AC horsepower loss

[ralph7]

Lot of mixed messages on this subject.

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[80FoxCoupe]

1

Shit. Headed to garage and pulling it now.....


















LOL

 

[17MagMetal]

Cut the belt and test drive to see if you feel any difference

It’s generally accepted that some rotational energy is being sucked by the compressor, the amount lost on a large V8 as a percentage is probably negligible.

There’s probably someone here with a dyno sheet with and without the AC belt displaying a WHP gain of 2 without.

 

[17MagMetal]

I literally race with the a/c on. The car is faster because the cooling fan is on more often reducing coolant temps and such. So A/C is plus 10 hp. Your analysis has a sign error.

This feels like a little bit of a “hot” take. Do you mean that you’ve got AC/Climate control set to hot?

I definitely blast my heater after any spirited drives/pulls to make me imagine that I’m helping evacuate some of the heat in the coolant.

 

[17MagMetal]

Shit. Headed to garage and pulling it now.....


















LOL

Just get some garden shears and free yourself of the parasitic loss lol.

 

[JetGray_Mach1]

This feels like a little bit of a “hot” take. Do you mean that you’ve got AC/Climate control set to hot?

I definitely blast my heater after any spirited drives/pulls to make me imagine that I’m helping evacuate some of the heat in the coolant.

Heater works like a charm for a overheating car

On my S197 the techs replaced my fan due to a minor fan noise under warranty. Long story short they installed it wrong, the wire melted and my car overheated The heater worked like a charm to keep the temps cool while I got home during traffic.

 

[17MagMetal]

Heater works like a charm for a overheating car

On my S197 the techs replaced my fan due to a minor fan noise under warranty. Long story short they installed it wrong, the wire melted and my car overheated The heater worked like a charm to keep the temps cool while I got home during traffic.

Sure, because it’s using heat from the coolant to supply that heat and cool off the overheating coolant in that case.

The A/C compressor uses cabin air and the engines rotation to circulate air and cool the car off. How would that lower coolant tempts and promote engine performance?

I’m only a shadetree scumbag and can be completely wrong here as well.

 

[Dana Pants]

This feels like a little bit of a “hot” take. Do you mean that you’ve got AC/Climate control set to hot?

I definitely blast my heater after any spirited drives/pulls to make me imagine that I’m helping evacuate some of the heat in the coolant.

These are literally my hvac settings while racing on a hot day. Forcing the main cooling fan on with A/C is way more effective than the hvac fan.

 

[Idaho2018GTPremium]

I agree with the poster above that said about 1 hp. You can calculate it. Assuming 7,000 btu/hr cooling capacity, that’s 2,050 watts of energy, but A/C have a coefficient of performance of at least 2, probably 3, which means an input of 680-1025 Watts, which is 0.9 - 1.4 hp. And I have heard it turns off at WOT as well.

 

[17MagMetal]

These are literally my hvac settings while racing on a hot day. Forcing the main cooling fan on with A/C is way more effective than the hvac fan.

Huh, I guess under those conditions that makes sense. I’ve just never heard of using the A/C to promote cooling and hp gains.

Wouldn’t the effort on track raise coolant temps high enough to force the fan to run at max capacity as well?

I’m not being nitpicky, I’m actually learning a thing or two about this car.

 

[K4fxd]

Forcing the main cooling fan on with A/C is way more effective than the hvac fan.

The fans on would cool better if the condenser wasn't being used. It gets hot so the fans are pulling hotter air than ambient.

The cooler cabin is nice but I'd have my tuner turn the fans on 100% at 180 degrees coolant temp or lower.

 

[K4fxd]

And I have heard it turns off at WOT as well.

So does the alternator.

 

[Dana Pants]

Huh, I guess under those conditions that makes sense. I’ve just never heard of using the A/C to promote cooling and hp gains.

Wouldn’t the effort on track raise coolant temps high enough to force the fan to run at max capacity as well?

I’m not being nitpicky, I’m actually learning a thing or two about this car.

the fan on temp thresholds are REALLY high from the factory. The A/C “trick” just delays the time until the car gets there. And increases the chances that your run starts with the coolest coolant possible.

 

[WildHorse]

So does the alternator.

Really ? No idea it turned off the charging as well at WOT.

 

[ice445]

the fan on temp thresholds are REALLY high from the factory. The A/C “trick” just delays the time until the car gets there. And increases the chances that your run starts with the coolest coolant possible.

This is true, stock programming means no fan until 217 cht or thereabouts. AC runs the low speed all the time. If your car has grille shutters the behavior is even more annoying.

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