not available to the rear wheels.

Blackbird, you need to retake high school physics and this time stay awake!

 

Ok now I'm trying to learn somthing here. I would have agreed with BlackbirdZ07 in that I thought the alternator was spinning anyway despite the demands on it. Are you telling me that the alternator has more drag per more load??? Hence more hp from motor is used with the more electronics on?? Are you sure about this one JFB ?? This is the first time in my 42 years that I've heard this. Now I could see if you have so much of an electric drain that the alternator is insufficiant to power ignition. But I never heard of the alternator needing more power to turn it because of higher demands on it.
Back in the day I used to follow the IASCA crank it up circuit with an S-10 blazer with a 5000 watt stereo system with a high power alternator and four batteries. I cant believe the lil' 2.8 litre v6 never missed a beat with all that demand on the alternator if this in fact is true.

 

Actually I made A's both semesters of college physics. My point was that the engine has to turn the alternator whether or not the alternator is supplying current to a fan. As far as I know, the alternator does NOT require less effort to turn if it's not suppling current. You're right, you don't get something for nothing, but when the battery is fully charged and there's little current being supplied, the alternator doesn't just go away, it causes the same drag on the engine that it always does. Think about it.

 

You can just swap the relay connectors to make the passenger side fan come on like the primary. 15 second fix.

I still think your crazy though.

 

I'm not advocating fan removal for street use unless it can be done without raising temps, but the alternator does drag more under more load. It's output is controlled by the regulator, obviously, and the greater the electrical demand the more drag on the engine. This is why drag cars often have a switch to cut out the alternator during their run. The alternator on modern cars with all of their electrical demand probably drains as much HP as an A/C compressor.

 

This thread is starting to get rediculous...

Bottom line, if you are that desperate for horsepower that you will remove a 3 lb fan to save weight and a fraction of a HP that it takes to drive the alternator that little bit extra to operate, then why stop there? Yank the radio and speakers, that uses alot more power than the one fan, and weighs more! Mechanical fans ate HP as we all know, which is one reason electric fans were born. Considering it doesnt even turn on until 238F, just when is it going to use that 1/4 HP that the alternator has to produce to run it? I don't know about the rest of you guys, but I sure as hell don't want my engine even getting that hot, let alone alowing it to go higher. By the time your engine gets that hot you already lost ALOT more HP than the alternator will use to help cool it down.

The motor WILL run hotter, and EVERYONE knows that you gain HP when you decrease temps, and lose it when you increase them. Plain and simple, fact not opinion. JFB, I am a Professional Engineer, and I have had alot more than just high school physics. A cooler motor makes more HP, that being said what fool would remove a fan that doesnt even turn on until 238F and weighs a whopping 3 lbs? Do you ever wonder why people ice down the intakes at the drag strip and turn theier cars off in the staging lanes?

Try the atkins diet or weightwatchers if you want to save a few lbs.

I find it hard to believe anyone would even post an idea like this, and even harder to believe that you guys are actually debating it.

And Blackbirds last post was right on the money.... If the battery is charged the alternator requires a certain amount of power to turn REGARDLESS of the current demand. Zero demand does not equal zero drag even if you use a cut off switch.

 

Obviously, it takes some power to turn anything but if the alternator is under load it takes even more power and the more load it is under, the more power it takes. Now I never studied physics, but have you ever turned the lights or other high draw accessory on and if the belt was loose, worn, etc. you hear the belt squeal? This would be the load on your alternator INCREASING! And by the way.... YOU'RE debating it too!

 

Actually I was trying to put a nail in the coffin. Not debating, merely pointing out what should be obvious to anyone with a shred of common sense.

You decided not to acknowledge what I said about temps vs HP... Interesting.

Either way, you are just continuing a stupid subject for the sake of arguing. The idea of removing an electric cooling fan that turns on at such a high temp is, in a word, idiotic.

The dead horse has now been beaten into glue.

Nuff said. Next subject.

 

That's because I was not debating those points, only alternator drag in general, my friend. And I can always use some glue!

 

I was right, you like to argue. Sorry, but I am not going to play your game, nor will I reply in this thread any further.

Have fun, you win, you can have the last word... happy?

 

It's a real challenge to make a 3,000 lb. C4 that is street legal and street reliable, and that is track legal and track reliable. And, I appreciate the helpful responses to my query.

The 3" core radiator with the oil cooler keeps the engine cool even in traffic - no fans needed (it doesn't turn on anyway because the thermostat hasn't switched hence this post)
On the track when averaging 100 mph - no fans needed. (they just impede the air flow through the radiator)
In traffic while waiting for the light to change - no horsepower needed. But just for fun what's the loss?
Let's say that the fan uses ¼ hp with an alternator efficiency of 70% with a belt efficiency of 85% = 0.42 hp. Now (of course) that would be recovered since the fan will make cooler water temps for a more efficient engine.

That 6 lb. fan removal is worth about 1/10 sec on a 90 sec lap, which amounts to about 18 car lengths in a 20 lap race. (Lap time is roughly proportional to the square root of mass/force, to a first approximation ignoring aero, etc.)
And that 0.42 hp would be worth another 10 to 14 car lengths. QED
But wait, I forgot to include the removal of the 1 oz. fan relay.
Hey we're all car crazy or we wouldn't be posting here.