When to delete AC on track car

[Car54]

I have a mostly track car with half cage, seats, harness, wheel. The car is street legal but I don't depend on it daily. I often trailer it, but I do drive it hours away for autox or 1 day local track events.

I've been battling over heating in the Florida summers while on track. I'm at the point where I think it's necessary to delete the aux fan, condenser, and AC belt.

What kind of improvements in track driving cooling can I expect? Is it worth the effort and around town sacrifice? Do you regret it?

[MasterKwan]

I regret it. The only benefit that I see is that it's a bit easier to work on and around the engine. The compressor simply isn't that heavy. If you don't race, I'd say never. I didn't notice any change in cooling but, then again, my cooling system was already more than adequate.

[Brent]

for me it will be when I tow it or when I have a cool suit setup

[CalRick]

If the cooling system is working properly, the A/C shouldn't make any difference when it's off.

[magnetic1]

Removing the condenser on the E46 M3 makes a HUGE difference for cooling. Not sure on an "E36"

[Car54]

My Z3 is already air flow challenged vs the typical E36.

This is all about more airflow through the radiator. Nothing to do with weight or speed. I'm just tired of running the damn heat in the summer.

[conway]

Bigger rad, stewart water pump.
I daily drove my m3 with out ac for 3 years. Don't regret it. I usually drive with the windows down anyway.

[Car54]

I have a Stewart and Mishimoto radiator.

Someone suggested I might have too much water flow and the water isn't hanging out in the radiator long enough to get cooled.

[NeilM]

I have a Stewart and Mishimoto radiator.

Someone suggested I might have too much water flow and the water isn't hanging out in the radiator long enough to get cooled.

That's thermodynamically absurd.

For your location and usage, keep the AC and fix the cooling system capacity.

Neil

[conway]

Are you using the stock clutch fan or electric?
Not sure about the m coupes, they have an aux fan as well? Are you running that too?

[Def]

I have a Stewart and Mishimoto radiator.

Someone suggested I might have too much water flow and the water isn't hanging out in the radiator long enough to get cooled.

That's ridiculous.

Concentrate on letting air get out of your engine bay. Z3s are really bad at building pressure up in the engine bay so you don't get much of a pressure differential to push air across the radiator. Duct your hood, make sure your shrouding up front is in good shape etc.


As for the AC question, I don't have it in my S13 (didn't really work when I bought it, so that made the decision easier). It definitely sucks for about 6 months out of the year here, but with the coolshirt I can always pop in some ice and get at least some comfort. I don't have a tow vehicle so it's 100% driven to events (which sucks when you customize your paintjob with a grass fire). The weight difference was easily noticeable, but that car is less than 2500 lbs, so maybe it's not quite as noticeable on a 3000+ lb car. I think it would be though. Average passenger car AC system is around 40-50 lbs mostly off the far front of the car.

[magnetic1]

Are you using the stock clutch fan or electric?
Not sure about the m coupes, they have an aux fan as well? Are you running that too?

Fan makes no difference on cooling when youre at speed.

[JSA]

I would like for someone to explain to me how moving water through the heat exchanger "too fast" doesn't make a difference on the delta. Yes, I took physics (among many other math classes) as well.

I removed my A/C which amounted to approximately 45 lbs for all parts from the firewall forward (I even removed the crank pulley so that I could remove the compressor bracket). I haven't removed the interior parts yet...

And after removing the aux fan and condenser it definitely opened the front of the car up to allow more air to reach the radiator. Plus there is more room in the engine bay to work on the motor.

I vote to remove it if it's a true "track car."

Good luck

[noodlexyz]

To answer simply...today is a good day to remove it! Weight is weight...the less you have the better!

-Ryan

[tammer]

I regret it. The only benefit that I see is that it's a bit easier to work on and around the engine. The compressor simply isn't that heavy. If you don't race, I'd say never. I didn't notice any change in cooling but, then again, my cooling system was already more than adequate.

I also didn't see a big effect on cooling, but I have a standard E36 with a wimpy M50 that doesn't generate too much heat. However, 40+ lbs removed from the nose of the car (compressor, dryer, lines, pulley, bracket, aux fan, condenser) is significant to me. I still have to drive the car to the track, but even on hot days it's not that big a deal. Also, you remove one more failure point. Compressor clutch can seize and create heat/drag, it's an extra belt in the way, you're carrying refrigerant that will leak out in an incident, you are adding airflow obstruction, etc.

The simplicity and cleanliness of the engine bay with no AC is a nice bonus. For example, if you have to change a motor mount or control arm at the track, the extra access on the exhaust side is great. If the car isn't a daily or even occasional-use car, ditch it.

-tammer

[odortiz]

it does make a big difference on flow through the radiator. i don't use AC on cars, so i never miss them when they are gone.

[Car54]

Are you using the stock clutch fan or electric?
Not sure about the m coupes, they have an aux fan as well? Are you running that too?

Stock clutch fan, diesel fan spaced out and into the oem shroud, oem aux fan, all stock shrouding, aluminum under pan. The car is doing the best it ever has in Florida with this setup but it's not enough.

[Z3racer701]

Stock clutch fan, diesel fan spaced out and into the oem shroud, oem aux fan, all stock shrouding, aluminum under pan. The car is doing the best it ever has in Florida with this setup but it's not enough.

If you're not getting stuck in traffic and basically trailering the car, then remove the fans, and the fans shroud. The shroud and fan just blocks the air flow out of the radiator at normal track speeds. As for water flow too fast throught the radiator: a thermostat in place should prevent that.

[Car54]

If you're not getting stuck in traffic and basically trailering the car, then remove the fans, and the fans shroud. The shroud and fan just blocks the air flow out of the radiator at normal track speeds. As for water flow too fast throught the radiator: a thermostat in place should prevent that.

Then I might as well just delete the AC. I've ran with no fans and for whatever reason, the fans help on the track. The mechanical is much better than a slim electric fan. I've also ran with no aux fan/shroud and that wasn't real good. AC without the auxfan is bad news for temps on the street.

[99MPower]

sounds like it's time to get rid of the damn thing.. I noticed a 10 degree drop in temps from the removal of the AC system.. (1999 M3 for reference with zionsville full alum setup with Spal fan)

[Def]

I would like for someone to explain to me how moving water through the heat exchanger "too fast" doesn't make a difference on the delta. Yes, I took physics (among many other math classes) as well.

If you increase flow through a heat exchanger you increase the average coolant temp across the core, increasing heat transfer. The delta across the radiator goes down, so you're introducing higher temp coolant back to the engine, but the flowrate is correspondingly higher, so the delta across the engine will be lower.


It's well documented that a closed loop liquid cooling loop will INCREASE in performance (i.e. heat transfer to ambient conditions) as flow increases. It will approach an asymptote, so obviously performance will not increase forever. Yet there are clear advantages to pushing flow to the turbulent region through as much of the system as possible and keeping the average temp across the heat exchanger (radiator) as high as possible.

[PbFut]

The only time I had any heat issues with the S54 or S52 MCoupe was when I did not use the OEM lower covers. That was running in So Cal heat. It took me a while to figure out that those covers improve flow through the radiator. As for AC. If you don't use it, remove but you are in Florida. Make sure you really don't use it. Otherwise just remove the belt for track to get a HP or two. Removing AC coil will help but again you should not need to if the lower covers are present.

[JSA]

If you increase flow through a heat exchanger you increase the average coolant temp across the core, increasing heat transfer. The delta across the radiator goes down, so you're introducing higher temp coolant back to the engine, but the flowrate is correspondingly higher, so the delta across the engine will be lower.

Are you saying that the delta between the incoming and outgoing coolant temperatures will be lower as in closer apart? If yes, then how can this help increase the performance of the cooling system?

It's well documented that a closed loop liquid cooling loop will INCREASE in performance (i.e. heat transfer to ambient conditions) as flow increases. It will approach an asymptote, so obviously performance will not increase forever. Yet there are clear advantages to pushing flow to the turbulent region through as much of the system as possible and keeping the average temp across the heat exchanger (radiator) as high as possible.

Please send me a link to the documents. I'd like to read them to try and understand this concept.

Thanks, and sorry to hi-jack but this is good info for all of us.

[Def]

Are you saying that the delta between the incoming and outgoing coolant temperatures will be lower as in closer apart? If yes, then how can this help increase the performance of the cooling system?

Lower delta = less of a difference between inlet/outlet coolant temps on the engine. I didn't ever say that was the "key" towards better system performance, it's just a result of higher coolant mass flow. It also helps stabilize temps across the engine so you don't get one part running much hotter (usually the back).

Please send me a link to the documents. I'd like to read them to try and understand this concept.

Thanks, and sorry to hi-jack but this is good info for all of us.

I don't know of any magic document that will explain it in terms you'd understand if what I wrote doesn't really click for you. I'm speaking from years of experience and formal education. If you really want to see some very basic instrumented tests, check out what the water cooled CPU guys are doing, as it's the same basic concept.

[JSA]

Lower delta means the heat exchanger isn't able to have a greater effect on cooling the water temp.... thus the reason why I will argue that slower coolant flow is better in this scenario.

I just asked for some of your reading material (as I'm sure it's online). I don't need for you to think you have to "dumb it down" for me... I'm a pretty smart guy. Please share it with me (us) if you don't mind.

I will say that cooling a microprocessor and combustion engine are lot different.