Rear deck lid fan for 930?

Brent 930 · 03-22-2004, 05:22 PM

Has anyone used a Spal fan or whatever at the rear deck lid to prevent the engine and stuff from heat soaking after you park the car? I'm thinking about a pull type fan in place of the condensor and trigger it by a thermal switch. What do you guys think?

Thanks,

Brent 83' 930

rick conrath · 03-22-2004, 06:08 PM

To get the kind of airflow that you would need to prevent heat soak, you would probably drain your battery. With the rear AC condensor and intercooler there is also little room for an auxilliary fan. I have a rear fan on my AC condensor....it does little to cool the engine compartment when sitting still.
Rick
'78 930

ZCAT3 · 03-22-2004, 06:43 PM

Hey Brent - I installed a fan on my rear AC condenser and it does help a bit. I think in stop and go traffic it provides additional air flow to the engine compartment but heat soaking the IC is not really a concern in those conditions. In any case, there is room. You would have even more room without the AC condenser.

911pcars · 03-22-2004, 07:04 PM

Since heat naturally rises, it may help to wire the fan so it helps draw air out of the engine compartment after shutdown. A timer or thermal relay will limit discharging the battery. The motor can also be wired with a relay to reverse the air direction to assist heat transfer when the engine is ON.

Sherwood

Brent 930 · 03-23-2004, 05:36 AM

Thanks guys, I do wonder about draining the battery and that would depend on a couple things. How big the fan or how much current draw from it and what temp rated switch to use. I think with the right fan (not too big) and a thermal switch rated for >100 deg. monitoring the heat of the IC might do the trick. This way it won't be on too long (I hope) and won't let the engine area heat soak. Some of these ideas are never really proven until you actually try them. Now I'm thinking of which way to flow the air for the best results.

Thanks again

rick conrath · 03-23-2004, 06:18 AM

I would think about recirculating the oil to help with the heat soak as well. I am a little skeptical about cooling the engine with an auxilliary fan, especially with 13 quarts of oil cooking in the oil lines. The turbos generate so much heat, that everything in the general area of the engine bay including the bumpers hold heat. I would wrap the turbos and the exhaust...attack it from the source. I have found that in a turbo engine bay a small electric fan is like throwing a bucket of water on a forest fire.
Rick
'78 930

5axis · 03-23-2004, 06:34 AM

I sort of remember a write up about a group of turbos running the Dragon a few years ago.(I think it was the dragon.) One of the memorable photos was the cars, outside a restaurant, parked in a line with all the tails up. It was a very cool photo. (pun intended) That would seem to be the quickest way to get the heat out of the engine compartment. Hosing it down excluded.

david 89 turbo cab

Brent 930 · 03-23-2004, 08:18 AM

Nope, can't get enough heat out by just having the deck lid up. You need a fan of some sort or it will heat soak badly in the summer. That is the IC which is really my main concern. I'm thinking of trying a fan next to the IC where the AC condensor was using the old shrouding for the stock IC. Then I need to make sure there is enough air for the intake. Worst case I blow some money and time.

turbodog · 03-23-2004, 09:34 AM

I'm a little confused here. Why would you care about cooling the intercooler after shutdown? It's temp only matters when the car is running. Raising the decklid after a hard run makes a some improvement in how fast the engine cools, but not huge. Try to improve your oil cooling, let it idle for a while after a hard run, and raise the decklid. Bring hot dogs and have lunch.

Brent 930 · 03-23-2004, 10:34 AM

Because after you park the car for 15min. but less than 2 hours everything will heat soak to 150+ deg. So when you get back in you will have to drive around for a while till things cool off. What do people do at the track? Let if heat soak then go back out and run around for a while till they can run boost again?

ZCAT3 · 03-23-2004, 12:35 PM

Brent is right - it is amazing how much heat the IC will store up. You can park the car and go back and touch the IC and it will be cool or warm. Come back 10 minutes later and it will be quite hot.

Brent - I used a flex-a-lite fan, but there are many out there that will fit. Without the AC condenser you should be able to get something in there that can really move some air. I think my fan is about 700 CFM. You may be able to get up to 1000 CFM. I would think running the fan for 10-15 minutes after shut down would not drain the battery very much as fans are not huge users of power. If you are concerned about battery drain, you can always carry one of the smaller battery helpers that plug into the cigarette lighter.

Bill

turbodog · 03-23-2004, 01:16 PM

I'm not sure how much you would gain with a fan to dissipate heat. An open decklid is going to be more effective than a fan; the larger opening allowing the heat to escape upward, the direction it wants to go. Now a year or so ago I was adding a spal fan to my terbatrol oil cooler. At one point during assembly I needed a place to set down the fan I was holding. It fit very nicely on top of the stock intercooler. That got me to thinking: Would a fan on the intercooler have the same effect on the charge air that the fan has on an oil cooler? Would running a fan rigged like this keep the intercooloer cooler after engine shutdown? I dunno.

Brent 930 · 03-23-2004, 01:48 PM

Thanks Bill, you can cook an egg on that IC after you park your car on a hot day. I have to do something about this, when I drive home I open the deck lid and get my $20 fan going while inside. Again I think controlling the fan by the IC temp for a little over 100 deg. would do the trick. I want the engine itself to stay warm but not the IC.

TD,

Would be alot more than just opening the deck lid for sure. You can pull the air out with a fan when it's parked if that will work better. A fan on the IC would help some while the car is on but the alternator fan will pull alot of air through it to start with. Yes, a fan on the IC (if you have the stock one) would help after the car is off. I came across a website where this guy put one on his stock IC and used the rear wiper control to power it from inside. Now I have an after market IC and a fan really doesn't fit well. I just brought the subject up since most people have tried everything and would help me decide what, if anything I would do about it.

Thanks

ZCAT3 · 03-23-2004, 02:22 PM

Brent - what happened to your water mist system? I would think spraying the IC with water mist after shut down would also cool it quite a bit.

Also, the pull air out of the engine bay vs. pull air into the engine bay is a bit of a debate. If the car is parked, do you want to blow fresh air onto the IC from the top or do you want to pull air from under the car through the hot engine and then out the decklid?

Brent 930 · 03-23-2004, 02:28 PM

It's still there and will get a copy of what I did tonight. I just don't think it will cut it without air flow.

As for the air flow direction since I can't mount a fan on top or below the IC yet it will be in place of the condensor, it would pull the air in a different way. It might even pull air through the top of the IC and then back out. With it setup this way I think pulling the air out would be better but if I could mount it on the IC I would push the air into the engine compartment.

ZCAT3 · 03-23-2004, 02:52 PM

It is no big deal either way as with most fans you can reverse polarity and the fan will turn the opposite direction. So you can play around and see which way works best. I have my fan pulling into the engine compartment as that is the way the air flows when moving.

89turbocabmike · 03-24-2004, 09:30 PM

Brent, why not use the misting system to cool the intercooler upon start-up when the air flow is in your favor? If you monitor IC temp you would know when it is safe to dip into the boost. Your concern is a valid one for longevities sake and I think of IC heat soak like I do a cold start. I don't get into it until the oil warms up, or this case, that the intercooler cools down. I'm going to get one of the andial type in/out IC temp gauges for summer.

Brent 930 · 03-25-2004, 05:10 AM

True and I do monitor the IC temps, for right now I decided to go with my original plan. Just hook up a Spal fan and sit it ontop of the IC in the pit. I will use the water before and after or even during that time. You can now call me the "Waterboy"

)

Sarah · Sarah's Garage

OK...I have to ask...what exactly does "heat soak" mean?

Brent 930 · 03-25-2004, 08:32 AM

When the thermal mass of something (like and IC) has stablized to the operating temperature of whatever the environment is. Say the outside ambient temperature of 100 deg. F or in this case the heat from the engine (but not the engine itself) of 150 deg. F for an example. Heat soak is a term used in the electronic industry.